title: Targeting unlesioned pharyngeal motor cortex improves swallowing in healthy individuals and after dysphagic stroke.
abstract: OBJECTIVE
  Patients with stroke experience swallowing problems (dysphagia); increased risk of aspiration pneumonia, malnutrition, and dehydration; and have increased mortality. We investigated the behavioral and neurophysiological effects of a new neurostimulation technique (paired associative stimulation [PAS]), applied to the pharyngeal motor cortex, on swallowing function in healthy individuals and patients with dysphagia from stroke.
  
  
  METHODS
  We examined the optimal parameters of PAS to promote plasticity by combining peripheral pharyngeal (electrical) with cortical stimulation. A virtual lesion was used as an experimental model of stroke, created with 1-Hz repetitive transcranial magnetic stimulation over the pharyngeal cortex in 12 healthy individuals. We tested whether hemispheric targeting of PAS altered swallowing performance before applying the technique to 6 patients with severe, chronic dysphagia from stroke (mean of 38.8 ± 24.4 weeks poststroke).
  
  
  RESULTS
  Ten minutes of PAS to the unlesioned pharyngeal cortex reversed (bilaterally) the cortical suppression induced by virtual lesion (lesioned: F(1,9) = 21.347, P = .001; contralesional: F(1,9) = 9.648, P = .013; repeated-measures analysis of variance) compared with sham PAS. It promoted changes in behavior responses measured with a swallowing reaction time task (F(1,7) = 21.02, P = .003; repeated-measures analysis of variance). In patients with chronic dysphagia, real PAS induced short-term bilateral changes in the brain; the unaffected pharyngeal cortex had increased excitability (P = .001; 95% confidence interval, 0.21-0.05; post hoc paired t test) with reduced penetration-aspiration scores and changes in swallowing biomechanics determined by videofluoroscopy.
  
  
  CONCLUSIONS
  The beneficial neurophysiological and behavioral properties of PAS, when applied to unlesioned brain, provide the foundation for further investigation into the use of neurostimulation as a rehabilitative approach for patients with dysphagia from stroke.
authors.affiliation: School of Translational Medicine - Inflammation Sciences, University of Manchester (part of the Manchester Academic Health Sciences Centre), Salford Royal Hospital, Salford, England.
authors.forename: Emilia
authors.initials: E
authors.lastname: Michou
authors.forename: Satish
authors.initials: S
authors.lastname: Mistry
authors.forename: Samantha
authors.initials: S
authors.lastname: Jefferson
authors.forename: Salil
authors.initials: S
authors.lastname: Singh
authors.forename: John
authors.initials: J
authors.lastname: Rothwell
authors.forename: Shaheen
authors.initials: S
authors.lastname: Hamdy
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002908:Chronic Disease; D003679:Deglutition; D003680:Deglutition Disorders / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D004599:Electric Stimulation Therapy; D004576:Electromyography; D004739:England; D019054:Evoked Potentials, Motor; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D009473:Neuronal Plasticity; D010609:Pharyngeal Muscles / Q000294:innervation*; D020127:Recovery of Function; D020521:Stroke / Q000150:complications / Q000503:physiopathology; D000071939:Stroke Rehabilitation; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D016896:Treatment Outcome; D014741:Video Recording