Mohamed Sabbahi

H-reflex changes under spinal loading and unloading conditions in normal subjects

OBJECTIVE The soleus H- reflex is usually tested clinically in patients lying prone, with the H-latency always the criterion of choice for detecting abnormality. However, stresses on the spine vary during lying, standing, loading (weight lifting) and unloading. So the objective of this study was to measure changes in the H-reflex under 4 different loading conditions and to investigate whether mechanical loading of the spine would affect the H-reflex parameters. METHODS Twenty healthy volunteers (22-46 years) with no history of significant low back pain or radiculopathy participated in the study. A Cadwell Excel electromyography unit was used to elicit and record the soleus H-reflex. The tibial nerve was stimulated at the popliteal fossa using 1 ms pulses at 0.2 pps of H-max. Each subject was tested under 4 different conditions: prone lying, free standing, standing while lifting 20% of his or her body weight, and standing while unloaded by 25% of his/or her body weight by a ZUNI II unloading system. For each subject, the peak-to-peak amplitudes of the maximum obtained H- reflex and the onset latencies of 8 separate traces were averaged for both lower extremities. Two-factor, repeated-measures ANOVAs were used to test the effect of the condition and side on the H-reflex amplitude and latency with ( approximately =0.025). RESULTS The H-reflex was inhibited during standing, loading and unloading as compared with prone lying. The H-reflex was recovered during loading as compared with during standing. There were no significant changes in the H-reflex latency under the 4 different conditions. Both lower extremities showed similar pattern of changes in the H-reflexes. CONCLUSIONS These results imply a significant interplay between peripheral and central mechanisms and their effects on the spinal motoneurons. This in turn suggests that testing of the H-reflex amplitude and latency under functional conditions, such as standing may be useful in detecting subtle changes in root impingement.

Soleus and vastus medialis H-reflexes: similarities and differences while standing or lying during varied knee flexion angles.

The H-reflex may be a useful measure to examine the lower extremity muscles activation and inhibition following an injury. Recording the vastus medialis H-reflex amplitudes in healthy subjects while standing or lying during varied knee flexion angles may establish a reference for comparison for patients with ACL injury. Vastus medialis and soleus H-reflexes were recorded from 14 healthy subjects while lying and standing during 0, 30, 45, and 60 degrees knee flexion. EMG unit was used to electrically stimulate the tibial and femoral nerves (using 0.5 ms pulses at 0.2 pps of H-maximum amplitude) and to record four traces of the soleus and vastus medialis H-wave and one trace of the M-wave peak-to-peak amplitudes. Repeated measures three-way ANOVAs were calculated with the global alpha=0.05. Results showed that (1) the average soleus H-reflex amplitude was significantly less during standing than lying across all knee flexion conditions, (2) the average vastus medialis H-reflex amplitudes showed no measurable significant differences between neutral standing compared with lying, (3) the average vastus medialis H-reflex amplitudes were significantly greater during standing knee flexion conditions (30, 45, and 60 degrees ) than lying or neutral standing, and (4) there were no differences between soleus and vastus medialis H-reflex amplitudes during lying across all knee flexion conditions. Data from H/M ratio follow the same pattern of H-amplitude. Recording the vastus medialis H-reflex amplitude during standing and knee flexion may be a reflective of the knee function. It is more specific than the soleus H-reflex because it reflects the changes in the excitability of the quadriceps motoneurons acting directly around the knee joint.

H-reflex amplitude asymmetry is an earlier sign of nerve root involvement than latency in patients with S1 radiculopathy

BackgroundBased on our clinical experience, the H-reflex amplitude asymmetry might be an earlier sign of nerve root involvement than latency in patients with S1 radiculopathy. However, no data to support this assumption are available. The purpose of this study was to review and report the electrophysiological changes in H-reflex amplitude and latency in patients with radiculopathy in order to determine if there is any evidence to support the assumption that H-reflex amplitude is an earlier sign of nerve root involvement than latency.ResultsPatients with radiculopathy showed significant amplitude asymmetry when compared with healthy controls. However, latency was not always significantly different between patients and healthy controls. These findings suggest nerve root axonal compromise that reduced reflex amplitude earlier than the latency parameter (demyelination) during the pathologic processes.ConclusionContrary to current clinical thought, H-reflex amplitude asymmetry is an earlier sign/parameter of nerve root involvement in patients with radiculopathy compared with latency.

The H-reflex modulation in lying and a semi-reclining (sitting) position

OBJECTIVE The purpose of this study was to compare motor pool excitability as measured by the H-reflex during lying prone and sitting in a semi-reclining position. DESIGN AND METHOD Twelve volunteer subjects were measured for maximum M-wave and H-wave during sitting and prone lying to determine an H/M ratio. Latency of each H-reflex was also measured. H-reflex responses were recorded during a control and a vibration condition in the two positions. A double-stimuli H-reflex recovery curve was also plotted for each subject in each relaxed position of sitting and lying. RESULTS No significant differences were observed between the prone lying and sitting positions for the any of the variables measured. CONCLUSIONS The present results showed no difference in H-reflex responses between sitting or lying and it is suggested that the subject/patient should be tested in a position which is most comfortable.

Soleus H-reflex measures in patients with focal and generalized dystonia

OBJECTIVE The purpose of this study was to examine neurophysiological characteristics of dystonia patients using electromyographic soleus H-reflex methods. METHODS Thirty normal healthy individuals were compared to 27 patients with focal (cervical) or generalized dystonia. Three H-reflex assessment methods were included: the ratio of maximum H-reflex to direct muscle potential (H/M ratio); vibration inhibition (H(v)/H(c) ratio); and H-reflex recovery curves (HRRC). RESULTS Average H/M ratios between groups were not statistically significant. The average H(v)/H(c) ratio for the generalized dystonia group was significantly greater than the focal dystonia and normal groups. Average values of the HRRC showed the generalized dystonia group had significantly greater disinhibition than the focal dystonia and control groups during the early inhibition phase. The HRRC for the focal dystonia group was greater than normal and more similar to the generalized dystonia group during the late phases of the recovery curve. The average value of the localized late facilitation phase for the focal dystonia group was significantly greater than the control group and less than the generalized dystonia group. No differences were observed between groups for the average localized late inhibition phase of the recovery curve. CONCLUSIONS Soleus H-reflex measures identified neurophysiologic differences between generalized dystonia, cervical dystonia and normal conditions. SIGNIFICANCE This methodology enables analysis of the underlying characteristics of dystonic pathologies using soleus H-reflex methods rather than upper extremity H-reflex techniques.

Vastus medialis H-reflex reliability during standing

Summary: Vastus medialis H-reflex is a valid measure to examine quadriceps muscle voluntary activation and inhibition after knee injury. Its reliability during repeated sessions has not been established. The purpose of this study was to establish the intrasession and intersession reliability of vastus medialis H-reflex amplitude recordings during standing with varied knee flexion angles (0, 30, 45, and 60 degrees). Electromyography unit was used to elicit and record the vastus medialis H-reflex from the right leg of five healthy subjects. The femoral nerve was stimulated using 0.5-millisecond pulses at 0.2 pps of H-maximum. Four recordings of the vastus medialis H-reflex amplitude were recorded in three trials for each knee flexion angle within each session for two consecutive days. Reliability was calculated using intraclass correlation coefficients (ICC). Intrasession reliability during standing with varied knee angles was high (ICC [2, 4] range from 0.76 to 0.98), and intersession reliability during standing with varied knee angles was moderate to high (ICC [2, 1] range from 0.51 to 0.84). Recording four traces of vastus medialis H-reflex amplitude per trial was reliable. Vastus medialis H-reflex amplitude recordings while standing during varied knee flexion are reliable within and between sessions.

H-reflex recovery curves differentiate essential tremor, Parkinson's disease, and the combination of essential tremor and Parkinson's disease.

Summary The purpose of this study was to examine H-reflex parameters among the pathophysiologic conditions of essential tremor (ET), Parkinson’s disease (PD), combined essential tremor with Parkinson’s disease (ETPD), and a control group. H-reflex latencies, amplitude of maximum H-reflex to maximum M-response ratio (H:M), vibration H-reflex to control H-reflex (Hv:Hc), and H-reflex recovery curves (HRRCs) were recorded and compared between a control group and patient groups with ET, early-stage PD, and with ETPD. No statistically or clinically significant differences were found between the patient groups and the control group for latency, H:M ratio, or Hv:Hc ratio. Significantly greater ratio values were observed for the PD group over the other groups for the HRRC tests at each interstimulus interval between 200 and 300 msec (p < 0.05), but values were not different between PD and ETPD patients for intervals between 350 and 1,000 msec. Patients with ET, PD, and ETPD apparently have different underlying pathologies. HRRC tests do not distinguish ET patients from normal, but differentiates specifically between PD and ETPD, and normal individuals. HRRC testing may be a useful method for evaluating pathologies between ET, PD, and ETPD patients.

Methods of H-reflex evaluation in the early stages of Parkinson's disease.

Summary Differentiating the early stages of Parkinson’s disease from the normal consequences of aging or from other common neurologic conditions can be diagnostically problematic. The purpose of this study was to compare methodologies for measuring motor neuron excitability of Parkinson’s disease patients with a control group. H-reflexes were monitored in 16 patients diagnosed in the early stages of Parkinson’s disease (Hoehn & Yahr stages I and II) compared with 30 subjects who were disease free. Methods of measurement included H-reflex latencies, the relative values of maximum H-reflexes to maximum direct motor responses (H-to-M ratio), the relative values of H-reflex amplitudes during vibration compared with control H-reflex amplitudes (Hv-to-Hc ratio), and double-stimulation H-reflex recovery curves using different interstimulus interval parameters. No significant differences were observed for the H-to-M or Hv-to-Hc ratios, or for the H-reflex latencies. The H-reflex recovery curves for the patients with Parkinson’s disease demonstrated significantly greater ratio amplitudes than the control group during the double-stimulus responses between the 150-msec and 700-msec interstimulus intervals. Although comparisons of simple H-reflexes and H-reflexes during vibration did not differentiate the patients in the early stages of Parkinson’s disease from the control group, the double-stimulation paradigm was a sensitive method for detecting early diagnoses of this disease.

Flexor carpi radialis H-reflex modulation during spinal loading and unloading with varied forearm postures.

Flexor carpi radialis (FCR) H-reflex is usually recorded with the patient in lying or sitting postures while the forearm is positioned in supination or pronation to detect C7 radiculopathy. Its amplitude is smaller during forearm supination compared with pronation for unclear reasons and its recordings during postural loading conditions (i.e., sitting or lying) have not been previously reported. The purpose of this study was to examine FCR H-reflex recordings during varied cervical spine loadings and forearm positions. The FCR maximum H-reflex amplitude was recorded from 15 healthy participants during lying, free-sitting and sitting-with-load while the forearm was positioned in either supination or pronation. Four traces were averaged for each combination of conditions. Two-way repeated-measure analysis of variances (2 × 3) was used to examine the statistical differences. The average FCR H-reflex amplitude was significantly greater during free-sitting and sitting-with-load compared with the lying body position. The average FCR H-reflex amplitude was significantly greater when the forearm was positioned in pronation compared with supination. The increase in FCR H-reflex amplitude (augmentation) during forearm pronation and sitting postures compared with supination and lying may have been the result of combined neural and mechanical effects. These results encourage FCR H-reflex recordings during sitting with the forearm in pronation.

Changes in pulmonary function and functional capacity in adolescents with mild idiopathic scoliosis: observational cohort study:

Objective This observational cohort study aimed to evaluate ventilatory function (VF) and functional exercise capacity (FEC) in mild adolescent idiopathic scoliosis (AIS). Methods Seventy-three adolescents with idiopathic scoliosis, aged approximately 10 to 17 years (mean age: 13.43 ± 1.27 years), with a Cobb angle less than 20° (mean: 16.44° ± 1.59°), met the inclusion criteria and were assigned to group A. Another 34 healthy adolescents with normal VF and FEC served as controls (group B). Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), maximum voluntary ventilation (MVV), and FEC (by the 6-minute walk test [6MWT]) were the main outcome measures. Results Post-study mean values of FVC, FEV1, FEV1/FVC, MVV, and the 6MWT were 2.42 ± 0.36 L and 3.26 ± 0.59 L, 2.14 ± 0.31 L and 3.03 ± 0.43 L, 88.13% ± 3.89% and 91.14% ± 4.67%, 76.96 ± 6.85 L/m and 107.61 ± 11.44 L/m, and 581.12 ± 12.25 m and 627.74 ± 15.27 m in groups A and B, respectively. Between-group comparisons showed significant differences in FVC, FEV1, FEV1/FVC, MVV, and the 6MWT. Conclusion Mild pulmonary and functional restrictions start early in mild AIS. This issue requires immediate intervention to prevent further deterioration.