Tuning fork examination reveals signs of conductive hearing loss. If cochlear involvement is present, a mixed hearing loss appears, with high frequencies more affected. In severe cases, tinnitus may interfere with pure-tone audiometry. Cochlear otosclerosis is characterized by presence of mixed or primary sensorineural hearing loss where air-bone gaps are minimal. Acoustic reflexes often are abnormal and may provide the earliest evidence of otosclerosis.
Observed abnormality depends on stage of disease.
Almost half the normal population may show initial increase in compliance at stimulus onset, but compliance increase seen at offset occurs only in stapedial fixation and is virtually pathognomonic. Advancing fixation affects both ipsilateral and contralateral acoustic reflexes, even in unilateral disease. In most cases, discrimination is much better than would be expected with the level of hearing loss. Low speech discrimination scores prognosticate poorly for postsurgical hearing improvement. In cases of well-advanced lesions, and in lesions with vestibular symptoms, expect several variations from classic presentation.