NCS-CMAP REPETITIVE STIMULATION STUDIES
SUMMARY
1. In healthy individuals, the presynaptic terminal releases 3-5x as much Ach as is required to activate the postsynaptic membrane, termed safety factor.
2. Repetitive stimulation studies are primarily useful for detection of NMJ abnormalities in which the safety factor is diminished.
3. Motor units fire at 30Hz to activate muscle contraction, there is build-up of pre-synaptic Ca2+ which facilitates the release of Ach, termed post-exercise facilitation.
4. Post-exercise exhaustion occurs 2-4 min after sustained exercise.
5. Used in diagnosis of MG, Lambert-Eaton myasthenic syndrome (LEMS), botulism. High specificity, 60%-70% sensitivity.
Reference(s)
Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].
