China
Africa
Explore chapters and articles related to this topic
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.
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.
What is Spasticity?
Published in Valerie L. Stevenson, Louise Jarrett, Spasticity Management, 2016
The stretch reflex pathway can be assessed experimentally by electrically stimulating Ia nerve afferents in the peripheral nerve. This activates the α motor neurons from the same muscle, and the subsequent muscle activation is measured using electrodes placed on the muscle; this is called the H reflex.7 The stimulation of the peripheral nerve will also directly activate the motor nerve, resulting in a short latency contraction of the muscle, termed the M response (Figure 1.3). The ratio of the maximal H and M responses (Hmax/Mmax) is often used experimentally as a measure of spasticity. In addition, when a motor nerve is stimulated, signals also run antidromically up the peripheral nerve; this can stimulate the parent α motorneuron, resulting in an orthodromic signal running down the nerve and activating the muscle, producing an F wave. These are shown diagrammatically in Figure 1.3. The F wave occurs at a longer latency than the M wave (as the pathway it travels is longer) and is more dispersed over time (chronodispersion). The F wave size depends on activating the α motorneuron; therefore, increases in its excitability associated with spasticity will result in increases in the F wave.8
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.
Asymmetry of Interhemispheric Connectivity during Rapid Movements of Right and Left Hands: A TMS-EEG Study
Published in Journal of Motor Behavior, 2022
Kiyoshige Ishibashi, Daisuke Ishii, Satoshi Yamamoto, Yoshitaka Okamoto, Masahiro Wakatabi, Yutaka Kohno
Using the double-pulse TMS method, Duque et al. (2007) found that IHI changes from being balanced at rest to being predominantly directed toward the ipsilateral primary motor cortex (M1) at the onset of movement. However, results obtained from the double-pulse TMS method likely include the effects of the spinal cord because the motor evoked potential (MEP) induced by TMS reflects the state of the neurons both in the motor cortex and spinal cord. Indeed, the H-reflex, which characterizes spinal cord excitability, increases in the time interval preceding voluntary movement (Hasbroucq et al., 2000; Kato & Kasai, 2000). In addition, it is frequently difficult to induce MEPs normally in patients with stroke or spinal cord injury since the corticospinal tracts are damaged in these patients (Curt & Dietz, 1999; Everaert et al., 2010; Veldema et al., 2018). Importantly, a relationship between abnormal IHI and poor motor recovery has been reported in stroke patients (Murase et al., 2004; Takeuchi & Izumi, 2012). Given the potentially confounding effects of the spinal cord and difficulty in inducing MEPs normally in patients, it is necessary to evaluate interhemispheric connectivity using a method that does not depend on the MEPs in order to clarify the functional asymmetry that exists between the left and right hemispheres during rapid body movements.