title: Patterns of abnormal motor cortex excitability in atypical parkinsonian syndromes.
abstract: OBJECTIVE
  Multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal-ganglionic degeneration (CBGD) are all clinically characterized by an akinetic-rigid syndrome together with a variety of additional signs. We hypothesised that these atypical parkinsonian syndromes (APS) will show distinctive patterns in their motor output upon transcranial magnetic stimulation (TMS) due to their different underlying anatomico-functional deficits.
  
  
  METHODS
  We performed single and paired-pulse TMS and assessed inhibitory and excitatory response parameters from the first dorsal interosseus muscles in 13 patients with MSA, 18 with PSP, 13 with CBGD, 15 patients with Parkinson's disease and 17 healthy subjects.
  
  
  RESULTS
  PSP and MSA patients had significantly enlarged response amplitudes at rest, reduced intracortical inhibition (ICI) and prolonged ipsi- and contralateral silent periods, whereas CBGD patients showed significantly increased motor thresholds, smaller response amplitudes at rest, shortened contralateral silent period, reduced transcallosal inhibition and a reduced ICI. In 22% of APS patients ipsilateral motor responses occurred in upper limb muscles irrespective of the underlying disease.
  
  
  CONCLUSIONS
  Our results indicate that motor cortex disinhibition is predominant in patients with PSP and MSA. In CBGD more severe neuronal cell loss in the motor cortex itself may lead to hypoexcitability of corticospinal and transcallosal pathways.
authors.affiliation: Department of Neurology, Charité, Humboldt University Berlin, 13353 Berlin, Augustenburger Platz 1, Germany. a.kuhn@ion.ucl.ac.uk
authors.forename: A A
authors.initials: AA
authors.lastname: Kühn
authors.forename: P
authors.initials: P
authors.lastname: Grosse
authors.forename: K
authors.initials: K
authors.lastname: Holtz
authors.forename: P
authors.initials: P
authors.lastname: Brown
authors.forename: B-U
authors.initials: BU
authors.lastname: Meyer
authors.forename: A
authors.initials: A
authors.lastname: Kupsch
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D055590:Electromagnetic Phenomena / Q000379:methods / Q000706:statistics & numerical data; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D020734:Parkinsonian Disorders / Q000503:physiopathology*; D018709:Statistics, Nonparametric