Cerebral correlates of muscle tone fluctuations in restless legs syndrome: A pilot study with combined functional magnetic resonance imaging and anterior tibial muscle electromyography

Spiegelhalder, Kai; Feige, Bernd; Paul, Dominik; Riemann, Dieter; van Elst, Ludger Tebartz; Seifritz, Erich; Hennig, Jürgen; Hornyak, Magdolna

doi:10.1016/j.sleep.2007.03.021

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Volume 9, Issue 2 , Pages 177-183, January 2008

Cerebral correlates of muscle tone fluctuations in restless legs syndrome: A pilot study with combined functional magnetic resonance imaging and anterior tibial muscle electromyography

Kai Spiegelhalder
- Department of Psychiatry and Psychotherapy, University Hospital, Hauptstraße 5, 79104 Freiburg, Germany
Bernd Feige
- Department of Psychiatry and Psychotherapy, University Hospital, Hauptstraße 5, 79104 Freiburg, Germany
Dominik Paul
- Department of Diagnostic Radiology, Section of Medical Physics, University Hospital, Hugstetter Straße 55, 79106 Freiburg, Germany
Dieter Riemann
- Department of Psychiatry and Psychotherapy, University Hospital, Hauptstraße 5, 79104 Freiburg, Germany
Ludger Tebartz van Elst
- Department of Psychiatry and Psychotherapy, University Hospital, Hauptstraße 5, 79104 Freiburg, Germany
Erich Seifritz
- University Hospital of Clinical Psychiatry, Bolligenstraße 111, 3000 Bern 60, Switzerland
Jürgen Hennig
- Department of Diagnostic Radiology, Section of Medical Physics, University Hospital, Hugstetter Straße 55, 79106 Freiburg, Germany
Magdolna Hornyak
- Department of Psychiatry and Psychotherapy, University Hospital, Hauptstraße 5, 79104 Freiburg, Germany
- Corresponding author. Address: University Medical Center, Department of Psychiatry and Psychotherapy, University Hospital, Hauptstraße 5, 79104 Freiburg, Germany. Tel.: +49 761 270 6501; fax: +49 761 270 6619.

Received 23 October 2006; received in revised form 19 March 2007; accepted 30 March 2007.

Abstract

Background

The pathology of restless legs syndrome (RLS) is still not understood. To investigate the pathomechanism of the disorder further we recorded a surface electromyogram (EMG) of the anterior tibial muscle during functional magnetic resonance imaging (fMRI) in patients with idiopathic RLS.

Methods

Seven subjects with moderate to severe RLS were investigated in the present pilot study. Patients were lying supine in the scanner for over 50min and were instructed not to move voluntarily. Sensory leg discomfort (SLD) was evaluated on a 10-point Likert scale. For brain image analysis, an algorithm for the calculation of tonic EMG values was developed.

Results

We found a negative correlation of tonic EMG and SLD (p <0.01). This finding provides evidence for the clinical experience that RLS-related subjective leg discomfort increases during muscle relaxation at rest. In the fMRI analysis, the tonic EMG was associated with activation in motor and somatosensory pathways and also in some regions that are not primarily related to motor or somatosensory functions.

Conclusions

By using a newly developed algorithm for the investigation of muscle tone-related changes in cerebral activity, we identified structures that are potentially involved in RLS pathology. Our method, with some modification, may also be suitable for the investigation of phasic muscle activity that occurs during periodic leg movements.

Keywords: fMRI, EMG, Restless legs syndrome, Periodic leg movements, Pathology, Neurophysiology