title: Motor excitability during movement imagination and movement observation in psychogenic lower limb paresis.
abstract: BACKGROUND
  Patients with a psychogenic paresis have difficulties performing voluntary movements. Typically, diagnostic interventions are normal. We tested whether patients with a psychogenic lower limb paresis exhibit abnormal motor excitability during motor imagery or movement observation.
  
  
  METHODS
  Transcranial magnetic stimulation (TMS) with single and paired pulses was used to explore motor excitability at rest, during imagination of ankle dorsiflexions and during watching another person perform ankle dorsiflexions. Results obtained in ten patients with a flaccid psychogenic leg paresis were compared with a healthy age-matched control group. In addition, results of two patients with a psychogenic fixed dystonia of the leg are presented.
  
  
  RESULTS
  During rest, motor excitability evaluated by motor thresholds, size of motor-evoked potentials (MEP) by single pulse TMS, intracortical inhibition and intracortical facilitation tested by paired-pulse TMS were similar in patients and healthy subjects. MEPs recorded in five patients during movement observation were also comparable across the two groups. During motor imagery, patient MEPs were significantly smaller than in the control group and smaller than during rest, indicating an inhibition.
  
  
  CONCLUSIONS
  In patients with motor conversion disorder, the imagination of own body movements induces a reduction of corticospinal motor excitability whereas it induces an excitability increase in healthy subjects. This discrepancy might be the electrophysiological substrate of the inability to move voluntarily. Watching another person perform movements induces a normal excitability increase, indicating a crucial role of the perspective and suggesting that focusing the patient's attention on a different person might become a therapeutic approach.
authors.affiliation: Department of Neurorehabilitation, Kliniken Schmieder, Allensbach, Germany. j.liepert@kliniken-schmieder.de
authors.forename: Joachim
authors.initials: J
authors.lastname: Liepert
authors.forename: Thomas
authors.initials: T
authors.lastname: Hassa
authors.forename: Oliver
authors.initials: O
authors.lastname: Tüscher
authors.forename: Roger
authors.initials: R
authors.lastname: Schmidt
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004213:Dissociative Disorders / Q000503:physiopathology; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007092:Imagination / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009068:Movement / Q000502:physiology*; D010291:Paresis / Q000503:physiopathology*; D013001:Somatoform Disorders / Q000503:physiopathology; D050781:Transcranial Magnetic Stimulation