Which type of dysarthria is specifically linked to cranial nerve involvement in ALS?

• A. Spastic Dysarthria
• B. Flaccid Dysarthria
• C. Ataxic Dysarthria
• D. Mixed Dysarthria

Answer: (B)

Flaccid dysarthria is specifically linked to cranial nerve involvement in Amyotrophic Lateral Sclerosis (ALS) due to the degeneration of lower motor neurons. In ALS, there is progressive damage that can affect both upper and lower motor neuron systems, but when it comes to cranial nerves, the lower motor neuron involvement leads to flaccid dysarthria. This results from muscle weakness, decreased muscle tone, and paresis (partial paralysis) that characterize flaccid dysarthria, impacting articulation, resonance, and vocal quality.

This motor speech disorder manifests because the affected cranial nerves are responsible for innervating the muscles necessary for speech production, leading to symptoms such as breathiness, hypernasality, and reduced intelligibility. While spastic dysarthria and ataxic dysarthria are also associated with motor neuron involvement, they arise from upper motor neuron lesions or issues with motor coordination, respectively. Mixed dysarthria develops when both upper and lower motor neuron involvement is present, common in more advanced stages of ALS, but it is not directly linked to cranial nerve involvement on its own.