1800 Results Thirty-three patients were included in the evaluation; 17 patients were excluded on the basis of the exclusion criteria described above. The excluded patients consisted of 15 patients whose diffusion images were degraded because of magnetic susceptibility and motion artefacts, one patient with spinal canal meningioma and one patient with syringohydromyelia. There were 15 patients in group 1 (“uncompressed spinal cords”) and 18 patients in group 2 (“compressed spinal cords”). Their demographic characteristics are summarized in Table 1. Uncompressed spinal cords were measured in a total of 26 ROIs in the group 1 patients (11 ROIs at C3–C4 spinal canal level, 13 ROIs at C4–C5 and 2 ROIs at C5–C6); values (means ± SD) for FA, ADC (10–3 mm2/s), RMSD (μm) and mean DK were 0.656 ± 0.041, 0.939 ± 0.033, 8.287 ± 0.098 and 0.905 ± 0.095, respectively. Compressed spinal cords were measured in a total of 20 ROIs in the group 2 patients. Six ROIs were placed at the C3–4 spinal canal level, 9 ROIs at C4–5 and 5 ROIs at C5–6. Because the Anderson–Darling test had revealed that the data were not normally distributed, statistical comparison of groups was performed by using the Mann–Whitney U test with Bonferroni correction. Gender and age of patients were not considered as covariates for analysis, because a preliminary analysis using Spearman’s correlation showed no significant correlations between them and the diffusion metrics. The average size (mean ±SD) of the ROI (in pixels) was 58 ±16 in group 1 and 57±14 in group 2; no significant difference was seen between the groups in relation to ROI size. In the compressed spinal cords, FA (0.606 ±0.075) and mean DK (0.802 ±0.095) were significantly lower and RMSD (8.446 ± 0.269) was significantly higher (P 00.0060, 0.0020 and 0.0062, respectively) than in the uncompressed cords. In- creased ADC (0.977 ± 0.134) was also observed in the Table 1 Demographic characteristics of subjects Group 1 (n015) Group 2 (n018) 7:8 50.5 (16.2) 6:12 63.3 (10.8) Eur Radiol (2012) 22:1797–1802 compressed cords, but this difference was not significant (P 00.45). Although symptoms of numbness and pain tended to be more frequently observed in group 2 than in group 1, statistical analysis was not able to be conducted because of the small number of patients. Discussion This is the first evaluation of various diffusion metrics using QSI analysis in the cervical spinal cords of patients with early cervical spondylosis. Our findings of decreased FA values and increased ADC values are consistent with those of previous studies [6, 7, 23], and they can be explained in part by increased permeability of the membranes due to chronic hypoperfusion [24] and disturbance of the arrange- ment of axons in the spinal cord [7]. In addition to this increase in ADC values, RMSD values in compressed spinal cords were greater than those in uncompressed cords, meaning that the space for free water was enlarged. In general, RMSD is not influenced by the viscosity of water. Moreover, using the relative maximum high b value of 2,000 s/mm2 avoids the influence of perfu- sion of the microcirculation. Therefore, an increase in the RMSD value can be explained instead by an increase in the permeability of the intra- and intercellular spaces. The decreases in FA and mean DK values can be explained by the possibility that microstructural changes in the spinal cord are independent of the orientation of the fibre tracts [19]. In general, decreased FA values mean axonal damage, i.e. degeneration of the white matter in the brain and spinal cord [25]. However, mean DK values can increase in conditions in which damage occurs along the axon bundles [19]. Therefore, the decrease in mean DK values suggested that the com- pressed lesions would show structural changes with not only disturbance of the arrangement of axons but also changes in the directions and components of the fibre tracts, including the grey matter. This is a very important finding in terms of evaluation of the cervical spinal cord, because past reports have focused on white matter damage [6, 7, 26]. In fact, when FA values are used as biomarkers for evaluation, the grey matter is difficult to evaluate. Experimental histological stud- ies [27] have shown abnormalities predominantly within the grey matter, and axonal degeneration and obvious demyelin- ation have rarely been seen with compressive cervical mye- lopathy. This indicates that microcirculatory disturbance plays an important role in the damage in the compressed spinal cord [28]. Therefore, assessment of the cervical spinal cord by using mean DK offers advantages over that using FA because both white matter and grey matter can be better characterized [14, 20, 29]. Overall, this technique may prove to be useful in the assessment of the severity and type of cord abnormality in Sex (male/female) Mean age (SD), years Symptomsa Numbness Pain Cervical vertigo Neck stiffness Hypalgesia Tremor Apraxia Jitteriness a Multiple symptoms were reported by some patients 6 6 2 2 2 1 1 1 11 11 1 2 1 2 1 0