Cerebellar speech representation: lesion topography in dysarthria as derived from cerebellar ischemia and functional magnetic resonance imaging.

Abstract

Lesion topography and the pathophysiological background of dysarthria due to focal cerebellar lesions have not yet been fully clarified. To investigate the lesion topography of dysarthria due to cerebellar ischemia and evaluate brainstem functions. Case studies. Eighteen right-handed patients with sudden-onset dysarthria and cerebellar ischemia with and without brainstem involvement and 19 healthy, right-handed, monolingual, German-speaking volunteers. In patients, we used multimodal electrophysiologic techniques to investigate brainstem functions. Functional magnetic resonance imaging (MRI) was performed in the 19 healthy volunteers. Activation tasks consisted of repetitive vertical silent movements of the tongue and lips at a self-paced rhythm. Cerebellar lesions and additional signs of brainstem involvement were observed in 11 patients with posterior inferior cerebellar artery, anterior inferior cerebellar artery, and superior cerebellar artery infarctions, respectively. In all other patients with isolated cerebellar infarction (n = 7), only the superior cerebellar artery territory (6 right-sided, 1 left-sided) was affected, and the common lesion site was the rostral paravermal region of the anterior lobe. Functional MRI in healthy volunteers indicated that the cerebellar representation of the tongue and orofacial muscles corresponds to that of the area involved in patients with cerebellar dysarthria. The results of this study demonstrate that articulatory movements of the tongue and orofacial muscles are involved in the activation of the rostral paravermal area of the anterior lobe. This location corresponds to the area involved in cerebellar ischemia in patients with dysarthria. Lesions in the upper paravermal area of the right cerebellar hemisphere, the site of coordination of articulatory movements of the tongue and orofacial muscles, may lead to the development of dysarthria that is unrelated to (often concomitant) brainstem infarctions.