存続性瘻声に対する外喉頭筋刺激療法

ELECTRIC STIMULATION OF THE EXTRINSIC LARYNGEAL MUSCLES FOR THE TREATMENT OF POSTMUTATIONAL FALSETTO VOICE

　I．はじめに

　存続性瘻声は，変声期をすぎても話声位が低下しないものであり，その原因および病態についてはなお不明な点が多く，治療法も未だ確立されたとはいい難い現状である。この疾患は稀ならずあるようで当科外来にも時々受診するが，病気の性質上あまり肉体的苦痛をおぼえないため治療途中で止めるものが多い。今回はそのうち以下に述べる如き治療を行ない得た症例につぎその概略を述べる。

　A man, aged 31, compalining of postmutational falsetto voice is treated by electric stimulation of the extrinsic laryngeal muscles, sternohyoideus sternothyroideus.

　Upon roentgenological examination, this patient spoke with high cranial position of the larynx and with a low caudal position of the hyoid bone, presumably because of the contraction of the hyothyroid muscle. The cricothyroid space narrowed during phonation apparently due to abnormal contraction of the cricothyroid muscle. The position of the voice was "a" ; the speech was monotonic.

　The sternohyoid and sternothyroid muscles were stimulated by a skin electrode with intensity of 15 V, duration lmsec and with interval at random. Immediately following this stimulation, the vocal pitch lowered from "a" to "c" , while the hyoid bone and the thyroid cartilage moved caudally.

　This stimulation was administered once a week for the total of 10 occasions. About 2 weeks after the stimulation therapy the patient was enabled to speak in the presence of a stranger in a low voice, and 10 monthes later he was able to speak with anyone in a low-pitched voice with some flexibility. Recently, the pitch of the patient's voice is found to be lowered by one octave, from "a" to "A" .