一過性全健忘の病理所見—自験例と文献的考察

PATHOLOGICAL FINDINGS IN AN AUTOPSIED CASE OF TRANSIENT GLOBAL AMNESIA

はじめに

　一過性全健忘は，一過性に出現する記憶障害に対して，1956年Bender^3）が"Syndrome of isolated epis—ode of confusion with amnesia"，また，1964年Fisher，Adams^9）が"Transient global amnesia"（以下TGA）として注目したことに端を発する疾患あるいは症状である。そして，その後本症例の報告が多くなされ，同様の症状が種々の疾患にみられることが知られてきた。さらに，最近ではとくに脳血管障害との関連性においての興味が寄せられている。しかしながら，本症自体は直接的に死因となる疾患ではなく，その典型例の剖検成績を欠いていたこともあり，その発症機序に関しては不明確な部分が多く残されている。著者らは，ほぼ典型的なTGAを経過してその約9ヵ月後に急性心不全で死亡した剖検症例を経験した。このような本症の剖検例の記載は，脳腫瘍の例を除いては内外の文献上にみられないものであり，非腫瘍性のTGAとしては世界第一例である。しかも，心房細動，頸動脈閉塞性病変などの脳卒中riskfactorを有した例であり，本症例は非腫瘍性あるいは脳血管障害性のTGAの病因を検索する上での意義あるものと考えられる。

Transient global amnesia (TGA) is a syndrome which was named by Fisher and Adams in 1964. Thereafter, many authors have reported about this syndrome, and recently, much attention has been paid on this syndrome as one of the cerebrovascular diseases. There has been no autopsied case of typ-ical TGA, because TGA is not a cause of death itself. The pathophysiological mechanism of TGA still remains to be clearly provided. We obtained one necropsied case which was considered typical TGA and died of acute heart failure 9 months after that episode of amnesia.

The patient was a right handed, 69-year-old male. He suffered from the attack of TGA on June 4, 1979. During the attack of TGA, he complained severe headache and his family noticed that his speech was dysarthric. On neurological examina-tion, left 10 th cranial nerve paresis and pyramidal signs on the left side were detected on admission. These abnormal findings gradually disappeared un-til 9 days after the attack of TGA. On EEG, no epileptic discharge was recognized. On cerebral angiogram, stenotic lesion of the right internal carotid artery was detected. Transient atrial fibril-lation was observed on ECG. He recovered fully except for permanent amnesia of the episodes dur-ing the attack and for about 2 hours before the attack of TGA. He died of acute cardiac trouble on March 4, 1980.

The pathological findings were as follows : In the cardiovascular system, mitral annulus calcification which was recently considered as one of the im-portant embolic source was observed. In the cen-tral nervous system, the brain was 1100 grams in weight, and atrophied moderately. Microscopically, many obvious changes were found, which were con-sidered to be caused by chronic cerebral ischemia. These changes included gliosis, nerve cell atrophy, neuronophagia and satellitosis. They accompanied severe arteriosclerotic changes of cerebral vascu-lature, as pseudocalcification, thickening of arterial endothel and tortuous appearance of small vessels. They were observed diffusely in global brain, but were more dominant in limbic systems of both side, especially in bilateral hippocampus and temporal pole of the brain.

Many causes of TGA have been reported. The pathogenesis of this case seemed to be transient cerebral ischemia, because of presence of the carotid lesion, atrial fibrillation and mitral annulus calcifica-tion. Some authors said that bilateral limbic le-sions were necessary for the occurrence of TGA, and others claimed that unilateral limbic impair-ment could produce the symptoms of TGA. How-ever, there has been no conclusion about this con-troversy for lack of autopsied case of typical TGA. We considered that the preexistence of latent bi-lateral limbic impairment played an important role as a base of the onset of TGA in this case. Tran-sient ischemia due to embolism of the right cere-bral hemisphere, including the right limbic system, triggered the sudden and transient appearance of clinical symptoms of TGA.