Cervical and Ocular Vestibular Evoked Myogenic Potential Recovery in Susac Syndrome: A Case Report

Abstract

Purpose: Susac syndrome (SS) is a rare autoimmune disorder that affects the brain and the retina and causes unilateral or bilateral sensorineural hearing loss. Although vestibular dysfunction is reported in SS, limited information is available underlying the vestibular pathophysiology. Method: The diagnosis of SS was established based on symptoms and diagnostic tools such as magnetic resonance imaging and fundus fluorescein angiography. The audiovestibular evaluation was done on the seventh day of admission (Session 1) into the emergency unit, whereas the second and third evaluations were done at 3-month (Session 2) and 8-month (Session 3) follow-ups after discharge, respectively. The audiovestibular test battery consisted of routine audiological tests, auditory brainstem response, and vestibular evoked myogenic potentials (VEMPs; both cervical and ocular). Results: We found unilateral sensorineural hearing loss and absent cervical VEMPs(cVEMPs) when testing the left ear during Session 1. In the following sessions, the unilateral hearing loss did not recover; however, cVEMPs were present bilaterally. The ocular VEMPs showed an increase in amplitude during Sessions 2 and 3. Conclusions: SS can selectively disrupt auditory and vestibular structures. It may present with unique findings of audiovestibular tests. A detailed audiovestibular evaluation may be essential in patients with SS. Supplemental Material: https://doi.org/10.23641/asha.21513843

Comprehensive Normative Data for Objective Vestibular Tests

“…The participants were seated on comfortable chairs. They turned their head opposite to the test ear on instruction to maintain adequate sternocleidomastoid muscle (SCM) tension when testing cVEMP [ 16 - 17 ]. For oVEMP, the participant was asked to fix at a point elevated approximately 30 degrees at a 60 cm distance from where they were seated [ 17 - 18 ].…”

“…They turned their head opposite to the test ear on instruction to maintain adequate sternocleidomastoid muscle (SCM) tension when testing cVEMP [ 16 - 17 ]. For oVEMP, the participant was asked to fix at a point elevated approximately 30 degrees at a 60 cm distance from where they were seated [ 17 - 18 ]. A feedback indicator box provided biofeedback of EMG activity to the participant during the recording.…”

“…The latency (P1 and N1) and amplitude (P1-N1 for cVEMP; N1-P1 for oVEMP) are manually marked on the normalized waveform. The stimulus and recording parameters [ 17 ] for cVEMP and oVEMP are given in Table 1 .…”

“…The latency (P1 and N1) and amplitude (P1-N1 for cVEMP; N1-P1 for oVEMP) are manually marked on the normalized waveform. The stimulus and recording parameters [17] for cVEMP and oVEMP are given in Table 1. Participants were seated in a dark room; the test goggles mounted with the monocular camera on the right eye were strapped tightly to the participant's head.…”