November 2002
Effects of Spastic Dysarthria on Communication
A Requirement for COMSC 712 Neural Processes of Communication
Spastic dysarthria is a motor speech disorder resulting from damage to the upper motor neurons. There is damage to both the direct (pyramidal) and indirect (extrapyramidal) activation pathways of the central nervous system (www.ucs.louisiana.edu). Unilateral lesion damage will affect cranial nerves VII (jaw movement) and XII (tongue movement). As a result, there will be drooping on one side of the face as well as the inability of the tongue to reach the side of the face opposite that of the lesion. Bilateral damage will have much more devastating results, affecting most or all processes of articulation (McCaffrey, 2000). Dysfunction of these motor pathways interferes with the transmission of messages controlling speech musculature movements.
Spastic dysarthria may be congenital or may develop during a person’s lifetime. It is a characteristic of neurological disorders resulting from cerebral palsy, Parkinson’s Disease, Amyotrophic Lateral Sclerosis (ALS), or multiple sclerosis (www.cslot.com). Stroke, encephalitis, cerebral anoxia, traumatic brain injury, and tumors may also attribute to spastic dysarthria (Leeper, 2002).
Results depend on the affected speech musculature. Spasticity of the muscles involved in speech creates increased muscle tone and resistance to muscle stretch or movement. A patient with spastic dysarthria will experience spastic paralysis and weakness resulting in loss of skilled movement. Infrequent swallowing due to impaired oral control may result in drooling. They may also display slow movement and experience a limited range of motion. As a result, patients affected by spastic dysarthria experience an increased effort to speak and fatigue when speaking (www.ucs.louisiana.edu).
Effect
on Communication
Phonation: Voice is usually described as strained or strangled, sounding harsh. Range and force is reduced. Phonation comes out as a low monopitch with very little variation in loudness. Pitch breaks are also common (www.ucs.louisiana.edu).
Articulation: Production of both final and initial consonants are imprecise. Distorted vowels are also characteristic (McCaffrey, 2000). Different classes of sounds are distorted since the anterior and posterior portions of the tongue are not affected equally. Spastic dysarthria can cause slow, labored articulation (www.ucs.louisiana.edu). Voice onset time for stops is short while voicing of voiceless stops, phoneme to phoneme transitions, and syllable and word duration are increased (McCaffrey, 2000).
Resonance: Movement of the palate can be severely reduced, resulting in nasalized speech (Leeper, 2002).
Prosody: The rate of speech is slow. Occasionally, there may be bursts of loudness. Phrases are short due to laryngeal constriction (McCaffrey, 2000).
Respiration: If respiration is affected, decreased respiration strength causes difficulty in sustaining phonation and loudness. Shallow inhalations and reduced exhalatory pressure are characteristic. There is also difficulty maintaining breath control due to antagonistic muscle contractions (Leeper, 2002).
A related problem associated with spastic dysarthria is dysphagia (McCaffrey, 2000). This is because vegetative functions also require movements of the velum, tongue and mandible.
Click here to listen to a sample of spastic dysarthric speech:
