title: Transcranial magnetic stimulation follow-up study in early Parkinson's disease: A decline in compensation with disease progression?
abstract: BACKGROUND
  A number of neurophysiological abnormalities have been described in patients with Parkinson's disease, but very few longitudinal studies of how these change with disease progression have been reported. We describe measures of motor cortex inhibition and plasticity at 6 and 12 mo in 12 patients that we previously reported at initial diagnosis. Given the well-known interindividual variation in these measures, we were particularly concerned with the within-subject changes over time.
  
  
  METHODS
  Patients were assessed clinically, and transcranial magnetic stimulation (TMS) was used to measure motor cortical excitability, inhibition (short interval intracortical inhibition, cortical silent period), and plasticity (response to excitatory paired associative stimulation protocol) in both hemispheres. All measurements were performed 6 mo and 12 mo after the baseline experiments.
  
  
  RESULTS
  Asymmetry in clinical motor symptoms was reflected in asymmetry of plasticity and inhibition. In the group as a whole, little change was seen in any of the parameters over 12 mo. However, analysis of within-individual data showed clear correlations between changes in clinical asymmetry and asymmetry of response to paired associative stimulation protocol and cortical silent period.
  
  
  CONCLUSIONS
  Longitudinal changes in cortical silent period and response to paired associative stimulation protocol in Parkinson's disease reflect dynamic effects on motor cortex that are related to progression of motor signs. They are useful objective markers of early disease progression that could be used to detect effects of disease-modifying therapies. The decline in heightened plasticity that was present at disease onset may reflect failure of compensatory mechanisms that maintained function in the preclinical state.
authors.affiliation: Sobell Department of Motor Neuroscience & Movement Disorders, UCL, Institute of Neurology, The National Hospital for Neurology & Neurosurgery, Queen Square, London, United Kingdom.|Department of Neurology, University of Ljubljana, Slovenia.
authors.forename: Maja
authors.initials: M
authors.lastname: Kojovic
authors.affiliation: Sobell Department of Motor Neuroscience & Movement Disorders, UCL, Institute of Neurology, The National Hospital for Neurology & Neurosurgery, Queen Square, London, United Kingdom.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Kassavetis
authors.affiliation: Department of Neurology and Psychiatry and Neuromed institute, "Sapienza" University of Rome, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bologna
authors.affiliation: Sobell Department of Motor Neuroscience & Movement Disorders, UCL, Institute of Neurology, The National Hospital for Neurology & Neurosurgery, Queen Square, London, United Kingdom.
authors.forename: Isabel
authors.initials: I
authors.lastname: Pareés
authors.affiliation: Movement Disorders Unit, Neurology Department, Hospital Universitario La Fe, Valencia, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Rubio-Agusti
authors.affiliation: Department of Neurology and Psychiatry and Neuromed institute, "Sapienza" University of Rome, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Berardelli
authors.affiliation: Department of Neurology and Psychiatry and Neuromed institute, "Sapienza" University of Rome, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Beraredelli
authors.affiliation: Sobell Department of Motor Neuroscience & Movement Disorders, UCL, Institute of Neurology, The National Hospital for Neurology & Neurosurgery, Queen Square, London, United Kingdom.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Edwards
authors.affiliation: Sobell Department of Motor Neuroscience & Movement Disorders, UCL, Institute of Neurology, The National Hospital for Neurology & Neurosurgery, Queen Square, London, United Kingdom.
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
authors.affiliation: Sobell Department of Motor Neuroscience & Movement Disorders, UCL, Institute of Neurology, The National Hospital for Neurology & Neurosurgery, Queen Square, London, United Kingdom.
authors.forename: Kailash P
authors.initials: KP
authors.lastname: Bhatia
mesh_terms: D000328:Adult; D000368:Aged; D018450:Disease Progression; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D010300:Parkinson Disease / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation
keywords: PAS; Parkinson's disease; progression; sensorimotor cortical plasticity; transcranial magnetic stimulation