Swallowing in ALS and motor neuron disorders

The dysphagia of ALS is characterized by an impaired oral stage of swallowing, which has a direct impact on the seemingly more robust pharyngeal stage. Increased duration of the volitional stage (PPRT) of swallowing, including DT and lingual motility deficits, appear to be the major contributors to the dysphagia. The abnormal temporospatial events during the oral stage of swallowing have a direct and significant effect on the more automatic, pharyngeal stage. Specifically, abnormal lingual movement may result in pharyngeal residue that is aspirated after the swallow is completed and respiration is resumed. ALS patients with bulbar involvement demonstrate more severe swallowing problems (such as aspiration); however, the current work indicates that predominantly nonbulbar ALS patients may also demonstrate dysphagia. The semisolid material was more effective than liquids in eliciting temporospatial abnormalities of swallowing in the nonbulbar group. Thus, more viscous materials may be most sensitive for eliciting behaviors indicative of the onset of bulbar dysfunction in patients who otherwise appear nonbulbar, or different neurophysiologic mechanisms are involved in swallowing the distinct types of substances.