NCS-SNAP & CNAP

SUMMARY

1. Sensory nerve action potentials (SNAP) and compound nerve action potentials (CNAP) both involve electrical stimulation of nerves and recording of the synchronized discharge of axons within the nerve at some distance from the point of stimulation.

2. The nerve is stimulated supra-maximally: the stimulator intensity is gradually increased and stopped when the response gets no larger.

3. This indicates that all available axons have been activated and increasing stimulation will activate no more axons.

4. Increasing stimulation substantially beyond this may falsely recruit other adjacent nerves.

5. One records from the same nerve at a specified distance from the point of stimulation. The synchronized discharge of all axons within the stimulated nerve is recorded.

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].