Extensor digitorum brevis test and resistance to botulinum toxin type A.
We studied 22 patients with dystonia to determine the normal range of values for the extensor digitorum brevis (EDB) test, and to determine its sensitivity and specificity in detecting resistance to botulinum toxin type A (BTX-A). Three compound muscle action potentials (CMAPs) elicited by peroneal nerve stimulation were averaged before and 2 weeks after injection of 20 units of BTX-A into the EDB. Amplitude and area ratios were calculated by dividing the averaged postinjection CMAP by the averaged preinjection CMAP values. The difference in means of this ratio between clinically sensitive and resistant subjects was statistically significant (P < 0.002). A normal range of <0.45 for each ratio was determined by adding two standard deviations to the ratio mean of 14 clinically sensitive subjects. Four of five resistant patients had values outside the normal range. The EDB test is a simple quantitative method of detecting resistance to BTX-A, with a sensitivity of 80% and specificity of 94%.
Gordon
Paul H
PH
Department of Neurology, ACC-2, University of New Mexico, 915 Camino de Salud NE, Albuquerque, New Mexico 87131, USA. pgordon@salud.unm.edu
Gooch
Clifton L
CL
Greene
Paul E
PE
D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D004351:Drug Resistance / Q000502:physiology*; D020821:Dystonic Disorders / Q000188:drug therapy* / Q000503:physiopathology; D004594:Electrophysiology; D006801:Humans; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D011237:Predictive Value of Tests
D019274:Botulinum Toxins, Type A