Abnormal White Matter Integrity in Elderly Patients with Idiopathic Normal-Pressure Hydrocephalus: A Tract-Based Spatial Statistics Study

We investigated white matter integrity utilizing diffusion tensor imaging in patients with idiopathic normal-pressure hydrocephalus (INPH) who had a positive response to the cerebrospinal fluid tap test and in age- and gender-matched Alzheimer's disease (AD) patients. We enrolled 28 patients with INPH, 28 patients with AD and 20 healthy controls. Tract-based spatial statistics demonstrated that INPH patients had lower fractional anisotropy (FA) in the anterior corona radiate (bilateral), corpus callosum, superior longitudinal fasciculus (bilateral), posterior thalamic radiation (bilateral), external capsule (bilateral) and middle cerebellar peduncle in comparison with the AD and control groups. Volume-of-interest analysis revealed that INPH patients, when compared to the AD and control groups, showed higher mean diffusivity in the anterior corona radiate (bilateral), corpus callosum, superior longitudinal fasciculus (bilateral), posterior thalamic radiation (left), external capsule (bilateral) and middle cerebellar peduncle. And gait dysfunction was significantly correlated with decreased FA in the splenium of the corpus callosum and right external capsule in INPH patients. Our findings may suggest a possibility for considering microstructural changes in white matter integrity in elderly patients as potential imaging markers for differentiation between INPH and AD and may help us understand the potential pathophysiology of gait disturbances associated with INPH.