Clinical Improvement after Shunt Surgery in Patients with Idiopathic Normal Pressure Hydrocephalus Can Be Quantified by Diffusion Tensor Imaging.

Background and purpose: White matter changes assessed by DTI typically reflect tract functionality. This study aimed to investigate DTI parameter alterations in important regions pre- and postshunt implantation in patients with idiopathic normal pressure hydrocephalus (iNPH), alongside assessing the relationship between DTI parameters and clinical improvement.

Materials and methods: Patients with probable iNPH underwent prospective preoperative MRI and comprehensive clinical work-up between 2017-2022. Patients with clinical symptoms of iNPH, positive result on a lumbar infusion test, and/or gait improvement after 120-hour lumbar drainage were diagnosed with iNPH and underwent shunt-placement surgery. Fractional anisotropy and mean diffusivity values for individual regions of interest were extracted from preoperative and postoperative MRI. These values were correlated with the clinical picture of individual patients.

Results: A total of 32 patients (73.59 ± 4.59 years) with definite iNPH were analyzed. Preoperative DTI characteristics of internal capsule and corona radiata correlated with the 1-year improvement in the Dutch Gait Scale postoperatively (all P < .036). Cognitive domain improvement after surgery in memory and psychomotor speed correlated with preoperative DTI values of cingulate gyrus (P = .050), uncinate fasciculus (P = .029), superior longitudinal fasciculus (P = .020), or corpus callosum (P < .045).

Conclusions: DTI characteristics of white matter regions reflect clinical improvement after shunt surgery in patients with iNPH. They tend to improve toward physiologic DTI values, thus further accentuating the benefit of shunt surgery in both clinical and radiologic pictures.