[Dysarthria due to small cerebral infarction--the localization of lesion and clinical characteristics].

We compared locations of infarctions and clinical characteristics for patients with dysarthria and those without dysarthria. Subjects were 40 patients with a small infarction in the corona radiata or junctional zone to the capsule and 13 patients with infarctions in the internal capsule. Left corona radiata/junctional zone infarctions were significantly smaller than right sided lesions. Dysarthria was associated more frequently with the corona/junctional lesions on the left side than the right sided lesions. Asymptomatic infarctions on the contralateral side were seen in 41% of the patients with dysarthria. In these cases, dysarthria continued longer and dysphagia occurred more frequently than the cases without right sided lesions. Corona radiata/junctional zone infarctions with dysarthria were located significantly more anteriorly than those without dysarthria. The corona radiata/junctional zone infarctions presenting with dysarthria alone, upper limb dominant hemiparesis, and lower dominant hemiparesis were located in the anterior, middle, and posterior areas, respectively. In conclusion, dysarthria may occur with unilateral small cerebral infarctions, more frequently with left sided lesions than with right sided lesions. It is assumed that the left corona radiata/junctional zone infarction may interrupt simultaneously the corticobulbar pathway and callosal fibers to the right hemisphere which transmit motor information for speech to the right hemisphere. It is also possible that there are individual variations in the proportion of crossed and uncrossed corticobulbar innervation, which may explain dysarthria with unilateral cerebral lesions in some patients. It was suggested that there is an anterior-posterior somatotopy in the corona radiata/junctional zone as well as in the internal capsule.