NCS-DEMYELINATION

SUMMARY

1. Sensory or motor amplitudes: normal or slightly reduced
2. Distal latencies: prolonged
3. Conduction velocities: significantly reduced
4. F wave latencies: significantly prolonged or absent
5. H reflex latencies: significantly prolonged or absent
6. Conduction block/temporal dispersion (> 50% drop in amplitude): present
7. EMG: polyphasic large motor units with reduced recruitment pattern & fibrillation potentials (neurogenic pattern, occurs in both axonal degeneration & demyelination)

TIP: axonal degeneration leads to a loss of amplitude (reflecting fewer functioning axons) & demyelination leads to prolonged conduction time (reflecting loss of myelin).

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].