To investigate the electrophysiological effects of focal vibration on the tendon and muscle belly in healthy people.
The miniaturized focal vibrator consisted of an unbalanced mass rotating offset and wireless controller. The parameters of vibratory stimulation were adjusted on a flat rigid surface as 65 µm at 70 Hz. Two consecutive tests on the different vibration sites were conducted in 10 healthy volunteers (test 1, the Achilles tendon; test 2, the muscle belly on the medial head of the gastrocnemius). The Hoffman (H)-reflex was measured 7 times during each test. The minimal H-reflex latency, maximal amplitude of H-reflex (Hmax), and maximal amplitude of the M-response (Mmax) were acquired. The ratio of Hmax and Mmax (HMR) and the vibratory inhibition index (VII: the ratio of the Hmax after vibration and Hmax before vibration) were calculated. The changes in parameters according to the time and site of stimulation were analyzed using the generalized estimating equation methods.
All subjects completed the two tests without serious adverse effects. The minimal H-reflex latency did not show significant changes over time (Wald test: χ2=11.62, p=0.07), and between the two sites (χ2=0.42, p=0.52). The changes in Hmax (χ2=53.74, p<0.01), HMR (χ2=20.49, p<0.01), and VII (χ2=13.16, p=0.02) were significant over time with the adjustment of sites. These parameters were reduced at all time points compared to the baseline, but the decrements reverted instantly after the cessation of stimulation. When adjusted over time, a 1.99-mV decrease in the Hmax (χ2=4.02, p=0.04) and a 9.02% decrease in the VII (χ2=4.54, p=0.03) were observed when the muscle belly was vibrated compared to the tendon.
The differential electrophysiological effects of focal vibration were verified. The muscle belly may be the more effective site for reducing the H-reflex compared to the tendon. This study provides the neurophysiological basis for a selective and safe rehabilitation program for spasticity management with focal vibration.
Citations
To evaluate the spasticity and electrophysiologic effects of applying extracorporeal shock wave therapy (ESWT) to the gastrocnemius by studying F wave and H-reflex.
Ten healthy adults and 10 hemiplegic stroke patients with ankle plantarflexor spasticity received one session of ESWT on the medial head of the gastrocnemius. The modified Ashworth scale (MAS), tibial nerve conduction, F wave, and H-reflex results were measured before and immediately after the treatment. The Visual Analogue Scale (VAS) was used during ESWT to measure the side effects, such as pain.
There were no significant effects of ESWT on the conduction velocity, distal latency and amplitude of tibial nerve conduction, minimal latency of tibial nerve F wave, latency, or H-M ratio of H-reflex in either the healthy or stroke group. However, the MAS of plantarflexor was significantly reduced from 2.67±1.15 to 1.22±1.03 (p<0.05) after applying ESWT in the stroke group.
After applying ESWT on the gastrocnemius in stroke patients, the spasticity of the ankle plantarflexor was significantly improved, with no changes of F wave or H-reflex parameters. Further studies are needed to evaluate the mechanisms of the antispastic effect of ESWT.
Citations
Method: The subjects were 37 patients and 30 normal controls. The patient group was composed of 28 patients with L5 radiculopathy and 9 patients with S1 radiculopathy, which were confirmed by clinical, radiological, and electrodiagnostic studies. Tibialis anterior H-reflex (TA-H reflex) was recorded from maximally contracting tibialis anterior muscle by averaging technique and submaximal stimulation of common peroneal nerve. Sensitivities and specificities were delineated from the several diagnostic criteria.
Results: In the normal controls, mean side to side difference in the TA-H reflex latency was 0.66⁑0.48 msec and mean amplitude ratio was 75⁑16%. The diagnostic criteria of abnormal TA-H reflex were latency difference above 1.62 msec and amplitude ratio less than 42.2%. The abnormal TA-H reflexes were shown in 17 out of 28 patients with L5 radiculopathy and 1 out of 9 patients with S1 radiculopathy. Sensitivity and specificity of TA-H reflex as a diagnostic criteria of L5 radiculopathy were 61% and 89%, respectively.
Conclusion: Tibialis anterior H-reflex might be useful in the diagnosis of L5 radiculopathy.
Objective: It is a widely accepted belief that paraspinal muscles tend to show spontaneous activity on needle electromyography early on in a radiculopathy and distal muscles become abnormal later on. But most studies have shown the limitations of using symptom duration when interpreting electrodiagnostic findings in radiculopathy. The purpose of this study was to determine the relationship between symptom duration and abnormal spontaneous activity in S1 radiculopathy confined to abnormal H-reflex.
Method: A retrospective study that collected the informations on symptom duration and spontaneous activity in paraspinal muscle and gastrocnemius for 112 patients with S1 radiculopathy diagnosed by unilateral H-reflex abnormality was undertaken.
Results: Abnormal spontaneous activity in paraspinal muscle had shown a significant negative correlation with symptom duration, that is a tendency to decrease its expression over symptom duration. On the contrary abnormal spontaneous activity in gastrocnemius muscle was rare at first a few weeks and became to show after 7 weeks. Patients with symptom duration over 1 year had higher incidence of having no abnormal spontaneous activities both in paraspinal and gastrocnemius muscle.
Conclusion: These results suggested that symptom duration had a potential role in the diagnosis of S1 radiculopathy when H-reflex were abnormal unilaterally.
Objective: To study the changes of magnetic evoked potentials by thinking of simple motion without actual muscle action of that motion.
Method: We use H-reflex to test the excitability of relevant pools of spinal motor neurons and Magnetic Evoked Potentials (MEPs) to study the core of brain motor activity. The H-reflex and MEPs were obtained in three different conditions. 1) non-facilitation (NF), that is, resting state without actual motion and without thinking of that motion. 2) volitional-faciliation (VF), with actual motion which is usual manner of facilitation of MEPs. 3) thinking-facilitation (TF), without actual motion but with imaginary thinking of that motion. We evaluate the thresholds, amplitudes and latencies of H-reflex and MEPs in each three condition.
Results: Comparing with the parameters in NF condition as a baseline, there were no significant changes in any parameters of H-reflex in TF condition, but there were significant changes in threshold and amplitude of H-reflex in VF. On the while there were significant changes both in VF and TF of MEPs. The amount of facilitation of MEPs were greater in VF than in TF; the amount threshold decrement, amplitude increment and latency decrement of MEPs were greater in VF than in TF.
Conclusion: Thinking of simple motion without actual muscle action of that motion could facilitate the MEPs, and this facilitation is induced by increasing activity of brain motor cortex not by that of spinal cord level.
Objective: To explore the clinical value of postoperative follow-up examination of F-wave and H-reflex in patients with lumbosacral radiculopathy and to clarify optimal timing of follow-up examination.
Method: The subjects were 17 patients with unilateral lumbosacral radiculopathy caused by disc herniation. In patients with the L5 radiculopathy, F-waves were obtained from extensor digitorum brevis and six parameters including minimal latency per height were used. In patients with the S1 radiculopathy, H-reflexes were obtained from gastrocnemius and amplitude and minimal latency were used as parameters. These parameters were evaluated preoperatively and postoperatively at week 1, 3, 6. These changes of the parameters and clinical findings were related.
Results: The parameters of peroneal F-wave and tibial H-reflex showed significant improvement at 3 weeks and 6 weeks after surgery. The improvements of these parameters were not related with clinical improvement at 1 week after operation, but these were significantly related with improvement of pain and muscle weakness at 3 weeks after operation.
Conclusion: These findings suggested that follow-up examination of F-wave and H-reflex were valuable for objective assessment of lumbosacral radiculopathy after operation and the optimal timing for follow-up study was 3 weeks after operation.
Objective: To investigate the effects of Jendrassik maneuver on latency and amplitude of the T-reflex and H-reflex of the soleus muscle in normal adults.
Method: The T-reflex and H-reflex tests were performed on sixty normal adults with standardized technique using the soleus muscle. The shortest latency and the largest peak-to-peak amplitude were chosen for representative values.
Results: The results were as follows: 1) There was a significant difference in latency of the T-reflex between with and without Jendrassik maneuver. 2) The increment ratio of the amplitude with Jendrassik maneuver was 88% in the T-reflex and 18% in the H-reflex. There were a significant difference in the amplitude of both reflexes between with and without Jendrassik maneuver. 3) A high correlation was present between the latency of H- & T-reflex and the length.
Conclusion: According to these results, we suggest that Jendrassik maneuver primarily increases the sensitivity of muscle spindles and decreases the presynaptic inhibition of the Ia terminals at cortical, subcortical and spinal levels. Jendrassik maneuver can be a useful tool in cases of clinically decreased or absent deep tendon reflex.
Objective: To investigate and compare the vibratory inhibition of H-reflex in the subjects with and without brain injury.
Method: H-reflex and the vibratory inhibition of H-reflexes were evaluated in thirty two limbs in subjects without brain injury and twenty two limbs in the brain injury patients. The maximal amplitudes of H-reflexes were recorded before and while vibrating the Achilles tendon. The ratio of the two trials (vibratory maximal H-reflex amplitude / previbratory maximal H-reflex amplitude) was defined as 'H-reflex vibratory inhibition'. H-reflex vibratory inhibition was correlated to the spasticity (Asworth scale).
Results: The mean values of H-reflex vibratory inhibition were 0.5361⁑0.0373 in the control group and 0.7539⁑0.0543 in the brain injured group. There was a significant difference between two groups. H-reflex vibratory inhibition tends to increase as the spasticity increases.
Conclusion: The vibratory inhibition of H-reflex was significantly decreased in the brain injured patients than in the controls. We conclude that the H-reflex vibratory inhibition can be used in the evaluation of the spasticity.
It has been reported that the electrical stimulation of nerves can cause the changes of anterior horn cell excitability and conduction velocity of the nerves in vivo and vitro studies. The purpose of this study is to evaluate the electrophysiologic changes of the peripheral nerves near the spinal cord by the electrical stimulation. Subjects were 20 healthy volunteers, with the age of 21 to 27 years. The conditioning current was an interferential current of 10 Hz and 100 Hz with the maximal tolerable intensity (18∼20 mA). Conditioning stimulation was applied to the paraspinal area between T9 and T12 for 15 minutes. Before and after the conditioning stimulation, we measured the peripheral nerve conduction, H-reflex, F-wave, and somatosensory evoked potential (SEP) of the tibial nerve. The results after the conditioning revealed that the tibial motor and sensory conductions were unchanged but the latency of the H-reflex was significantly prolonged with a significant reduction of H amplitude and H/M ratio (p＜0.01). The latency, duration, and F-ratio of the F-wave were significantly increased and the amplitude of the F-wave was significantly reduced (p＜0.01). P1 latency was significantly prolonged in the cortical tibial SEP (p＜0.01). Change of N1P1 amplitude was not meaningful (p＞0.05). There was no statistical difference between the changes by a high or low frequency stimulation. These results suggest that a certain conditioned electrical stimulation of peripheral nerves near the spinal cord may cause the decrement of anterior horn cell excitability, and the inhibition of the alpha motor nerve and sensory nerve conductions near the spinal cord.
Many factors have been identified which to affect the rate of propagation of impulses along motor fibers. These include temperature changes around the nerve, diameter of the axon, degree of myelinization, age of infants, and local environment of the nerve. Motor nerve conduction velocity and Hoffman's reflex latency have been used to assess the degree of myelination and maturation of the nervous system. The conduction velocities in infants of a short gestational age are significantly lower than those of the fullterm infants. The extrauterine myelination and maturation might increase nerve conduction velocity. We measure the median motor nerve conduction velocity, compound muscle action potentials amplitude and H-reflex latency of premature infants to determine the neurological maturation after birth. The premature infants with gestational age above 37 weeks have a significantly higher conduction velocity and a shorter H-reflex latency than those of gestational age below 37 weeks. The premature infants with weight over 2.5 kg have a significantly higher conduction velocity, larger compound muscle action potentials amplitude and a shorter H-reflex latency than those of weight below 2.5 kg. And there is a statistically significant negative correlation of the H-reflex latency with the postmenstrual age. The determination of motor nerve conduction velocities and H-reflex latencies seem to be an additional method in assessing the degree of maturity in infants after birth.
First
Prev
