Improvement of the vestibular functions as measured by video head Impulse test in patients undergoing ventriculoperitoneal shunt surgery for Idiopathic normal pressure Hydrocephalus: Moving Forward in a yet unexplored territory

Introduction: Idiopathic Normal pressure hydrocephalus (iNPH) is the most common form of reversible dementia in the elderly. Few were investigated about CSF dynamic disturbances and brainstem functions, though it could be a potentially interesting and yet “unexplored” territory. The objective was to evaluate high-frequency VOR through VHIT before and after ventriculoperitoneal (VPS) shunting. Materials and Methods: We investigated a total of 9 patients suffering a confirmed from iNPH diagnosis. Patients underwent video Head Impulse Test (vHIT) before and 10 days after VPS. The VOR measurement was performed focusing on the horizontal semicircular canals (HSC) and on both sides. The PR and saccadic profiles were investigated through vHIT. For each patient, we recorded age, sex, and comorbidities. Results: Our preliminary results showed a generally reduced gain in the pre-operative phase (average gain on both sides: 0.66 ± 0.14) and an increase in gain in the post-operative phase, detectable at the first re-evaluation (average gain at the first post-operative −-operative: 0.79 ± 0.11) and an increased PR preoperatively (average PR on both sides 44.8 ± 28.25) with a reduction in PR postoperatively (average PR on both sides 27.57 ± 21.88). Such results, despite the small cohort, were significant. Furthermore, an interesting age-related effect was outlined for PR and saccades profile. Conclusions: The increase in VOR gain is a constant finding as is the reduction in saccade amplitude. The saccadic organization seems to increase after VPS in most patients. Chemical-physical and hydrodynamic variations of the cerebrospinal fluid may explain the parameters change and the improvement of the vestibular function.