視床出血による記憶障害の検討

Study of Amnesia Caused by Thalamic Hemorrhage

要旨　目的：視床出血による記憶障害に関しては，前核，背内側核出血例や，脳室穿破例に多く，脳室穿破による記憶障害は背内側核の障害を原因としている報告が多い．回復期リハビリテーション病棟に入退院した亜急性期視床出血の記憶障害に関して検討した．方法：50例を対象とし，記憶に関しては入退院時のFIMの記憶項目で検討した．結果・考察：本研究では背内側核出血が記憶障害をきたしやすい傾向はなく後外側核出血と同等であった．後外側核出血では30例中18例で脳室穿破しており，脳室穿破した症例で記憶障害が高度であった．背内側核出血は6例中5例と高頻度に脳室穿破していた．脳室穿破した後外側核出血と背内側核出血の比較でも記憶障害は同等であった．これらの結果と，視床出血による記憶障害がエピソード記憶障害であることから，脳室穿破症例の記憶障害の原因は，情動記憶に関与するYakovlev回路の一部である背内側核障害に起因したものではなく，脳室穿破したことによる側脳室とモンロー孔周囲のPapez回路への影響が主体ではないかと思われた．

　Abstract　Background and Purpose : Many cases of amnesia caused by thalamic hemorrhage involve anterior nucleus hemorrhage, dorsomedial nucleus hemorrhage, and intraventricular rupture. In the present study, intraventricular rupture was studied with a focus on cases with hematoma compression at the fornix. Methods : Of 116 patients with thalamic hemorrhage admitted to our hospital, 50 patients aged ＜70 years who had hemorrhage during their first stroke confined to the thalamus, internal capsule, and corona radiata, and who neither developed hydrocephalus nor showed dementia prior to onset were investigated. Thalamic hemorrhages were classified by CT findings and the extent of intraventricular rupture. Memory was studied by the FIM memory scores on admission and discharge. Results and Conclusion : Patients with dorsomedial nucleus hemorrhage showed no tendency toward amnesia and were equivalent to patients with posterolateral nucleus hemorrhage, which does not usually result in amnesia on its own. Of the 30 patients with posterolateral nucleus hemorrhage, a high degree of amnesia was observed in the 18 with intraventricular rupture. A high proportion of patients with dorsomedial nucleus hemorrhage experienced intraventricular rupture (5 of 6 patients). Equivalent degrees of amnesia were observed in patients with intraventricular rupture with dorsomedial nucleus hemorrhage and those with posterolateral nucleus hemorrhage. The present findings in conjunction with the fact that amnesia in thalamic hemorrhage involves episodic memory impairment suggest that amnesia in patients with dorsomedial or posterolateral nucleus hemorrhage or with intraventricular rupture does not stem from damage to the dorsomedial nucleus, which is part of the Yakovlev circuit involved in emotional memory. Instead, the primary cause appears to be the effects of intraventricular rupture on the Papez circuit surrounding the lateral ventricle and foramen of Monro.