A 28-year-old woman has slight hearing difficulty but a normal pure tone audiogram and a Type A tympanogram. Stapedial reflex testing shows a biphasic 'on-off' pattern. This finding indicates:

• A Ossicular discontinuity
• B Early otosclerosis with incipient stapes fixation ✓
• C Retrocochlear lesion
• D Normal middle ear function

Explanation

In early otosclerosis, before an air-bone gap develops, the partially fixed footplate produces the characteristic 'on-off' or diphasic stapedial reflex: contraction occurs when tone starts, relaxes as fixation resists displacement, and repeats when tone stops. Tympanogram remains Type B because middle ear compliance is preserved. Ossicular discontinuity abolishes the reflex entirely, and a normal study would show a sustained biphasic-free reflex.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.