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Neurologic Diagnosis
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
The H-reflex is a late motor response evoked by a low-intensity, submaximal stimulus to the motor nerve. It is regularly present in the calf muscles after stimulation of the posterior tibial nerve but not in other nerves. It is named in honor of Hoffman's description in 1918. When present, the response is of smaller amplitude than the supramaximal M-wave, but, unlike the F-wave, of consistent latency, configuration, and occurrence. It is thought to be due to a monosynaptic spinal reflex, with selective activation of the Ia sensory fibers from the muscle spindles ascending to the spinal cord, then synapsing with and activating the anterior horn cells.
Spinal Cord and Reflexes
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The H-reflex, or Hoffmann reflex, is elicited by electrical stimulation of a muscle nerve, as illustrated in Figure 11.12. As the stimulus strength is increased from a low level, the largest Ia sensory fibers are stimulated first. This is because the largest fibers have the smallest internal resistance; so, for a given voltage stimulus applied externally to the mixed nerve, the voltage across the axonal membrane of the largest-diameter fibers will reach threshold first (Section 4.3.1). Two APs will be generated in the vicinity of the cathode-stimulating electrode and will travel in opposite directions (Figure 11.12a, top of diagram). The AP that reaches the sensory endings of the primary afferents will simply depolarize these endings temporarily and is extinguished (left-pointing dashed arrow). The AP that travels along an Ia fiber to the spinal cord reaches the synapse of this fiber on an α-motoneuron of the homonymous muscle. The APs generated in the α-motoneurons by the excited Ia fibers will travel along the axons of the α-motoneurons to the muscle, causing it to contract. The EMG recorded is the H-response, illustrated in the top trace of Figure 11.12b. The response shown has a latency of about 20 ms. Of this, about 0.5 ms is the delay at the synapse between the Ia fibers and the α-motoneurons, the rest being propagation time of the APs along the Ia fibers and the axons of the α-motoneurons. When the stimulus strength is large enough to excite all the Ia fibers in the nerve, the H-response reaches its maximum.
Nerve
Published in Manoj Ramachandran, Tom Nunn, Basic Orthopaedic Sciences, 2018
Mike Fox, Caroline Hing, Sam Heaton, Rolfe Birch
The H reflex is the electrophysiological equivalent of a deep tendon reflex. It is elicited by a submaximal stimulation of Aα afferent fibres from muscle stretch receptors that enter the dorsal horn and synapse with alpha motor neurons, resulting in a motor response on completion of the monosynaptic reflex arc (apart from in the soleus muscle). The H reflex can be difficult to record, which limits its applicability. It is absent or delayed in polyneuropathies and radiculopathies, but it may also be absent in patients over 60 years of age.
Effect of inhibitory kinesiotaping on spasticity in patients with chronic stroke: a randomized controlled pilot trial
Published in Topics in Stroke Rehabilitation, 2022
Mahdad Mehraein, Zahra Rojhani- Shirazi, Ahmad Zeinali Ghotrom, Nasrin Salehi Dehno
H-reflex is created by the electrical stimulation of the Ia sensory fibers (afferent fibers) as an impulse. This impulse bypasses the posterior horn of the spinal cord where it forms a synapse with alpha motorneuron and eventually creates a Compound Muscle Action Potential (CMAP), which is recorded as the H-reflex.30 The ratio of the maximum H-reflex amplitude to the maximum M-wave amplitude, a muscle response which appears through direct activation of the motor fibers, (Hmax/Mmax ratio) is used as an index to objectively evaluate spasticity by the reflecting excitability of motor neurons.32 Since spasticity is triggered by increased stimulation of alpha motor neuron, Hmax/Mmax ratio could be used as an accurate measure of motorneuron excitability.33 Sensitivity of Hmax/Mmax ratio has been previously confirmed34 and shown to be a reliable measure of spasticity.35
Investigation of the changes in the presynaptic inhibition in association with the subthalamic nucleus stimulation in Parkinson’s disease
Published in Neurological Research, 2022
Halil Onder, Bektas Korkmaz, Bilge Gonenli Kocer, Selcuk Comoglu
A Shapiro-Wilk test was used to test for normality (all P > 0.09). An analysis of variance (ANOVA) with the within-subject factors (repeated measures) H-latency, H amplitude, M amplitude, H/M amplitude, H threshold, and M threshold was conducted on the averaged relative H-reflex amplitudes of the PD patients to test our hypothesis of a STIM effect on autogenic inhibition in this group. The analyses were performed for both the right side and the left side, separately. Besides, the analyses of variance were repeated after evaluating the results of the right side and the left side investigations as separate variables, and also for the results of the dominant side. A Spearman’s correlation test was used to assess the relationship between the H-reflex responses and the clinical parameters. Data are presented as mean ± SEM (standard error of the mean). The statistical analyses were performed using the SPSS 26.
Relationship between soleus H-reflex asymmetry and postural control in multiple sclerosis
Published in Disability and Rehabilitation, 2022
Gregory S. Cantrell, David J. Lantis, Michael G. Bemben, Chris D. Black, Daniel J. Larson, Gabriel Pardo, Cecilie Fjeldstad-Pardo, Rebecca D. Larson
The Hoffmann reflex (H-reflex) is an electrical stimulation-induced analogue of the monosynaptic reflex elicited by activation of group Ia sensory fibers [12]. Maximal H-reflex amplitude (Hmax) compared with maximal motor response (Mmax) resulting from direct activation of alpha-motor neurons has been previously used to assess spinal excitability of motor neurons. Moreover, the soleus H-reflex is one of the more commonly studied reflexes in spinal excitability investigations, due to the convenient accessibility of the tibial nerve [12,13], and was of interest in the present study due to its role in posture. While the soleus H-reflex has been assessed in people with MS [5,14], it has not yet been compared between legs, nor has a potential link between soleus H-reflex asymmetry and postural stability in people with MS been evaluated. Therefore, supported by previous research demonstrating bilateral asymmetries in people with MS, the purpose of this study was to test the hypotheses that the soleus H-reflex differs between legs in people with MS, and soleus H-reflex asymmetry is associated with postural control.