Normal pressure hydrocephalus: Increase of utricular input in responders to spinal tap test

Abstract

Objective: To investigate whether there is a change in ocular (oVEMP) and cervical (cVEMP) vestibular evoked myogenic potentials in patients with normal pressure hydrocephalus (NPH) before and after spinal tap test (STT).

Methods: In 25 patients (6 females, age 62-83years) c/oVEMP were measured before and after STT. Patients with an increase of >20% of walking velocity were classified as responders (n=10). VEMP were also measured in a control group of 13 non-NPH patients.

Results: All patients had reproducible oVEMP; 68% had cVEMP. There was a significant increase of the peak-to-peak (pp) oVEMP amplitude after STT in responders (8.5±2.7 to 18.9±7.5μV (p=0.010)). No significant changes were found in non-responders (13.4±7.6 to 15.3±8.6μV) or controls (12.4±7.6 to 12.5±6.8μV). There were no significant differences in cVEMP before and after spinal tap test (STT).

Conclusion: One third of patients with suspected NPH had impaired otolith function. Responders to STT only had a significant increase of oVEMP and thereby utricular input, probably due to a decrease of pressure.

Significance: Both findings indicate that otolith dysfunction may contribute to imbalance in NPH and that increased utricular function after STT may be relevant for gait improvement.

Keywords: Clinical neurology; Normal pressure hydrocephalus; Otolith function; VEMP; Vestibular evoked myogenic potentials.