Spontaneous Electromyographic Activity Research Articles

Abnormal spontaneous electromyographic activity in myasthenia gravis causing a diagnostic confusion: a case report and literature review

Some cases of myasthenia gravis (MG) with abnormal spontaneous activity (ASA) in needle electromyography (EMG) have been reported, but the associated clinical characteristics remain to be fully elucidated. We report the case of a 36-year-old male with MG in whom ASA was observed. This study highlights that ASA may appear in needle EMG in patients with severe MG who predominantly have bulbar and/or respiratory involvement. Care is needed because this often accompanies myopathic features and can be misdiagnosed as myopathy.

Ultra-early amplitude decrement after repetitive nerve stimulation supports early neuromuscular junction injury in amyotrophic lateral sclerosis: a prospective cross-sectional study.

The dying-back hypothesis holds that the damage to neuromuscular junctions and distal axons in amyotrophic lateral sclerosis occurs at the earliest stage of the disease. Previous basic studies have confirmed early damage to neuromuscular junctions, but it is difficult to obtain such evidence directly in clinical practice. In this prospective cross-sectional study, we recruited 22 patients with early amyotrophic lateral sclerosis with disease duration < 12 months and with clinical symptoms limited to the upper limbs. We also recruited 32 healthy controls. Repetitive nerve stimulation was performed, and patients were followed for 12 months. We found a significant change in the response to repetitive nerve stimulation in amyotrophic lateral sclerosis patients without spontaneous electromyographic activity. Patients that were prone to denervation had an increased decrement response of target muscles after repetitive nerve stimulation. These results suggest that changes in response to repetitive nerve stimulation may occur before denervation in amyotrophic lateral sclerosis patients. The damage to lower motor neurons is more obvious in patients with a higher percentage of repetitive never stimulation-related amplitude decrements. This study was approved by the Institutional Ethics Committee of Peking University Third Hospital (approval No. M2017198) on August 24, 2017.

Inhibition and facilitation of nociceptively evoked muscular activity by fentanyl or dexmedetomidine in isoflurane-anaesthetized pigs

ObjectiveTo investigate motor and cardiovascular responses to dexmedetomidine or fentanyl in isoflurane-anaesthetized pigs. Study designExperimental, balanced, block randomized, two-group design. AnimalsA group of 16 crossbred pigs, 55 ± 8 days (mean ± standard deviation) old. MethodsDeltoid electromyography (EMG) was recorded during isoflurane anaesthesia. Electrical stimulation using 5, 10, 20 and 40 mA of the distal right thoracic limb elicited a nociceptive withdrawal reflex (NWR), quantified by the area under the curve (AUC) for the simulation intensity versus EMG amplitude response curve. Latency to movement evoked by clamping a claw for maximum 60 seconds was noted. Arterial blood pressure and pulse rate were recorded. Data were sampled at baseline and during dexmedetomidine 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 μg kg–1 hour–1 or fentanyl 5, 10, 20, 40, 80 and 160 μg kg–1 hour–1 infusions. The influence of infusion rate on NWR AUC and spontaneous EMG was analysed using a mixed model, with p < 5%. ResultsNWR AUC increased at fentanyl 5 μg kg–1 hour–1 but decreased at fentanyl 40, 80 and 160 μg kg–1 hour–1 and dexmedetomidine 4.0 and 8.0 μg kg–1 hour–1. All pigs at fentanyl 80 μg kg–1 hour–1, and three pigs at dexmedetomidine 8.0 μg kg–1 hour–1 had mechanical latencies greater than 60 seconds. Spontaneous EMG activity increased accompanied by visually evident ‘shivering’ at fentanyl 5, 10 and 20 μg kg–1 hour–1 but decreased at dexmedetomidine 2, 4 and 8 μg kg–1 hour–1. Clinically relevant effects of increasing infusion rates on blood pressure or pulse rate were not observed. Conclusion and clinical relevanceIf anaesthetic plane or antinociception is evaluated in pigs, response to claw clamping and NWR will not necessarily give uniform results when comparing drugs. If only one method is used, results should be interpreted cautiously.

An Implantable System For Chronic In Vivo Electromyography

Electromyography (EMG) measures the muscle response to electrical stimulation or spontaneous activity of motor units and plays an important role in assessing neuromuscular function. Chronic recording of EMG activity reflecting a muscle's reinnervation status after nerve injury has been limited, due to the invasive nature of traditional EMG recording techniques. In this regard, an implantable system is designed for long-term, in vivo EMG recording and nerve stimulation. It has been applied and tested in a study on reinnervation of laryngeal muscles. This system consists of 1) two bipolar electrode nerve cuffs and leads for stimulating each of two nerves: the recurrent laryngeal nerve (RLN) and internal branch of the superior laryngeal nerve (SLN); 2) two EMG recording electrodes and leads for each of the two laryngeal muscles: posterior cricoarytenoid (PCA) muscle and thyroarytenoid-lateral cricoarytenoid (TA-LCA) muscle complex; and 3) a skin receptacle interfacing all implanted lead terminals to an external recording preamplifier and stimulator using a connection cable. The wire leads are Teflon-coated, multi-filament, type 316 stainless steel. They are coiled and can stretch during body movement of the awake animal to prevent lead breakage and electrode migration. This system is implanted during an aseptic surgery. Afterwards, baseline EMG recordings are performed before the RLN is transected in the second surgery to study muscle reinnervation. Throughout the study, multiple physiological sessions are conducted in the anesthetized animal to obtain evoked and spontaneous EMG activity that reflects the reinnervation status of laryngeal muscles. The system is compact, free of infection over the course of the study, and highly durable. This implantable system can provide a reliable platform for research in which long-term recording or nerve stimulation is required in an anesthetized or freely moving animal.

When electrodiagnosis for tremor reveals a rare peripheral disease

Objectives Spinal and bulbar muscular atrophy (SBMA) (or Kennedy's disease) is a rare X-linked neurodegenerative disorder associated with limb and bulbo-facial paresis, sensory symptoms and tremor. Tremor usually precedes peripheral motor signs by a decade. It is supposed to result from several peripheral mechanisms [1] . Results Here we report a case of a 42 years-old patient who was addressed to the department for exploration of isolated bilateral upper limb tremor. Surface polymyographic examination revealed numerous spontaneous and short (7–12 ms) bursts at rest consistent with fasciculations and associated with a postural myoclonic tremor as well as with exaggerated physiological tremor of 8–10 Hz. Detailed clinical examination showed a generalized areflexia, cramps, mild paresis of upper limbs, gynecomastia and facial myokymia. Conventional electromyography (EMG) showed a chronic motor denervation in the muscles of the four limbs and the face with normal motor nerve conduction; however, fasciculations were not detected by needle EMG. In sensory nerves of four limbs, a homogeneous decrease of action potentials amplitudes was found consistent with axonal sensory neuropathy. Altogether, these findings were strongly suggestive of a SBMA. Genetic testing for CAG repeats in the androgen receptor gene is under investigation. As a reference, we show typical surface EMG recordings of upper limbs and neurophysiological characteristics of tremor of a patient with genetically documented SBMA (48 CAG triplets) at a more severe stage of the disease. Conclusion Spontaneous surface EMG activity compatible with fasciculations might be a valuable marker of a neuropathic tremor and potentially a revealing sign of SBMA.

Stenosis and Neurologic Level Discrepancies in Cervical Spondylotic Myelopathy

BackgroundCervical spondylotic myelopathy (CSM) is the most common cause of cord dysfunction in older individuals. CSM involves either the upper motor neuron or lower motor neuron (LMN) in the cervical spine. The neurologic level of the LMN lesion does not usually correspond with the structural level detected via magnetic resonance imaging (MRI). ObjectiveTo examine the relationship between the structural level of stenosis and the neurologic level of LMN involvement in patients with CSM. DesignRetrospective descriptive study. SettingTertiary hospital. PatientsPatients with cervical spondylotic myelopathy, aged 41-79 years. MethodsWe reviewed electromyography (EMG) and magnetic resonance imaging (MRI) findings from 17 patients with CSM to objectively show the relation between the structural level of stenosis and the neurologic level with LMN involvement. Main Outcome MeasurementsThe structural level was defined by spinal canal stenosis with definite cord compression on MRI. The neurologic level was determined by myotomes with abnormal spontaneous activity on EMG. ResultsIn all patients but one, myotomes with abnormal spontaneous EMG activity were one to 4 levels lower than the stenotic canal shown on MRI. ConclusionsLMN involvement in CSM is usually not concordant with the structural lesion. For accurate diagnosis and treatment, physicians should recognize that myotomal involvement in CSM is often due to canal stenosis one to 4 levels above the lesion. Level of EvidenceIII

Correlation of Creatine Kinase Levels with Clinical Features and Survival in Amyotrophic Lateral Sclerosis.

To evaluate serum creatine kinase (CK) levels of amyotrophic lateral sclerosis (ALS) patients and to explore the relationship between CK levels and the clinical characteristics and survival prognosis of ALS patients. We analyzed the CK levels of 185 ALS patients who underwent long-term follow-up. The relationship between CK levels and clinical features including sex, age, disease duration, site of onset, body mass index (BMI), serum creatinine (Cr), and spontaneous electromyographic activity was analyzed by univariate analysis and multiple linear regression. Kaplan-Meier and Cox proportional hazards models were used to explore whether CK levels were independently correlated with survival prognosis of ALS. Baseline serum CK was raised in 43% of participants. The median CK level was 160 U/L (range: 20-2,574 U/L), and 99% of patients had a baseline serum CK level less than 1,000 U/L. CK levels were significantly higher in male patients than in female patients [204 (169) versus 117 (111) U/L, p < 0.001] and in patients with limb onset ALS than with bulbar onset ALS (p < 0.001). CK levels were also correlated with serum Cr (p = 0.011) and the spontaneous potential score of electromyography (EMG) (p = 0.037) but not correlated with age (p = 0.883), disease duration (p = 0.116), or BMI (p = 0.481). Log CK was independently correlated with survival of ALS patients (HR = 0.457, 95% confidence interval 0.221-0.947, p = 0.035) after adjusting for age, sex, site of onset, serum Cr, and BMI. Serum CK levels of ALS patients were correlated with sex, site of onsite, serum Cr, and spontaneous activity in EMG. Serum CK could be an independent prognostic factor for survival of ALS patients.

The presence of spontaneous EMG activity in sternocleidomastoid is associated with ventilatory dysfunction in ALS

We investigated electromyography (EMG) of the sternocleidomastoid (SCM) in 128 patients with amyotrophic lateral sclerosis (ALS) including correlation with forced vital capacity (FVC) and ALS Functional Rating Scale scores. The presence of fibrillation potentials and positive sharp waves in the SCM was significantly more frequently observed in patients with an FVC <80% (31/49, 63%) than in patients with an FVC≥80% (34/79, 43%). This study suggests that the SCM could be concomitantly involved with primary respiratory muscles in ALS. This is of value since needle EMG is a less invasive procedure in SCM than in the diaphragm or intercostal muscles.

Needle electromyography in carpal tunnel syndrome: is it valuable or predictable?

Needle electromyography (EMG) examination is not crucial in establishing the diagnosis of carpal tunnel syndrome (CTS). However, the presence of axonal loss in needle EMG helps clinicians determine a treatment strategy such as surgery. The aim of this study was to investigate whether needle EMG in CTS patients is essentially needed or could be predicted using other nerve conduction study (NCS) parameters. This study included 100 patients with clinical and NCS-proven CTS, as well as 50 age-matched and sex-matched controls. All individuals were evaluated using electrodiagnostic techniques, including median distal latency, compound muscle action potential (CMAP), forearm motor nerve conduction velocity, median peak latency, sensory nerve action potentials, and sensory nerve conduction velocity. All CTS patients underwent EMG examination of the abductor pollicis brevis muscle, and the presence or absence of spontaneous EMG activity was recorded. Comparison of the NCS parameters between CTS patients with and without spontaneous EMG activity revealed that the main determinant parameters for spontaneous activity were CMAPs, sensory nerve action potentials, and forearm motor nerve conduction velocities. However, logistic regression analysis showed that CMAP was the most powerful predictor of the presence of spontaneous activity (P = 0.000, odds ratio = 12.154). It can be concluded that median nerve CMAP amplitudes are the most powerful predictors of the occurrence of spontaneous EMG activity. However, EMG examination is still valuable in some CTS patients and NCS cannot completely replace needle EMG examination in these patients.

Effects of partial neuromuscular blockade on lateral spread response monitoring during microvascular decompression surgery

ObjectiveWe evaluated the effect of partial neuromuscular blockade (NMB) and no NMB on successful intraoperative monitoring of the lateral spread response (LSR) during microvascular decompression (MVD) surgery. MethodsPatients were randomly allocated into one of three groups: the TOF group, the NMB was targeted to maintain two counts of train-of-four (TOF); the T1 group, maintain the T1/Tc (T1: amplitude of first twitch, Tc: amplitude of baseline twitch) ratio at 50%; and the N group, no relaxants after tracheal intubation. Successful LSR monitoring was defined as effective baseline establishment and maintenance of the LSR until dural opening. ResultsThe success rate of LSR monitoring was significantly lower in the TOF group. But, there was no significant difference between T1 and N. The detection rate of spontaneous free-run electromyography (EMG) activity was significantly higher in the N group compared with the TOF and T1 groups. ConclusionsPartial NMB with a target of T1/Tc ratio at 50% allows good recording of LSR with same outcome as surgery without NMB, and reduced spontaneous EMG activity. SignificanceWe suggested the availability of partial NMB for intraoperative LSR monitoring.

Intraoperative monitoring of the abducens nerve in extended endonasal endoscopic approach: A pilot study technical report

BackgroundTo determine the reliability and usefulness of intraoperative monitoring of the abducens nerve during extended endonasal endoscopic skull base tumor resection. MethodsWe performed abducens nerve intraoperative monitoring in 8 patients with giant clival lesions recording with needle electrodes sutured directly into the lateral rectus muscles of the eye to evaluate spontaneous electromyographic activity and triggered responses following stimulation of the abducens nerves. ResultsA total of 16 abducens nerves were successfully recorded during endoscopic endonasal skull base surgeries. Neurotonic discharges were seen in two patients (12% [2/16] abducens nerves). Compound muscle action potentials of the abducens nerves were evoked with 0.1–4mA and maintained without changes during the neurosurgical procedures. No patient had new neurological deficits or ophthalmological complications post-surgery. ConclusionsIntraoperative monitoring of the abducens nerve during the extended endonasal endoscopic approach to skull base tumors appears to be a safe method with the potential to prevent neural injury through the evaluation of neurotonic discharges and triggered responses.

Spontaneous electromyographic activity of the tongue in amyotrophic lateral sclerosis

Detection of denervation in muscles in the craniobulbar area is important to assure widespread lower motor neuron involvement in the diagnosis of amyotrophic lateral sclerosis (ALS). The value of spontaneous activity analysis in needle electromyography (EMG) of the tongue has been questioned in the recent literature. Spontaneous activity in the tongue and sternocleidomastoid (SCM) muscles was reviewed retrospectively in 17 ALS patients. Needle EMG showed spontaneous activity in the tongue in 14 of 17 patients (82%) and in 6 patients of 17 (35%) in SCM. Spontaneous EMG activity in the tongue was found in patients with and without bulbar symptoms. Needle EMG is a valuable method for assessing clinical and subclinical involvement of the tongue in patients with bulbar and limb onset ALS. Adequate relaxation of the tongue is a prerequisite for proper spontaneous activity recording.

Which nerve conduction parameters can predict spontaneous electromyographic activity in carpal tunnel syndrome?

ObjectiveWe investigate electrodiagnostic markers to determine which parameters are the best predictors of spontaneous electromyographic (EMG) activity in carpal tunnel syndrome (CTS). MethodsWe enrolled 229 patients with clinically proven and nerve conduction study (NCS)-proven CTS, as well as 100 normal control subjects. All subjects were evaluated using electrodiagnostic techniques, including median distal sensory latencies (DSLs), sensory nerve action potentials (SNAPs), distal motor latencies (DMLs), compound muscle action potentials (CMAPs), forearm median nerve conduction velocities (FMCVs) and wrist–palm motor conduction velocities (W–P MCVs). All CTS patients underwent EMG examination of the abductor pollicis brevis (APB) muscle, and the presence or absence of spontaneous EMG activities was recorded. Normal limits were determined by calculating the means±2 standard deviations from the control data. Associations between parameters from the NCS and EMG findings were investigated. ResultsIn patients with clinically diagnosed CTS, abnormal median CMAP amplitudes were the best predictors of spontaneous activity during EMG examination (p<0.001; OR 36.58; 95% CI 15.85–84.43). If the median CMAP amplitude was ⩽2.1mV, the rate of occurrence of spontaneous EMG activity was >95% (positive predictive rate >95%). If the median CMAP amplitude was higher than the normal limit (>4.9mV), the rate of no spontaneous EMG activity was >94% (negative predictive rate >94%). An abnormal SNAP amplitude was the second best predictor of spontaneous EMG activity (p<0.001; OR 4.13; 95% CI 2.16–7.90), and an abnormal FMCV was the third best predictor (p=0.01; OR 2.10; 95% CI 1.20–3.67). No other nerve conduction parameters had significant power to predict spontaneous activity upon EMG examination. ConclusionsThe CMAP amplitudes of the APB are the most powerful predictors of the occurrence of spontaneous EMG activity. Low CMAP amplitudes are strongly associated with spontaneous activity, whereas high CMAP amplitude are less associated with spontaneous activity, implying that needle EMG examination should be recommended for the detection of spontaneous activity in those CTS patients whose NCS reveals CMAP amplitudes between 2.1mV and the lower normal limit (4.9mV in the present study). SignificanceUsing NCS, electromyographers can predict the presence of spontaneous EMG activity in CTS patients.

Prediction of neurological outcome using bispectral index in patients with severe acute brain injury

To predict consciousness recovery and outcome of patients with severe acute brain injury using the bispectral index (BIS). Materials and methods: A prospective study of 189 brain-injured patients was made when they were without sedatives for at least 24 h. BIS, 95% spectral edge frequency (SEF), burst suppression ratio (SR), total power (TP), spontaneous electromyographic activity (EMG), and signal quality index (SQI) were recorded continuously for 30 min. Neurologic conditions were measured with the Glasgow Coma Score (GCSBIS) when recording BIS. Patients were followed for 30 days after injury to assess consciousness recovery and outcome. Results: There were statistically significant differences in BIS measurements between patients that recovered consciousness or survived and those who did not. The best correlation coefficients for patients' outcome were 0.738 for GCSBIS, 0.639 for SR, and 0.591 for BIS. As to the patients' consciousness recovery, the best coefficients were 0.656 for GCSBIS, 0.526 for BIS, and 0.511 for SR. According to the area under the receiver operating characteristic curve, the best values to predict consciousness recovery and survival were GCSBIS and BIS, and for unconsciousness and death, the best parameters were SR, APACHE II score, and SEF. Conclusion: BIS measurement is useful to predict consciousness recovery and outcome in severe acute brain injury.

Role of intra-operative neurophysiologic monitoring during decompression and neurolysis after peripheral nerve injury: Case report

This paper reports the case of a patient presenting motor and sensitive deficits of the left forearm and hand after a traumatic injury of the median, ulnar, and radial nerves. Decompression and neurolysis of the three nerves was performed. Spontaneous electromyographic activity and the amplitude of compound muscle action potentials (CMAPs) were monitored. Surgery led to an increased amplitude of the aforesaid parameters and a long-term clinical improvement.

Neuromuscular involvement in vegetative and minimally conscious states following acute brain injury

The aim of this study was to evaluate the presence of neuromuscular involvement in patients in vegetative and minimally conscious states (VS, MCS) following acute brain injury. Twenty-two patients (11 in VS, 11 in MCS) admitted to a rehabilitation department underwent nerve conduction, electromyography (EMG) for spontaneous activity and direct muscle stimulation (DMS). Twenty (90.9%) showed abnormal nerve conduction studies, 19 (86.4%) had spontaneous EMG activity, and 7 (31.8%) had abnormal DMS. The time spent in the intensive care unit correlated significantly with the amplitude of the compound muscle action potential of the ulnar nerve and with the amplitude of the sensory nerve action potential of the sural nerve (p < 0.05). No significant differences were found between patients in VS and MCS. Neurophysiological data indicative of neuromuscular involvement are common in patients in VS and MCS. This study underlines the need to implement strategies to prevent and to treat neuromuscular complications in patients in VS and MCS.

Fibromyalgia, myofascial pain, tender points and trigger points: splitting or lumping?

Myofascial trigger points (MTPs) have long been a contentious issue in relation to fibromyalgia, and poorly defined pain complaints in general. Can MTPs be reproducibly identified? Do MTPs have valid objective findings, such as spontaneous electromyographic activity, muscle microdialysis evidence for an inflammatory milieu or visualization with newer ultrasound techniques? Is fibromyalgia a syndrome of multiple MTPs, or is focal muscle tenderness a manifestation of central sensitization? These issues are discussed with relevance to a recent paper reporting that manual palpation of active MTPs elicits the spontaneous pain experienced by fibromyalgia patients.

Artifact on Electromyography Produced by an Implanted Sacral Nerve Stimulator

A patient with muscle cramps was referred for nerve conduction studies and electromyography. Her study demonstrated bursts of spontaneous electromyography activity, which waxed and waned in amplitude with a "dive bomber"-like sound. The abnormal finding was found to be an artifact from an implanted sacral nerve stimulator for bladder incontinence.

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Spontaneous Electromyographic Activity During Microvascular Decompression in Trigeminal Neuralgia

Intraoperative monitoring of spontaneous facial nerve electromyographic activity during surgery for microvascular decompression in trigeminal neuralgia was evaluated. Fifteen patients with trigeminal neuralgia underwent surgery for microvascular decompression. During the entire operation, free-running facial nerve electromyographic signals were recorded. The data were analyzed with respect to waveform patterns known from vestibular schwannoma-surgery. Special regard was given to the occurrence of A-trains that are associated with postoperative paresis in patients operated on vestibular schwannoma. The spectrum of the observed activities matched patterns known from surgery of vestibular schwannoma; even A-trains, a pattern known to be an indicator of postoperative deterioration of facial nerve function (Romstöck et al., J Neurosurg 2000;93:586-593), were seen in 3 of the 15 patients with trigeminal neuralgia. The quantity of A-trains observed was much less than it is known from patients operated on tumors of the cerebellopontine angle. None of the trigeminal neuralgia-patients experienced postoperative deterioration of facial nerve function. The present study shows that A-trains do not only occur during tumor surgery, but also during procedures with indirect manipulation of the facial nerve. They do not necessarily lead to postoperative paresis as long as certain thresholds concerning amount and length of these A-trains are not exceeded.