How does dysarthria result from damage to the nervous system?

Dysarthria is a motor speech disorder that occurs when neurological damage impairs the ability of nerves to transmit messages to the muscles responsible for speech production.1

The nervous system controls speech through fibers that emerge from the motor cortex and connect with the cranial and spinal nerves, which in turn regulate the muscles of the lips, tongue, jaw, and those involved in respiration, phonation, and nasality. When damage occurs to these neural pathways or the associated brain structures, the connection between the brain's motor commands and the physical execution of speech is disrupted.12

Depending on the location and extent of the damage, this interference results in weak, uncoordinated, slow, or lost muscle movement. While aphasia is a disorder of language processing, dysarthria is specifically a mechanical failure of the motor system to execute the movements necessary for clear articulation and pronunciation. Acquired causes of this damage include stroke, brain injury, tumors, infections, or progressive neurological diseases such as Parkinson disease, multiple sclerosis, or amyotrophic lateral sclerosis.13