Inhibitory effect of dry needling on the spontaneous electrical activity recorded from myofascial trigger spots of rabbit skeletal muscle

OBJECTIVE

Dry needling of myofascial trigger points can relieve myofascial pain if local twitch responses are elicited during needling. Spontaneous electrical activity (SEA) recorded from an active locus in a myofascial trigger point region has been used to assess the myofascial trigger point sensitivity. This study was to investigate the effect of dry needling on SEA.

DESIGN

Nine adult New Zealand rabbits were studied. Dry needling with rapid insertion into multiple sites within the myofascial trigger spot region was performed to the biceps femoris muscle to elicit sufficient local twitch responses. Very slow needle insertion with minimal local twitch response elicitation was conducted to the other biceps femoris muscle for the control study. SEA was recorded from 15 different active loci of the myofascial trigger spot before and immediately after treatment for both sides. The raw data of 1-sec SEA were rectified and integrated to calculate the average integrated value of SEA.

RESULTS

Seven of nine rabbits demonstrated significantly lower normalized average integrated value of SEA in the treatment side compared with the control side (P < 0.05). The results of two-way analysis of variance show that the mean of the normalized average integrated value of SEA in the treatment group (0.565 +/- 0.113) is significantly (P < 0.05) lower than that of the control (0.983 +/- 0.121).

CONCLUSIONS

Dry needling of the myofascial trigger spot is effective in diminishing SEA if local twitch responses are elicited. The local twitch response elicitation, other than trauma effects of needling, seems to be the primary inhibitory factor on SEA during dry needling.

Interexaminer reliability of the palpation of trigger points in the trunk and lower limb muscles

OBJECTIVES

To determine the interexaminer reliability of palpation of three characteristics of trigger points (taut band, local twitch response, and referred pain) in patients with subacute low back pain, to determine whether training in palpation would improve reliability, and whether there was a difference between the physiatric and chiropractic physicians.

DESIGN

Reliability study.

SETTING

Whittier Health Campus, Los Angeles College of Chiropractic.

PARTICIPANTS

Twenty-six nonsymptomatic individuals and 26 individuals with subacute low back pain.

INTERVENTION

Twenty muscles per individual were first palpated by an expert and then randomly by four physician examiners.

MAIN OUTCOME MEASURES

Palpation findings.

RESULTS

Kappa scores for palpation of taut bands, local twitch responses, and referred pain were .215, .123, and .342, respectively, between the expert and the trained examiners, and .050, .118, and .326, respectively, between the expert and the untrained examiners. Kappa scores for agreement for palpation of taut bands, twitch responses, and referred pain were .108, -.001, and .435, respectively, among the nonexpert, trained examiners, and -.019, .022, and .320, respectively, among the nonexpert, untrained examiners.

CONCLUSIONS

Among nonexpert physicians, physiatric or chiropractic, trigger point palpation is not reliable for detecting taut band and local twitch response, and only marginally reliable for referred pain after training.

Bilateral femoral neuropathy after vaginal hysterectomy

A case of bilateral femoral neuropathy as a complication of vaginal hysterectomy is presented. A 45-year-old woman developed weakness of both quadriceps, absence of bilateral knee jerks, and numbness over bilateral anteromedial thighs and medial lower legs after a vaginal hysterectomy. Electromyographic examination revealed evidence of denervation in the bilateral quadriceps. A nerve conduction study showed prolonged distal latencies and markedly reduced amplitude of the compound muscle action potentials in bilateral femoral nerves. It is suggested that this complication is caused by a microvascular and/or local mechanical injury of the femoral nerve, which is compressed beneath the tough inguinal ligament in a sustained posture with the hip joint in an extreme abduction and external rotation position. The prognosis was excellent with almost complete recovery within 10 weeks. The complication may be preventable by minimizing operating time, changing the patient's posture, and limiting the degree of flexion, abduction, and external rotation of the hip.

Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points

OBJECTIVE

To review recent clinical and basic science studies on myofascial trigger points (MTrPs) to facilitate a better understanding of the mechanism of an MTrP.

DATA SOURCES

English literature in the last 15 years regarding scientific investigations on MTrPs in either humans or animals.

STUDY SELECTION

Research works, especially electrophysiologic studies, related to the pathophysiology of MTrP.

DATA SYNTHESIS

(1) Studies on an animal model have found that a myofascial trigger spot (MTrS) in a taut band of rabbit skeletal muscle fibers is similar to a human MTrP in many aspects. (2) An MTrP or an MTrS contains multiple minute loci that are closely related to nerve fibers and motor endplates. (3) Both referred pain and local twitch response (characteristics of MTrPs) are related to the spinal cord mechanism. (4) The taut band of skeletal muscle fibers (which contains an MTrP or an MTrS in the endplate zone) is probably related to excessive release of acetylcholine in abnormal endplates.

CONCLUSION

The pathogenesis of an MTrP appears to be related to integrative mechanisms in the spinal cord in response to sensitized nerve fibers associated with abnormal endplates.

Phentolamine effect on the spontaneous electrical activity of active loci in a myofascial trigger spot of rabbit skeletal muscle

OBJECTIVE

To investigate the effect of phentolamine, a sympathetic blocking agent, on the spontaneous electrical activity (SEA) recorded from a locus of a myofascial trigger spot (MTrS), equivalent to a human trigger point, in rabbit skeletal muscle.

DESIGN

Randomized control trial.

SETTING

A university medical laboratory.

PATIENTS OR OTHER PARTICIPANTS

Nine adult New Zealand rabbits.

INTERVENTION

In the experimental group phentolamine mesylate (1mg/kg) was injected into the external iliac artery, followed by flushing with normal saline. The control group was treated with normal saline instead of phentolamine using the same procedure.

MAIN OUTCOME MEASURES

SEA was recorded from multiple active loci of MTrSs in the biceps femoris muscle: initially SEA in the same locus was recorded before and immediately after phentolamine (or normal saline) injection; then SEA was recorded from 25 different active loci. The mean of the average integrated signal (AIS) of SEA was analyzed, comparing the effects of phentolamine and normal saline on SEA.

RESULTS

In the same active locus, the AIS of SEA showed statistically a linear decay with time after phentolamine injection, with a correlation coefficient of .56 at p < .05. However, no statistical relationship could be derived for the control group data with time by using regression analysis, probably because of large variations among the rabbits and movement artifacts during the experiment. In 25 different loci in the phentolamine group, the mean of the AIS of SEA (7.92 microV) was significantly lower than that of the control group (9.89 microV) at p < .05.

CONCLUSIONS

The results support the hypothesis that the autonomic nervous system is involved in the pathogenesis of myofascial trigger points. The application of the AIS as an evaluation index seems to be feasible in the quantitative measurement of SEA.

Association of active myofascial trigger points and cervical disc lesions

We investigated the occurrence of active myofascial trigger points in specific muscle groups in relation to the existence of cervical disc bulging at various levels. One hundred and five patients (48 men, 57 women; mean age, 45.8 +/- 12.1 yr) who had active trigger points in the neck or upper back after trauma were divided into two groups on the basis of magnetic resonance imaging (MRI) evidence of bulging disc(s). The discN group consisted of 46 patients who had normal MRI findings in the cervical spine. The other 59 patients, with mild cervical disc bulging, were assigned to the disc' group. The correlations between specific muscles with active trigger points (clinical finding) and cervical disc lesions at specific levels (MRI finding) were analyzed. There were significant associations between the level of disc lesion and the muscles with trigger points, namely C3-4 lesions with levator scapulae and latissimus dorsi trigger points; C4-5 lesions with splenius capitis, levator scapulae, and rhomboid minor trigger points; C5-6 lesions with splenius capitis, deltoid, levator scapulae, rhomboid minor, and latissimus dorsi trigger points; and C6-7 lesions with latissimus dorsi and rhomboid minor trigger points. For each disc level, the average pain intensity (assessed using a numerical analog scale) of trigger points in certain correlated muscles (as indicated above) in the disc group was significantly higher than that in the discN group (p < 0.05 for all disc levels). We conclude that active trigger points are more likely to occur in certain muscles in the presence of cervical disc lesions at specific levels.

Myofascial trigger points in intercostal muscles secondary to herpes zoster infection of the intercostal nerve

Chronic pain in the chest wall is a major complication after herpes zoster infection of intercostal nerves. It is usually difficult to control pain of such origin. Two cases are reported of postherpetic neuralgia after herpes zoster infection involving the intercostal nerves. Both patients had shooting, burning, aching, and localized pain in the muscle supplied by the involved intercostal nerves 1 to 3 months after onset. Compression palpation of a tender spot in one of these muscles induced a referred pain that followed the corresponding interspace, usually in the distal anterior direction. Local twitch responses could be elicited during injection of 0.5% or 1% lidocaine into one of these tender spots; the pain in the interspace was consistently eliminated immediately after injection. One patient had complete pain relief after three series of injections. The effect of pain relief for the other patient lasted for 1 to 2 weeks after the initial injection and lasted progressively longer (up to 2 months) after repeated injections. It appears that many of the tender spots formed in intercostal muscles after herpes zoster are myofascial trigger points that respond to injection with referred pain, local twitch responses, and immediate pain relief.

The immediate effectiveness of electrical nerve stimulation and electrical muscle stimulation on myofascial trigger points

This study is designed to investigate the immediate effectiveness of electrotherapy on myofascial trigger points of upper trapezius muscle. Sixty patients (25 males and 35 females) who had myofascial trigger points in one side of the upper trapezius muscles were studied. The involved upper trapezius muscles were treated with three different methods according to a random assignment: group A muscles (n = 18) were given placebo treatment (control group); group B muscles (n = 20) were treated with electrical nerve stimulation (ENS) therapy; and group C muscles (n = 22) were given electrical muscle stimulation (EMS) therapy. The effectiveness of treatment was assessed by conducting three measurements on each muscle before and immediately after treatment: subjective pain intensity [(PI) with a visual analog scale], pressure pain threshold [(PT) with algometry], and range of motion [(ROM) with a goniometer] of upper trapezius muscle (lateral bending of cervical spine to the opposite side). When the effectiveness of treatment was compared with that of the placebo group (group A), there was significant improvement in PI and PT in group B (P < 0.01) but not in group C (P > 0.05). The improvement of ROM was significantly more in group C (P < 0.01) as compared with that in group A or group B. When each group was divided into two additional subgroups based on the initial PI, it was found that ENS could reduce PI and increase PT significantly (P < 0.05), but did not significantly (P > 0.05) improve ROM, as compared with the placebo group for both subgroups. EMS could significantly (P < 0.05) improve ROM, but not PT, better than the placebo groups, for either subgroup. It could reduce PI significantly more (P < 0.05) than placebo controls only for the subgroup with mild to moderate pain, but not with severe pain. For pain relief, ENS was significantly better (P < 0.05) than EMS; but for the improvement of ROM, EMS was significantly better (P < 0.05) than ENS. It is concluded that ENS is more effective for immediate relief of myofascial trigger point pain than EMS, and EMS has a better effect on immediate release of muscle tightness than ENS.

Referred pain elicited by palpation and by needling of myofascial trigger points: a comparison

OBJECTIVE

To investigate the occurrence of referred pain (ReP) elicited by palpation (Pal-ReP) or by needle injection (Inj-ReP) of myofascial trigger point (MTrP), and to assess the correlated factors, including the pain intensity of an active MTrP and the occurrence of local twitch response (LTR).

DESIGN

Correlational study.

PATIENTS

Ninety-five patients who were treated with MTrP injections.

INTERVENTION

MTrP injections.

MAIN OUTCOME MEASURE

Pain intensity of MTrP and occurrence of Pal-ReP, Inj-ReP, and LTR.

RESULTS

Both Pal-ReP and Inj-ReP were elicited in 53.9% of MTrPs, Inj-ReP, but not Pal-ReP, was elicited in 33.7% of MTrPs. Both Pal-ReP and Inj-ReP were unobtainable in 12.3% of MTrPs. The occurrence of ReP was significantly correlated to the pain intensity of active MTrP and the occurrence of LTR.

CONCLUSION

ReP could be elicited more frequently by needling than by palpation. The frequency of occurrence in ReP mainly depends on pain intensity of an active MTrP.

Spontaneous electromyographic potentials in cervical cord-injured patients are related to dysesthetic pain

A total of 61 traumatic cervical cord-injured patients were included in this study. Needle electromyography and nerve conduction study were performed at 6 to 24 weeks postinjury. Correlation between the presence of spontaneous electromyographic potentials and the presence of dysesthetic pain, as well as other clinical characteristics including age, gender, level of injury, severity of injury, spasticity, duration of injury, and performance of spinal surgery was statistically analyzed. Of the 31 patients who had spontaneous electromyographic potentials in their hands, 27 (87%) had dysesthetic pain in their limbs. Only 9 (30%) of the other 30 patients without spontaneous potentials developed dysesthetic pain. A significant correlation (P < 0.001) between the presence of spontaneous electromyographic potential and dysesthetic pain was found. The presence of spontaneous electromyographic potentials was also significantly (P < 0.05) correlated with severity of injury but not with age, gender, injury level, duration of injury, operation, and spasticity. In conclusion, the presence of spontaneous electromyographic potentials in cervical cord-injured patients was significantly related to the presence of dysesthetic pain. They occurred more often in patients with more severe injury.

Interrater reliability in myofascial trigger point examination

The myofascial trigger point (MTrP) is the hallmark physical finding of the myofascial pain syndrome (MPS). The MTrP itself is characterized by distinctive physical features that include a tender point in a taut band of muscle, a local twitch response (LTR) to mechanical stimulation, a pain referral pattern characteristic of trigger points of specific areas in each muscle, and the reproduction of the patient's usual pain. No prior study has demonstrated that these physical features are reproducible among different examiners, thereby establishing the reliability of the physical examination in the diagnosis of the MPS. This paper reports an initial attempt to establish the interrater reliability of the trigger point examination that failed, and a second study by the same examiners that included a training period and that successfully established interrater reliability in the diagnosis of the MTrP. The study also showed that the interrater reliability of different features varies, the LTR being the most difficult, and that the interrater reliability of the identification of MTrP features among different muscles also varies.

Difference in pain relief after trigger point injections in myofascial pain patients with and without fibromyalgia

OBJECTIVE

To compare responses to trigger point (TrP) injection between patients having both myofascial pain syndrome (MPS) caused by active TrPs and fibromyalgia syndrome (FMS) and patients with MPS due to TrPs but without FMS.

DESIGN

Prospective design blinded measurement, before- after trial.

SETTING

A pain control medical clinic.

PATIENTS

Group 1: MPS + FMS; Group 2: MPS only. All patients (9 in each group) had active TrPs in the upper trapezius muscle.

INTERVENTION

Myofascial TrP injection with 0.5% xylocaine.

MAIN OUTCOME MEASURES

Subjective pain intensity (PI), pain threshold (PT), and range of motion (ROM) were assessed before, immediately after, and 2 weeks after TrP injection.

RESULTS

In a comparison of preinjection measures to immediate postinjection measures, only ROM was significantly improved (p < .05) in Group 1 patients; all three parameters were significantly improved (p < .05) in the Group 2 patients who had only MPS. Two weeks after injection, both groups showed significant improvement (p < .05) in all three measured parameters as compared to preinjection measurements. In a comparison of the two groups, the immediate effectiveness of TrP injection was significantly less (p < .05) in Group 1 than in Group 2 for all three parameters. Two weeks after injection, the degree of improvement in PT or ROM (but not PI) was not significantly different between two groups. Postinjection soreness (different from myofascial pain) was more severe, developed sooner, and lasted longer in Group 1 than in Group 2.

CONCLUSION

Trigger point injection is a valuable procedure for pain relief for patients in both group. Patients with FMS are likely to experience significant but delayed and attenuated pain relief following injection of their active TrPs compared to myofascial pain patients with similar TrPs but without FMS. Also, FMS patients are likely to experience significantly more postinjection soreness for a longer period of time.

Splinting and local steroid injection for the treatment of ulnar neuropathy at the elbow: clinical and electrophysiological evaluation

OBJECTIVE

To compare the effects of splinting alone in the treatment of ulnar nerve lesion at the elbow with the effects of applying a local steroid injection in addition to splinting.

DESIGN

Twelve nerves of 10 patients were randomly assigned into two groups: 5 nerves in Group A were treated with elbow splinting only; 7 nerves in Group B were treated with local steroid injection in addition to splinting. Therapeutic effects were assessed 1 and 6 months after treatment.

SETTING

Patients were selected from an outpatient clinic of a VA Medical Center.

PATIENTS

Ten patients (12 nerves) with ulnar neuropathy at the elbow confirmed by electrodiagnostic tests.

INTERVENTIONS

Elbow splint was given to patients of both Groups A and B. A single dose of 40 mg triamcinolone plus 1 mL of 1% lidocaine was injected around the ulnar nerve at the elbow of Group A patients.

MAIN OUTCOME MEASURES

Clinical evaluation of symptoms and signs, and ulnar motor and sensory nerve conduction studies were performed before, 1 month after, and 6 months after treatment.

RESULTS

There was significant improvement in symptoms in both groups at 1 and 6 months after treatment. Ulnar motor nerve conduction velocity across the elbow improved at 1 month in Group A only, but showed improvement at 6 months in both groups. There was no significant change in the other parameters either at 1 or 6 months in both groups. In comparing the differences between Groups A and B regarding the changes at 1 or 6 months after treatment, there was no significant difference between the two groups in all parameters.

CONCLUSIONS

Splint application alone is adequate to improve the symptoms and ulnar nerve conduction across the elbow. The addition of a steroid injection did not provide further benefit in the treatment of cubital tunnel syndrome.

Pathophysiology of myofascial trigger point

Myofascial trigger point is a sensitive spot in a palpable taut band of skeletal muscle fibers. Two important clinical characteristics of trigger points, referred pain and local twitch response, can be elicited by mechanical stimulation (palpation or needling). The trigger point is usually activated by acute or chronic injury to a muscle, tendon, ligament, joint, disc or nerve. Recent human and animal studies have suggested that the pathogenesis of either referred pain or local twitch response is related to integration in the spinal cord. It has been proposed that there are multiple sensitive loci in a trigger point region. A sensitive locus may contain one or more sensitized nociceptive nerve endings. Mechanical stimulation of a sensitive locus can elicit a local twitch response which is frequently associated with characteristic referred pain. Theoretically, sensitive loci can be found in any site of a skeletal muscle, but is usually distributed with highest concentration near the endplate region where a trigger point is frequently found. The trigger point is a common pathogenic pathway of muscle pain from different causes.

Prediction of reflex sympathetic dystrophy in hemiplegic patients by electromyographic study

BACKGROUND AND PURPOSE

This study was designed to investigate the correlation between reflex sympathetic dystrophy syndrome (RSDS) in hemiplegic patients and spontaneous electromyographic (EMG) activity, as well as to determine the predictive value of spontaneous EMG activity in early diagnosis of RSDS.

METHODS

An EMG and nerve conduction velocity study of the weak upper limb was conducted on 70 hemiplegic patients at 3 to 4 weeks after cerebrovascular disease (either cerebral hemorrhage or infarction). Clinical assessment for development of the RSDS was done during the following 6 months. The correlation of RSDS development with the presence of spontaneous EMG activity and certain clinical parameters (including sex, age, side affected, cause of stroke, sensory impairment, spasticity, and shoulder subluxation) was analyzed statistically.

RESULTS

Of the 46 patients who exhibited spontaneous activity, 30 (65%) developed clinical RSDS in their hemiplegic upper extremity, whereas only 1 (4%) of the other 24 patients with no spontaneous EMG activity developed clinical RSDS within 6 months after the onset of hemiplegia (P < .001). The correlation of RSDS development with the presence of shoulder subluxation and sensory impairment in the hemiplegic side was statistically significant. Neither age, sex, severity of spasticity, nor etiology of stroke had a significant correlation with the development of clinical RSDS.

CONCLUSIONS

There is significant correlation between the presence of spontaneous EMG activity and the development of clinical RSDS in the hemiplegic upper extremity after stroke. It is concluded that spontaneous EMG activity in the hemiplegic hands of stroke patients might be a good predictor of the future development of clinical RSDS.

Most dorsal root ganglion neurons of the adult rat survive nerve crush injury

Severe crush of the rat sciatic nerve does not result in any significant cell death among motor neurons (Swett et al., 1991a). The present study reports on the survival of the dorsal root ganglion (DRG) neurons in the same experiments. From 15 to 187 days after crush of the left sciatic nerve, the common peroneal or sural nerve was cut and labeled distal to the injury with a mixture of horseradish peroxidase (HRP) and its wheatgerm agglutinin conjugate (WGA:HRP). In other cases, the crush injury was made far enough distally on a peroneal or sural branch to permit labeling several millimeters proximal to the injury. The procedures for reconstructing the regenerated DRG neuron populations were identical to those used in an earlier study describing the normal sciatic DRG neuron populations in the rat (Swett et al., 1991b). The normal peroneal nerve contains 2699 +/- 557 DRG neurons. When the peroneal nerve was crushed near its point of origin from the sciatic and labeled 10 mm distal to the injury, 2186 +/- 163 DRG neurons were counted, suggesting a decrease of about 19% (p < 0.01). However, when the entire sciatic nerve was crushed, distal labeling of the peroneal nerve revealed a mean number of 2578 +/- 291 DRG neurons, an insignificant reduction (p > 0.2). When the peroneal nerve was labeled proximal to a peroneal crush site, a similar number of DRG neurons (2563 +/- 412) was counted. Results following sural nerve crush were similar. The sural nerve normally contains 1675 +/- 316 DRG neurons. When the nerve was labeled distal to the injury, 1558 +/- 64 DRG neurons were counted--a number almost identical to that found (1529 +/- 240) when this nerve was labeled proximal to the injury. The results demonstrate that within 6 months of severe crush injury of the rat sciatic nerve, the vast majority of DRG neurons survive and regenerate new axons distally beyond the injury site, presumably to reinnervate their original targets.

Lidocaine injection versus dry needling to myofascial trigger point. The importance of the local twitch response

This study was designed to investigate the effects of injection with a local anesthetic agent or dry needling into a myofascial trigger point (TrP) of the upper trapezius muscle in 58 patients. Trigger point injections with 0.5% lidocaine were given to 26 patients (Group I), and dry needling was performed on TrPs in 15 patients (Group II). Local twitch responses (LTRs) were elicited during multiple needle insertions in both Groups I and II. In another 17 patients, no LTR was elicited during TrP injection with lidocaine (9 patients, group Ia) or dry needling (8 patients, group IIa). Improvement was assessed by measuring the subjective pain intensity, the pain threshold of the TrP and the range of motion of the cervical spine. Significant improvement occurred immediately after injection into the patients in both group I and group II. In Groups Ia and Ib, there was little change in pain, tenderness or tightness after injection. Within 2-8 h after injection or dry needling, soreness (different from patients' original myofascial pain) developed in 42% of the patients in group I and in 100% of the patients in group II. Patients treated with dry needling had postinjection soreness of significantly greater intensity and longer duration than those treated with lidocaine injection. The author concludes that it is essential to elicit LTRs during injection to obtain an immediately desirable effect. TrP injection with 0.5% lidocaine is recommended, because it reduces the intensity and duration of postinjection soreness compared with that produced by dry needling.

Persistence of local twitch response with loss of conduction to and from the spinal cord

A local twitch response (LTR) is a brisk contraction of a taut band of skeletal muscle fibers elicited by snapping palpation of a trigger point (TrP) in that band. The LTR is a clinically valuable objective sign that confirms the presence of a myofascial TrP. A transient burst of electromyographic (EMG) activity can be recorded from taut band fibers when an LTR is elicited by snapping palpation of TrP. A previous study of the human extensor digitorum muscle during ischemia suggested that both central and local pathways can be involved in the propagation of LTRs. In this study, EMG activity of LTRs in the third finger extensor muscle were recorded bilaterally in a patient with a unilateral brachial plexus lesion. This patient had complete loss of nerve conduction involving the posterior cord of the right brachial plexus as confirmed by EMG and nerve conduction studies and by neurological examination at 6 months after injury. EMG activity (measured as discharge duration and maximal amplitude) on the paralyzed side was significantly reduced (p < 0.01) as compared with the unaffected side, but had not disappeared. Three more studies were done at 7, 8, and 17 months after injury when the motor and sensory functions were recovered progressively. The EMG activity of LTRs recovered on the paralyzed side in parallel with the motor and sensory recovery. These findings indicate that the transmission of LTR depends mainly on the central nervous system with a possible minor degree of local transmission.

Conduction of the dorsal digital branches of the radial nerve to the long finger

Orthodromic conduction of the radial nerve digital branches to the third digit from the anatomic snuffbox has rarely been described. This paper describes a technique for measuring conduction of the lateral and medial digital branches of the radial nerve to the third digit at a distance of 10cm from the base of the digit to the anatomic snuffbox. An evoked response from the lateral digital branch was recorded in each of the 56 nerves tested. Responses had an average latency of 2.10 +/- .18msec. Responses from the medial digital branches of the nerve were obtained in only 55% of the 49 nerves tested. Responses had an average latency of 2.11 +/- .21msec. When no appreciable response was recorded at the anatomic snuffbox from the medial digital branch, a response was recorded from the ulnar nerve at the volar wrist at 14cm.

All peroneal motoneurons of the rat survive crush injury but some fail to reinnervate their original targets

This is a quantitative study of the motoneuronal population of the rat's common peroneal nerve following severe crush injury of the sciatic nerve or its component branches. The crush was performed unilaterally under anesthesia for 60 seconds with hemostat jaws covered with tubing to form a smooth, 2 mm long, injured zone. Recovery from injury was allowed for 14 to 188 days. It was measured behaviorally using the sciatic functional index (SFI) and electrophysiologically by comparing the conduction velocity and amplitudes of evoked muscle action potentials prior to injury, and again after injury just before the nerve was labeled with horseradish peroxidase (HRP), and/or its wheat germ agglutinin conjugate (WGA-HRP), 48-72 hours before sacrifice. The motoneurons were retrogradely labeled on both sides so that the uninjured side might serve as a control. On the injured side the nerves were labeled either distal or proximal to the crush site. The tibialis anterior muscles on both sides were removed and weighted. Spinal segments L2 to L6 were cut in serial, frozen cross-sections. HRP reaction products were formed using TMB as the chromogen. The normal peroneal nerve was found to contain 634 +/- 26 motoneurons (22 cases). The number of motoneurons labeled 5-15 mm distal to the injury site (22 cases) was 535 +/- 69 or 84.4% of normal. In 12 cases in which the nerve was labeled 5 mm proximal to the injury normal population numbers (648 +/- 30) were found. These counts demonstrated that the unlabeled 15.6% in the distal labeled cases had not vanished as a result of cell death. Instead, the unlabeled group was composed mainly of small motoneurons whose axons probably had not regenerated distal to the crushed zone. Mean soma size of injured neurons increased to maximum 3-6 weeks after injury and then gradually decreased in size over the following weeks to nearly normal values. This transient increase in size was due to two factors: 1) soma swelling in response to axonal injury, and 2) absence of many small motoneurons, presumably gamma-motoneurons, which were either incapable of, or prevented from, regenerating beyond the injury zone long after larger motoneurons had reinnervated their targets. SFI scores, muscle weights, and amplitude ratios of evoked potentials recovered to control values by 70-80 days post-injury. Conduction velocities remained 20-25% below normal at the end of 80 days.(ABSTRACT TRUNCATED AT 400 WORDS)

Reversible nerve conduction block in patients with polyneuropathy after ultrasound thermotherapy at therapeutic dosage

This study investigated the effect of ultrasound on nerve conduction in patients with polyneuropathy. Eight able-bodied controls (Group C) and 16 patients with clinical and physiologic evidence of polyneuropathy were tested. Eight patients (Group NP) had no aching pain symptoms; eight patients (Group P) had severe aching pain, burning sensation, unpleasant tingling, and/or hyperesthesia in the lower extremities. For two minutes, therapeutic ultrasound in doses of 0.5, 1.0, and 1.5W/cm2 were applied over the anterior surface of the leg along the pathway of the deep peroneal nerve. Peroneal nerve conduction studies were performed before, during, and after ultrasound treatment. The compound muscle action potential (CMAP) was recorded from the extensor digitorum brevis muscle. Nerve conduction studies on all eight patients in Group P revealed a significant decrease (41.4% and 44% reduced for doses of 1.0W/cm2 and 1.5W/cm2, respectively; p less than .05) in amplitude of CMAP (from baseline to the first negative peak), and an increase (6.4% and 6.7% increased for doses of 1.0W/cm2 and 1.5W/cm2, respectively; p less than .05) in proximal latency one minute after ultrasound application with a dose of 1.0 or 1.5W/cm2, but not with a dose of 0.5W/cm2 (p greater than 0.1). Changes returned to pretreatment values within five minutes of cessation of ultrasound therapy. In Groups C and NP, there were no significant changes in amplitudes of CMAP or proximal latency before, during, or after ultrasound therapy at a dose of 0.5, 1.0, or 1.5W/cm2. It was concluded that ultrasonic therapy with therapeutic dosage may cause a reversible conduction block on patients with painful polyneuropathy.

Short-term exposure to a 1.5 tesla static magnetic field does not affect somato-sensory-evoked potentials in man

The literature is contradictory regarding the effect of static magnetic fields on the function of the central nervous system of mammals. Since human subjects are exposed to intense static magnetic fields during magnetic resonance imaging, it is important to determine if the static magnetic field adversely affects the nervous system of man. Therefore, somato-sensory evoked potentials (SEPs) elicited from median nerve stimulation were measured in 11 normal subjects before and during short-term exposure to a 1.5 Tesla static magnetic field. Specially modified instrumentation was used to record SEPs that were unperturbed by the static magnetic field. There were no statistically significant differences in the N20 or P25 latencies or in the amplitude from N20 negative peak to P25 positive peak of the SEPs obtained before compared to those recorded during exposure to the static magnetic field. In addition, there were no changes in the waveforms associated with exposure to the static magnetic field. We conclude that short-term exposure to a 1.5 Tesla static magnetic field does not affect SEPs (i.e., nerve conduction and synaptic transmission were within normal limits) in normal human subjects.

Local steroid injection: its effect on the recovery of nerve conduction in experimental neuropathy

This study was designed to investigate the effectiveness of local steroid injection on the recovery of nerve conduction in acute compression neuropathy. Experimental neuropathy with complete conduction block was produced by mechanical compression of the caudal nerves of 24 rats. Five days after compression, the compression site was injected with 0.2 mL Dexamethasone acetate (8 mg/mL suspension) in eight rats (group A), and 0.2 mL normal saline in another eight rats (group B). The remaining eight rats (group C) received no injection. Motor nerve conduction velocity (NCV) over the compressed segment, as well as amplitude of the evoked compound muscle action potential (CMAP) recorded from the segmental tail muscles, were measured before nerve compression and three times per week after nerve compression. The recovery rates of NCV of the caudal nerve were not significantly different among the three groups. The recovery rate of amplitude of CMAP in group A was significantly higher than that in groups B or C (p less than 0.01). However, there was no significant difference in recovery rate of the amplitude of CMAP between groups B and C. It is concluded that local steroid injection to the site of nerve compression may facilitate the recovery of nerve conduction block but not the recovery of demyelinative lesion.

Peroneal nerve entrapment at the knee localized by short segment stimulation

The purpose of this study was to evaluate the usefulness of short segment stimulation (SSS) of the peroneal nerve at the knee in order to localize the site of compression and/or entrapment of the nerve. Eighteen patients with suspected peroneal nerve palsy and 28 controls were studied by SSS of the peroneal nerve across the knee. Compound muscle action potentials (CMAPs) were obtained from the extensor digitorum brevis muscle after successive supramaximal stimuli of the nerve at 2 cm intervals, starting 4 cm distal (D4 and D2) and ending 6 cm proximal (P2, P4, and P6) to the fibular head prominence (P). In patients the average conduction times from D2 to P, P to P2, and P2 to P4 were significantly (P less than 0.05) longer and the average amplitude of CMAPs at P, P2, P4, and P6 significantly (P less than 0.05) lower than those of controls. Fourteen patients showed statistically significant reduction in amplitude and prolongation of conduction time in one or more short segments. Three patients had prolongation of conduction time only and one patient had reduction in amplitude only. When nerve conduction of the entire 10-cm segment across the knee was tested by the conventional method, only nine showed reduction in amplitude from proximal stimulation, or slowing of motor conduction velocity across the 10-cm segment or both. It was concluded that the SSS technique is a sensitive and reliable procedure for the detection of mild compression or entrapment of the peroneal nerve around the knee.

Increased skin temperature after vibratory stimulation

The skin temperature effect of vibratory stimulation was studied in 28 healthy subjects. Vibration (50 Hz or 100 Hz) was applied to the volar surface of the left forearm for 15 min. Skin temperature of the bilateral forearms was measured before and immediately after cessation of vibration and at 5 and 10 min postvibration. Vibration at 100 Hz for 15 min on all 28 subjects was associated with a temperature increase of 4.20 +/- 0.79 degrees F that was significantly (P less than 0.01) higher than that in the controls (0.38 +/- 0.33 degrees F). Skin temperature decreased to previbration levels by 50 min of postvibration. The 11 subjects who received 50-Hz vibration for 15 min showed a skin temperature increase (0.75 +/- 0.23 degrees F) in the vibrated forearm significantly (P less than 0.01) higher than that in the control forearm (0.11 +/- 0.17 degrees F). All measurements decreased to previbration skin temperatures by 10-min postvibration. Vibration at 100 Hz also produced skin erythema in all subjects, whereas 50-Hz vibration produced no erythema. The mechanism by which 100-Hz vibration relieves pain is largely unclear, but it could be associated with increased skin temperature and erythema.

Early smooth horizontal eye movement: a favorable prognostic sign in patients with locked-in syndrome

Locked-in Syndrome (LIS) is a rare clinical entity consisting of quadriplegia, paralysis of lower cranial nerves, mutism, and bilateral paresis of horizontal gaze. The prognosis is usually poor. Most patients who do survive have severe residual impairment or develop chronic LIS. Review of the literature shows that recovery has been reported but not systematically studied, particularly with respect to early prognostic signs. We report a case of LIS with bilateral pontine infarctions shown by MRI. Severe neurological deficits included quadriplegia, paresis of horizontal gaze, facial paralysis, and bulbar palsy. Horizontal eye movements were present and smooth by the second week after onset. The patient had almost full functional motor recovery within four months, after a comprehensive rehabilitation program. Fourteen other reported cases of LIS with full recovery had documented recovery of lateral gaze in the early stage. In addition, smooth horizontal gaze is the most frequent activity in incomplete LIS. Early recovery of horizontal eye movement may indicate that the brain lesion is limited and may be a good prognostic sign in LIS.

Electrophysiologic recovery of acute conduction block of rat tail nerve

The recovery of experimental compression neuropathy with prolonged conduction block of the caudal nerve was studied electrophysiologically in 48 adult Sprague-Dawley albino rats divided equally into six groups. The pressure applied in groups A, B, C, D, E, and F was approximately 20kg/cm2 for 20 minutes, 20kg/cm2 for 10 minutes, 20kg/cm2 for 5 minutes, 10kg/cm2 for 20 minutes, 20kg/cm2 for 10 minutes, and 10kg/cm2 for 5 minutes, respectively. The motor nerve conduction velocity (NCV) and the amplitude of the evoked compound muscle action potential (CMAP) were measured before and periodically after nerve compression. The period of initial complete block was significantly longer in the high pressure groups than in the lower ones, and also significantly longer in the nerves compressed for 20 minutes than for those compressed for five or ten minutes. Thus, the severity of conduction block seems to be related to both pressure and duration of compression. Once the conduction block began to recover, the recovery rate of conduction block (recovery rate of amplitude ratio of CMAP, proximal/distal) was not significantly different. The recovery rate of demyelinative lesion (NCV recovery rate) was also not significantly different among the six groups. The degree of compression seems to determine the severity of the initial conduction block, but not the subsequent recovery rate of conduction.

Averaged axillary F-loop latency of median and ulnar nerves

Axillary F-loop latencies (AFLL) were measured on median and ulnar nerves of 54 normal volunteers. The median and ulnar nerves were stimulated at the wrist and at the axilla 25cm distal to the sternal notch. The compound muscle action potentials were recorded from thenar and hypothenar muscles. Averaged tracings from 32 consecutive stimuli at the wrist were obtained. The averaged F-wave latencies were measured to the peak (Fwp) of the averaged F-wave. The M-wave latencies from wrist and axilla stimulation were measured to the onset of the wave (Mw and Ma, respectively). The averaged AFLL (a-AFLL) was calculated as (Fwp + Mw)-2 Ma. The average values of a-AFLL were 14.12 +/- 0.88msec for median nerve, and 13.97 +/- 0.90msec for ulnar nerve. There was no significant difference between male and female subjects, nor between the right and left sides. Seven subjects with EMG evidence of C8 or C8 to T1 radiculopathy, although manifesting normal AFLL gauged by the regular method (ie, measured to the onset of the shortest F-wave latency among eight tracings), had significantly longer "averaged AFLL" in both median and ulnar nerves of the affected side than the a-AFLL obtained from the normal side. It is concluded that the a-AFLL is a more sensitive measure than the "regular AFLL" in the assessment of proximal nerve lesion (especially C8 or C8 to T1 radiculopathy).

Averaged F-wave conduction velocity of peroneal nerve

Averaged F-wave conduction velocities (a-FWCV) of peroneal nerve were measured on 38 healthy volunteers and 22 patients with clinical and electromyographic evidence of unilateral L5 or L5 + S1 radiculopathy. The peroneal nerve was stimulated supramaximally at the fibular head and the compound muscle action potential was recorded from the extensor digitorum brevis muscle. Averaged tracings from 32 consecutive stimuli were obtained. The averaged F-wave latency (Fp) and M-wave latency (Mp) were measured from the stimulating artifact to the peak of the waves. The distance (D) between the stimulating point and the T12 spinous process was measured. The value of a-FWCV was calculated as 2D/(Fp-Mp-1) m/second. In normal subjects, the average value of a-FWCV was 56 +/- 4, and there was no significant difference between males and females, nor between the right and left sides. The differences among the tests administered at different times on the same subject were also statistically insignificant. Of the 22 patients, 17 had subnormal value of a-FWCV if the lower normal limits were defined as mean minus 2.5 SD (i.e., 46 m/second) calculated from the normal control value. However, only one of them had subnormal value of FWCV calculated by the conventional method (without averaging technique). All the patients with two root (L5 + S1) involvement had subnormal a-FWCV. It is concluded that the a-FWCV is a more sensitive measure than the conventional FWCV in the assessment of L5 radiculopathy.

Ultrasound thermotherapy effect on the recovery of nerve conduction in experimental compression neuropathy

Bilateral tibial nerves of 18 albino rats were mechanically compressed between knee and ankle. Beginning on the fifth day after compression, ultrasound thermotherapy of 0.5 or 1.0watt/cm2 was applied over the area of nerve compression in one limb for one minute three times per week. The other side (control) was not treated. Motor distal latency (DL), motor nerve conduction velocity (NCV) of the segment with nerve compression, and amplitude of the evoked compound muscle action potential (ACMAP) were measured before and immediately after nerve compression and two or three times per week after compression. The recovery rates of NCV and ACMAP of the tibial nerve treated with ultrasound of 0.5watt/cm2 were significantly faster than those of the control nerve. There was no significant change in the recovery rate of DL. However, if ultrasound of 1.0watt/cm2 was applied, the recovery rate of ACMAP of the treated nerve was slower than that of the control nerve. There were no significant changes in the recovery rates of DL and NCV. Low doses of ultrasound thermotherapy may facilitate recovery of compression neuropathy, but higher doses may induce an adverse effect.

Electrophysiologic studies of the median nerve and its palmar cutaneous branches after nerve grafting

Electromyography (EMG) and nerve conduction studies were performed on a patient with an incomplete lesion of the median nerve involving the motor fibers to the thenar muscles, the palmar cutaneous branches, and the sensory fibers to the index finger. The studies were done before, and 13 weeks, 16 weeks, and one year after grafting. The preoperative electrodiagnostic evaluation showed abnormalities involving the median motor fibers and the palmar cutaneous branch. Electromyography of the opponens pollicis and abductor pollicis brevis before surgery showed severe active denervation. Thirteen weeks after nerve grafting, the median motor distal latency was prolonged and the amplitude of the evoked potential of the median motor and index finger digital sensory nerves were decreased. At 16 weeks, both the latency and amplitude showed improvement, as did EMG of the affected muscles. One year later, the electrophysiologic findings were normal except for a slightly prolonged median motor distal latency. Clinical and functional improvement after grafting correlated well with the electrophysiologic findings. We conclude that EMG and nerve conduction studies are useful tools for following the progression of recovery after nerve grafting.

Learning ability of young rats is unaffected by repeated exposure to a static electromagnetic field in early life

Infant albino rats were exposed to a static electromagnetic field of 0.0 Tesla (control) or 0.5 Tesla (experimental) for 14 postnatal days. Following a 1-month rest period, the experimental (13 males and 10 females) and control (11 males and 14 females) rats were trained on four successive reversals of a position habit in a single-unit enclosed T-maze that was adapted for the use of escape-avoidance of mild foot shock as a motive. There was no significant difference in learning ability between the experimental and control groups in terms of total (initial combined with repetitive) errors committed over the four reversal problems. While the females tended to make more errors than the males, this difference was likewise insignificant.

Rehabilitation in dual disability of hemiplegia and upper extremity amputation: two case reports

Dual disability involving amputation and hemiplegia is relatively rare. The vast majority of these cases involve lower extremity amputations. In this report two patients sustained a right-sided hemiplegia complicating an old left upper extremity amputation. Through the comprehensive rehabilitation program these two patients were able to make gains, especially in some activities of daily living and in lower extremity functions. Since some of the upper extremity activities, such as dressing or bathing, could not be accomplished, it appears that patients with upper extremity amputation who have a contralateral hemiplegia have a poorer prognosis for achieving functional independence than patients with lower extremity amputation and similar neurologic loss.

Static magnetic field influence on human nerve function

In an attempt to understand the possible neural mechanism mediating the effects of a static magnetic field (SMF), nerve conduction velocity (NCV) and excitability index (EI), measured as the ratio of the amplitude of the submaximally evoked compound muscle action potential during or after magnetic exposure to that before exposure from the same intensity of stimulation of the motor nerve, were studied on ten normal volunteers (aged 17 to 39), when the nerve was exposed to an SMF of 1 tesla (T) for 15 seconds. NCV and EI were measured before, during (5, 10, and 15 sec) and three minutes after magnetic exposure. Both NCV and EI were measured on median nerve in all ten subjects, the peroneal nerve in seven subjects, while the ulnar nerve was measured for only EI in eight subjects. There was no significant change in NCV over the segment exposed to the magnetic field. However, EI was significantly increased during the magnetic exposure in all three nerves. The effects were observed as early as five seconds after exposure and disappeared by three minutes after exposure. It is concluded that the excitability of the motor nerve is increased when it is exposed to an SMF with a density of 1T.

Static magnetic field influence on rat tail nerve function

Motor nerve conduction and excitability were measured on the tail nerve of anesthetized rats before and after the nerve was exposed perpendicularly to a static electromagnetic field of various intensities and durations. There was no significant change in either the distal latencies or the amplitudes of the compound muscle action potential (CMAP) measured from stimulating the tail nerve after it was exposed to the electromagnetic field with a density up to 1.2 Tesla (T) for a duration of 60 seconds. However, the nerve excitability expressed as changes of the amplitudes of the submaximally evoked CMAP increased significantly when the tail nerve was exposed to a magnetic field with a density higher than 0.5T for more than 30 seconds. The finding that an electromagnetic field increases motor nerve excitability suggests a possible mechanism of its therapeutic effects.

Cervical radiculopathy. Clinical, radiographic and EMG findings

This retrospective study reviewed clinical, radiographic, and electromyographic (EMG) findings in 108 patients with cervical radiculopathy. Radiographic evaluation included measurements of the size of the intervertebral foramina and the space for the intervertebral disk. The results showed that the clinical findings correlated well with the EMG abnormalities but not with the radiographic findings. The extent of the intervertebral foramen and the disk space narrowing correlated poorly with the severity of EMG abnormalities. It is suggested that radiographic findings alone may be an inadequate basis for a diagnosis of cervical radiculopathy. EMG examination may be very helpful in such a diagnosis and may be more accurate in assessing radiculopathy than the plain films in certain cases.

Geophysical variables and behavior: XXVII. Magnetic necklace: its therapeutic effectiveness on neck and shoulder pain: 2. Psychological assessment

The efficacy of magnetic necklaces (maximum static magnetic field 0.13 T) in controlling chronic neck and shoulder pain was studied. A double-blind experiment was performed on four groups of human adults (Total N = 101). The experimental design involved 52 subjects with chronic pain (35 women, 17 men) and 49 without symptoms of pain (20 women, 29 men). They were assigned in near-equal numbers into subgroups in which magnetic or nonmagnetic necklaces were worn 24 hr. a day for 4 wk. Subjective reports and psychological testing indicated that there were no statistically significant differences among treatment subgroups before treatment. Subjects in the pain group reported a statistically significant reduction in frequency and severity of pain immediately after treatment. However, treatment condition (magnetic vs nonmagnetic) did not significantly affect subjective reports, indicating that the reported improvement is attributable to the placebo effect.

Metabolic effects of exhaustive training of athletes

Sixteen athletes (11 men, 5 women), averaging 21 years of age, were studied before and after four weeks of daily exhaustive exercise (six days/week) during an endurance training course. In comparing blood chemistries before and after training, concentrations of blood glucose, total serum lipids, serum triglycerides, and serum cholesterol were significantly reduced; serum free fatty acid ( SFFA ) level was significantly increased; and serum protein and serum phospholipid concentrations remained unchanged. It was concluded that exhaustive training produces reduced blood glucose (but not clinically significant hypoglycemia) with increased fat utilization as a result of depletion of carbohydrate storage and that such training reduces the resting levels of serum cholesterol and serum triglycerides. The increased hematocrit, serum Na+, and serum K+ concentrations observed were presumably due to plasma water loss from excessive perspiration. Concentrations of blood urea nitrogen (BUN) and serum glutamic-oxaloacetic transaminase (SGOT) were increased significantly; serum glutamic-pyruvic transaminase (SGPT) and serum creatinine showed no significant changes. None of the athletes showed evidences of water-electrolyte deficiency syndrome, renal dysfunction, or liver cell damage, despite a persistent mild degree of dehydration and catabolic state noted after training.

Magnetic necklace: its therapeutic effectiveness on neck and shoulder pain

The effect of the magnetic necklace on chronic neck and shoulder pain was studied on 101 volunteers, 46 males and 55 females. A double-blind method was applied on 4 divided groups (with pain vs without pain matched with magnetic vs nonmagnetic necklace). All the subjects wore the necklace 24 hours per day for 3 weeks. Subjective evaluation from the subjects with pain, either with magnetic or nonmagnetic treatment, was performed before and 3 weeks after the necklace treatment, and revealed a significant placebo effect in terms of decrease in intensity or frequency of pain. The objective tests with electrodiagnostic procedures were done before the treatment and at 3 weekly intervals. The proximal conduction time of the ulnar nerve was significantly reduced by magnetic treatment in the subjects without pain but was not changed in the subjects with pain. There was no significant change in the excitation threshold of the suprascapular nerve in all subjects. The possible mechanism of magnetic effects on pain and the prospect of magnetotherapy for pain relief in physical medicine are discussed.

Axillary F-loop latency of ulnar nerve in normal young adults

F waves were studied with stimulation of the ulnar nerve in normal subjects (25 men and 15 women, with an average age of 26.5 years) using an EMG machine that permits the simultaneous display of 8 sweeps. The axillary F-loop latency (AFLL), defined at the conduction time between the axilla (25cm from the sternal notch) and the spinal cord, was 9.17 +/- 0.81msec when 8 F responses were measured but was 8.57 +/- 1.00msec when 40 F responses were used. Data from men and women showed no significant statistical difference. The mean plus 2 standard deviations were 10.8 and 10.6msec for 8 and 40 responses, respectively. On the basis of these findings, an AFLL longer than 11msec should be considered abnormal in the young adult. Four measures repeated at weekly intervals showed no significant difference from week to week, indicating that the technique can be consistently and reliably applied at different times. The average duration of the F complex was 15.78 +/- 2.55msec and was about 80% of the average duration of the M wave.