脳性麻痺児の視覚性誘発反応について

VISUALLY EVOKED RESPONSES IN CEREBRAL PALSIED CHILDREN

I．はじめに

　脳性麻痺の脳波に関する研究成果は数多くの人によつて報告されており，棘波，徐波などの異常脳波がかなり多くの例で出現することが認められている^{16）18）20）25）31）36）37）}しかし脳性麻痺の病像が多彩なためか報告者によつてその成果がかなり異なつている。また脳性麻痺における脳波の診断的役割については多くの研究者によつて討議されているが，生理学的，機能的な面からの観察は少ないように思われる。

　脳波の生理学的意義について佐藤ら^26），佐藤^{27）28）29）}は安静時脳波の平均時間経過を示す自己相関図は単一衝撃刺激による脳波導出部の脳の平均反応の時間経過を表わし，脳波のスペクトル密度は単一衝撃刺激の反応のスペクトルを示すことを明らかにした。さらに種々の頻度の周期的感覚刺激を加えた際の脳波の平均反応（相互相関図とそのスペクトル）から得られる脳波の周波数応答は導出部脳の活動性の周波数パタンを表わすだけでなく，安静時脳波のスペクトル密度と同等であることなどを解明した。これにもとづいて著者ら^32）は脳性麻痺児の脳波のデータ処理を行ない，自己相関図と周波数応答について検討し，いくつかの異常所見を認めすでに報告した。さらに佐藤ら^30）はデータ処理用竃子計算機の使用によつてより正確な誘発反応を求め，動物や人間の脳の活動性の解析を行なつている。

Visually evoked responses were studied in eleven cerebral palsied and seven normal control children during the waking resting state. The flash light stimulus was delivered to the closed eyes of the sub-jects in sequences of 1 f/sec and at random. Elec-trodes for electroencephalographic (EEG) potentials were placed on the subject's scalp by ten-twenty system. Fifty responses contaminated by background activities in the EEG potentials, which were recorded on the magnetic tape through 8-channel polygraph and 8-channel data recorder, were summated in the length of 500 msec by the Digital Computer For Data Processing (ATAC-401).

In agreement with other authors, the normal evoked responses were comprised of an initial, sec-ondary or late and rhythmic after potentials. Com-pared the responses of the palsied patients with those of normal subjects with respect to the general configuration, sequential appearance, bilateral sym-metry, amplitudes and peak latencies of each response components, little differences except some of the peak latencies were observed between them. How-ever, a significant reduction in the peak latencies of late component and after potentials was verified in most of the patients.

Taking the current concept on the late and after potentials into consideration, it would be capable of inferring from this evidence that there may possibly be a sort of release phenomenon from inhibitory control activity in the non-specific system of such cerebral palsied patient that are impaired mildly or moderately in their motor activities.