Entrapment neuropathy in patients with spastic cerebral palsy

OBJECTIVES: We performed nerve conduction and needle electromyographic tests in 29 patients with spastic cerebral palsy (SCP) and severe limb deformities. Nerve conduction abnormalities were detected in 32 of 400 sensory or motor nerves, while 11 of 29 patients (37.9%) showed abnormal nerve conduction, indicating one or more entrapment neuropathies. Patients with SCP develop severe joint contractures and deformities due to spastic muscle tone and limited muscle and joint use/flexibility; these contractures and deformities can, in turn, cause nerve damage, possibly as a result of the stretching, angulation or compression mechanisms in the anatomic fibro-osseous passages, where nerves are particularly susceptible.     

Usefulness of electrodiagnostic techniques in the evaluation of suspected tarsal tunnel syndrome: an evidence-based review

This evidence-based review was performed to evaluate the utility of nerve conduction studies (NCSs) and needle electromyography (EMG) in the diagnosis of tibial neuropathy at the ankle (tarsal tunnel syndrome, TTS). A total of 317 articles on TTS were identified that were published in English from 1965 through April 2002, from the National Library of Medicine MEDLINE database. All articles were reviewed on the basis of six selection criteria. The results of this search revealed that four articles met five or more criteria. All four articles examined the use of electrodiagnostic (EDX) techniques for the evaluation of patients with clinically suspected TTS, and were included in this practice parameter. Each of these four studies was considered to meet Class III level of evidence. NCSs were abnormal in some patients with suspected TTS. Sensory NCSs were more likely to be abnormal than motor NCSs but the actual sensitivity and specificity could not be determined. The sensitivity of needle EMG abnormalities could not be determined. NCSs may be useful for confirming the diagnosis of tibial neuropathy at the ankle, recommendation Level C. Well-designed studies are needed to evaluate more definitively EDX techniques in TTS.     

Gender, muscle, and velocity comparisons of mechanomyographic and electromyographic responses during isokinetic muscle actions

The purpose of this study was to examine the responses of peak torque (PT), mean power output (MP), mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) in males and females during maximal, concentric isokinetic muscle actions. Subjects performed maximal leg extensions at 60 degrees s(-1), 120 degrees s(-1), 180 degrees s(-1), 240 degrees s(-1), 300 degrees s(-1), 360 degrees s(-1), 420 degrees s(-1), and 480 degrees s(-1). No gender differences were observed, but there were muscle-specific differences for the patterns of MMG MPF, EMG amplitude, and EMG MPF. The MP and MMG amplitude increased to 180-240 degrees s(-1), plateaued, and then decreased to 480 degrees s(-1). MMG MPF for the VL and VM remained unchanged to 300 degrees s(-1), but then increased to 480 degrees s(-1). The EMG amplitude for the RF and EMG MPF for the VL decreased across velocity. Overall, these findings indicated that there were muscle-specific, velocity-related differences in the associations among motor control strategies (EMG amplitude and MPF) and the mechanical aspects of isokinetic muscular activity (MMG amplitude and MPF).     

Single fiber electromyography in 78 patients with amyotrophic lateral sclerosis

Background Single fiber electromyography (SFEMG) is a sensitive technique for detecting abnormalities in neuromuscular transmission and is mainly used in the diagnosis of neuromuscular junction disorders, such as myasthenia gravis. While the process of denervation-reinnervation in amyotrophic lateral sclerosis (ALS) can also result in immature collateral nerve terminals and instability of neuromuscular transmission, the purpose of this study was to investigate the changes and clinical values of SFEMG in patients with ALS.Methods Volitional SFEMG was performed on the extensor digitorum communis (EDC) of 78 patients with ALS (men 52, women 26) who had been previously diagnosed by history, clinical features, and neurophysiological studies. The mean jitter, the percentage of jitter >55 μs, the impulse blocking percentage, and fiber density (FD) were determined. These results were compared to normal controls. In addition, the SFEMG indices were analyzed for correlations with the duration of ALS, the EDC strength score on the Medical Research Council (MRC) scale, and spontaneous activity detected by EMG studies. Results SFEMG indices were abnormal in all patients with ALS. Mean jitter ranged from 30 to 178 μs (mean 80.2 μs); the percentage of jitter >55 μs ranged from 5% to 100% (mean 60.5%). In addition, the impulse blocking percentage ranged from 0% to 90% (mean 28.1%) and FD ranged from 1.4 to 4.1 (mean 2.6). Mean jitter, the percentage of jitter >55 μs, and the blocking percentage in 57 patients with definite or probable ALS were significantly higher than in patients with possible or suspected ALS. MRC scores of the EDC negatively correlated with mean jitter, the percentage of jitter >55 μs, blocking percentage, and FD. Conclusions SFEMG is the most sensitive tool for diagnosing definite or probable ALS. Increased jitter, blocking percentage, and FD can indicate the degree of immature collateral sprouts and motor end plates resulting from the progressive denervation and reinnervation associated with ALS, and may be helpful in evaluating prognosis.     

Sphincter electromyography in diagnosis of multiple system atrophy: technical issues

Possible technical reasons for the controversy over the role of sphincter electromyography (EMG) in the diagnosis of multiple system atrophy (MSA) were analyzed. In a review of the literature, a high sensitivity (>60%) was found reported in 11 studies that included late components, and no value of the test was found in 4 studies that excluded them. This was also corroborated in a pilot study of 5 patients with probable MSA. With late components included, the mean motor unit potential (MUP) duration was prolonged in all 4 patients with an adequate single-MUP analysis sample and, with late components excluded, in 2 of 5 patients on multi-MUP analysis. At least in diagnostic EMG of MSA patients, late components should be included in the measurement of MUP duration.     

Clinical utility of electrodiagnostic consultation in suspected polyneuropathy

Although paresthesias of the distal lower limbs are characteristic features of polyneuropathy, they may also herald the presence of a focal neuropathy, polyradiculopathy, or myelopathy. Electromyography and nerve conduction studies (EMG/NCS) are widely used in the evaluation of such symptoms, but their utility has not been subjected to vigorous scrutiny. We investigated the clinical impact of the electrodiagnostic consultation in assessing suspected polyneuropathy. When compared with the clinical impression, the result of the electrodiagnostic consultation was confirmatory in only 39% of all patients, and changed the diagnosis or uncovered an additional diagnosis in 43%. An alternative diagnosis was likely when either weakness was present (75%) or the Achilles stretch reflex was preserved (48%). These data support the use of EMG/NCS in the diagnostic evaluation of patients presenting with distal paresthesias, especially in those with preserved Achilles reflexes or motor deficits.     

Reperfusion response changes induced by repeated,sustained contractions in normal human masseter muscle

The purpose was to evaluate the intramuscular reperfusion response characteristics associated with repeated isometric contractions in normal human masseter. Intramuscular blood volume was quantified with a near-infrared spectroscopic device that measured the total haemoglobin (Hb) concentration in the muscle. Electromyographic (EMG) activity from the masseter and total bite forces were also recorded. Sixteen healthy volunteers, eight females and eight males, without masticatory muscle pain participated. They were asked first to clench their teeth for as long as possible at 50% of their maximum voluntary contraction (MVC). This was followed by a 60s rest and then immediately by a standard clenching task (50% MVC for 30s) and a 60s recovery period, immediately after which they were asked to repeat exactly the same procedure, with a final 5 min recovery period after the second 30s contraction. Bite force, EMG and Hb concentration were measured continuously and the duration of the two endurance tasks and the amplitudes of all recorded signals were compared (first trial versus second trial). Specifically, the difference between the lowest Hb (trough) seen during the standardised 30s contractions and the highest (peak) seen just after them was assessed. The trough-to-peak difference in Hb concentration of the second standard contraction task was significantly smaller than that of the first standard task (P<0.05, paired t-test). These data show that with sustained effort the post-contraction vasodilatory reperfusion responses of the human masseter are diminished, suggesting a progressive desensitisation of the vasodilatory system.     

A physiotherapeutic approach to craniomandibular disorders: a case report

This is a case report of a 19-year-old female who presented with a unilateral weakness of the right masseter muscle evidenced by electromyographic examination. The presence of a mandibular deviation to the right during opening because of this weakness was treated with neuromuscular electrical stimulation (NMES). After the physiotherapeutic treatment, the electrical activity of the right masseter muscle increased during function and the mandibular deviation disappeared. Electromyography (EMG) can have a useful role in the determination of the muscular profile, and for evaluating therapeutics.     

Literature review of the usefulness of repetitive nerve stimulation and single fiber EMG in the electrodiagnostic evaluation of patients with suspected myasthenia gravis or Lambert-Eaton myasthenic syndrome

A retrospective literature review of the electrodiagnosis of myasthenia gravis (MG) and Lambert--Eaton myasthenic syndrome (LEMS) through July 1998 was performed for the purpose of generating evidence-based practice parameters. There were 545 articles identified, of which 13 articles met at least three of the six criteria set previously by the American Association of Electrodiagnostic Medicine (AAEM). An additional 21 articles were identified from review articles or the references of these first 13 articles leading to a total of 34 articles. Results of studies utilizing repetitive nerve stimulation (RNS) showed that a 10% decrement in amplitude from the first to fourth or fifth intravolley waveform while stimulating at 2--5 HZ is valid for the diagnosis of MG. The degree of increment needed for the diagnosis of LEMS is at least 25% but most accurate when greater than 100%. Abnormal jitter or impulse blocking are the appropriate criteria for diagnosis of neuromuscular junction (NMJ) disorders when using single fiber electromyography (SFEMG). SFEMG is more sensitive than RNS for the diagnosis of disorders of neuromuscular transmission, but may be less specific and may not be available. Therefore, RNS remains the preferred initial test for MG and LEMS.     

Contralateral reinnervation of midline muscles in facial paralysis.

We report on a patient with recovery of activity of the left orbicularis oris and nasalis muscles 3 months after a complete left facial palsy. Stimulation of the affected facial nerve evoked no responses, whereas contralateral facial nerve stimulation showed polyphasic responses with very long latencies in the nasalis and orbicularis oris muscles. Needle electromyography (EMG) revealed abnormal spontaneous activity in the left orbicularis oris muscle. The motor unit action potentials on the left side of the face could be recruited only during marked contraction of the corresponding muscles on the right and were of low voltage and polyphasic ("nascent potentials"). Contralateral reinnervation is probably due to sprouting of terminal branches crossing the midline of the face and innervating bundles of muscle fibers on the affected side. This phenomenon seems unfamiliar to most clinicians. Whether the activity is due to conduction along nerve fibers or muscle fibers crossing the midline is discussed.