Cortical Processing of Swallowing in ALS Patients with Progressive Dysphagia – A Magnetoencephalographic Study

Abstract

Amyotrophic lateral sclerosis (ALS) is a rare disease causing degeneration of the upper and lower motor neuron. Involvement of the bulbar motor neurons often results in fast progressive dysphagia. While cortical compensation of dysphagia has been previously shown in stroke patients, this topic has not been addressed in patients suffering from ALS. In the present study, we investigated cortical activation during deglutition in two groups of ALS patients with either moderate or severe dysphagia. Whole-head MEG was employed on fourteen patients with sporadic ALS using a self-paced swallowing paradigm. Data were analyzed by means of time-frequency analysis and synthetic aperture magnetometry (SAM). Group analysis of individual SAM data was performed using a permutation test. We found a reduction of cortical swallowing related activation in ALS patients compared to healthy controls. Additionally a disease-related shift of hemispheric lateralization was observed. While healthy subjects showed bilateral cortical activation, the right sensorimotor cortex was predominantly involved in ALS patients. Both effects were even stronger in the group of patients with severe dysphagia. Our results suggest that bilateral degeneration of the upper motor neuron in the primary motor areas also impairs further adjusted motor areas, which leads to a strong reduction of ‘swallowing related’ cortical activation. While both hemispheres are affected by the degeneration a relatively stronger activation is seen in the right hemisphere. This right hemispheric lateralization of volitional swallowing observed in this study may be the only sign of cortical plasticity in dysphagic ALS patients. It may demonstrate compensational mechanisms in the right hemisphere which is known to predominantly coordinate the pharyngeal phase of deglutition. These results add new aspects to our understanding of the pathophysiology of dysphagia in ALS patients and beyond. The compensational mechanisms observed could be relevant for future research in swallowing therapies.

Tongue thickness evaluation using ultrasonography can predict swallowing function in amyotrophic lateral sclerosis patients

“…It has been reported that the oropharyngeal transit time of ALS patients is longer than that of healthy subjects (Cha, 1989;Kawai et al, 2003;Higo et al, 2004;Teismann et al, 2011;Ruoppolo et al, 2013). In this study, in contrast to the VF temporal analysis, tongue thickness was found to be associated with the oral preparatory and transit time but not with the pharyngeal transit time, independent of the bulbar-related subscores.…”

Trends in Research Literature Describing Dysphagia in Motor Neuron Diseases (MND): A Scoping Review

“…Still, the majority of studies reporting swallowing physiology/function present observations in descriptive terms, limiting our ability to compare results across studies or measure discrete degrees of change. For example, hyolaryngeal excursion is often reported as “reduced” (e.g., [33,45,60]), however, when measured in reference to a scalar or anatomical marker, the results are more variable (e.g., [51,65]). Quantification of swallowing physiology has largely been limited to studies using manometry (e.g., [40,59,66]) and EMG (e.g., [67,68]).…”

Introducing a Virtual Lesion Model of Dysphagia Resulting from Pharyngeal Sensory Impairment

“…For artifact correction, each individual's coregistered EMG signal was used to identify swallowing acts as previously published [18][19][20]. Stimulation episodes contaminated by swallows were rejected.…”

“…Stimulation episodes contaminated by swallows were rejected. By applying a fourth order two-pass Butterworth filter prior to further computations, MEG data were filtered within five different frequency bands: theta (4-8 Hz), alpha (8-13 Hz), beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), low gamma (30-60 Hz), and high-gamma (60-80 Hz).…”