Hearing change after shunt placement in elderly patients with idiopathic normal-pressure hydrocephalus

Abstract

Hearing changes have been reported in patients with hydrocephalus. Most authors have hypothesized that hearing changes in patients with hydrocephalus are due to relative endolymphatic hydrops. We examined the hearing changes in 53 elderly patients who underwent shunt surgery for normal pressure hydrocephalus between January 2012 and March 2018. More than half of the patients already had moderate to severe hearing loss before the surgery. Significant hearing loss after the surgery was observed at 500 Hz in the right ear, and at 125 Hz and 250 Hz in the left ear. Twelve patients (22.6%) showed hearing change by 10 dB or more were at average hearing thresholds of 250, 500, 1,000, 2,000 and 4,000 Hz. Of all the patients, 8 (15.1%) showed hearing loss, and 4 (7.5%) showed hearing improvement after the surgery. The age, sex, shunt technique, side of shunt, shunt system, valve pressure, cognitive functions, physical functions, and body mass index were compared among the groups showing no change, hearing loss, and hearing improvement, and no significant differences were found. The hearing thresholds prior to the surgery were not different between the hearing loss group and the group that showed no hearing change ; however the hearing thresholds for low frequencies worsened significantly in the left ear in hearing loss group. The hearing thresholds in the low, middle, and high frequencies were worse prior to the surgery in the hearing improvement group as compared to the group that showed no hearing change, but there were no significant differences between the two groups after the surgery. We agree with previous reports that hearing loss after surgery is due to relative endolymphatic hydrops. We also hypothesize that hearing improvement is due to release from the relative increase of the perilymphatic pressure. One half of the patients with hearing loss showed no improvement, and 3 patients needed to start using hearing aids after the surgery. We think that it is necessary to pay attention to hearing problems as one of the risks of shunt surgery.