Neurotologic Findings of Idiopathic Acute Unilateral Audiovestibulopathy

Background and Purpose: Unlike acute unilateral vestibulopathy or vestibular neuritis (AUVP/VN), of which the diagnosis is made based on well-established neurotologic findings, the diagnosis of idiopathic acute unilateral audiovestibulopathy (iAUAV, also known as labyrinthitis) still requires further elucidation. Methods: We retrospectively reviewed the medical records of patients with first-onset acute audiovestibulopathy (AAVS) in a referral-based university hospital in South Korea between March 2018 and September 2024. The results of video-oculography, video head-impulse, and other neurotologic evaluations were included for analysis. In addition, an MRI dedicated to the inner ear was conducted. The findings were compared with 80 patients with AUVP/VN. Results: A total of 73 patients with iAUAV (age range = 20–85 years, mean age ± SD = 60 ± 18 years, 33 male) were included in the analyses. 26% and 12% of patients showed ipsilesional nystagmus and predominant downbeat nystagmus, respectively. The vestibulo-ocular reflex (VOR) gain was decreased in horizontal (HC, n = 41), posterior (PC, n = 23), and anterior canals (AC, n = 9), showing more frequent involvement of PC compared to those with AUVP/VN (p = 0.002). Positive MRI results were found in 28 patients with iAUAV (28/68, 41%), showing high signal intensities over the vestibule (n = 27), cochlea (n = 25), HC (n = 21), PC (n = 21), and AC (n = 7) on MRIs. Conclusions: Patients with iAUAV can show various neurotologic findings that deviate from typical AUVP/VN. Recognition of these findings can aid in a deeper understanding of the pathophysiology of iAUAV, which is distinct from AUVP/VN, and differentiation from other etiologies of AAVS that can have a debilitating prognosis.