Flaccid dysarthria

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Dysarthria is defective articulation of sounds or words of neurologic origin.(1-3) In neurologic patients, the speech abnormalities most often encountered are dysarthria and aphasia. The essential difference is that aphasia is a disorder of language and dysarthria is a disorder of the motor production or articulation of speech. In dysarthria, language functions are normal and the patient speaks with proper syntax, but pronunciation is faulty because of a breakdown in performing the coordinated muscular movements necessary for speech production. Dysarthria may result from any central or peripheral disturbance of the innervation of the articulatory muscles, or diseases involving the neuromuscular junction or the muscles involved in speech production. A commonly used classification separates dysarthria into flaccid, spastic, ataxic, hypokinetic, hyperkinetic and mixed types. The two most common types are flaccid and spastic.

Flaccid dysarthria often results from weakness of the soft palate, larynx, and tongue due to such conditions as ALS or MG.(4) The speech is “thick,” as though the mouth were filled with soft food. In advanced cases, speech is reduced to unintelligible laryngeal noises. In MG, the dysarthria becomes more severe with prolonged talking and may reach the point of anarthria. Thomas Willis, who provided one of the first descriptions of MG in 1672, wrote of a woman who, when she tried to talk for a prolonged period, “temporarily lost her power of speech and became mute as a fish.”

The video shows a woman with severe flaccid dysarthria due to bulbar ALS. She can pronounce the labials in baby but not the palatal k sounds in cupcake or the lingual t sounds in ate or train.

For a discussion of spastic dysarthria see http://neurosigns.org/wiki/Spastic_dysarthria.

References

1. Campbell WW. Barohn RJ. DeJong's the neurologic examination, 8th ed. Philadelphia: Wolters Kluwer, 2020.

2. Campbell WW. Clinical signs in neurology: a compendium. Philadelphia: Wolters Kluwer Health, 2016.

3. Enderby, P. Disorders of communication: dysarthria. Handb Clin Neurol. 2013; 110:273-81.

4. Tomik B, Guiloff RJ. Dysarthria in amyotrophic lateral sclerosis: A review. Amyotroph Lateral Scler. 2010;11:4-15.