Hearing loss from acute carbon monoxide intoxication.

A case of fluctuating sensorineural hearing loss from acute carbon monoxide (CO) poisoning with presentation of a U-shaped audiogram is reported. Acute CO intoxication seems to involve vestibular function more frequently than auditory function. Hearing loss is uncommon, but when present, may often display a U-shaped audiometric curve. Decrease in hearing sensitivity probably results from hypoxia to the cochlea, VIII nerve and brain stem nuclei. Fluctuation in hearing sensitivity may be an early manifestation of acute CO exposure, and requires periodic audiometric examination until the hearing has stabilized.