H-reflex and Its Role in EMG Laboratory and Clinical Practice

Authors: Z. Kadaňka Jr.
Authors‘ workplace: Neurologická klinika LF MU a FN Brno
Published in: Cesk Slov Neurol N 2017; 80(6): 641-646
Category: Review Article
doi: https://doi.org/10.14735/amcsnn2017641


H-reflex is the most extensively studied reflex in the electrophysiological literature. It is no longer considered to be strictly monosynaptic since it has been shown to contain a shorter monosynaptic and longer oligosynaptic component. It is widely used in EMG laboratories. The relative ease with which the H-reflex can be elicited makes it an attractive clinical tool. However, we must take into account the limitations to H-reflex examination in neurophysiology. This concerns the choice of appropriate methods used to elicit the H-reflex (correct location of stimulating and recording electrodes) and correct evaluation of amplitude and latency, which are influenced by many factors (including the phenomenon presynaptic of inhibition and post-activating depression). The H-reflex is not exclusively monosynaptic, it consists of monosynaptic and oligosynaptic pathways. This reflex is not an equivalent of tendon jerk reflex because it bypasses muscle spindle mechanisms. With correct interpretation, the H-reflex is a useful tool for diagnosing sensorimotor polyneuropathy, plexopathy, radiculopathy S1 and static nerve lesions. It has been used in sports medicine research to evaluate musculoskeletal injuries and can be used as a tool to assess the neurophysiologic mechanism underlying the recovery of walking after spinal cord injuries. H-reflex modulation is also used to monitor the degree of hypertonia in the study of spasticity.

Key words:
H-reflex – electromyography – presynaptic inhibition – post-activation depression – polyneuropathy – radiculopathy S1 – lumbar plexopathy

The author declares he has no potential conflicts of interest concerning drugs, products, or services used in the study.

The Editorial Board declares that the manuscript met the ICMJE “uniform requirements” for biomedical papers.


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