発声障害患者における声門閉鎖反射の電気生理学的検討

Glottal closure reflex was induced by electrically stimulating the internal branch of the superior laryngeal nerve in normal subjects and patients with disturbances of phonation. In the present study, characteristics of glottal closure reflex were analyzed and electrophysiological difference between the normal subjects and the patients was examined.

The patients with adductor spasmodic dysphonia, essential voice tremor or in the recovery process from idiopathic recurrent nerve paralysis were included. The internal branch of the superior laryngeal nerve on one side was stimulated electrically and the muscular responses from the bilateral thyroarytenoid muscles were recorded. To examine habituation, the recovery curves, R 1 and R 2, were prepared by giving two stimuli successively. The internal between two stimuli was varied from 100 to 5000 msec. Stimulation of the internal branch of the superior laryngeal nerve induced R 1 on the stimulated side and R 2 on both sides. These response patterns were analogous to those of the blink reflex. However. their latencies were fairly long. The latency of R 1 on the stimulated side was about 16 msec and the latency of R 2 on the stimulated side and opposite side were 55 to 70 msec respectively. It was assumed that both the R 1 and R 2 were polysynaptic reflex, and seemed to go through complicated course.
In the normal subjects, R 2 response was inhibited at stimulation intervals below 1000 msec indicating habituation. In the patients in the recovery process from idiopathic recurrent nerve paralysis, the pattern of habituation resembled to that in the normal subjects. However, in the patients with adductor spasmodic disphonia and essential voice tremor, R 2 was not inhibited. These results suggested that adductor spasmodic disphonia might be an abnormality of the inhibitory system in the central nervous system and one of the symptoms shown by essential voice tremor.
It was concluded that the glottal closure reflex induced by stimulation of the internal branch of the superior laryngeal nerve would be applicable to clinical practice as a useful test to find abnormality in the central regulatory system of the larynx.