錯書を呈したCerebellar cognitive affective syndromeの1例

A Case of Cerebellar Cognitive Affective Syndrome Exhibiting Paragraphia

はじめに

　小脳の主たる機能として運動の調節や制御があるが，最近では小脳と高次脳機能の関係が注目されている^1）．また，近年発展した神経放射線学および神経解剖学などの面からも，小脳の高次脳機能への関わりについて様々な報告がなされている^2,3）．小脳の障害による高次脳機能障害はCerebellar cognitive affective syndrome（CCAS）として臨床報告され^4），その主症状の1つに言語障害があるが，過去に錯書を呈した症例の報告はない．今回，我々は錯書を発端に高次脳機能障害が明らかとなった小脳出血の1例を経験したので報告する．

Abstract : Paragraphia due to cerebellar cognitive affective syndrome (CCAS) has not been reported previously. This report presents a patient with cerebellar hemorrhage, showing cognitive dysfunctions including paragraphia. A 74-year-old right-handed man was hospitalized with sudden dizziness. CT demonstrated a small hemorrhage in the right cerebellar dentate nucleus. He also exhibited gait disturbance due to mild truncal ataxia and became aware of errors while writing his dairy. Neuropsychological assessments showed phonological paragraphia with Kana characters and semantic paragraphia with Kanji characters, as well as mild auditory comprehension and verbal memory disorders. Although MRI did not detect any abnormality in the cerebral hemispheres, SPECT demonstrated decreased cerebral blood flow in the left angular gyrus, frontal lobe and parieto-occipital lobe, predominantly on the left side. On neuropsychological assessment 3 months after stroke, the patient's paragraphia and auditory comprehension disorder had subsided, but his verbal memory disturbance remained. The clinical features in this case differed from those of CCAS cases previously reported. In particular, the lesion considered responsible for the cognitive dysfunctions in this case involved the right dentate nucleus, which is supplied by the superior cerebellar artery, but not the posterior inferior cerebellar artery, and especially the presence of dis-orders in writing ability, such as paragraphia. The possible mechanism of paragraphia in this case might be a reduction of cerebral blood flow in the angular gyrus due to a crossed cerebello-cerebral diaschisis. However, this case suggests that the right dentate nucleus contributes to the neuropsychological mechanism of writing.