White Matter Characteristics of Idiopathic Normal Pressure Hydrocephalus: A Diffusion Tensor Tract-Based Spatial Statistic Study

Using magnetic resonance-diffusion tensor imaging (DTI), we examined white matter changes within the brains of patients diagnosed with idiopathic normal pressure hydrocephalus (INPH). We analyzed data for 24 INPH patients who were presented with typical clinical symptoms (gait disturbance, dementia, and/ or urinary incontinence) and Evans index > 0.3, and compared these with the control data from 21 elderly persons (≥ 60 years). DTI brain images were obtained with a 3T scanner. Fractional anisotropy (FA) brain maps were generated using a computer-automated method, and tract-based spatial statistics (TBSS) were then applied to compare the FA brain maps of the INPH and control groups in standard space. The TBSS data were further investigated using region-of-interest (ROI) analyses. ROIs were set within the corpus callosum, the posterior limb of the internal capsule (PLIC), and the cerebral peduncle in reference to a standard brain template. Compared with the control group, FA values in the INPH group were significantly lower in the corpus callosum and just significantly higher in the PLIC, but no significant differences were evident in the cerebral peduncle. The much lower FA values in the corpus callosum, but not the slightly higher FA values in the PLIC, were associated with more severe clinical symptoms such as gait disturbance. The lower FA values in the corpus callosum may offer a clue to solve the pathophysiology of INPH.