Short latency afferent inhibition and facilitation in patients with writer's cramp.
Patients with writer's cramp (WC) show abnormalities of sensorimotor integration possibly contributing to their motor deficit. We studied sensorimotor integration by determining short-latency afferent inhibition (SAI) in 12 WC patients and 10 age-matched healthy controls. A conditioning electrical median nerve stimulus was followed 14 to 36 msec later by transcranial magnetic stimulation of the contralateral primary motor cortex, and motor evoked potentials (MEP) were recorded from the relaxed or contracting abductor pollicis brevis muscle (APB). SAI was normal in WC but during APB relaxation SAI was followed by abnormal MEP facilitation, which was absent during APB contraction and in the controls. These findings suggest that somatosensory short-latency inhibitory input into the primary motor cortex is normal in WC, whereas a later excitatory input, which very likely reflects the long-latency reflex II, is exaggerated.
Kessler
Kirn R
KR
Motor Cortex Laboratory, Department of Neurology, J.W. Goethe University, Frankfurt/Main, Germany. k.kessler@em.uni-frankfurt.de
Ruge
Diane
D
Ilić
Tihomir V
TV
Ziemann
Ulf
U
D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology*; D000704:Analysis of Variance; D016022:Case-Control Studies; D020821:Dystonic Disorders / Q000503:physiopathology*; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000187:drug effects / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008280:Magnetics; D008297:Male; D008475:Median Nerve / Q000502:physiology / Q000528:radiation effects; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology* / Q000528:radiation effects; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D009433:Neural Inhibition / Q000502:physiology* / Q000528:radiation effects; D011930:Reaction Time / Q000502:physiology* / Q000528:radiation effects