Auditory fatigue in patients with stapedius muscle paralysis

Experiments were performed in 18 patients with peripheral facial palsy (Bell's palsy) including unilateral stapedius muscle paralysis. After exposure to narrow band noise centered at 0.5 kHz temporary threshold shift at 0.75 kHz was significantly higher in the ear with paralysis than in the normal ear. After exposure to 2.0 kHz narrow band noise there was no difference in TTS at 3.0 kHz between affected and non-affected ear. It was concluded that the stapedius reflex has a protective function against low frequency sound exposure and suggested that this protection might be extended to higher frequencies only when high frequency noise also contains low frequency components.