強直性痙攣発作を示す1例

A CASE WITH TONIC SEIYURE

Ｉ．はじめに

　痙攣発作のなかには強直性痙攣が唯一，あるいは著しく前景に立つものがあり，それが全身性に起こる場合にはcerebellar fitsあるいはmesencephalic seizure^1）とよばれている。一方，強直性痙攣発作が身体の一部に限局して起こり，多く意識障害を伴わず，短時間（多く1分以内）で終わる発作もまれに報告されている。これらは1800年代の終わりごろまではテタニーの特殊型と考えられたが^2）3），その後の臨床観察により，てんかんの一種と考えられ，spastic epilepsy^4），　extrapyramidal epile—psy^5），　striatal epilepsy^6），　subcortical epilepsy^7），　toni—sche Hirnstammkrämpfe^8）などとよばれており，皮質下，脳幹部の起源であると考えられてきた。しかしPenfield　＆　Jasper^1）は類似の発作がsupplementary motor areaの焦点によつても起こることを示し，これをsuppleme—ntary motor seizureとよんだ。

　このように身体の一部に起こる強直性痙攣発作は，その発生機序はかならずしも明らかにされずに種々の名称でよばれている。

A case with tonic seizure in a 22 year-old man was reported. He developed an unusual tonic seizure at 21 years of age. Being preceeded by a peculiar sensation in the right ankle, the right foot dorsi-flexed. The right knee and hip joints flexed and the right thigh slightly rotated externally. The face grimaced. The head flexed and slightly rotated right. The right arm extended and abducted. The trunk flexed and then rotated toward left. Similar attacks occurred approximately five to six times every night during sleep. He awoke at the initia-tion of the peculiar sensation and the attack would last for approximately 30 seconds without accom-paning pain or loss consciousness.

The attacks were rarely precitated by a passive over-extension or sudden shock on the right ankle, and by a psychic excitement. They varied in their degree from a minor attack with only sensory aura to a moderate attack with tonic spasm and posturing without loss of consciousness, and to asevere attack with generalized tonic-clonic convul-sion as well as with loss of consciousness.

Neurological examination between attacks revealed no abnormality. Electroencephalogram during rest was normal, whereas a combined activation with in-travenous bemegride and photic stimulation pro-voked a grand mal seizure, and intravenous adminis-tration of diphenhydramine produced a spike and wave complex and occasional paroxysms of small spike without showing any focality. Somatosensory evoked cortical potentials from the left parietal region by stimulation of the median nerve and the right tibial nerve presented a partial decrease of components P₁-N₂. Nitrazepam showed a remarkable effect to inhibit the attacks.

Tonic seizures without loss of consciousness similar to the case presented have been reported occasion-ally assuming that their focus might be at the brain stem, at or near the supplementary motor area and in special occasion, especially in multiple sclerosis, at the spinal cord. In the present case a possible focus was estimated to be at the left supplementary motor area because of the resmblance of the clinical picture of attacks to those reported as such.