A survey is given of the literature on the sensitivity of the vestibular system to audio-frequency sound and vibration in animals. It is also shown that responses to such stimuli can be evoked in man. On the basis of these results it was decided to perform a fenestration of the horizontal semicircular canal in three profoundly deaf volunteers, with normal sensitivity of the vestibular system. The first results are promising: the threshold for audio-frequency vibration in the operated ears improved markedly. Furthermore, the subjects reported perception of environmental sounds using a bone conductor hearing aid.

This paper discusses the capacity of sound perception in 5 profoundly deaf subjects in whom a "fenestra" was previously formated on the lateral semicircular canal. The ability of sound and vibration perception after fenestra formation in profoundly deaf subjects with normal function of the vestibular apparatus has been described previously. The experiments for this procedure were done on pigeons by Wit & Bleeker. The subjects aged from 22 to 34 years. Causes of deafness varied. Their hearing threshold was bilaterally higher than 95 dB HL and their vestibular apparatus was of normal excitability bilaterally when tested with a caloric test. In all 5 patients the ear conduction hearing threshold remained the same, but the ability of vibration perception improved significantly, and ranged postoperatively between 30 and 45 dB HL. The frequency dynamic range was from 125 to 2,000 Hz in 4 subjects, and from 125 to 4,000 Hz in 1 subject. The patients claimed to have perceived higher intensities, but with a variable dynamic range from frequency to frequency. The intensity range amounted to between 15 and 40 dB. The obtained data of vibration perception ability are discussed.

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ABR waveforms were analyzed in 63 subjects with tumors of the pontocerebellar angle. The tumors were diagnosed by CT scan and the diagnoses were surgically confirmed. According to the latency changing and amplitude size, the ABR waveforms were classified into seven types (0, A, B, C, D, E and F). All tumors were divided into groups (depending on size), and into subgroups (depending on type). Types 0–E were found in tumors of all sizes. Type C of the brain stem response (BSR) waveform (only 1 deflexion present) was revealed in 75 % of tumors greater than 20 mm. In this case tumor size may be predicted with the significance level of 5 %. Type F of the BSR waveform was found in tumors other than neuromas. Contralateral BSR is affected by tumors greater than 20 mm, and from the statistic point of view significantly more often by neuroma (significance level 5 %) than by other tumors.

Failure of additional diagnostic procedures to distinguish MSA patients required a precise understanding of their clinical specificities. Our results support this statement.