Dysarthria in bilateral thalamic infarction. A case study.

A patient suffering from bilateral thalamic infarction in the region supplied by the paramedian arteries sparing the internal capsules underwent acoustic analysis of sentence utterances. The results were compared with the findings obtained in parkinsonian subjects, in patients with upper motor neuron lesions, and in normal subjects. Acoustic measurements revealed increased pitch, monotonous speech, rough voice quality, and normal speech tempo concomitant with articulatory impreciseness in terms of incomplete closure productions. This constellation resembled parkinsonian dysarthria. Damage to the thalamic projection area of the pallidal efferents, therefore, seems to be the most probable cause of the patient's speech disorders. In parkinsonian subjects stereotactical lesions of this structure ameliorate rigor, but not akinesia. Thus, our patient's speech deficits, and by analogy the corresponding parkinsonian dysarthric disturbances, may be considered akinetic signs.