Unilateral vestibular loss following systemic gentamicin: A rare complication with clinical relevance

Abstract

Systemic gentamicin vestibulotoxicity is usually bilateral; unilateral involvement is exceptional and may be clinically subtle. We report a 79-year-old man with three weeks of constant gait instability, worse during walking and body turns, after intramuscular gentamicin 80 mg every 12 h for 10 days for a urinary tract infection. He had no true vertigo, autonomic symptoms, or visual motion sensitivity. Examination showed corrective saccades on rightward head impulse testing (HIT) and left-beating horizontal nystagmus after head-shaking and mastoid vibration. Audiometry showed previously documented mild bilateral hearing loss. Brain MRI showed chronic hypoxic–ischemic leukoencephalopathy, but neurological assessment found no central cause. Dynamic posturography demonstrated a vestibular dysfunction pattern, and videonystagmography confirmed right vestibular areflexia on ice-water caloric testing. Vestibular Evoked Myogenic Potentials (VEMPs) were preserved bilaterally, suggesting relative otolith sparing. Vestibular rehabilitation led to substantial improvement over 12 months, with mild residual unsteadiness during rapid head movements. This case illustrates that systemic gentamicin may produce unilateral canal-predominant vestibular loss and supports targeted vestibular assessment when new imbalance appears after treatment.