Stiff-person syndromes: motor cortex hyperexcitability correlates with anti-GAD autoimmunity.
OBJECTIVE
S: To investigate whether motor cortex excitability is enhanced in both stiff-person syndrome (SPS) and its "plus" variant, progressive encephalomyelitis with rigidity (PER), and related to autoimmunity against glutamic acid decarboxylase (GAD).


METHODS
The authors compared 21 patients with SPS or PER (7 untreated, 14 treated) with 14 age-matched healthy controls and used transcranial magnetic stimulation (TMS, paired-pulse paradigm) to investigate intracortical inhibition (ICI) and intracortical facilitation (ICF). GAD autoantibody levels in serum and CSF were determined by radioimmunoassay.


RESULTS
The authors found significantly enhanced motor cortex excitability in untreated SPS and PER patients. GABAmimetic medication significantly reduced ICF but did not affect ICI. Motor cortex excitability was more enhanced in patients with GAD antibodies than in patients without GAD antibodies and correlated positively with GAD antibody levels in CSF.


CONCLUSIONS
The motor cortex is hyperexcitable in SPS and PER patients. However, hyperexcitability is partly masked by GABAmimetic treatment. Correlation of elevated GAD antibody levels with enhanced ICF suggests that motor cortex hyperexcitability in SPS and PER is related to anti-GAD autoimmunity.
Koerner
Claudia
C
Department of Neurology, Ruprecht-Karls-University Heidelberg, FRG. koerner@zi-mannheim.de
Wieland
Bettina
B
Richter
Wiltrud
W
Meinck
Hans-Michael
HM
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood / Q000134:cerebrospinal fluid; D020274:Autoimmune Diseases of the Nervous System / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology / Q000503:physiopathology*; D004558:Electric Stimulation / Q000295:instrumentation; D004574:Electromagnetic Fields; D004679:Encephalomyelitis / Q000276:immunology / Q000503:physiopathology*; D019054:Evoked Potentials, Motor; D005260:Female; D018757:GABA Modulators / Q000627:therapeutic use; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D007527:Isoenzymes / Q000276:immunology*; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000187:drug effects / Q000503:physiopathology* / Q000528:radiation effects; D009433:Neural Inhibition / Q000187:drug effects / Q000528:radiation effects; D011930:Reaction Time; D012016:Reference Values; D016750:Stiff-Person Syndrome / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects
D001323:Autoantibodies; D018757:GABA Modulators; D007527:Isoenzymes; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2