Dysarthria is characterized by dysfunction of the structures implicated in the control, initiation, and coordination of speech output: lips, tongue, jaw, palate, and larynx, which are innervated by the facial, glossopharyngeal, vagal, and hypoglossal nerves. Lesions that cause dysarthria occur in one of several locations along the neuraxis. This chapter presents the clinical features of dysarthria resulting from stroke and its associated neurological signs. Ischemic lesions of the upper motor neuron system may be unilateral or bilateral, cortical or subcortical. Ischemic lesions in the vertebrobasilar territory can result in both upper and lower motor neuron involvement. Ataxic dysarthria is the result of lesions occurring in the territory of the superior cerebellar and posterior inferior cerebellar arteries. Dysarthria can follow ischemic lesions of the extrapyramidal system occurring in the vascular territories of the deep penetrating branches of the anterior and middle cerebral arteries.

This chapter reviews the epidemiology, clinical phenotype, and genetic basis of the heritable forms of amyotrophic lateral sclerosis (ALS) and other disorders of the lower motor neuron (LMN) including Kennedy's disease, the spinal muscular atrophies (SMA), and hereditary motor neuropathies (HMN). The first successful genome-wide linkage study on FALS described linkage to chromosome 21q21. Mutations were subsequently identified in the gene encoding Cu/Zn superoxide dismutase (SOD1). Many people with sporadic ALS seek genetic counseling once they become aware that ALS can be genetic and are better informed about gene testing. The implications of gene screening should always be discussed in detail with the family prior to testing. Consent and DNA from an affected individual should be obtained before predictive testing in at-risk individuals is considered. The penetrance of different SOD1 mutations in particular varies greatly and must be taken into consideration when ascribing risk to a particular gene carrier.