Dysarthria and lacunar stroke: pathophysiologic aspects

We investigated the supranuclear tracts involved in speech production in 8 patients with dysarthria associated with a single lacunar stroke. Magnetic resonance imaging revealed the lesion site in 7 out of 8 patients. We tested corticobulbar tract function using transcranial magnetic stimulation and demonstrated impairment of the corticolingual projections in all the patients and in 5 patients impairment of the corticofacial projections. Sensory function in the oral cavity was impaired in 1 out of 8 patients. 99mTc hexamethyl-propylene amine oxime-single-photon emission computerized tomography (HMPAO-SPECT) imaging, performed in 5 patients, showed cerebellar diaschisis in 1, suggesting additional cerebropontocerebellar tract impairment. Dysarthria observed in the 2 patients with impaired sensation in the oral cavity or with cerebellar diaschisis did not differ from the dysarthria found in the other patients. We conclude that interruption of the corticolingual pathways to the tongue is crucial in the pathogenesis of dysarthria following extracerebellar lacunar stroke.