H-reflex to S1-root stimulation improves utility for diagnosing S1 radiculopathy

ObjectiveThe H-reflex on stimulation of the tibial nerve in the popliteal fossa is routinely used in the diagnosis of first sacral (S1) nerve-root radiculopathy. The H-reflex latency, however, is considered to lack sensitivity since a small change from the focal root pathology can be diluted in a relatively long reflex latency. We have studied the soleus H-reflex elicited by stimulation of the S1 nerve root at the S1 foramen. The normal values for the S1-foramen H-reflex have been reported in a previous study, but there are no definitive reports in patients with S1 radiculopathy. This study was undertaken to determine whether stimulating at the S1 nerve root can improve the utility of the H-reflex for detecting an S1-root lesion.MethodsA randomised paired-study design was utilised to evaluate two H-reflexes: one elicited with tibial nerve stimulation and one elicited with S1-root stimulation. Fifty-five patients with unilateral S1 radiculopathy, confirmed by clinical, electrodiagnostic and magnetic resonance imaging (MRI) evidences were studied. A high-voltage electrical stimulator was used to elicit H-reflexes bilaterally at the S1 foramen and L4/L5 spine level. Latencies were compared with previously generated normal values and similar responses from the asymptomatic leg, focussing on the interval between the peak of M- and H-waves (HMI).ResultsOn the symptomatic side, 39 of the 55 patients had abnormal tibial H-reflex latencies and 54 patients had abnormal responses on S1-foramen stimulation (absent in 18; HMI prolonged >0.4 ms in 36). On the asymptomatic side, all 55 patients had normal tibial H-reflexes, and 52 had normal responses on S1-foramen stimulation. In three patients, the HMI was abnormal on S1-foramen stimulation. In 46 patients tested with L4/L5-level stimulation, H-reflex was present in 39 and absent in seven. The latency of the M-wave to S1 stimulation was normal.ConclusionsAbnormal S1-root H-reflexes reveal lesions at the S1 root in patients with normal tibial H-reflexes; therefore, enhancing diagnostic sensitivity. The appearance of the H-reflex to L4/L5-level stimulation in patient with absent H-reflex to S1-foramen stimulation further localises the site of S1 nerve-root lesion to the L5/S1 spine level. Thus, H-reflex to S1-root stimulation significantly increases the diagnostic sensitivity for S1 radiculopathy.SignificanceIn our study, the S1-root H-reflex with high-voltage electrical stimulation has shown greater sensitivity than the tibial H-reflex in evaluating S1 compressive radiculopathies. An abnormal S1-root H-reflex helps to localise the lesion to the S1 root in patients with concurrent abnormal tibial nerve H-reflex, which may increase diagnostic specificity.     

Muscle hypertrophy due to scarring of the S1 nerve root

Segmental muscle enlargement occurs in a variety of neurogenic conditions. We present a patient with calf hypertrophy, likely produced by continuous neuromuscular irritability and compensatory type 1 and type 2 muscle fiber hypertrophy. The underlying lesion of the S1 nerve root was caused by scarring, which could be demonstrated by Gadolinum enhanced, fat saturated magnetic resonance imaging. Thus, the application of this technique is recommended in otherwise etiologically unclear cases of neurogenic muscular lesions in order to detect chronic nerve root pathology.     

Soleus H-reflex inhibition during gait initiation in Parkinson's disease.

The soleus H-reflex excitability during gait initiation was investigated in Parkinson's disease. Eleven patients participated in this study. Patients stepped forward as soon as the start signal flashed. Soleus H-reflex was evoked from the trailing leg 100, 300, or 600 msec after the start signal. The electromyographic activity in the soleus muscle immediately before evoking the H-reflex and the ankle joint motion were recorded. The soleus H-reflex was inhibited 300 msec after the start signal. The amount of the soleus H-reflex inhibition was inversely correlated with the Hoehn and Yahr stage; Items 14, 29, and 31 of the Unified Parkinson's Disease Rating Scale; and the delay of the onset of the ankle dorsiflexion from the start signal. In contrast, the amount of electromyographic activity immediately before evoking the H-reflex was not significantly correlated with those measures but was significantly correlated with Item 22 of the Unified Parkinson's Disease Rating Scale. Those findings indicate that the amount of soleus H-reflex inhibition during gait initiation depends on the severity of the disease. Abnormality of descending command may be related to the severity-dependent H-reflex inhibition.     

Soleus H-reflex modulation and paired reflex depression from prone to standing and from standing to walking

Patterns of soleus H-reflex modulation as a function of posture, task, and reflex activation history were assessed with three experimental paradigms: lying prone compared with standing unsupported; standing compared with the initiation of walking; and standing compared with the mid stance phase of walking. Paired H-reflexes, 80 ms apart, were evoked under each condition. The paired reflex depression (PRD), the percentage depression of the second H-reflex relative to the first H-reflex, was modulated independently of the first H-reflex across the postures and tasks. These results reveal divergent patterns of segmental reflex modulation and support the idea that segmental reflexes are controlled by multiple mechanisms.     

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.     

Voluntary contraction and responses to submaximal cervical nerve root stimulation

Voluntary contraction of hand muscles increases compound muscle action potential (CMAP) amplitudes evoked by submaximal electrical percutaneous cervical stimulation (EPCS). This has been reported to be due to an intraspinal, presynaptic mechanism. We studied the effects of voluntary contraction on hypothenar CMAP amplitudes in 5 volunteers following electrical peripheral nerve stimulation at the wrist, EPCS, magnetic stimulation at the neck and the effects of a conditioning subthreshold cortical magnetic stimulus on CMAPs evoked by EPCS at rest. CMAP amplitudes increased with voluntary contraction of the target muscle, regardless of type or location of stimulus (P < 0.001). No increase in CMAP amplitude occurred when a conditioning transcranial stimulus was employed with EPCS (P = 0.35). Our findings indicate a peripheral rather than central mechanism underlies this effect of voluntary contraction. It is probably related to the recruitment order of motor axons, comparing voluntary activation with electrical or magnetic stimulation. © 1994 John Wiley & Sons, Inc.     

Soleus H-reflex tests in causalgia-dystonia compared with dystonia and mimicked dystonic posture

Dystonia in the causalgia-dystonia syndrome is characterized by a fixed dystonic posture. To identify involvement of central pathophysiologic mechanisms, we analyzed soleus H-reflex tests in five patients with causalgia-dystonia. Soleus H-reflex test results in these patients differed from those in healthy controls but were similar to those in purely dystonic patients and healthy controls mimicking dystonic posture. The results suggest involvement of supraspinal mechanisms in the abnormal posture of causalgia-dystonia.     

Improved methodology for lumbosacral nerve root stimulation

The site of S1–S2 root activation following percutaneous high-voltage electrical (ES) and magnetic stimulation were located by analyzing the variations of the time interval from M to H soleus responses elicited by moving the stimulus point from lumbar to low thoracic levels. ES was effective in activating S1–S2 roots at their origin. However, supramaximal motor root stimulation required a dorsoventral montage, the anode being a large, circular surface electrode placed ventrally, midline between the apex of the xiphoid process and the umbilicus. Responses to magnetic stimuli always resulted from the activation of a fraction of the fiber pool, sometimes limited to the low-thresholds afferent component, near its exit from the intervertebral foramina, or even more distally. Normal values for conduction velocity in motor and 1a afferent fibers in the proximal nerve tract are provided. © 1996 John Wiley & Sons, Inc.     

Soleus H-reflex; depression induced by ballistic voluntary arm movement in human

A biomechanical and neurophysiological analysis of anticipatory postural adjustments associated with the early phase of a voluntary arm movement was carried out in normal human subjects. Arm elevation, performed at maximal velocity, was studied with unilateral arm movement in freely and counterbalanced (suspended in a safety harness) standing humans. The ground reaction force of both legs, tangential acceleration of the shank and electromyographic activity (EMG) of the anterior deltoid (AD), biceps femoris (BF) and soleus (Sol) muscles were recorded. Sol H-reflexes of both legs were also elicited. To examine how the la inhibitory and presynaptic inhibitory pathways are related to anticipatory postural adjustments, additional Sol H-reflexes were elicited using the classical conditioning-test technique (time interval 2 and 15 ms, respectively). In this study, we systematically described biomechanical and EMG phenomena that precede and follow the onset of voluntary arm movements. Prior to and during the arm movement (i.e. AD activation), a sequence of EMG modifications occurred in ipsilateral BF and Sol muscles. Those modifications preceding BF activation included silent phases in Sol EMG and depression of Sol H-reflexes. By comparing EMG modifications with depressions of the Sol H-reflex, we conclude that Ia and presynaptic inhibitory pathways do not play a specific role in those Sol H-reflex depressions. Moreover, because Sol H-reflex depression occurs in both freely standing and counterbalanced postures, anticipatory postural adjustment appear to be preprogrammed in the central nervous systems unrelated to peripheral neural mechanisms. Since changes of EMG activities of ipsilateral BF and Sol appeared simultaneously and Sol H-reflex depressions were dependent on EMG activities of ipsilateral BF, control commands to anticipatory postural adjustment would excite BF and inhibit Sol.     

Transfer of normal S1 nerve root to reinnervate atonic bladder due to conus medullaris injury

Introduction: Neurogenic bladder dysfunction after spinal cord injury (SCI) is a major medical and social problem. In this study we assessed the effectiveness of neurogenic bladder reinnervation in patients with SCI using a normal S1 nerve root. Methods: Nine patients with bladder dysfunction caused by injury to the low conus medullaris (S2–S5) underwent a novel surgical procedure in which the unilateral proximal end of the S1 ventral root (VR) was anastomosed to the distal end of the S2 and S3 VRs. Results: Seven patients regained satisfactory bladder control within 8–12 months after VR microanastomosis. The average residual urine volume decreased from 186.0 ± 35.0 ml to 43.0 ± 10.0 ml, and no urinary infections occurred. Conclusions: These results suggest the effectiveness of bladder innervation by S1 nerve transfer, which could provide a new approach for the reconstruction of atonic bladder function caused by low conus medullaris injuries. Muscle Nerve, 2013     

Soleus nerve transfer to deep peroneal nerve for treatment of foot drop

Different mechanisms including knee dislocation, replacement surgery, nerve tumor, lumbar disc herniation, sharp injury, and gunshot wound lead to foot drop. Several surgical techniques have been used for treatment of foot drop, however, they have had sub-optimal outcomes. Soleus branch of tibial nerve is a good donor for nerve transfer for treatment of foot drop. In this is retrospective study, we reviewed medical records of 6 consecutive patients with sustained foot drop following injury to lumbar root or peroneal nerve, who underwent transfer of the soleus branch of tibial nerve to deep peroneal nerve during 2014–2016. The mean age of the patients was 44.8 years and duration of injury to surgery and follow-up was 8.3 and 14.6 months, respectively. At the end of the follow-up, ankle dorsiflexion force was M4 in two patients (with traumatic peroneal nerve injury with M3 toe extension) and was M2 in one patient. There were three patients with lumbar degenerative disease. Of these patients, two showed M0 and one patient experienced M1 ankle dorsiflexion. We recommend that transfer of soleus nerve to deep peroneal nerve is used as an alternative technique for treatment of foot drop.     

The H-reflex to magnetic stimulation of lower-limb nerves.

We elicited H-reflexes by magnetic and electrical stimulation of several different nerves in 10 healthy subjects and two patients with S-1 radiculopathy. The posterior tibial nerve at the popliteal fossa and the femoral nerve at the inguinal ligament were tested with both electrical and magnetic stimulation; the proximal sciatic nerve was tested only with magnetic stimulation. Muscle activity was recorded from the soleus muscle for posterior tibial and sciatic nerve stimulation and from the vastus medialis muscle for femoral nerve stimulation. No significant difference was found between the latency of H-reflexes evoked by magnetic or electrical stimulation. With magnetic stimulation, the mean (+/- SD) Ia sensory fiber conduction velocity in the proximal segment of the sciatic nerve was 72.4 +/- 3.3 m/s, while the motor nerve fiber conduction velocity in the same portion of the nerve was significantly slower, at 60.6 +/- 2.0 m/s. In two patients with unilateral S-1 radiculopathy, the latency of the H-reflex from the soleus muscle to both magnetic and electrical stimulation of the posterior tibial nerve was absent or prolonged on the affected side. Magnetic stimulation can be used to study the H-reflex and Ia fiber conduction velocity and is particularly advantageous when testing deeply located nerve trunks.     

Soleus H-reflex tests and clinical signs of the upper motor neuron syndrome.

Soleus H-reflex tests are used for elucidating pathophysiological mechanisms in motor control. The cumulative vibratory inhibition of the soleus H-reflex, the ratio of the reflex to direct muscle potential (H to M ratio) and the recovery curve of the soleus H-reflex were studied in 38 patients with varying signs of the upper motor neuron syndrome for a possible relation with clinical features. The results were compared with those obtained from a group of healthy volunteers. The magnitude of vibratory inhibition decreased with increase of hypertonia. The H to M ratio increased as the activity of the tendon reflex was enhanced and correlated to a lesser degree with muscle tone. Both the H to M ratio and late facilitation of the soleus H-reflex recovery curve were elevated in clonus. The findings suggest that alterations in the results of soleus H-reflex tests relate to specific clinical features of the upper motor neuron syndrome. Possible pathophysiological implications are discussed.     

Reinnervation of the gastrocnemius muscle by the contralateral S1 nerve root

Functional regeneration after transposition of a ventral nerve root was established in the adult cat. Reconstruction of the ventral root, using microsurgical methods, directed the right S1 ventral nerve root to innervate the left gastrocnemius muscle. Stimulus-induced unit responses were recorded from the left gastrocnemius muscle 5 to 8 months after the root cross, demonstrating the reestablishment of neuromuscular connections. The innervation of the left gastrocnemius muscle by neurons in the right ventral horn of the spinal cord was verified by injecting horseradish peroxidase into the muscle. Horseradish peroxidase reaction product was located in alpha and gamma motor neurons in the right S1 segment of the spinal cord. Computer-assisted determination of the soma area of the labeled neurons was compared with a normal S1 innervation of the gastrocnemius muscle. Analysis of the percentage of cells of a given soma area demonstrated an overall decrease in soma area in the operated animals. Because ventral root reconstruction can result in innervation of a foreign muscle, studies such as this may encourage repair or reconstruction of nerve roots to gain some functional recovery after spinal cord or nerve root injuries.     

Soleus H-reflex modulation pattern for a fine angle of hip and knee joint passive movement

OBJECTIVE: To elucidate whether hip and knee joint movement modulate soleus H-reflex, the authors measured the soleus H-reflex for a very fine angle during movement. METHODS: Eight healthy subjects participated. The knee and hip joints were passively flexed and extended ranging from 0 degrees to 120 degrees simultaneously. RESULTS: In the flexion phase, H-reflex decreased. It decreased more during fast movement. In the extension phase, H-reflex increased markedly. CONCLUSION: By measuring for a fine angle, it was clearly found that the stretch of the muscles around the knee and hip joints caused the changes in soleus H-reflex.