無難聴性耳鳴

TINNITUS WITHOUT HEARING LOSS

　Ⅰ．緒言

　耳鳴を主訴として来院する患者のなかには，純音域値検査にて異常が認められない例がある。

　著者は耳鳴を訴える患者のうち，鼓膜所見に異常がなく，純音気導聴力損失値が全周波数にわたつて15dB以内のものを無難聴性耳鳴と命名し，最近2年間に当科を受診した無難聴性耳鳴の患者のうちから20名を無作為に抽出し，耳鳴の検査，各種聴覚検査，および神経学的検査を行ない，さらに一部の患者については治療経過を観察し，検討を加えたので報告する。

　The purpose of this paper is to discuss the tinnitus unaccompanied by hearing losses but may be found by means of the case history and audiometric tests. The patients were selected from those who suffered tinnitus but whose pure tone hearing losses were within 15 dB in all frequencies.

　Various kinds of audiometric tests were performed on 20 selected patients.

　The following results were obtained : (1) The tinnitus was non-vibratory type in all cases, one half of the number being unilateral and the other half bilateral.

　(2) The pure tone frequencies similar to the tinnitus were mostly 4 KHz.

　(3) The pure tone loudness similar to the tinnitus, in most cases, was 10-15 dB above threshold.

　(4) The recruitment phenomenon tests and TTS phenomenon tests were negative in all cases.

　(5) The usual speech tests were found to be abnormal in 2 cases.

　(6) The filtered and interrupted speech tests were found to be abnormal in 12 cases.

　(7) The binaural summation tests and directional hearing tests were found to be normal in all cases.

　As the results of these findings and anamnesis the site of the lesions in 10 cases were suspected to be at the central auditory pathway, the acoustic nerve in 1 case, in the cochlea in 1 case, in the middle ear or the cochlea in 1 case and undeterminable in 7 cases.

　The drug therapy was effective in only 2 cases.