視床障害による精神症状

Psychiatric symptoms associated with thalamic lesions.

I．緒言

　視床の損傷により，運動障害，知覚障害などの神経症状や失語，失認などの巣症状のほかに，意識障害，記憶・認知機能，発動性，注意力，情動の障害など，より広汎な大脳皮質の機能異常が関与していると考えられる精神症状が起こりうる。視床にはさまざまな機能を有する諸核が密集しているため，精神症状と病変部位の臨床病理学的対応が困難な場合が少なくない。血管支配のvariationが多い。このような事情から，大脳皮質の病変による精神症状に比して未知の問題が多く残されている。本稿では，精神症状の出現に関与する視床の機能および血管支配に関する解剖学的事項，精神症状の概観および各精神症状についての問題点について述べ，症例を呈示する。

Patients with thalamic lesions may present psychiatric symptoms such as disturbance of con-sciousness, attention, emotion, and motivation, akinetic mutism and dementia. Thalamic nuclei involved in such cases are,(1) those which have close connections with the association areas of the cerebral cortex such as dorsomedial nucleus and pulvinar, and (2) those which belong to the nonspecific (diffuse) projection system (intralaminar nucleus, midline nuclei, and reticular nucleus).

Although these nuclei have connections with wide areas of the cerebral cortex, the intensity of thalamic projections is different among cortical regions. Therefore, focal cortical symptoms may outstand amongst generalized mental deficits in patients with thalamic lesions. The frontal lobe, in particular, is closely related to the dorsomedial nucleus. Thus, patients with medial thalamic lesions often present symptoms resembling the frontal lobe syndrome, and show the decrease of cerebral blood flow in the frontal lobe.