Vertigo and hearing loss in a patient with infective endocarditis

A 70-year-old man was admitted for infective endocarditis of the aortic valve. On admission, his medications included oral metoprolol 50 mg twice daily for hypertension. Broad-spectrum antibiotic therapy was started: intravenous gentamicin 80 mg three times daily and intravenous vancomycin 1 g twice daily, both adjusted for renal function. On the ninth day of therapy, he reported vertigo, unsteadiness, and new bilateral hearing loss. He noted difficulty following conversations and a feeling of being off-balance. Physical examination was notable for horizontal nystagmus, a positive Romberg test, and an unsteady gait. Pure tone audiometry revealed bilateral down-sloping sensorineural hearing loss, with thresholds of 40 dB at 4 kHz and 60 dB at 8 kHz. Laboratory results showed therapeutic vancomycin trough levels and gentamicin levels within the target range. Renal function had declined from baseline, with an estimated glomerular filtration rate of 45 mL/min/1.73 m². The metoprolol was continued. On day 10, gentamicin was discontinued and ceftriaxone 2 g once daily was started. The vertigo and unsteadiness gradually improved over the following week, while the hearing loss remained unchanged at discharge. Due to the potentially serious nature of such symptoms, a rechallenge was not attempted. The possibility of an infected embolic event was considered, but the absence of focal neurological deficits and the bilateral nature of the symptoms made this less likely. Vancomycin was also considered, but serum levels were therapeutic and ototoxicity is less common at these levels.