Causes of Dysarthria

Speech is performed through movements involving the facial, oral, and pharyngolaryngeal muscles. The motor system consists of upper motor neurons, lower motor neurons, neuromuscular junctions, and muscles. This pathway is regulated by several systems such as basal ganglia circuits and the cerebellar system, which results in smooth motor function. When any pathway is damaged, dysarthria occurs. In terms of segmental diagnosis, dysarthria is classified into pyramidal, extrapyramidal, ataxic, and flaccid types. Pyramidal dysarthria is caused by upper motor neuron damage, which exhibits spastic paralysis. Extrapyramidal dysarthria is caused by basal ganglia damage, which manifests as hypokinetic or hyperkinetic disorders. Ataxic dysarthria is caused by cerebellar system damage. Flaccid dysarthria is caused by impairment to lower motor neurons, neuromuscular junctions, and muscular disorders.