Auditory brain stem responses (BSR) were studied in five cases including 2 acoustic neurinomas, degenerative type of myoclonus epilepsy, pontine glioma and the 4-th ventricle tumor. They showed typical BSR suspecting of brain stem lesions, and the BSR patterns were compared with those of animal experiments for discussion of the topographical differential diagnosis. In two patients with acoustic neurinoma, nothing but wave I was recognized at the pathologic side, and normal BSR was recorded at the healthy side. The BSR was similar to that of a cat destructed ipsilateral cochlear nucleus. In the patient with degenerative type of myoclonus epilepsy, wave I was reconized only in both sides. In the patient with pontine glioma, wave 1, 2 and 3 at the right side and wave 1 and 2 at the left side were recognized, but the following components were obscured in both sides. The right side response was considered similar to BSR of a cat destructed bilat. inf. colliculus, and the left side one was similar to that of a cat with destruction of bilat. Sup. olivery nucleus complex. In the patient with the 4-th ventricle tumor, wave 1, 2, 3 and 4 were recognized in both sides, and probably wave 5 was depressed in both sides. BSR was considered similar to that of a cat with destruction of contralateral inf. colliculus or contralateral sup. olivery nucleus complex. It was considered that the BSR pattern was suggestive of a medial lesion of the upper portion of the brain stem. The data of animal experiments could not be applied to the clinical use, but it could be very useful for topographical differential diagnosis of the brain stem lesions.
When auditory evoked slow vertex response (SVR) was examined, the effect on the averaged EEG by applying white noise to the unexamined ear at several. sound levels was studied. The recording of the evoked response and the determinations were carried out by Juntendo Method. The results were as follows; 1) Evoked response on the averaged EEG with white noise at appropriate sound level had tendency to appear clearer than without white noise. 2) As for the sound level of white noise to apply, about 40dB over hearing threshold or estimated threshold of the unexamined ear seemed appropriate for showing evoked response clearly. 3) Without acoustic stimuli, the averaged EEG was little influenced by white noise at about 40dB over hearing threshold or estimated threshold of the unexamined ear.
Six latencies were measured of the stapedial refiex by analyzing compliance curves in an inkwriting recorder connected to an impedance audiometer. To produce stapedial riflex, pure tone (500-4000Hz) stimuli were presented to the opposite ear of 20 Japaneses (19-20 years of age) with the normal eardrums and with no known history of ear diseases. The following results were obtained: As the stimuli increased in each frequency, latency-stimulus curves indicated that (1) initial reflex response and precontraction response decreased, (2) reflex relaxation and reflex decay increased, and (3) initial off response did not show much changes. There were the following relations between the latencies: initial reflex response <reflex contraction time initial off response <reflex contraction time initial off response <reflex decay precontraction response<initial off response Numerical data were presented in figures and tables.