Dysphagia and hemispheric stroke: a transcranial magnetic study

Area of Science:

• Neuroscience
• Neurology
• Rehabilitation Medicine

Background:

• Dysphagia is a frequent and debilitating outcome following hemispheric stroke.
• Understanding the neural mechanisms underlying post-stroke dysphagia is crucial for effective management.

Purpose of the Study:

• To evaluate the utility of transcranial magnetic stimulation (TMS) in assessing swallowing function.
• To investigate swallowing-related motor cortical projections in healthy individuals and stroke survivors.

Main Methods:

• Transcranial magnetic stimulation (TMS) was employed to study motor cortical projections to the upper esophageal sphincter.
• Participants included 45 acute mono-hemispheric stroke patients (26 with dysphagia) and 20 healthy volunteers.

Main Results:

• In healthy subjects, TMS elicited motor evoked potentials (MEPs) in the esophagus, with slight hemispheric differences in optimal excitability.
• Stroke patients with dysphagia exhibited significantly abnormal MEPs (smaller amplitude, longer latency, smaller cortical map area) in the affected hemisphere compared to non-dysphagic patients and controls.
• Abnormal MEPs were detected in 92.3% of dysphagic patients versus 26% of non-dysphagic patients.

Conclusions:

• The motor cortex bilaterally represents esophageal function, with a more anterior 'hot spot' in the right hemisphere.
• Stroke severity and neuroplasticity in the unaffected hemisphere play significant roles in the development of dysphagia.