Background: Idiopathic normal pressure hydrocephalus (iNPH) is one of the treatable causes of dementia in elderly by shunt
placement surgery. Diffusion tensor imaging (DTI) can demonstrate the alteration of white matter microfiber. The corticospinal tract (CST) is white matter fiber responsible in part of motor function and gait.
Objective: This study was to compare microfiber alteration of the CST between iNPH patients and normal controlled subjects.
Material and Method: Fifteen clinically diagnosed definite iNPH patients and 15 normal controlled subjects underwent MRI study with DTI. All iNPH patients had gait disturbance and clinical improvement after shunt placement surgery. Probabilistic tractography of the CST were performed and comparison of DTI parameters included fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) in iNPH and normal controlled groups.
Results: There were statistically significant increase of MD (p<0.001), AD (p<0.001) and RD (p<0.001) in iNPH patients
compared with normal controlled subjects, whereas FA of iNPH patients was slightly decreased but not statistically significant
different when compared with the normal controlled group (p = 0.75).
Conclusion: DTI parameters, especially MD, AD and RD can be used to evaluate alteration of white matter microfiber of the CST, which was responsible in part of alteration of motor function and gait disturbance in iNPH patients. We hope that our
study will lead to further investigation about other role of DTI in iNPH patients.

Keywords: Normal pressure hydrocephalus, Diffusion tensor imaging, Corticospinal tract