右視床前核梗塞により道順障害をきたした1例

A Case of Defective Route Finding following Right Anterior Thalamic Infarction

はじめに

　道順障害は，熟知した地域内で，ある地点から他の地点への道順想起が障害される病態である^1）。その責任病巣は，右半球脳梁膨大後域および周辺領域にあたる側頭～頭頂～後頭葉内側部が一般的に想定されている。既報では両側脳梁膨大部^2），左頭頂―後頭葉内側部^3，4），右辺縁葉後端部^1，5），両側上頭頂葉^6），左後大脳動脈領域^7），右下側頭葉^3，8）の病変にて生じたとするものもある。

　今回われわれは，右視床前核の脳梗塞にて道順障害をきたした1例を経験した。同部位の病変での道順障害はこれまで報告されておらず，貴重な症例と考えられたため報告する。

Abstract

　Defective route finding is a symptom in which an indivisual demonstrates inhibility to find the way in the familiar places.　This symptom arises from lesions at the right parieto-occipital region and the right posterior part of the splenium of the corpus callosum.　We present a case of defective route finding resulting from the right anterior thalamic infarction.

　A 63-year-old right-handed man abruptly presented with difficulty in route finding on his way home.　Neither spatial neglect nor agnosia was observed with pictures of his house and surrounding streets.　Although there was an attention disturbance, his activities of daily living were spared.　Brain MRI revealed a fresh infarction at the right anterior nucleus of the thalamus.　Single photon emission computed tomography using ¹²³ I-methyltyrosine showed hypoperfusion at the right parieto-occipital region as well as the right thalamus.　Neuropsychological tests showed visuospatial memory disturbance.　To our knowledge, this is the first report of defective route finding caused by the right anterior thalamic infarction.　The right anterior thalamic nucleus might be involved in the visuospatial recognition circuit.

(Received: November 1,2007,Accepted: July 22,2008)