The H-reflex test is performed using an electric stimulator, which gives usually a square-wave current of short duration and small amplitude (higher stimulations might involve alpha fibers, causing an F-wave, compromising the results), and an EMG set, to record the muscle response.

acute inflammatory demyelinating polyneuropathy
H reflexes involve conduction in proximal as well as distal fibers. Absent H reflexes are characteristic of acute inflammatory demyelinating polyneuropathy (Guillain–Barré syndrome). This loss of H reflexes occurs early and may be an isolated finding in patients studied within several days after onset of illness.

The H reflex is basically an electrophysiologically recorded Achilles muscle stretch reflex. It is performed by stimulating the tibial nerve in the popliteal fossa. Needle EMG is used to assess both nerve and muscle function.

The H-reflex can normally be seen in many muscles but is easily obtained in the soleus muscle (with posterior tibial nerve stimulation at the popliteal fossa), the flexor carpi radialis muscle (with median nerve stimulation at the elbow), and the quadriceps (with femoral nerve stimulation).

The mean H-reflex latency was 30.3 +/- 2.4 ms, and the upper limits of normal (mean + 2 SD) for the various categories of age and height ranged from 30.0 to 38.2 ms. In addition, the upper limits of normal were derived as the 97th percentiles of observed latency values.

The H-reflex (or Hoffmann’s reflex) is a reflectory reaction of muscles after electrical stimulation of sensory fibers (Ia afferents stemming from muscle spindles) in their innervating nerves (for example, those located behind the knee). An M-wave, an early response, occurs 3-6 ms after the onset of stimulation.

The procedure to elicit the H-reflex usually involves applying a percutaneous electric stimulus to a mixed nerve. For example, when eliciting the soleus H-reflex, a 1-millisecond square wave pulse is applied to the posterior tibial nerve in the popliteal fossa.

Because it is largely monosynaptic, the latency of an H-reflex depends mainly on the lengths and conduction velocities of the afferent and efferent axons in the peripheral nerve.

Eliciting the H reflex by direct stimulation of the S1 root may enhance their utility for detecting an S1 radiculopathy. 32 Increase in the stimulus threshold has been noted in patients with neurogenic claudication when studied after reproduction of their symptoms with walking. 33

The H-reflex is a monosynaptic reflex elicited by sub maximal stimulation of the tibial nerve and recorded from the calf muscle. ↑ 1.0 1.1 Igor Stiler.

Radiculopathy is not a specific condition, but rather a description of a problem in which one or more spinal nerves are affected. The nerve or nerves may be inflamed, had lack of blood flow, or may be affected by a disease in part or totally.

Lumbosacral radiculopathy (LSR) is a common clinical problem that involves L5and S1 nerve roots. Late potentials are electro diagnostically elicited responses in muscle that appear more than 10-20 milliseconds after stimulation of motor nerves.