Carhart Notch
Pronunciation: KAR-hart notch
A mechanical artefact on the bone-conduction audiogram—characteristically a dip of approximately 5–15 dB at 2000 Hz—associated with stapes fixation in otosclerosis.
Full Definition
The Carhart notch is not a true sensorineural deficit but rather a mechanical resonance artefact caused by the inability of the ossicular chain to vibrate normally when the stapes is fixed. It appears on the bone-conduction audiogram as a focal depression typically around 2000 Hz and may give the false impression of a sensorineural component to the hearing loss. Following successful stapedectomy, the Carhart notch usually resolves, confirming its mechanical rather than cochlear origin. Named after audiologist Raymond Carhart, the proper noun 'Carhart' should always be capitalised. Editors must distinguish it from the audiometric notch associated with noise-induced hearing loss.
Usage
Usage note: 'Carhart' must be capitalised as an eponym. The notch is a bone-conduction artefact, not a genuine cochlear finding; editors should flag any text that describes it as indicating sensorineural hearing loss.
In Context
- "A Carhart notch at 2000 Hz on the bone-conduction trace suggested underlying otosclerosis." — Audiological assessment report
- "Resolution of the Carhart notch post-stapedectomy confirmed the mechanical basis of the threshold elevation." — Post-operative audiology outcome report