NMDA-mediated mechanisms in cortical excitability changes after limb amputation.
OBJECTIVE
The aim of our study was to determine the role of N-methyl-d-aspartate (NMDA)-mediated mechanisms in cortical excitability changes after limb amputation, and their possible relationship to phantom pain.


METHODS
Sixteen upper limb amputees who were suffering from chronic phantom pain received the NMDA-antagonist memantine or placebo for 3 weeks. Intracortical inhibition (ICI) and intracortical facilitation (ICF) were determined at baseline and on day 21 using transcranial magnetic stimulation. Simultaneously, phantom pain intensity was assessed.


RESULTS
Memantine reduced ICF and enhanced ICI to roughly the same extent as seen in healthy subjects in a previous study. These changes were not correlated to the reduction of phantom pain.


CONCLUSIONS
We therefore conclude that NMDA-mediated mechanisms influence changes of ICI and ICF occurring after limb amputation. However, our results suggest that these cortical excitability changes and phantom pain are independent of each other.
Schwenkreis
P
P
Department of Neurology, Ruhr-University Bochum, BG-Kliniken Bergmannsheil, Buerkle-de-la-Camp-Platz 1, D-44789 Bochum, Germany. Peter.Schwenkries@ruhr-uni-bochum.de
Maier
C
C
Pleger
B
B
Mansourian
N
N
Dertwinkel
R
R
Malin
J-P
JP
Tegenthoff
M
M
Zenz
M
M
D000328:Adult; D000368:Aged; D000671:Amputation, Surgical; D002540:Cerebral Cortex / Q000187:drug effects* / Q000503:physiopathology*; D004311:Double-Blind Method; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008559:Memantine / Q000008:administration & dosage / Q000494:pharmacology*; D008875:Middle Aged; D010147:Pain Measurement; D010591:Phantom Limb / Q000378:metabolism / Q000503:physiopathology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034941:Upper Extremity
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D008559:Memantine