[Memantine and Complex Regional Pain Syndrome (CRPS): effects of treatment and cortical reorganisation].
BACKGROUND
In recent studies a central nervous system involvement in the pathogenesis of Complex Regional Pain Syndrome (CRPS) was suggested, stimulating the introduction of central acting drugs. Animal studies have demonstrated an increased expression of the N-methyl-D-aspartate (NMDA) receptors in experimental neuropathic pain.


OBJECTIVE
The aim of this study was to investigate the relationship between NMDA receptor blockers and CRPS.


METHODS
Three patients suffering from CRPS of one upper extremity where treated with oral NMDA antagonist Memantine for eight weeks. Patients expressed their pain levels with a visual analog scale ranging from zero to ten at rest and after fist clenching. Furthermore, the range of movement of the fingers and the wrist were documented. To assess force, a pinchmeter and a dynamometer were used. Cortical reorganisation was studied with functional Magnetic Resonance Imaging (fMRI) and Magnetoencephalography (MEG).


RESULTS
Six months after treatment with Memantine no rest pain was present in any of the patients. Furthermore, an increase in finger movement was observed after six-month follow-up with no deficits and free movement ranges. Additionally, wrist movement was improved and an increase of force was measured after six months with the dynamometer and the pinchmeter. Moreover the functional impairment, cortical reorganisation was observed in all patients before treatment. These changes returned to a normal pattern after eight weeks of treatment with Memantine.


CONCLUSIONS
These first results demonstrate central nervous system involvement in the development and maintenance of CRPS. The results (functional, pain, fMRI, MEG) after treatment with Memantine indicate the importance of the NMDA receptor system in neuropathic pain syndromes and provide a promising approach for the treatment of CRPS.
Sinis
N
N
Klinik für Hand-, Plastische, Rekonstruktive und Verbrennungschirurgie, BG-Unfallklinik, Eberhard-Karls-Universität Tübingen. nsinis@bgu-tuebingen.de
Birbaumer
N
N
Schwarz
A
A
Gustin
S
S
Unertl
K
K
Schaller
H-E
HE
Haerle
M
M
D000284:Administration, Oral; D020918:Complex Regional Pain Syndromes / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D018691:Excitatory Amino Acid Antagonists / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D008559:Memantine / Q000009:adverse effects / Q000627:therapeutic use*; D008875:Middle Aged; D010147:Pain Measurement; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013997:Time Factors; D016896:Treatment Outcome
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D008559:Memantine