Recruitment curve of the soleus H reflex in patients with neurogenic claudication

Abstract

The diagnosis of neurogenic claudication (NC) remains uncertain when no definite signs of radicular lesions are found in electrophysiological testing. However, the functional deficit could be demonstrated during the brief time in which the patients complain of pain and weakness in the muscles of the lower limbs after walking. We have used electrophysiological testing of the H reflex and the F wave to document the transient functional derangement expected to occur at the radicular level in patients with NC after walking. We examined the recruitment curve of the soleus H reflex, and the chronodispersion of the posterior tibial nerve F wave, at rest and after a walking exercise that triggered their symptoms in 10 patients with NC, with no positive electrophysiological findings of radicular lesion. The same studies were performed in 5 age‐matched healthy volunteers, used as control subjects, who were asked to walk for 30 min. At rest before walking, no abnormalities were found in any of the patients. After walking, the H wave showed a transient increase in its threshold with respect to that of the M wave in 7 patients (70%). Such abnormality lasted for a mean period of 7 min. In 2 of these patients there was also an increase in the F‐wave chronodispersion. Our data suggest that nerve conduction is transiently blocked in large myelinated fibers at a radicular level in patients with NC after walking. Partial interruption of the H‐reflex circuit could be one of the pathophysiological mechanisms underlying NC. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:985–990, 1998.

The H-reflex as a probe: Pathways and pitfalls

“…1C(ii) the H-reflex is plotted against the corresponding M-wave. The slope of the ascending limb of the H-reflex/stimulus recruitment curve warrants attention because it provides information about the reflex gain (input-output relationship) (Mazzocchio et al, 2001;Pastor and Valls-Sole, 1998). Further, this slope is best fitted with a sigmoid (and not a linear) function that takes into consideration the amplitude of the maximal H-reflex (H max ) and the stimulus required to evoke a response equivalent to half the H max (see more details in Klimstra and Zehr, 2008).…”

Recruitment curve of the soleus H-reflex in chronic back pain and lumbosacral radiculopathy

“…We therefore investigated whether the recruitment curve of the soleus H-reflex might be a further diagnostic criterion for assessing S1 root function in patients with chronic back pain and radiculopathy. This procedure basically consists of establishing the electrical threshold necessary for eliciting the H-reflex which depends on the activation of the most excitable Ia afferent fibers[5]. Since these fibers are most susceptible to compression – or ischemia-induced effects[6], a significant increase in the threshold for the H-reflex may be suggestive of partial conduction block or differential slowing of conduction, not yet affecting the latency of the H-reflex.…”

Lumbar spinal stenosis: Assessment of cauda equina involvement by electrophysiological recordings

“…Electrophysiological recordings have also been applied during treadmill-or walking-stress tests to increase the diagnostic sensitivity in less symptomatic LSS patients [16,33,34,39,44]. In patients with mild LSS, electrophysiological recordings were pathological in an exercise treadmill test, but this was the case in patients both with and without neurogenic claudication [2].…”