Soleus H-Reflex Change in Poststroke Spasticity: Modulation due to Body Position

Purpose. This study is aimed at exploring how soleus H-reflex change in poststroke patients with spasticity influenced by body position. Materials and Methods. Twenty-four stroke patients with spastic hemiplegia and twelve age-matched healthy controls were investigated. Maximal Hoffmann-reflex (Hmax) and motor potential (Mmax) were elicited at the popliteal fossa in both prone and standing positions, respectively, and the Hmax/Mmax ratio at each body position was determined. Compare changes in reflex behavior in both spastic and contralateral muscles of stroke survivors in prone and standing positions, and match healthy subjects in the same position. Results. In healthy subjects, Hmax and Hmax/Mmax ratios were significantly decreased in the standing position compared to the prone position (Hmax: p = 0.000 , Hmax/Mmax: p = 0.016 ). However, Hmax/Mmax ratios were increased in standing position on both sides in poststroke patients with spasticity (unaffected side: p = 0.006 , affected side: p = 0.095 ). The Hmax and Hmax/Mmax ratios were significantly more increased on the affected side than unaffected side irrespective of the position. Conclusions. The motor neuron excitability of both sides was not suppressed but instead upregulated in the standing position in subjects with spasticity, which may suggest that there was abnormal regulation of the Ia pathway on both sides.

The associations between radiological and neurological findings of degenerative cervical myelopathy: radiological analysis based on kinematic CT myelography and evoked potentials of the spinal cord

OBJECTIVE Neurological and imaging findings play significant roles in the diagnosis of degenerative cervical myelopathy (DCM). Consistency between neurological and imaging findings is important for diagnosing DCM. The reasons why neurological findings exhibit varying sensitivity for DCM and their associations with radiological findings are unclear. This study aimed to identify associations between radiological parameters and neurological findings in DCM and elucidate the utility of concordance between imaging and neurological findings for diagnosing DCM. METHODS One hundred twenty-one patients with DCM were enrolled. The Japanese Orthopaedic Association (JOA) score, radiological parameters, MRI and kinematic CT myelography (CTM) parameters, and the affected spinal level (according to multimodal spinal cord evoked potential examinations) were assessed. Kinematic CTM was conducted with neutral positioning or at maximal extension or flexion of the cervical spine. The cross-sectional area (CSA) of the spinal cord, dynamic change in the CSA, C2–7 range of motion, and C2–7 angle were measured. The associations between radiological parameters and hyperreflexia, the Hoffmann reflex, the Babinski sign, and positional sense were analyzed via multiple logistic regression analysis. RESULTS In univariate analyses, the upper- and lower-limb JOA scores were found to be significantly associated with a positive Hoffmann reflex and a positive Babinski sign, respectively. In the multivariate analysis, a positive Hoffmann reflex was associated with a higher MRI grade (p = 0.026, OR 2.23) and a responsible level other than C6–7 (p = 0.0017, OR 0.061). A small CSA during flexion was found to be significantly associated with a positive Babinski sign (p = 0.021, OR 0.90). The presence of ossification of the posterior longitudinal ligament (p = 0.0045, OR 0.31) and a larger C2–7 angle during flexion (p = 0.01, OR 0.89) were significantly associated with abnormal great toe proprioception (GTP). CONCLUSIONS This study found that the Hoffmann reflex is associated with chronic and severe spinal cord compression but not the dynamic factors. The Babinski sign is associated with severe spinal cord compression during neck flexion. The GTP is associated with large cervical lordosis. These imaging features can help us understand the characteristics of the neurological findings.

Acute Effects of Kinesiology Taping Stretch Tensions on Soleus and Gastrocnemius H-Reflex Modulations

This study examined the acute effects of stretch tensions of kinesiology taping (KT) on the soleus (SOL), medial (MG), and lateral (LG) gastrocnemius Hoffmann-reflex (H-reflex) modulation in physically active healthy adults. A cross-over within-subject design was used in this study. Twelve physically active collegiate students voluntarily participated in the study (age = 21.3 ± 1.2 years; height = 175.6 ± 7.1 cm; body weight = 69.9 ± 7.1 kg). A standard Y-shape of KT technique was applied to the calf muscles. The KT was controlled in three tension intensities in a randomised order: paper-off, 50%, and 100% of maximal stretch tension of the tape. The peak-to-peak amplitude of maximal M-wave (Mmax) and H-reflex (Hmax) responses in the SOL, MG, and LG muscles were assessed before taping (pre-taping), taping, and after taping (post-taping) phases in the lying prone position. The results demonstrated significantly larger LG Hmax responses in the pre-taping condition than those in the post-taping condition during paper-off KT (p = 0.002). Moreover, the ΔHmax/Mmax of pre- and post-taping in the SOL muscle was significantly larger during 50%KT tension than that of paper-off (p = 0.046). In conclusion, the stretch tension of KT contributes minor influence on the spinal motoneuron excitability in the triceps surae during rest.

Repetitive Peripheral Magnetic Stimulation of Wrist Extensors Enhances Cortical Excitability and Motor Performance in Healthy Individuals

Repetitive peripheral magnetic stimulation (rPMS) may improve motor function following central nervous system lesions, but the optimal parameters of rPMS to induce neural plasticity and mechanisms underlying its action remain unclear. We examined the effects of rPMS over wrist extensor muscles on neural plasticity and motor performance in 26 healthy volunteers. In separate experiments, the effects of rPMS on motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), direct motor response (M-wave), Hoffmann-reflex, and ballistic wrist extension movements were assessed before and after rPMS. First, to examine the effects of stimulus frequency, rPMS was applied at 50, 25, and 10 Hz by setting a fixed total number of stimuli. A significant increase in MEPs of wrist extensors was observed following 50 and 25 Hz rPMS, but not 10 Hz rPMS. Next, we examined the time required to induce plasticity by increasing the number of stimuli, and found that at least 15 min of 50 and 25 Hz rPMS was required. Based on these parameters, lasting effects were evaluated following 15 min of 50 or 25 Hz rPMS. A significant increase in MEP was observed up to 60 min following 50 and 25 Hz rPMS; similarly, an attenuation of SICI and enhancement of ICF were also observed. The maximal M-wave and Hoffmann-reflex did not change, suggesting that the increase in MEP was due to plastic changes at the motor cortex. This was accompanied by increasing force and electromyograms during wrist ballistic extension movements following 50 and 25 Hz rPMS. These findings suggest that 15 min of rPMS with 25 Hz or more induces an increase in cortical excitability of the relevant area rather than altering the excitability of spinal circuits, and has the potential to improve motor output.

Effect of Long-Term Classical Ballet Dance Training on Postactivation Depression of the Soleus Hoffmann-Reflex

Classical ballet dancing is a good model for studying the long-term activity-dependent plasticity of the central nervous system in humans, as it requires unique ankle movements to maintain ballet postures. The purpose of this study was to investigate whether postactivation depression is changed through long-term specific motor training. Eight ballet dancers and eight sedentary subjects participated in this study. The soleus Hoffmann reflexes were elicited at after the completion of a slow, passive dorsiflexion of the ankle. The results demonstrated that the depression of the soleus Hoffmann reflex (i.e., postactivation depression) was larger in classical ballet dancers than in sedentary subjects at two poststretch intervals. This suggests that the plastic change through long-term specific motor training is also expressed in postactivation depression of the soleus Hoffmann reflex. Increased postactivation depression would strengthen the supraspinal control of the plantarflexors and may contribute to fine ankle movements in classical ballet dancers.

Reliability of the Soleus H-Reflex in Different Sitting Postures

The Soleus (SOL) Hoffmann reflex (H-reflex) is commonly recorded in sitting position. However, the reliability of recording is unknown. We assessed the reliability of SOL H-reflex amplitude measurements across multiple traces and sessions during erect, slumped, and slouched sitting postures using the generalizability theory. Five traces of the SOL H-reflex maximum amplitude (Hmax) were recorded from 10 healthy participants during erect, slumped, and slouched sitting postures in two sessions. A decision study analysis was then conducted to calculate the reliability coefficients of the Hmax for five traces and two sessions and to mathematically calculate the coefficients for seven and ten traces, and one and three sessions in the three sitting postures. For five traces and two sessions, the results showed reliability coefficients between 0.970 and 0.971, 0.980 and 0.979, and equal to 0.943 for erect, slumped, and slouched sitting, respectively. Averaging five traces of the Hmax in a single recording session was sufficient to obtain acceptable reliability in the three sitting postures (reliability range, 0.892–0.988). It was concluded that the SOL Hmax can be recorded during erect, slumped, and slouched sitting postures with adequate reliability.

Relationship between muscle spindles and myofascial trigger spots according to Hoffmann reflex pathway and tissue morphology characteristics in a rat model

Objectives: To determine how muscle spindles are involved in the pathophysiology of chronic myofascial trigger spots (MTrSs, similar to myofascial trigger points) in a rat injury model according to the characteristics of the Hoffmann reflex (H-reflex) and the anatomical relationship between muscle spindles and MTrSs. Methods: 16 male Sprague-Dawley rats (7 weeks old) were randomly divided into experimental and control groups. A blunt strike injury and eccentric exercise were applied to the gastrocnemius muscle of rats in the experimental group once a week for 8 weeks as a MTrS modelling intervention. Subsequently, the rats were reared normally and rested for 4 weeks. At the end of the 12th week, the rats were examined for the presence of MTrSs defined by the detection of a palpable taut band exhibiting both a local twitch response and spontaneous electrical activity. After modelling, evocation of the H-reflex and morphological examination of muscle spindles and MTrSs were conducted. Results: The threshold (0.35±0.04 mA) of the H-reflex and latency (1.24±0.18 ms) of the M wave recorded at MTrSs were not significantly different to those at non-MTrSs (P>0.05). Compared with non-MTrSs, a lower Mmax (4.28±1.27 mV), higher Hmax (median (IQR) 0.95 (0.80–1.08) mV) and Hmax/Mmax (median (IQR) 0.21 (0.16–0.40)), and shorter H wave latency (4.60±0.89 ms) were recorded at MTrSs (P<0.05). Morphologically, there was a close anatomical relationship between the MTrS cells and the muscle spindles. Discussion: Compared with normal muscles, the H-reflex myoelectrical activity was enhanced and some muscle spindles might have been influenced by active MTrSs. Thus, muscle spindles may play an important role in the pathological mechanism underlying myofascial trigger points.