Vestibular system in infants after systemic aminoglycoside therapy

OBJECTIVES: The ototoxic action of systemic therapy with aminoglycoside antibiotics leading to the loss of inner ear hair cells is well recognized. The mitochondria-mediated pathway of apoptosis may play a role in inducing the apoptosis of vestibular hair cells due to aminoglycoside toxicity. Aminoglycosides are, nevertheless, routinely used for treatment of vital infections in neonatologic departments. Although there is a strong supposition that aminoglycosides can influence the vestibular function in infants, the routine examination of the infants' inner ear does not include vestibular tests. The purpose of the present study was to evaluate vestibular function in a group of infants prior to and after administration of systemic aminoglycosides, using caloric tests and vestibular-evoked myogenic potentials (VEMPs). METHODS: VEMPs and auditory brainstem responses were recorded and caloric stimulation was performed in 68 infants aged 2.5-3.5 months: 40 healthy controls and 28 infants after therapy with amikacin, 15mg/(kgday) in three doses. The therapy duration varied from 10 to 14 days. In 18 infants antibiotic therapy was administered for a respiratory infection, and in 10 for sepsis. Infants with other risk factors of inner ear damage and treated with more than one ototoxic drug were excluded from the study. The tests were performed on the day of admission to hospital and repeated on the day of discharge. RESULTS: The results of all tests were normal on admission. On the day of discharge, no reaction to caloric stimulation was elicited in six patients and no VEMPs were recorded in four subjects. Hearing thresholds were normal in all the individuals during both examinations. CONCLUSIONS: The vestibular organ in infants after systemic therapy with amikacin may be damaged more frequently than the cochlear organ. The horizontal canal is more vulnerable to aminoglycosides, as compared to the saccule. The vestibular organ should be routinely examined in infants after systemic treatment with aminoglycosides.