2023 Workshop Handout Bundle-Repetitive Nerve Stimulation

Repetitive Nerve Stimulation

Pdf Summary

The document presents detailed information from Dr. Taylor Harrison's workshop at the AANEM 2023 Annual Meeting on Repetitive Nerve Stimulation (RNS). It includes material originally prepared in May 1984 and updated in 1995, primarily focusing on neuromuscular junction physiology and its application in diagnosing neuromuscular disorders.<br /><br />**Normal Physiology**:<br />- RNS examines neuromuscular transmission by repetitively stimulating motor nerves and observing muscle responses.<br />- Key elements include the action potential at the nerve terminal, calcium influx, acetylcholine (Ach) release, and muscle fiber depolarization.<br />- The "safety factor" is the buffer exceeding the necessary depolarization needed to generate a muscle fiber action potential, ensuring muscle contraction.<br /><br />**Disease States**:<br />1. **Myasthenia Gravis (MG)**: Autoantibodies target Ach receptors, reducing the safety factor and causing muscle weakness. The document discusses diagnostic sensitivity, treatment exercises, and the importance of adequate temperature and limb immobilization during tests.<br />2. **Lambert-Eaton Myasthenic Syndrome (LEMS)**: Autoantibodies reduce Ach release by targeting presynaptic calcium channels, resulting in low motor amplitudes. Cholinergic facilitation post-exercise is a diagnostic indicator.<br />3. **Botulism**: Similar features to LEMS, with botulinum toxin preventing Ach release. Electrodiagnostic profiles include low motor amplitudes and post-exercise facilitation.<br /><br />**RNS Laboratory Techniques**:<br />- Routine sensory and motor nerve conductions should precede RNS. Tests are evaluated by comparing the amplitude and area of compound muscle action potentials (CMAPs).<br />- Standard procedures involve 2-3 Hz slow RNS and 30-50 Hz fast RNS. Proper limb temperature is critical to avoid false results.<br />- MG and LEMS diagnostics include noting CMAPs before and after brief exercise periods, with a 10-20% change in amplitude as a significant diagnostic indicator.<br /><br />**Reporting Results**:<br />- Reports should include stimuli number, stimulation rate, muscle condition, and decrement/increment calculation methods. Include waveform data to allow independent review by referring physicians.<br /><br />**Preparation Information:**<br />- This comprehensive guide stems from various studies and clinical references, recommending rigid protocols for accurate diagnostics and interpretations of RNS to identify related neuromuscular disorders.<br /><br />The document also emphasizes accurate technique application, keeping technical issues and physiological discrepancies in check to ensure diagnostic integrity.

Keywords

Repetitive Nerve Stimulation

RNS

Dr. Taylor Harrison

AANEM 2023

neuromuscular junction

nmj

Myasthenia Gravis

Lambert-Eaton Myasthenic Syndrome

Botulism

electrodiagnostic profiles

compound muscle action potentials

nmj

neuromuscular junction