Carhart notch
Pronunciation: KAR-hart notch
A characteristic audiometric depression in bone-conduction thresholds at 2000 Hz, classically associated with otosclerosis, representing a mechanical rather than sensorineural loss.
Full Definition
The Carhart notch is a well-recognised audiometric artefact characterised by an apparent reduction in bone-conduction sensitivity, maximal at 2000 Hz (typically by approximately 15 dB), that occurs in patients with otosclerosis and other forms of mechanical middle ear fixation. It is a mechanical phenomenon caused by the altered resonant properties of the ossicular chain rather than a true sensorineural deficit, and it typically resolves following successful surgical correction (e.g., stapedectomy). Editors must ensure the eponym is capitalised ('Carhart notch') and not confused with a genuine sensorineural component on the audiogram. The term appears frequently in ENT and audiology operative and diagnostic reports and must be rendered precisely.
Usage
Usage note: Always capitalise 'Carhart' as it is an eponym. Do not describe the notch as evidence of sensorineural hearing loss; clarify it is a mechanical artefact. It is distinct from the noise-induced notch typically seen at 4000 Hz.
In Context
- "The preoperative audiogram revealed a Carhart notch at 2000 Hz, consistent with the diagnosis of otosclerosis." — ENT surgical report
- "The editor queried the author's description of the Carhart notch as a sensorineural component and requested clarification." — Peer-review correspondence