Cerebral correlates of muscle tone fluctuations in restless legs syndrome: a pilot study with combined functional magnetic resonance imaging and anterior tibial muscle electromyography.
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 50 min 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.
Spiegelhalder
Kai
K
Department of Psychiatry and Psychotherapy, University Hospital, Hauptstrasse 5, 79104 Freiburg, Germany.
Feige
Bernd
B
Paul
Dominik
D
Riemann
Dieter
D
van Elst
Ludger Tebartz
LT
Seifritz
Erich
E
Hennig
Jürgen
J
Hornyak
Magdolna
M
D001921:Brain / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009129:Muscle Tonus / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010865:Pilot Projects; D012148:Restless Legs Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D012720:Severity of Illness Index