An Exploratory Study of Auditory Brainstem Responses and Hearing Thresholds in Essential Tremor

TL;DR

This study explores hearing function in essential tremor patients, finding more high-frequency hearing loss and subtle brainstem response changes.

Contribution

The study identifies a higher prevalence of high-frequency hearing loss and specific brainstem auditory response changes in essential tremor patients.

Findings

High-frequency hearing loss is significantly more common in essential tremor patients compared to controls.

Brainstem auditory evoked potential (BAEP) latencies are prolonged in essential tremor patients, suggesting delayed peripheral auditory input.

Medium-latency auditory evoked potentials (MLAEP) show no significant differences between essential tremor patients and controls.

Abstract

Background and Objectives: Essential tremor (ET) is the most prevalent movement disorder, yet its neurophysiological basis remains incompletely understood. Emerging evidence indicates that ET may involve non-motor manifestations, including auditory dysfunction. Given the anatomical convergence of tremor-related and auditory pathways at the brainstem level, electrophysiological assessment of the auditory system may provide insights into ET pathophysiology. This study aimed to evaluate auditory pathway function in patients with essential tremor using conventional audiometry, brainstem auditory evoked potentials (BAEP), and medium-latency auditory evoked potentials (MLAEP), and to examine their associations with tremor characteristics. Materials and Methods: Thirty patients with ET (mean age 56.6 ± 19.2 years; 15 women) and 30 healthy controls with similar age and sex distribution underwent pure-tone audiometry, BAEP, and MLAEP recordings. Tremor severity and distribution were assessed using a standardized evaluation based on the Fahn–Tolosa–Marin Tremor Rating Scale. Results: Conventional audiometry demonstrated normal hearing thresholds in 63.3% of ET patients and 83% of controls, while sensorineural hearing loss was observed in 36.6% and 16.6%, respectively (p > 0.05). High-frequency hearing loss (HFHL) was significantly more prevalent in the ET group (p = 0.003). BAEP analysis revealed significant prolongation of peak latencies in right-sided waves II and III and left-sided waves I and II in ET patients compared with controls (p < 0.05), whereas interpeak latencies (I–III, III–V, I–V) did not differ between groups. MLAEP latencies (Na, Pa, Nb) showed no significant differences between ET patients and controls (all p > 0.05) and were not associated with tremor severity, disease duration, or hearing asymmetry. Conclusions: High-frequency hearing loss is more prevalent in essential tremor, and selective BAEP latency changes observed in the context of preserved interpeak intervals suggest predominantly delayed peripheral auditory input rather than a primary brainstem conduction abnormality. Preserved MLAEP responses indicate relative sparing of thalamocortical auditory processing, supporting the concept of essential tremor as a multisystem network disorder in which altered auditory input may interact with broader network-level mechanisms.

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