Quality and Patient Safety Articles-Electrodiagnostic Findings After Chemodenervation

Electrodiagnostic Findings After Chemodenervation

Pdf Summary

This AANEM patient safety case highlights how prior botulinum toxin treatment can affect electrodiagnostic (EDX) testing. In a patient receiving serial onabotulinum toxin A injections for chronic migraine, EDX abnormalities may appear in the injected muscles and can resemble a presynaptic neuromuscular junction disorder.  

The correct finding is <strong>D: fibrillation potentials in the right upper trapezius muscles</strong>, assuming that muscle was injected as part of the migraine protocol. Botulinum toxin blocks acetylcholine release at the neuromuscular junction, which can cause denervation-like changes in treated muscles. Reported EDX findings include reduced or absent response to low-frequency repetitive nerve stimulation, facilitation at higher frequencies, increased jitter, early fibrillation potentials, and evolving motor unit action potential changes over time.  

These effects are most prominent about <strong>15 to 30 days after treatment</strong> and may be seen not only in injected muscles but occasionally in distant muscles as well. Because of this, clinicians interpreting EDX studies should always consider the location and timing of recent chemodenervation to avoid misdiagnosing the patient with a broader neuromuscular disease or radiculopathy.  

In short, recent botulinum toxin injections can create localized neurophysiologic abnormalities that must be distinguished from true pathologic findings.

Keywords

botulinum toxin

electrodiagnostic testing

neuromuscular junction

nmj

fibrillation potentials

onabotulinum toxin A

chronic migraine

repetitive nerve stimulation

chemodenervation

upper trapezius

denervation-like changes