NCS-H REFLEX OR WAVES

SUMMARY

1. H waves (named after Dr. Hoffman) utilize a pathway similar to a muscle stretch reflex except depolarization commences at the 1a afferent fiber rather than muscle spindle.

2. Afferent path: sensory 1a afferent fiber. Efferent path: alpha-motor neurons.

3. Latency is measured to the onset of the response - first departure from the baseline.

4. Latencies will depend upon height/leg length and reference values take this into account.

5. H waves are useful in evaluating S1 radiculopathies, but less useful in evaluating chronicity than needle EMG.

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].