Experimental hyperthyroidism fails to expedite reinnervation of muscles denervated by crushing sciatic nerves in rabbits.

The time for initial reinnervation of tibialis anterior muscle after sciatic nerve crushing was measured in rabbits treated with intraperitoneal injections of 3,3′,5-triiodothyronine, 1 μg/kg body weight/day. The sciatic nerve was crushed in the thigh, just above its division into lateral and medial popliteal nerves. The method used to determine the beginning of reinnervation consisted of EMG recordings of (a) muscular potentials evoked by electrical stimulation of the sciatic nerve, below the crushed point, and (b) spontaneous action potentials during activity; the muscle tested was the tibialis anterior. The time for initial reinnervation averaged 43.6 ± 1.15 days in treated rabbits, and 43.2 ± 1.78 days in vehicle-injected animals. The distance from the site of crushing to the point where the anterior tibial nerve enters the tibialis anterior muscle was measured in each animal and the regeneration rate was calculated; this parameter averaged 1.48 ± 0.05 mm/day in treated rabbits, and 1.50 ± 0.04 mm/day in control animals. Therefore, no effect of 3,3′,5-triiodothyronine at the dosage used on the reinnervation process of muscles denervated by a crushed sciatic nerve could be demonstrated.     

Analysis of F-wave in metabolic neuropathies: a comparative study in uremic and diabetic patients

Motor nerve conduction study along the entire length of the ulnar and tibialis posterior nerves was carried out in 30 diabetics compared with 30 uremic patients and 30 control subjects. The conduction in the proximal and the distal nerve segments was evaluated by the determination of the M and F latencies, MNCV (between the stimulus sites), FWCV (between the spinal cord and the stimulus sites), and F-ratio (conduction time ratio of proximal to distal segment). In both groups of patients the lower limbs appear much more involved than the upper, where the ulnar nerve is more commonly affected in uremic than in diabetic patients. In diabetic neuropathy the motor conduction abnormalities are diffuse over the total length of the nerve, but more marked distally in the ulnar nerve.     

Reduced Nerve Blood Flow In Diabetic Rats Is A Reflection Of Hindlimb Muscle Wasting

We examined the influence of muscle wasting, as a result of streptozotocin-induced diabetes, on sciatic nerve laser Doppler flux (SNLDF), as an index of nerve blood flow, and conduction velocity (NCV). We compared dietary-restricted weight-reduced non-diabetic rats with controls and with diabetic rats and we studied the effects of clenbuterol, an anabolic β-adrenoceptor agonist, in control and diabetic rats. Dietary restriction reduced the weights of hindlimb muscles—extensor digitorum longus, soleus and gastrocnemius—half as much as did streptozotocin-diabetes and clenbuterol increased muscle weights in control and diabetic rats. This gave a hierarchy of muscle weights in the order—clenbuterol-controls, untreated controls, weight-reduced non-diabetics, clenbuterol-diabetics and untreated diabetics. Diabetes without treatment reduced SNLDF by 51% (p < 0.01); dietary restriction by 25% (p < 0.01) and there were proportional increases associated with clenbuterol treatment. Combined muscle weights regressed closely with SNLDF (r²=0.69; p < 0.001) and, when the latter was expressed relative to muscle weights, a similar value was obtained for all five groups—there were no significant differences. Thus, sciatic nerve blood flow is closely related to hindlimb muscle weight and the effect of diabetes on nerve blood flow may be secondary to muscle wasting. Sciatic/tibialis motor and sensory conduction velocities were also reduced by muscle wasting in the dietary restricted group of non-diabetic rats, but, unlike nerve Doppler flux, it was unaffected by clenbuterol.     

The bimodal jitter: a single fibre electromyographic finding

The jitter, obtained by SFEMG recordings, mainly reflects the neuromuscular transmission time variability and is usually Gaussian distributed. Here is reported the bimodal distribution of the interpotential intervals, the flip-flop phenomenon. Long flip-flop in cases of reinnervation may indicate alternatively continuous and saltatory nerve conduction. Short flip-flop in normal subjects may be due to muscle fibre interaction or nerve conduction irregularities.     

Reinnervation of the tibialis anterior following sciatic nerve crush injury: a confocal microscopic study in transgenic mice

Transgenic mice whose axons and Schwann cells express fluorescent chromophores enable new imaging techniques and augment concepts in developmental neurobiology. The utility of these tools in the study of traumatic nerve injury depends on employing nerve models that are amenable to microsurgical manipulation and gauging functional recovery. Motor recovery from sciatic nerve crush injury is studied here by evaluating motor endplates of the tibialis anterior muscle, which is innervated by the deep peroneal branch of the sciatic nerve. Following sciatic nerve crush, the deep surface of the tibialis anterior muscle is examined using whole mount confocal microscopy, and reinnervation is characterized by imaging fluorescent axons or Schwann cells (SCs). One week following sciatic crush injury, 100% of motor endplates are denervated with partial reinnervation at 2 weeks, hyperinnervation at 3 and 4 weeks, and restoration of a 1:1 axon to motor endplate relationship 6 weeks after injury. Walking track analysis reveals progressive recovery of sciatic nerve function by 6 weeks. SCs reveal reduced S100 expression within 2 weeks of denervation, correlating with regression to a more immature phenotype. Reinnervation of SCs restores S100 expression and a fully differentiated phenotype. Following denervation, there is altered morphology of circumscribed terminal Schwann cells demonstrating extensive process formation between adjacent motor endplates. The thin, uniformly innervated tibialis anterior muscle is well suited for studying motor reinnervation following sciatic nerve injury. Confocal microscopy may be performed coincident with other techniques of assessing nerve regeneration and functional recovery.     

Peripheral neuropathy in late onset spinocerebellar ataxia

We studied 10 patients with late onset spinocerebellar ataxia including electrophysiological and muscle biopsy examinations. Nerve conduction studies of eight patients revealed axonal neuropathy, and six cases also showed signs of the involvement of the lower motor neuron. In 9 patients quantitative analysis of single motor unit potentials (MUPs) of the tibialis anterior or biceps brachii muscles showed mild to severe neuropathic changes and in all 10 patients the histopathological examination of the tibialis anterior showed mild to severe neuropathic changes. Neither nerve conduction studies, quantitative MUP analysis, nor histological findings of the muscle were related to the severity of duration of the disease.     

Effects of 660‐nm gallium–aluminum–arsenide low‐energy laser on nerve regeneration after acellular nerve allograft in rats

Purpose : The purpose of this study was to explore and discuss the effects of 660‐nm gallium–aluminum–arsenide low‐energy laser (GaAlAs LEL) irradiation on neural regeneration after acellular nerve allograft repair of the sciatic nerve gap in rats. Methods : Eight male and female Sprague–Dawley rats were used as nerve donors, and 32 healthy Wistar rats were randomly divided into four groups: normal control group, acellular rat sciatic nerve (ARSN) group, laser group, and autograft group. Twelve weeks after surgery, nerve conduction velocity, restoration rate of tibialis anterior wet muscle weight, myelinated nerve number, and calcitonin gene‐related peptide (CGRP) protein and mRNA expression of the spinal cord and muscle at the injury site were quantified and statistically analyzed. Results : Compared with the ARSN group, laser therapy significantly increased nerve conduction velocity, restoration rate of tibialis anterior wet muscle weight, myelinated nerve number, and CGRP protein and mRNA expression of the L₄ spinal cord at the injury site. Conclusions : These findings demonstrate that 660‐nm GaAlAs LEL therapy upregulates CGRP protein and mRNA expression of the L₄ spinal cord at the injury site and increases the rate of regeneration and target reinnervation after acellular nerve allograft repair of the sciatic nerve gap in rats. Low‐energy laser irradiation may be a useful, noninvasive adjunct for promoting nerve regeneration in surgically induced defects repaired with ARSN. Synapse 64:152–160, 2010. © 2009 Wiley‐Liss, Inc.     

Femoral nerve involvement in diabetics

Background and purpose:  In this study, the conduction of the femoral nerve has been evaluated in diabetic patients without clinical signs of femoral nerve involvement and in a group of healthy subjects.
Methods:  Forty-eight patients have been included in the study. Patients have been examined in terms of neuropathy and their neuropathy scores have been calculated. In addition to the nerve conduction studies have been performed. The findings of the diabetic patients have been compared with those of the 26 healthy volunteers.
Results:  There has been a statistically significant difference between diabetics and the healthy volunteers in the control group in terms of both femoral nerve motor latency and amplitude. The femoral latencies of patients have significantly been related to the total neuropathy score. A significant difference between diabetic patients without polyneuropathy and the controls was observed with respect to their femoral latencies.
Conclusion:  In our study, femoral nerve conduction abnormalities have been determined in diabetics who clinically did not have femoral nerve involvement. It has been observed that these abnormalities become more evident as the polyneuropathy of the patients becomes more serious. Our study has shown that femoral nerve conductions may increase the sensitivity of the diagnosis of polyneuropathy.     

The effects of chronic muscular activity on age-related changes in single fiber electromyography

Single fiber electromyography ( SFEMG ) of the extensor digitorum communis (EDC) muscle and nerve conduction studies were performed on healthy, active elderly men (66-77 years old) to assess age-related changes in neuromuscular physiology and the effect of long-term increased muscular activity on these changes. The following two groups were studied: a control group and a group composed of men with occupationally greater usage of hand extensors. Fiber density and mean jitter were essentially the same in both groups; however, in the hand-user group there was greater variability in mean jitter and a significant increase in the prevalence of potential pairs with increased jitter or blocking. In both groups, slower nerve conduction velocities and lower amplitudes of sensory and motor evoked potentials tended to correlate with increased jitter and fiber density. These electrophysiological changes in healthy aged men are consistent with an extremely mild process of nerve terminal denervation and reinnervation. Although long-term increased synaptic activity did not greatly alter the rate or extent of this process, it did produce a higher incidence of abnormal potential pairs and greater variability in mean jitter.     

Reflex responses from the sural nerve to tibialis anterior muscle in hemiplegic patients: the relation between the responses and Babinski sign]

Stimulation of the sural nerve of healthy subjects induced short latency inhibition in the ipsilateral tibialis anterior muscle and facilitation in peroneal muscle. We examined lower limb muscle responses after stimulation of the sural nerve in 19 patients with hemiplegia caused by cerebro-vascular disease and compared them with the control responses. The sural nerve was stimulated electrically (3 or 5 square wave pulses of 0.5 ms repeated at 250 Hz) during weak tonic contraction. Stimulation was triggered to average the rectified surface electromyography (EMG) of the test muscle. Usually 100 - 200 sweeps were averaged. After stimulation, the tibialis anterior muscle on the affected side of the hemiplegic patients showed the patterns of inhibition, facilitation, and no response, whereas all responses on the unaffected side, except those of one patient, were inhibition. The peroneal muscle on both sides showed only facilitation as in the controls. Abnormal responses of the tibialis anterior muscle on the affected side were present in many patients who had the Babinski sign. Abnormal responses in the tibialis anterior muscle of the affected side may have been due to contributions by disinhibition of the flexor reflex, late-recruited motor units or both.     

Use of single fiber EMG and macro EMG in study of reinnervation

The use of single fiber EMG and macro EMG in studies of reinnervation is discussed. SFEMG gives information about changes in the topography of the motor unit and in function of transmission in terminal nerve, motor endplate and muscle fiber. Dynamics of reinnervation may be studied with this technique. The amount of reinnervation is obtained from macro EMG studies. The capacity for reinnervation is discussed for a few conditions as well as factors that limit the reinnervation process.     

AAEE case report #12: Common peroneal mononeuropathy at the fibular head

Common peroneal mononeuropathies, usually located at the fibular head, are one of the many causes of foot-drop, a condition often evaluated in the electromyography laboratory. If appropriate nerve conduction studies are performed and particular muscles studied on needle myography, a satisfactory diagnosis can almost always be provided for what may be a perplexing problem clinically. With all peroneal mononeuropathies, the compound muscle action potential amplitude of the peroneal motor tibialis anterior nerve conduction studies, stimulating distal to the fibular head, is a semi-quantitative measure of the number of viable fibers supplying the tibialis anterior and allows for accurate prognostication regarding the foot-drop.     

Detection of early motor involvement in diabetic polyneuropathy using a novel MUNE method – MScanFit MUNE

ObjectiveDetection of motor involvement in diabetic polyneuropathy (DPN) by nerve conduction studies (NCS) does not occur until there is substantial loss of motor units, because collateral reinnervation maintains compound muscle action potential (CMAP) amplitude. Motor unit number estimation (MUNE) methods may therefore be more sensitive. This study was undertaken to test whether the novel method, MScanFit MUNE (MScan) can detect motor involvement in DPN despite normal NCS.MethodsFifty-two type-2 diabetic patients and 38 healthy controls were included. The median nerve was examined in all participants using standard NCS and a detailed CMAP scan, used for MScan. Additional lower extremity NCS in patients were used for DPN diagnosis.ResultsOf 52 diabetic patients, 21 had NCS-defined DPN while lower extremity NCS were normal in 31 patients. MScan motor unit number and size showed higher sensitivity and incidence of abnormality than motor NCS parameters, and a similar sensitivity to sensory NCS.ConclusionsMScan is able to detect motor axonal damage at times when collateral reinnervation limits NCS changes.SignificanceMScan is a sensitive method to detect motor involvement in DPN, which our data suggests is present as early as sensory.     

实验性糖尿病大鼠的单纤维肌电图研究

目的:分析链脲佐菌素(STZ)诱导的糖尿病大鼠坐骨神经的神经传导速度和腓肠肌单纤维肌电图的特点,评价两种检查方法对糖尿病多发性神经病早期诊断的价值.方法:健康雄性SD大鼠经腹腔注射STZ60mg穔g-1诱导成1型糖尿病大鼠模型(糖尿病组),在注射STZ后4、6、8、10和12周进行坐骨神经神经传导检查和腓肠肌单纤维肌电...     

Muscle coordination in hindlimbs of mice after bilateral nerve regeneration

The common peroneal nerve was transected bilaterally in 25 adult mice. Nerve stumps were immediately readapted without nerve suture. Before transection and after nerve regeneration the muscle coordination of tibialis anterior (TA) and medial gastrocnemius (MG) muscle was examined by electromyographic recordings from both muscles (EMG) during free running. Using a personal computer, the degree of muscle coordination between TA and MG was determined by calculating a coordination index. In normal mice an antagonistic innervation pattern was observed. After nerve transection and regeneration the degree of muscle coordination of TA and MG substantially decreased with great interindividual but also great intraindividual variation. In 16 mice there was no correlation between the coordination index of the left and right hindlimbs. In nine out of 25 mice reinnervation was absent on one side. These results suggest that nerve regeneration by axonal sprouting to appropriate or foreign muscles occurs at random and that there are no intraindividual factors which might promote the finding of the proper target muscle.     

Effects of steroid hormones on muscle reinnervation after nerve crush in rabbit

The ability of an association of three steroid hormones to influence the reinnervation process and the trophism of rabbit muscles denervated by crush of the sciatic nerve was investigated. The beginning of reinnervation was established with electromyographic recordings from the tibialis anterior muscle. The distance from the site of crushing to the point where the motor nerve enters the tibialis anterior muscle was then measured in each animal, and the nerve regeneration velocity (mm/day) was calculated: a slightly but significantly higher (P less than 0.001) mean value was found in treated animals compared with untreated ones. When soleus and extensor digitorum longus (EDL) muscles were histochemically examined 50 days after lesion, a larger mean diameter of type 2c fibers was found in treated than in untreated animals, pointing out a possible useful effect of the treatment. On the contrary, the size reduction of EDL type 2b fibers was more pronounced in treated rabbits, indicating a catabolic influence of the drugs on this fiber type.     

Distal slowing of motor nerve conduction velocity in diabetic polyneuropathy.

Using the latencies of M response and F wave, motor nerve conduction was assessed along the entire course of the nerve from the spinal cord to the muscle in 102 diabetics and 74 control patients. In diabetics, latencies were increased and conduction velocity decreased over both proximal and distal segments. However, the latency ratio of the proximal to distal segment (F ratio) was slightly but significantly smaller in diabetics (mean +/- SD:0.93 +/- 0.14, 1.35 +/- 0.20, 1.09 +/- 0.19 and 1.02 +/- 0.19 for median, ulnar, tibial and peroneal nerves, respectively) than in control patients (1.05 +/- 0.09, 1.41 +/- 0.12, 1.17 +/- 0.13 and 1.08 +/- 0.12). These findings suggest that motor conduction abnormalities in diabetic polyneuropathy are diffuse over the total length of the nerve, but more intense in the distal than proximal segment. An additional finding in diabetics was that both proximal and distal segments were more frequently affected in the lower than in the upper extremities.     

Changes in afferent activities from tibialis anterior muscle after nerve repair by self-anastomosis

In order to study sensory nerve plasticity after nerve injury and repair, recordings were made from afferent axons innervating the tibialis anterior muscle in rats under several different experimental conditions. In two groups of rats, reinnervation of the denervated tibialis anterior was examined 2.5 months (group A) and 7 months (group B) after section, along with self-anastomosis of the common peroneal nerve. The other rats (group C) were examined 2.5 months after the nerve was cut and ligatured to its stumps to avoid axonal regeneration. No evoked potentials and no activation in response to any test agent were found in group C rats. We found a significant increase in the proportion of group I-II fibers and a significant decrease in group IV fibers in the group B rats when compared with group A (P < 0.05 and P < 0.01) and control animals (P < 0.01 and P < 0.01). A higher conduction velocity was measured in group IV fibers in group B rats when compared with group A (P < 0.01) and the controls (P < 0.01). The proportion of afferent units showing an optimal discharge in response to tendon vibration at 70 Hz (range 0-100 Hz) was higher in groups A and B (72.2 and 80%, respectively) than in the controls (36.8%). The response of muscle afferents to KCl (1-20 mM) and lactic acid (0.5-3 mM) concentrations was markedly depressed in group A rats (P < 0.05), whereas it was restored and even accentuated in group B animals when compared with the controls (P < 0.05). Electrically induced fatigue (3 min, 10 Hz) significantly activated (P < 0.05) muscle afferents only in controls. The present study indicates that after self-anastomosis of a cut hindlimb muscle nerve, sensory innervation was markedly modified in the direction of enhanced mechanosensitivity to high-frequency tendon vibration and depressed metabosensitivity.     

Amplitude of sensory nerve action potential in early stage diabetic peripheral neuropathy： an analysis of 500 cases

Early diagnosis of diabetic peripheral neuropathy is important for the successful treatment of diabetes mellitus. In the present study, we recruited 500 diabetic patients from the Fourth Affiliated Hospital of Kunming Medical University in China from June 2008 to September 2013：221 cases showed symptoms of peripheral neuropathy （symptomatic group） and 279 cases had no symptoms of peripheral impairment （asymptomatic group）. One hundred healthy control subjects were also recruited. Nerve conduction studies revealed that distal motor latency was longer, sensory nerve conduction velocity was slower, and sensory nerve action potential and amplitude of compound muscle action potential were significantly lower in the median, ulnar, posterior tibial and common peroneal nerve in the diabetic groups compared with control subjects. Moreover, the alterations were more obvious in patients with symptoms of peripheral neuropathy. Of the 500 diabetic patients, neural conduction abnormalities were detected in 358 cases （71.6%）, among which impairment of the common peroneal nerve was most prominent. Sensory nerve abnormality was more obvious than motor nerve abnormality in the diabetic groups. The amplitude of sensory nerve action potential was the most sensitive measure of peripheral neuropathy. Our results reveal that varying degrees of nerve conduction changes are present in the early, asymptomatic stage of diabetic peripheral neuropathy.     

Nerve and muscle biopsy: electrophysiology and morphology in polyneuropathy.

We correlated the results of biopsy of a muscle nerve, a sensory nerve, and tibialis anterior muscle with electrophysiologic studies in 13 patients with sensorimotor polyneuropathy and 6 patients with normal findings. There were significant correlations between teased fiber changes and conduction abnormalities in both muscle nerves and sensory nerves. The density of large myelinated fibers in the lateral fascicle of the deep peroneal (LFDP) nerve correlated significantly with both the motor unit estimate and compound action potential amplitude of the extensor digitorum brevis (EDB) muscle. Other characteristics of the EDB muscle compound action potential related poorly to teased fiber abnormalities. There was good correlation of needle electrode study of the EDB muscle with teased fiber analysis of the LFDP nerve and with the morphology of the tibialis anterior muscle in 75 percent of the cases, and only minor discrepancies in the remainder. These results emphasize the close relationship between certain structural and electrophysiologic changes in subacute and chronic polyneuropathy.