Diffusion tensor imaging study of pediatric patients with congenital hydrocephalus: 1-year postsurgical outcomes
Authors: Mangano Francesco T. , Altaye Mekibib , McKinstry Robert C. , Shimony Joshua S. , Powell Stephanie K. , Phillips Jannel M. , Barnard Holly , Limbrick David D. , Holland Scott K. , Jones Blaise V. , Dodd Jonathan , Simpson Sarah , Mercer Deanna , Rajagopal Akila , Bidwell Sarah , Yuan Weihong 
Published: May 2016

OBJECTIVE
The purpose of this study was to investigate white matter (WM) structural abnormalities using diffusion tensor imaging (DTI) in children with hydrocephalus before CSF diversionary surgery (including ventriculoperitoneal shunt insertion and endoscopic third ventriculostomy) and during the course of recovery after surgery in association with neuropsychological and behavioral outcome.

METHODS
This prospective study included 54 pediatric patients with congenital hydrocephalus (21 female, 33 male; age range 0.03–194.5 months) who underwent surgery and 64 normal controls (30 female, 34 male; age range 0.30–197.75 months). DTI and neurodevelopmental outcome data were collected once in the control group and 3 times (preoperatively and at 3 and 12 months postoperatively) in the patients with hydrocephalus. DTI measures, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) values were extracted from the genu of the corpus callosum (gCC) and the posterior limb of internal capsule (PLIC). Group analysis was performed first cross-sectionally to quantify DTI abnormalities at 3 time points by comparing the data obtained in the hydrocephalus group for each of the 3 time points to data obtained in the controls. Longitudinal comparisons were conducted pairwise between different time points in patients whose data were acquired at multiple time points. Neurodevelopmental data were collected and analyzed using the Adaptive Behavior Assessment System, Second Edition, and the Bayley Scales of Infant Development, Third Edition. Correlation analyses were performed between DTI and behavioral measures.

RESULTS
Significant DTI abnormalities were found in the hydrocephalus patients in both the gCC (lower FA and higher MD, AD, and RD) and the PLIC (higher FA, lower AD and RD) before surgery. The DTI measures in the gCC remained mostly abnormal at 3 and 12 months after surgery. The DTI abnormalities in the PLIC were significant in FA and AD at 3 months after surgery but did not persist when tested at 12 months after surgery. Significant longitudinal DTI changes in the patients with hydrocephalus were found in the gCC when findings at 3 and 12 months after surgery were compared. In the PLIC, trend-level longitudinal changes were observed between preoperative findings and 3-month postoperative findings, as well as between 3- and 12-month postoperative findings. Significant correlation between DTI and developmental outcome was found at all 3 time points. Notably, a significant correlation was found between DTI in the PLIC at 3 months after surgery and developmental outcome at 12 months after surgery.

CONCLUSIONS
The data showed significant WM abnormality based on DTI in both the gCC and the PLIC in patients with congenital hydrocephalus before surgery, and the abnormalities persisted in both the gCC and the PLIC at 3 months after surgery. The DTI values remained significantly abnormal in the gCC at 12 months after surgery. Longitudinal analysis showed signs of recovery in both WM structures between different time points. Combined with the significant correlation found between DTI and neuropsychological measures, the findings of this study suggest that DTI can serve as a sensitive imaging biomarker for underlying neuroanatomical changes and postsurgical developmental outcome and even as a predictor for future outcomes.