Yonago Acta medica 1996;37:107-116

ABR Topograms in Patients with Acoustic Neuroma and Application of Source Derivation Method

Hironori Makino, Saburo Sugihara, Shin Kawakami*, Yasuaki Tanaka* and Misao Tomomori

Otorhinolaryngological Clinic and *Neurosurgical Clinic, San-in Rosai Hospital, Yonago 683, Japan

Auditory brainstem responses (ABRs) to monaural click stimulation were depicted as topograms in 6 patients with acoustic neuroma before and after surgery and in 6 age-matched normal subjects. Regular topograms were compared with topograms revised by the source derivation method. Regular topograms of normal subjects showed contralateral lateralization with greater amplitude in positive Waves I and III. The other waves did not show lateralization. Statistical differences between patients and normal subjects were not significant in latencies of Waves I, III and V and in interpeak latencies of Waves I-III, I-V and III-V. However, the patients' parameter values tended to be higher than the 95% confidence limit of normal subjects. No differences were apparent between patients' paired parameters before and after surgery. ABR results and hearing preservation state findings were inconsistent in 2 of the 6 patients.

Key words: auditory brainstem response; evoked potentials; tumor; topography

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