title: Characterization of corticobulbar pharyngeal neurophysiology in dysphagic patients with Parkinson's disease.
abstract: OBJECTIVE
  Dysphagia in patients with Parkinson's disease, persisting despite dopaminergic treatment, affects intake of nutrients and medication, and reduces quality of life (QOL). We investigated the neurophysiologic mechanisms that contribute to dysphagia in these patients, on and off L-3,4-dihydroxyphenylalanine (levodopa), using transcranial magnetic stimulation.
  
  
  METHODS
  We studied 26 patients with Parkinson's disease (age, 65 ± 9 y; 10 men). Dysphagia and QOL were first assessed with qualitative questionnaires. Twelve hours after patients were taken off levodopa, they underwent cortical transcranial magnetic stimulation mapping of the pharyngeal musculature and trigeminal (bulbar) transcranial magnetic stimulation, as well as videofluoroscopy to examine swallowing. The analyses were repeated after administration of levodopa.
  
  
  RESULTS
  Eleven patients initially reported dysphagia and reduced QOL scores. Videofluoroscopy identified 10 patients with swallowing impairments on and off levodopa, and 6 patients with swallowing impairments only on levodopa; the remaining 10 subjects showed no swallowing impairments, on or off the drug. While patients were on levodopa, those with swallowing impairments had bilateral increases in pharyngeal cortical excitability compared with those with no swallowing impairment (P < .05). By contrast, with medication, amplitudes of brainstem reflexes were altered only in patients with swallowing impairments on levodopa; these were decreased compared with when the patients were off levodopa.
  
  
  CONCLUSIONS
  In patients with Parkinson's disease, dopaminergic medications such as levodopa can negatively affect swallowing. The increased cortical excitability observed in dysphagic patients after they begin taking levodopa likely results from compensatory mechanisms, perhaps secondary to subcortical disease, because we observed associated inhibition of brainstem reflexes in patients with affected swallowing on medication. UK clinical trials registration no., 9882.
authors.affiliation: Centre for Gastrointestinal Sciences, Institute of Inflammation and Repair, University of Manchester, Manchester Academic Health Sciences Centre, Salford Royal Hospital, Salford, United Kingdom.
authors.forename: Emilia
authors.initials: E
authors.lastname: Michou
authors.affiliation: Centre for Gastrointestinal Sciences, Institute of Inflammation and Repair, University of Manchester, Manchester Academic Health Sciences Centre, Salford Royal Hospital, Salford, United Kingdom. Electronic address: shaheen.hamdy@manchester.ac.uk.
authors.forename: Shaheen
authors.initials: S
authors.lastname: Hamdy
authors.affiliation: Centre for Gastrointestinal Sciences, Institute of Inflammation and Repair, University of Manchester, Manchester Academic Health Sciences Centre, Salford Royal Hospital, Salford, United Kingdom.
authors.forename: Mary
authors.initials: M
authors.lastname: Harris
authors.affiliation: Centre for Gastrointestinal Sciences, Institute of Inflammation and Repair, University of Manchester, Manchester Academic Health Sciences Centre, Salford Royal Hospital, Salford, United Kingdom.
authors.forename: Adil
authors.initials: A
authors.lastname: Vania
authors.affiliation: Department of Neurology, Salford Royal Hospital National Health System (NHS) Trust, Salford, United Kingdom.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Dick
authors.affiliation: Department of Neurology, Salford Royal Hospital National Health System (NHS) Trust, Salford, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Kellett
authors.affiliation: Institute of Neurology, University College London, London, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Rothwell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000978:Antiparkinson Agents / Q000009:adverse effects / Q000627:therapeutic use; D003680:Deglutition Disorders / Q000503:physiopathology*; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007980:Levodopa / Q000009:adverse effects / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications*; D011712:Pyramidal Tracts / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D050781:Transcranial Magnetic Stimulation; D006113:United Kingdom
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa
keywords: Brain; Compensation; Nervous System; Neurodegeneration