Journal of Psychosomatic Research
Volume 70, Issue 1 , Pages 59-65, January 2011

Motor excitability during movement imagination and movement observation in psychogenic lower limb paresis

  • Joachim Liepert

      Affiliations

    • Department of Neurorehabilitation, Kliniken Schmieder, Allensbach
    • Department of Neurology, University of Freiburg, Germany
    • Corresponding Author InformationCorresponding author. Kliniken Schmieder, Department of Neurorehabilitation, Zum Tafelholz 8, D-78476 Allensbach, Germany. Tel.: +49 7533 8081236; fax: +49 7533 8081441.
    • ,
  • Thomas Hassa

      Affiliations

    • Department of Neurorehabilitation, Kliniken Schmieder, Allensbach
    • ,
  • Oliver Tüscher

      Affiliations

    • Department of Neurology, University of Freiburg, Germany
    • ,
  • Roger Schmidt

      Affiliations

    • Department of Psychotherapeutic Neurology, Kliniken Schmieder, Konstanz
    • Department of Psychotherapeutic Neurology, Kliniken Schmieder, Gailingen

Received 8 February 2010; received in revised form 8 June 2010; accepted 9 June 2010. published online 11 August 2010.

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.

Conclusion

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.

Keywords: Motor conversion disorder, Psychogenic paresis, Motor excitability, Transcranial magnetic stimulation, Motor imagery, Action observation

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PII: S0022-3999(10)00252-7

doi:10.1016/j.jpsychores.2010.06.004

Journal of Psychosomatic Research
Volume 70, Issue 1 , Pages 59-65, January 2011

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