Fatigue associated EMG behavior of the first dorsal interosseous and adductor pollicis muscles in different groups of subjects

We have studied the fatigue-associated behavior of surface EMG in two histochemically different muscles of the hand: first dorsal interosseous (FDI) and adductor pollicis (AP; relatively more type I fibers in AP than in FDI). During a fatigue test evoked by electrical stimulation of the ulnar nerve, the mean amplitudes of compound muscle action potentials (M-waves) exhibited the same overall pattern for both muscles: a rapid phase of potentiation followed by a gradual decline. However, if the group of subjects was subdivided on the basis of hand length, significant differences emerged in the reactions of AP: in large hands, no fatigue-associated M-wave decline was seen, whereas in small hands a distinct decline was observed. A possible explanation for this phenomenon might be the presence of a greater amount of EMG contamination from other muscles in smaller hands. In the supposedly “cleaner” recordings from larger hands, significant differences between FDI and AP were observed with regard to their fatigue-associated EMG reactions (M-wave depression in FDI but not in AP). The direction of these differences was in accordance with expectations on the basis of known differences in histochemical fiber type composition. © 1994 John Wiley & Sons, Inc.     

Ephaptic transmission in hemifacial spasm: a single-fiber EMG study

In two patients with hemifacial spasm (HFS), single-fiber EMG recordings in facial muscles demonstrated low jitter in the late responses produced by stimulation of peripheral branches to other facial muscles. Surgical decompression of the facial nerve in one patient was followed by clinical improvement and disappearance of the abnormal late responses. These observations are consistent with the hypothesis that there is ephaptic transmission among peripheral branches of the facial nerve at the site of compression in HFS.     

Effect of electrode location on surface electromyography changes due to eccentric elbow flexor exercise

Experiments were carried out to determine whether the location of electrodes has an effect on eccentric exercise–induced changes in surface electromyography (sEMG) variables in the biceps brachii muscle. sEMG signals were recorded with a grid of 64 electrodes before and up to 4 days post‐exercise. Root mean square (RMS) and mean power frequency (MNF) were calculated for: (1) each channel; (2) as an average of all channels; and (3) as an average of individual channel rows and columns. Mean muscle‐fiber conduction velocity (CV) was estimated similarly but was based on double‐differential channels. Maximal isometric voluntary torque decreased 21.3 ± 5.6% post‐exercise. The average sEMG variables decreased after the exercise and recovered 2 days (RMS and CV) or 4 days (MNF) post‐exercise. Site‐dependent changes were observed in sEMG variables. We conclude that site‐dependent changes in sEMG variables after eccentric exercise can be detected and are influenced in part by anatomical factors. Muscle Nerve, 2009     

颅内电极脑电图监测对癫痫致痫灶的定位作用

目的探讨颅内电极脑电图（EEG）监测对癫痫致痫灶的定位作用。方法对经临床、影像学和常规EEG检查不能确定致痫灶部位的20例难治性颞叶癫痫患者，应用立体定向技术，经双侧颞叶植入硬膜下条状电极进行长时间EEG监测，观察发作期及发作间期EEG变化，结合常规EEG、MRI检查结果对癫痫灶进行综合定位；术后随访，评估致痫灶定位的准确性。结果20例患者颅内电极埋藏时间为1—5d，每例监测到／〉2次临床发作并记录发作间期和发作期的异常放电活动。20例患者发作期颅内电极EEG均能准确定位，15例致痫灶发作间期与发作期一致，2例发作间期为双侧棘波，3例发作间期定位与发作期不一致。术后按Engel疗效分级：发作消失13例（65％），显著改善3例（15％），良好3例（15％），无效1例（5％）。未出现因颅内电极安置所致的并发症。结论颅内电极EEG监测可为癫痫手术治疗提供可靠的病灶定位依据。     

颅内电极脑电图监测对癫(癎)致(癎)灶的定位作用

目的探讨颅内电极脑电图(EEG)监测对癫致灶的定位作用。方法对经临床、影像学和常规EEG检查不能确定致灶部位的20例难治性颞叶癫患者,应用立体定向技术,经双侧颞叶植入硬膜下条状电极进行长时间EEG监测,观察发作期及发作间期EEG变化,结合常规EEG、MRI检查结果对癫灶进行综合定位;术后随访,评估致灶定位的准确性。结果20例患者颅内电极埋藏时间为1～5d,每例监测到≥2次临床发作并记录发作间期和发作期的异常放电活动。20例患者发作期颅内电极EEG均能准确定位,15例致灶发作间期与发作期一致,2例发作间期为双侧棘波,3例发作间期定位与发作期不一致。术后按Engel疗效分级:发作消失13例(65%),显著改善3例(15%),良好3例(15%),无效1例(5%)。未出现因颅内电极安置所致的并发症。结论颅内电极EEG监测可为癫手术治疗提供可靠的病灶定位依据。     

Localization of motoneurons innervating deep and superficial facial muscles in the rat: a horseradish peroxidase and electrophysiologic study

In the rat, distribution of the motoneurons supplying the deep facial muscles (DFM)--the posterior belly of the digastric (VP) and the stylohyoid (SH) muscles--and the superficial facial muscles (SFM) was studied using the horseradish peroxidase (HRP) method and the antidromic field-potential method. The HRP was injected individually into the VP or SH or applied directly to the central end of the facial nerve cut immediately before it enters the parotid gland. Electrical stimulation was administered to the common stem of the branches innervating the VP or SH and to the facial nerve trunk just before entering the parotid gland. Both VP and SH motoneurons were found not in the main but in the accessory facial nucleus, within which the VP motoneurons were more numerous and more dorsorostrally extended than were the SH motoneurons. Motoneurons supplying the SFM were confined within the main facial nucleus. Evidence was found that the distribution of antidromic field potentials evoked by stimulation at the above sites coincided with the distribution of motoneurons supplying either the DFM or SFM obtained from the HRP experiment. In the rat, the accessory and main facial nuclei can be considered to be the mass of motoneurons exclusively innervating the DFM and SFM, respectively.     

Static load magnitude is a risk factor in the development of cumulative low back disorder

Occupations requiring frequent periods of static lumbar flexion are known epidemiologically to be risk factors for the development of cumulative low back disorder. The impact of the load magnitude sustained during a series of short static lumbar flexions followed by an equally long rest period on the development of a cumulative low back disorder was addressed in an in vivo feline model. Static loads of 20, 40, and 60 N were applied over 10 min of flexion followed by 10-min rest sessions that were repeated six times (for a total of 2 h) while monitoring lumbar viscoelastic creep (laxity) and reflex electromyographic (EMG) activity from the multifidus muscles. Creep and EMG were also monitored over 7 h of rest following the six flexion-rest sessions. It was found that the creep developed in the 10-min flexion periods did not recover completely during the following 10 min of rest, giving rise to a large cumulative creep at the end of the work-rest session. Muscle activity demonstrated spasms during the static flexion periods as well as initial and delayed hyperexcitability during the 7-h rest period. Loads of 20 and 40 N did not result in delayed hyperexcitability, whereas loads of 60 N resulted in delayed hyperexcitability. Statistical analysis demonstrated that increased load significantly intensified the magnitude of the hyperexcitabilities (P < 0.05). Thus, repeated periods of static lumbar flexion were found to result in a transient neuromuscular disorder with an intensity directly related to the load magnitude, which should be considered a compounding risk factor.     

Single-fiber EMG with a concentric needle electrode: validation in myasthenia gravis

We performed a retrospective study to validate whether a disposable concentric needle electrode (CNE) can be used in place of a single-fiber (SF) electrode for jitter measurements in myasthenia gravis (MG). Normal values for voluntary contraction of orbicularis oculi (OO) and extensor digitorum communis (EDC) were collected from 20 healthy subjects. The method was validated by a retrospective analysis of 56 consecutive MG patients, the "gold standard" being a positive acetylcholine receptor (AChR) antibody titer at the time of the electrophysiological (electromyography) study and the clinical diagnosis. Receiver operating characteristic (ROC) curves were constructed to define maximal sensitivity and specificity of the technique. The sensitivity was 96.4% (95% confidence interval 87.5%-99.6%), with no false-positive results, similar to traditional SF EMG and confirming that the disposable CNE is a justifiable alternative.     

Sudden loading perturbation to determine the reflex response of different back muscles: a reliability study

In this study we estimate the reliability of reflex response variables to identify the main sources of variability and to estimate appropriate measurement strategies to obtain more reliable measures. Back muscle surface electromyography (EMG) was recorded in healthy males during anteriorly-directed sudden loading perturbations applied to the trunk. Measures of EMG reflex latency and amplitude were obtained. The generalizability theory was used as a framework to estimate the magnitude of the different variance components and the reliability of the measures corresponding to various simulations of different measurement strategies. Reliability of the different variables was poor to moderate (intraclass correlation coefficient range 0-0.62). Averaging scores across homologous muscles and several trials were strategies to achieve more acceptable reliability. The reflex response of back muscles is inherently variable, and a large measurement effort is necessary to obtain reliable and, consequently, valid and responsive estimations of this neuromuscular function.     

American Association of Neuromuscular & Electrodiagnostic Medicine evidenced-based review: use of surface electromyography in the diagnosis and study of neuromuscular disorders

Surface electromyography (sEMG) measures myoelectrical signals recorded from sensors placed on the skin surface. The non-invasive nature of sEMG makes it a potentially useful technology for studying diseases of muscle and nerve. Reviews published by the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) and the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (AAN), covering 1964-1994 and 1952-1998, respectively, concluded that sEMG adds no clinical utility over conventional needle EMG (nEMG) for the diagnosis of neuromuscular disease. The AANEM sEMG task force reevaluated the diagnostic utility and added value of this technology for the study of neuromuscular disease based on a contemporary review of relevant literature published between January 1994 and February 2006. The present review concludes that sEMG may be useful to detect the presence of neuromuscular disease (level C rating, class III data), but there are insufficient data to support its utility for distinguishing between neuropathic and myopathic conditions or for the diagnosis of specific neuromuscular diseases. sEMG may be useful for additional study of fatigue associated with post-poliomyelitis syndrome and electromechanical function in myotonic dystrophy (level C rating, class III data).     

Localization of reward-relevant neurons in the pontine tegmentum: a moveable electrode mapping study

Monopolar moveable stimulation electrodes were implanted in male adult rats in order to map the reward substrate in the pontine tegmentum. Electrodes were implanted 6 mm below the surface of the skull and subsequently lowered by steps of 0.16 or 0.32 mm. Each bar press in a Skinner box delivered a train (0.4 s in duration) of cathodal rectangular pulses of fixed intensity (200 microA) and width (0.1 ms). Self-stimulation was recorded from zero to maximum performance by varying the number of pulses per train. The rewarding effectiveness of the stimulation at each positive site was inferred by determining the frequency threshold. Out of 476 sites that were sampled, 137 supported self-stimulation. Eighty-one percent of the positive sites (111 out of 137) were located within 1 mm of the midline. Of the 181 sites that were sampled in the region posterior to the caudal end of the dorsal raphe, only 9 sites (less than 5%) supported self-stimulation. These results suggest that the majority of neurons that constitute the brainstem reward substrate either originate from and/or terminate in the rostral pons.     

Primary solitary hydatid cyst in paraspinal cervical muscles: a case report and review of the literature

Hydatid disease caused by Echinococcus granulosus and Echinococcus multilocularis commonly presents with pulmonary and hepatic cysts. Primary paraspinal muscle cysts are a rare presentation. We report a case of hydatid cyst within paraspinal muscles presenting with cervical mass and associated pain. The hydatid disease serological test was negative. Neither hepatic nor pulmonary cystic lesions were found. Radiographic findings were unspecific for hydatid cysts. Surgical resection was planned due to the provisional diagnosis of muscular cystic neoplasm. During surgery, a cyst containing a clear liquid was found. The cyst wall was excised and the surgical field was irrigated with hypertonic saline. The patient's symptoms resolved by discharge day. Postoperative pathological examinations revealed a muscular hydatid cyst.     

On-line flexibility of the cognitive tuning of corticospinal excitability: a TMS study in human gait

Human subjects have been found to be able to cognitively prepare themselves to resist to a TMS-induced central perturbation by selectively modulating the corticospinal excitability (CS). The aim of this study was to investigate the on-line adaptability of this cognitive tuning of CS excitability during human gait. Transcranial magnetic stimulation (TMS) was used both as a central perturbation evoking a movement and as a tool for quantifying the CS excitability before the movement was evoked. TMS was applied at mid-stance (evoking additional hip extension) or at the beginning of the swing (evoking hip flexion) with a random phase, thus evoking unpredictable flexion or extension movement. This was compared to a condition of fixed phase, in which the subjects knew in advance the direction of the evoked movement. In both conditions, we compared the amplitude of the TMS-evoked movement and the motor-evoked potentials (MEPs) of the muscles acting at the hip joint (RF/BF) according to two opposite instructions, either to cognitively prepare to "let go", or to cognitively prepare to "compensate" for the evoked movements. The results showed that the subjects were able to compensate for random TMS-evoked movements, but with a lower performance level in comparison to the fixed TMS-evoked movements. When they succeeded in the random-phase condition, the subjects used the same preparation strategy as in the fixed-phase condition; preparing to compensate resulted in a selective increase in the CS excitability to those muscles which would be involved in counteracting the possible central perturbation. This requires continuous change in the tuning of CS excitability within the stride and thus reveals the high flexibility of the cognitive tuning of CS excitability during gait.     

Turns amplitude analysis of the orbicularis oculi and oris muscles.

OBJECTIVE: The aim of the study was to determine whether 'clouds' from turns amplitude analysis obtained from the orbicularis oculi and oris muscles without force monitoring can be used to differentiate pathological processes affecting the face. METHODS: The interference pattern from orbicularis oculi and orbicularis oris was studied using a concentric needle electrode. Data-points from 20 normal subjects were plotted on a logarithmic scale of mean amplitude between turns versus turns/second, from which linear regression analysis defined the 95% confidence intervals. This enabled us to draw the boundaries of the normal cloud on a linear plot. Data-points from the interference pattern in two pathological cohorts, of 6 patients receiving botulinum toxin injections (representing a neurogenic model), and 6 patients with a muscle dystrophy (representing a myopathic model) were plotted against the normal cloud. These findings were compared and correlated with the mean durations obtained on motor unit action potential analysis from these same two facial muscles. RESULTS: The majority of patients receiving botulinum toxin injections into their facial muscles showed a pattern of high amplitude with low turns/s, or low amplitude with a low-to-normal range of turns/s in both facial muscles. These findings were associated with high-duration motor unit action potentials in most cases. In the myopathic group of patients 66% showed a pattern of low amplitude with low-to-normal range of turns/s in O oculi and O oris. This correlated with short-duration motor unit action potentials in both facial muscles. CONCLUSIONS: We have demonstrated that turns amplitude analysis without force monitoring can be used to study the interference pattern from facial muscles and can be applied to differentiate primary neurogenic from myopathic pathological processes. SIGNIFICANCE: Turns amplitude analysis without force monitoring in the facial muscles can be used as an effective and practical method of interference pattern analysis to complement findings from conventional motor unit action potential analysis.     

The Combat Experience Log: a web-based system for the in theater assessment of war zone stress

This article presents preliminary data on the Combat Experience Log (CEL) - a web-based prospective data collection system for the in theater assessment of war zone stressors and stress reactions. 177 U.S. Army soldiers deployed to Iraq took part in the study. The overall response rate was 90.1% and the majority of CEL responders perceived the CEL system to be quite easy and convenient to use, and relevant to their war-zone experiences. Preliminary data on stress reactions, CEL utilization and soldier satisfaction are encouraging and suggest that the CEL assessment system offers a potentially useful assessment tool for enhancing our understanding of war-zone stress experiences and their contribution to PTSD and other combat stress disorders.     

Fatigue in type I fiber predominance: a muscle force and surface EMG study on the relative role of type I and type II muscle fibers

The relative proportions of fiber types within muscle and the characteristics of these fiber types are important determinants of the surface electromyogram (SEMG) during fatigue. In this study, patients suffering from congenital myopathy characterized by a strong type I fiber predominance were studied. Six patients with 95-100% type I fibers, 2 patients with 80% type I fibers, and 12 healthy volunteers participated in an ischemic, isomeric, intermittent exercise test of m. quadriceps femoris at 80% MVC. Considering the results of the morphometric analysis of muscle biopsy specimen and of the anthropometric estimated muscle-bone volume, it was found that type I muscle fibers had a lower force generating capacity than type II fibers. The initial conduction velocity along the muscle fiber membrane (MFCV) was low in patients with 95-100% type I fibers. During the ischemic exercise test, the 95-100% type I fibers showed less fatigability than type II fibers, which was reflected by a nearby absent decrease of the muscle membrane excitability as measured by the MFCV, and only a slight increase of the SEMG amplitude compared with patients having 80% type I fibers and controls. The absence of a definite MFCV decrease was related to the nearby lacking lactate formation in 95-100% type I fibers.     

Evidence for transneuronal degeneration in the spinal cord in man: a quantitative investigation of neurons in the intermediate zone after long-term amputation of the unilateral upper arm

Does transneuronal degeneration occur in the neurons of the spinal intermediate zone following degeneration of the anterior horn cells in man? To investigate this possibility, we carried out a quantitative examination of neurons in the cervical intermediate zone of a 56-yearold man who had suffered accidental amputation of the right upper arm 38 years prior to death. Recently, we reported that the cervical anterior horn cells of this patient were reduced in number not only on the amputation side but also on the spared side. The present study revealed that medium-sized neurons in the cervical intermediate zone, which were considered to be internuncial neurons, were decreased in number on both the amputation and the spared sides, but less so on the spared side. These findings indicate that retrograde transneuronal degeneration occurs in the internuncial neurons following degeneration of the anterior horn cells caused by amputation. Sequentially to this, degeneration of the commissural neurons in the intermediate zone secondary to that of the internuncial neurons may induce degeneration of the neurons in the intermediate zone and the anterior horn cells on the spared side.     

Telovelar approach for choroid plexus papilloma in the foramen of Luschka: a safe way using a neuromonitor

Background

Tumors located in the 4th ventricle are always challenging to neurosurgeons, especially tumors that extend to the cerebellopontine (CP) angle by the foramen of Luschka. Recent advances in microsurgical technique, including the neuromonitor and brainstem mapping, facilitate the surgical resection of tumors located in the foramen of Luschka. Herein, we present the use of the telovelar approach to access a choroid plexus papilloma within the right foramen of Luschka.

Case presentation

A 28-year-old female presented with a history of sudden onset pulsatile headache and syncope twice without prodrome. The brain MRI revealed a 4th ventricular tumor deviated to the right foramen of Luschka and extending to the CP angle, 2.2 cm in diameter. There was no secondary hydrocephalus due to the patent foramen of Magendie and left foramen of Luschka. The patient underwent suboccipital craniotomy and C1 laminectomy with a telovelar approach. The right tonsil was elevated and teal chloride was incised from the foramen of Magendie to the telovelar junction. The tumor was centrally decompressed, and the margin was gently dissected from the brainstem and cerebellum peduncles. Functions of the facial, cochlear, glossopharyngeal, vagus, and hypoglossal nerves and nuclei were monitored. Mapping of the facial nucleus, ambiguous nucleus, and hypoglossal nucleus was also done. Total tumor removal was achieved and the histology showed choroid plexus papilloma. No functional neurological disorientation was observed after surgery.

Conclusion

The report demonstrated a safe and effective surgical approach to the foramen of Luschka. The approach yielded a better view of the foramen of Luschka laterally, and up to the middle cerebellar peduncle superiorly. Also, it minimized neural damage, and preserved the function of the cranial nerves and nucleus.