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Neuromuscular Features Associated With Motor Speech Disorder
6 Neuromuscular Features Associated With Motor Speech Disorder

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6 Neuromuscular features which are associated with motor speech disorders
  1. Strength
  2. Speed
  3. Range
  4. Steadiness
  5. Tone
  6. Accuracy

Strong Speedy Rangers Steadied Tony Actors


Muscles have to be strong enough to perform their function, able to contract over time w/o excessive fatigue & contract against resistance.

Muscle weakness can alter the performance of the 3 major speech valves (laryngeal, velopharyngeal, andarticulatory) and be displayed in all components of speech production (respiration, phonation, resonance, articulation, and prosody).

Weakness most apparent in lower motor neuron (LMN) or final common pathway (FCP) lesions, therefore in flaccid dysarthrias.


The quick, unsustained,discrete movements that are medicated through the direct activation UMN pathway input to alpha motor neurons.

Slow movements predominate (except in hyperkinetic dysarthria); slow to start, slow in their course, slow to stop.

Reduced speed can occur at all 3 speech valves and during all components of speech production.

Slow movements strongly affect prosodic speech features, with the effects most apparent in spastic dysarthria.


The distance traveled by speech structures.  Decreased range is common at all rates of speech.

Decreased range of motion is often associated with hypokinetic dysarthria ( & sometimes excessively rapid rate), while abnormal variability in range is common in ataxic and hyperkinetic dysarthrias.

Range abnormalities often have a major influence on the prosodic features of speech, sometimes resulting in restricted or excessive prosodic variations.

Steadiness 1

Steadiness breakdowns result in involuntary movements or hyperkinesis.

Tremor is the most common, being the repetitive rhythmic oscillations of a body part.  Types:

  • postural tremor - when a structure is maintained against gravity
  • action tremor - during movement
  • terminal tremor - toward the end of a movement
  • resting tremor - at rest


Steadiness 2

More severe tremor can affect prosody, most easily perceived during sustained vowel production.

Another type of involuntary movement consists of random movements that vary in speed, duration, and amplitude, affecting movement at all 3 speech valves and during all major components of speech production.

The primary source of abnormal speech in hyperkinetic dysarthrias, they affect prosody and accuracy.


The resting tautness or laxity of a muscle which creates a stable framework upon which rapid voluntary movements can be superimposed. The gamma loop and indirect activation pathway are crucial for proper maintenance of tone.

Changes in tone may fluctuate slowly or rapidly, in a regular or irregular fashion.

Alterations in tone may occur in all speech vavles and during all components of speech.  When consistently reduced, associated with flaccid dysarthria, when consistently increased, associated with spastic or hypokinetic dysarthria.


The outcome of well-timed and coordinated activities of all the other neuromuscular features (strength, speed, range, steadiness, & tone).

Inaccurate planning or programming of movements can cause speech errors.  Errors may be predictable or random, if timing errors.

May occur at all the speech valves and at all levels of speech production, but are perceived most easily in articulation and prosody.

If timing errors, usually associated w/ ataxic dysarthria or apraxia of speech.  If random involuntary movement, it can reflect hyperkinetic dysarthria.

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