Neuromuscular Disorders (Dysarthria) in Adults
What Are Neuromuscular Disorders (Dysarthria)?
Dysarthria can result from congenital conditions, or it can be acquired at any age as the result of a neurologic injury, disease, or disorder.
Dysarthria refers to a group of neurogenic speech disorders characterized by “abnormalities in the strength, speed, range, steadiness, tone, or accuracy of movements required for breathing, phonatory, resonatory, articulatory, or prosodic aspects of speech production” (Duffy, 2020, p. 3). These changes are due to one or more sensorimotor problems, including weakness or paralysis; incoordination; involuntary movements; or excessive, reduced, or variable muscle tone (Duffy, 2020). Dysarthria can adversely affect the intelligibility of speech and/or naturalness of speech. Dysarthria may also co-occur with other neurogenic language, cognitive, and swallowing disorders.
The predominant framework for differentially diagnosing dysarthria is based on a perceptual method of classification (Darley et al., 1969a, 1969b, 1975). This method primarily relies on the auditory perceptual attributes of speech that point to the underlying pathophysiology. The perceptual attributes are used to characterize the dysarthrias and, along with pathophysiological information, can help identify an underlying neurologic illness.
The primary types of dysarthria identified by perceptual attributes and the associated localization of pathophysiology (Duffy, 2020) are as follows:
- Flaccid- associated with disorders affecting the lower motor neuron pathways and motor units.
- Spastic- associated with bilateral disorders of the upper motor neuron system.
- Ataxic- associated with disorders of the cerebellar control circuit.
- Hypokinetic- associated with disorders of the basal ganglia control circuit.
- Hyperkinetic- associated with disorders of the basal ganglia control circuit.
- Unilateral upper motor neuron- associated with unilateral disorders of the upper motor neuron system.
- Mixed- various combinations of dysarthria types (e.g., spastic–ataxic, flaccid–spastic).
Undetermined- Perceptual features are consistent with dysarthria but do not clearly fit into any of the identified dysarthria types.