How does damage to the nervous system cause dysarthria?

Dysarthria is a motor speech disorder caused by neurological damage that impairs the ability of the nervous system to transmit signals to the muscles required for speech production.1

In the human brain, fibers emerge from the motor cortex and connect to the cranial and spinal nerves that control the muscles of the lips, tongue, jaw, throat, and larynx. When disease or injury damages these pathways or the associated nuclei in the brain stem, the muscles responsible for articulation, phonation, respiration, and nasality may become weak, uncoordinated, or paralyzed.213

The specific manifestations of dysarthria depend on the location and extent of the neurological damage. For example:1
* Bulbar dysarthria occurs when the bulbar nuclei in the brain stem are damaged, often resulting in faint speech or total muteness.3
* Cerebellar dysarthria arises from damage to the cerebellum, which is responsible for fine motor coordination, leading to disorganized or ataxic speech patterns.3
* Parkinson disease can cause dysarthria characterized by rigid or tremulous speech patterns due to the underlying neurological affliction.3

Ultimately, this damage disrupts the complex somatomotor functions necessary for clear speech, resulting in symptoms like slurred, slow, or inaudible articulation.12