Electrocochleographic evaluation of hearing loss in acoustic neuromas.
OBJECTIVE
This study aimed to clarify the pathophysiology involved in the cause of hearing impairment due to acoustic neuromas (AN) with electrocochleograph (ECoG).


METHODS
The study design was a retrospective case study.


METHODS
This study was conducted in a tertiary referral center.


METHODS
Thirty-four patients diagnosed as having AN by magnetic resonance imaging between 1988 and 1995.


METHODS
Diagnostic.


METHODS
The authors made a comparison between the patients' ECoG findings and the size of their tumors as determined by magnetic resonance imaging and a pure-tone audiometry (PTA). The disparity between the threshold of PTA and the detective threshold of compound action potential (CAP) or that of the cochlear microphonics (CM) was calculated. When the threshold of the PTA was worse than the detective threshold of the CAP or the CM, the disparity was regarded as indicating a hearing loss of retrocochlear origin.


RESULTS
There was no correlation found between tumor size and the detective threshold of CAP or CM. Disparity was found to correlate with tumor size.


CONCLUSIONS
These findings seem to indicate that retrocochlear damage in AN increases parallel to the growth of the tumor and that retrocochlear damage can be detected by the ECoG before surgery.
Tanaka
F
F
Department of Otolaryngology, Nagasaki University, School of Medicine, Sakamoto, Japan.
Tsukasaki
N
N
Nakao
Y
Y
Shigeno
K
K
Kobayashi
T
T
D000328:Adult; D000368:Aged; D001300:Audiometry, Evoked Response / Q000379:methods*; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000503:physiopathology; D003390:Cranial Nerve Neoplasms / Q000150:complications* / Q000473:pathology; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000150:complications* / Q000473:pathology; D012189:Retrospective Studies; D012720:Severity of Illness Index; D000159:Vestibulocochlear Nerve / Q000473:pathology