Otolith function in Usher type II syndrome

Area of Science:

• Otolaryngology
• Neuroscience
• Genetics

Background:

• Usher syndrome type II (USH2) is a genetic disorder causing hearing and vision loss, with previously assumed intact vestibular function.
• Emerging evidence suggests otolith vestibular receptors may be involved in USH2 pathophysiology.

Purpose of the Study:

• To evaluate the dynamic function of otolith vestibular receptors in individuals with Usher syndrome type II.
• To correlate vestibular function test results with patient-reported outcomes for balance and dizziness.

Main Methods:

• Twenty-two USH2 patients and age-matched controls underwent comprehensive vestibular testing, including cervical and ocular vestibular evoked myogenic potentials (c-VEMPs and o-VEMPs).
• Vestibular test results were analyzed alongside scores from the Activities Balance Scale (ABC) and Dizziness Handicap Inventory (DHI).

Main Results:

• Absence of c-VEMPs was noted in 15 USH2 patients compared to 4 controls (p=0.034).
• Significant differences in o-VEMP N1 latencies, N1-P1 amplitudes, and asymmetry ratios were observed between USH2 patients and controls (p<0.010, p<0.003, p<0.014, respectively).
• A strong correlation was found between o-VEMP amplitude and DHI scores in USH2 patients (p=0.003).

Conclusions:

• The study indicates the presence of otolith dysfunction in Usher syndrome type II, independent of subjective dizziness.
• Integrating vestibular evoked myogenic potential testing into the clinical assessment of USH2 patients can improve disease characterization and management.