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Extensor digitorum brevis test and resistance to botulinum toxin type A
Paul H Gordon1, Clifton L Gooch, Paul E Greene
1Department of Neurology, ACC-2, University of New Mexico, 915 Camino de Salud NE, Albuquerque, New Mexico 87131, USA. pgordon@salud.unm.edu
Muscle & Nerve
|November 27, 2002
Summary
The extensor digitorum brevis (EDB) test effectively identifies resistance to botulinum toxin type A (BTX-A) injections. This simple quantitative method shows high sensitivity and specificity in dystonia patients.
Area of Science:
- Neurology
- Clinical Electrophysiology
Background:
- Dystonia is a neurological movement disorder.
- Botulinum toxin type A (BTX-A) is a common treatment for dystonia.
- Assessing BTX-A resistance is crucial for treatment efficacy.
Purpose of the Study:
- To establish normal reference values for the extensor digitorum brevis (EDB) test.
- To evaluate the sensitivity and specificity of the EDB test in detecting BTX-A resistance.
Main Methods:
- Studied 22 dystonia patients undergoing BTX-A treatment.
- Measured compound muscle action potentials (CMAPs) before and after EDB injection.
- Calculated amplitude and area ratios of CMAPs to assess BTX-A effect.
Main Results:
- A statistically significant difference in CMAP ratios was observed between sensitive and resistant patients (P < 0.002).
- A normal EDB test ratio range of <0.45 was established.
- The EDB test demonstrated 80% sensitivity and 94% specificity for detecting BTX-A resistance.
Conclusions:
- The EDB test provides a simple, quantitative measure for BTX-A resistance.
- This electrophysiological method aids in managing BTX-A treatment for dystonia.