OBJECTIVEThe object of this study was to use diffusion tensor imaging (DTI) and tract-based spatial statistics (TBSS) to characterize the long-term effects of hydrocephalus and shunting on white matter integrity and to investigate the relationship of ventricular size and alterations in white matter integrity with headache and quality-of-life outcome measures.METHODSPatients with shunt-treated hydrocephalus and age- and sex-matched healthy controls were recruited into the study and underwent anatomical and DTI imaging on a 3-T MRI scanner. All patients were clinically stable, had undergone CSF shunt placement before 2 years of age, and had a documented history of complaints of headaches. Outcome was scored based on the Headache Disability Inventory and the Hydrocephalus Outcome Questionnaire. Fractional anisotropy (FA) and other DTI-based measures (axial, radial, and mean diffusivity; AD, RD, and MD, respectively) were extracted in the corpus callosum and internal capsule with manual region-of-interest delineation and in other regions with TBSS. Paired t-tests, corrected with a 5% false discovery rate, were used to identify regions with significant differences between patients and controls. Within the patient group, linear regression models were used to investigate the relationship between FA or ventricular volume and outcome, as well as the effect of shunt-related covariates.RESULTSTwenty-one hydrocephalus patients and 21 matched controls completed the study, and their data were used in the final analysis. The authors found significantly lower FA for patients than for controls in 20 of the 48 regions, mostly posterior white matter structures, in periventricular as well as more distal tracts. Of these 20 regions, 17 demonstrated increased RD, while only 5 showed increased MD and 3 showed decreased AD. No areas of increased FA were observed. Higher FA in specific periventricular white matter tracts, tending toward FA in controls, was associated with increased ventricular size, as well as improved clinical outcome.CONCLUSIONSThe study shows that TBSS-based DTI is a sensitive technique for elucidating changes in white matter structures due to hydrocephalus and chronic CSF shunting and provides preliminary evidence that DTI may be a valuable tool for tailoring shunt procedures to monitor ventricular size following shunting and achieve optimal outcome, as well as for guiding the development of alternate therapies for hydrocephalus.
Keywords: AD = axial diffusivity; ALIC = anterior limb of internal capsule; CGC = cingulate gyrus component of the cingulum; CGH = hippocampal component of the cingulum; DTI = diffusion tensor imaging; FA = fractional anisotropy; FDR = false discovery rate; FOHR = frontal occipital horn ratio; HDI = Headache Disability Inventory; HOQ = Hydrocephalus Outcome Questionnaire; ICP = intracranial pressure; MD = mean diffusivity; NPH = normal pressure hydrocephalus; PLIC = posterior limb of internal capsule; PVWM = periventricular white matter; QoL = quality of life; RD = radial diffusivity; ROI = region of interest; SVS = slit ventricle syndrome; TBSS = tract-based spatial statistics; chronic shunting; diagnostic technique; diffusion tensor imaging; gCC = genu of corpus callosum; headache; pediatric hydrocephalus; quality of life; sCC = splenium of corpus callosum; tract-based spatial statistics.