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PubMed1979

Telemetered electromyography of flexor digitorum profundus and flexor digitorum superficialis in Pan troglodytes and implications for interpretation of the O. H. 7 hand.

The importance of knuckle-walking in the locomotor repertoire of African apes raises the possibility that the long digital flexors may be specially adapted more to meet the demands of ground quadrupedalism than those of suspension. To investigate this possibiltiy, the activities of the flexor digitorum superficialis and flexor digitorum profundus were studied by means of telemetered electromyography in three chimpanzees. Results clearly indicate that the fasciculi of the muscles to digits bearing weight in knuckle-walking are not called upon to contract in quadrupedal postures or in slow and moderately fast quadrupedal locomotion except to help clear the fingers from the ground as the forelimb begins its recovery stroke. At the most rapid speeds, a slight to moderate level of activity sometimes occurs in the latter half of stance phase. The long digital flexors display maximum and sustained activity during suspension. It is concluded that any role for these muscles in maintenance of stability at the metacarpophalangeal joints during knuckle-walking must be predominantly passive. Prominent markings for insertions of these muscles in a fossil hand (such as O.H. 7) suggest use of the forelimb in suspensory climbing behaviors.

Adaptation, Biological↗

PubMed2005

Jaw-muscle electromyography during chewing in Belanger's treeshrews (Tupaia belangeri).

We examined masseter and temporalis recruitment and firing patterns during chewing in five male Belanger's treeshrews (Tupaia belangeri), using electromyography (EMG). During chewing, the working-side masseters tend to show almost three times more scaled EMG activity than the balancing-side masseters. Similarly, the working-side temporalis muscles have more than twice the scaled EMG activity of the balancing-side temporalis. The relatively higher activity in the working-side muscles suggests that treeshrews recruit less force from their balancing-side muscles during chewing. Most of the jaw-closing muscles in treeshrews can be sorted into an early-firing or late-firing group, based on occurrence of peak activity during the chewing cycle. Specifically, the first group of jaw-closing muscles to reach peak activity consists of the working-side anterior and posterior temporalis and the balancing-side superficial masseter. The balancing-side anterior and posterior temporalis and the working-side superficial masseter peak later in the power stroke. The working-side deep masseter peaks, on average, slightly before the working-side superficial masseter. The balancing-side deep masseter typically peaks early, at about the same time as the balancing-side superficial masseter. Thus, treeshrews are unlike nonhuman anthropoids that peak their working-side deep masseters early and their balancing-side deep masseters late in the power stroke. Because in anthropoids the late firing of the balancing-side deep masseter contributes to wishboning of the symphysis, the treeshrew EMG data suggest that treeshrews do not routinely wishbone their symphyses during chewing. Based on the treeshrew EMG data, we speculate that during chewing, primitive euprimates 1) recruited more force from the working-side jaw-closing muscles as compared to the balancing-side muscles, 2) fired an early group of jaw-closing muscles followed by a second group of muscles that peaked later in the power stroke, 3) did not fire their working-side deep masseter significantly earlier than their working-side superficial masseter, and 4) did not routinely fire their balancing-side deep masseter after the working-side superficial masseter.

Animals↗

PubMed2006

Masseter electromyography during chewing in ring-tailed lemurs (Lemur catta).

We examined masseter recruitment and firing patterns during chewing in four adult ring-tailed lemurs (Lemur catta), using electromyography (EMG). During chewing of tougher foods, the working-side superficial masseter tends to show, on average, 1.7 times more scaled EMG activity than the balancing-side superficial masseter. The working-side deep masseter exhibits, on average, 2.4 times the scaled EMG activity of the balancing-side deep masseter. The relatively larger activity in the working-side muscles suggests that ring-tailed lemurs recruit relatively less force from their balancing-side muscles during chewing. The superficial masseter working-to-balancing-side (W/B) ratio for lemurs overlaps with W/B ratios from anthropoid primates. In contrast, the lemur W/B ratio for the deep masseter is more similar to that of greater galagos, while both are significantly larger than W/B ratios of anthropoids. Because ring-tailed lemurs have unfused and hence presumably weaker symphyses, these data are consistent with the symphyseal fusion-muscle recruitment hypothesis stating that symphyseal fusion in anthropoids provides increased strength for resisting forces created by the balancing-side jaw muscles during chewing. Among the masseter muscles of ring-tailed lemurs, the working-side deep masseter peaks first on average, followed in succession by the balancing-side deep masseter, balancing-side superficial masseter, and finally the working-side superficial masseter. Ring-tailed lemurs are similar to greater galagos in that their balancing-side deep masseter peaks well before their working-side superficial masseter. We see the opposite pattern in anthropoids, where the balancing-side deep masseter peaks, on average, after the working-side superficial masseter. This late activity of the balancing-side deep masseter in anthropoids is linked to lateral-transverse bending, or wishboning, of their mandibular symphyses. Subsequently, the stresses incurred during wishboning are hypothesized to be a proximate reason for strengthening, and hence fusion, of the anthropoid symphysis. Thus, the absence of this muscle-firing pattern in ring-tailed lemurs with their weaker, unfused symphyses provides further correlational support for the symphyseal fusion late-acting balancing-side deep masseter hypothesis linking wishboning and symphyseal strengthening in anthropoids. The early peak activity of the working-side deep masseter in ring-tailed lemurs is unlike galagos and most similar to the pattern seen in macaques and baboons. We hypothesize that this early activity of the working-side deep masseter moves the lower jaw both laterally toward the working side and vertically upward, to position it for the upcoming power stroke. From an evolutionary perspective, the differences in peak firing times for the working-side deep masseter between ring-tailed lemurs and greater galagos indicate that deep masseter firing patterns are not conserved among strepsirrhines.

Animals↗

PubMed2004

Electromyography guides toward subgroups of mutations in muscle channelopathies.

Myotonic syndromes and periodic paralyses are rare disorders of skeletal muscle characterized mainly by muscle stiffness or episodic attacks of weakness. Familial forms are caused by mutations in genes coding for skeletal muscle voltage-gated ion channels. Exercise is known to trigger, aggravate, or relieve the symptoms. Therefore, exercise can be used as a functional test in electromyography to improve the diagnosis of these muscle disorders. Abnormal changes in the compound muscle action potential can be disclosed using different exercise tests. We report the outcome of an inclusive electromyographic survey of a large population of patients with identified ion channel gene defects. Standardized protocols comprising short and long exercise tests were applied on 41 unaffected control subjects and on 51 case patients with chloride, sodium, or calcium channel mutations known to cause myotonia or periodic paralysis. These tests disclosed significant changes of compound muscle action potential, which generally matched the clinical symptoms. Combining the responses to the different tests defined five electromyographic patterns (I-V) that correlated with subgroups of mutations and may be used in clinical practice as guides for molecular diagnosis. We hypothesize that mutations are segregated into the different electromyographic patterns according to the underlying pathophysiological mechanisms.

Action Potentials↗

PubMed2006

Cold extends electromyography distinction between ion channel mutations causing myotonia.

OBJECTIVE: Myotonias are inherited disorders of the skeletal muscle excitability. Nondystrophic forms are caused by mutations in genes coding for the muscle chloride or sodium channel. Myotonia is either relieved or worsened by repeated exercise and can merge into flaccid weakness during exposure to cold, according to causal mutations. We designed an easy electromyography (EMG) protocol combining repeated short exercise and cold as provocative tests to discriminate groups of mutations. METHODS: Surface-recorded compound muscle action potential was used to monitor muscle electrical activity. The protocol was applied on 31 unaffected control subjects and on a large population of 54 patients with chloride or sodium channel mutations known to cause the different forms of myotonia. RESULTS: In patients, repeated short exercise test at room temperature disclosed three distinct abnormal patterns of compound muscle action potential changes (I-III), which matched the clinical symptoms. Combining repeated exercise with cold exposure clarified the EMG patterns in a way that enabled a clear correlation between the electrophysiological and genetic defects. INTERPRETATION: We hypothesize that segregation of mutations into the different EMG patterns depended on the underlying pathophysiological mechanisms. Results allow us to suggest EMG guidelines for the molecular diagnosis, which can be used in clinical practice.

Action Potentials↗

PubMed2007

Improving functional magnetic resonance imaging motor studies through simultaneous electromyography recordings.

Specially designed optoelectronic and data postprocessing methods are described that permit electromyography (EMG) of muscle activity simultaneous with functional MRI (fMRI). Hardware characterization and validation included simultaneous EMG and event-related fMRI in 17 healthy participants during either ankle (n = 12), index finger (n = 3), or wrist (n = 2) contractions cued by visual stimuli. Principal component analysis (PCA) and independent component analysis (ICA) were evaluated for their ability to remove residual fMRI gradient-induced signal contamination in EMG data. Contractions of ankle tibialis anterior and index finger abductor were clearly distinguishable, although observing contractions from the wrist flexors proved more challenging. To demonstrate the potential utility of simultaneous EMG and fMRI, data from the ankle experiments were analyzed using two approaches: 1) assuming contractions coincided precisely with visual cues, and 2) using EMG to time the onset and offset of muscle contraction precisely for each participant. Both methods produced complementary activation maps, although the EMG-guided approach recovered more active brain voxels and revealed activity better in the basal ganglia and cerebellum. Furthermore, numerical simulations confirmed that precise knowledge of behavioral responses, such as those provided by EMG, are much more important for event-related experimental designs compared to block designs. This simultaneous EMG and fMRI methodology has important applications where the amplitude or timing of motor output is impaired, such as after stroke.

Adult↗

PubMedDate not supplied

Cricoarytenoid subluxation, computed tomography, and electromyography findings.

A case of cricoarytenoid subluxation secondary to endotracheal intubation and documented by computed tomography (CT) and electromyography (EMG) is reported. Successful endoscopic reduction of the displaced arytenoid is confirmed by CT. The normal anatomy and physiology of the cricoarytenoid joint is presented and the literature regarding this rarely reported injury is reviewed. Based on this review and the case reported, a treatment plan is proposed.

Arytenoid Cartilage↗

PubMedDate not supplied

Evoked electromyography of the eleventh nerve and trapezius muscle.

Values and criteria for abnormality of the eleventh nerve evoked electromyography (EEMG) have been determined. The nerve conduction velocity and duration appear to be relatively consistent from subject to subject. Amplitude of response, while varying significantly from subject to subject, remains relatively constant when the right shoulder is compared to the left shoulder and when a retest is performed.

Accessory Nerve↗

PubMed1975

Electromyography and mechanics of mastication in the albino rat.

The masticatory apparatus in the albino rat was studied by means of electromyography and subsequent estimation of muscular forces. The activity patterns of the trigeminal and suprahyoid musculature and the mandibular movements were recorded simultaneously during feeding. The relative forces of the individual muscles in the different stages of chewing cycles and biting were estimated on the basis of their physiological cross sections and their activity levels, as measured from integrated electromyograms. Workinglines and moment arms of these muscles were determined for different jaw positions. In the anteriorly directed masticatory grinding stroke the resultants of the muscle forces at each side are identical; they direct anteriorly, dorsally and slightly lingually and pass along the lateral side of the second molar. Almost the entire muscular resultant force is transmitted to the molars while the temporo-mandibular joint remains unloaded. A small transverse force, produced by the tense symphyseal cruciate ligaments balances the couple of muscle resultant and molar reaction force in the transverse plane. After each grinding stroke the mandible is repositioned for the next stroke by the overlapping actions of three muscle groups: the pterygoids and suprahyoids produce depression and forward shift, the suprahyoids and temporal backward shift and elevation of the mandible while the subsequent co-operation of the temporal and masseter causes final closure of the mouth and starting of the forward grinding movement. All muscles act in a bilaterally symmetrical fashion. The pterygoids contract more strongly, the masseter more weakly during biting than during chewing. The wide gape shifts the resultant of the muscle forces more vertically and moreposteriorly. The joint then becomes strongly loaded because the reaction forces are applied far anteriorly on the incisors. The charateristic angle between the almost horizontal biting force and the surface of the food pellet indicates that the lower incisors produce a chisel-like action. Tooth structure reflects chewing and biting forces. The transverse molar lamellae lie about parallel to the chewing forces whereas perpendicular loading of the occlusal surfaces is achieved by their inclination in the transverse plane. The incisors are loaded approximately parallel to their longitudinal axis, placement that avoids bending forces during biting. It is suggested that a predominantly protrusive musculature favors the effective force transmission to the lower incisors, required for gnawing. By grinding food across transversely oriented molar ridges the protrusive components of the muscles would be utilized best. From the relative weights of the masticatory muscles in their topographical relations with joints, molars and incisors it may be concluded that the masticatory apparatus is a construction adapted to optimal transmission of force from muscles to teeth.

Animals↗

PubMed1980

Gross structure and function of the quadriceps femoris in Lemur fulvus: an analysis based on telemetered electromyography.

Analysis based on telemetered electromyography from the quadriceps femoris of Lemur fulvus, a Malagasy prosimian, during walking, galloping, leaping, and a variety of postural behaviors partially confirms and partially contradicts earlier hypothesized functions of this musculoskeletal complex. As predicted on the basis of morphological criteria (large physiological cross-section and long parallel fibers), the vastus lateralis is of special functional significance in leaping. This relatively large muscle consistently initiates the leap and frequently undergoes a very long period of force enhancement via active stretch. By contrast, the vastus intermedius fails to exhibit increased electrical activity and undergoes little or no active stretch during jumps. The myological details of vastus intermedius (short fibers, no fusion with other components), therefore, cannot be accounted for as adaptations to leaping. Rather, a primary postural role is indicated for the vastus intermedius, because in normal resting postures, with the knee quite flexed, it alone is continuously active. The existence of a fibrocartilaginous superior patella in the tendon of vastus intermedius, however, is most plausibly related to the complex tensile and compressive stresses generated in the tendon during the completely hyperflexed phase of leaping. The phasic patterning of the quadriceps femoris of Lemur fulvus does not point to any special role of the vastus lateralis or vastus intermedius during walking and galloping; it does indicate very different patterns of muscle recruitment in comparison to those in nonprimate mammals and some anthropoid primates. The forward cross walk (diagonal sequence, diagonal couplets) of primates versus the backward cross gait (lateral sequence) of most other mammals probably accounts for some of these differences. Lemur fulvus lacks the degree of elastic storage and release of kinetic energy in the quadriceps femoris that characterizes the gallop of dogs, cats, and Erythrocebus patas.

Animals↗

PubMed1988

Quantitative electromyography of the masticatory muscles of Pteropus giganteus (Megachiroptera).

Mastication has been studied by cinematography and quantitative electromyography while flying foxes, Pteropus giganteus, were freely feeding on standardized pieces of apple, soaked raisin, and banana. The primarily orthal mandibular movements are caused by mainly bilaterally symmetrical firing of all the masticatory muscles. Asymmetric activity in the superficial and deep masseter and medial pterygoid causes slight protrusion early in opening. Slight lateral deviations at the end of opening and at the start of closing are caused by asymmetric and asynchronous activity in the pterygoids and digastrics, and by asynchronous firing of the deep temporalis and zygomaticomandibularis. Food consistency affects movement characteristics as well as characteristics of muscular activity. In this study electromyograms were digitized and the number of spikes and mean amplitude per interval (set by the filming rate) recorded. Although a significant correlation exists between descriptors, the product thereof appears to be the best predictor of certain kinematic variables (cycle length and maximum excursion of the mandible). On the other hand, the changes in magnitude of muscular activity as a function of the position of a cycle in the reduction sequence and as a function of food consistency are more translated in a variation of the mean amplitude than in a variation of the number of spikes per interval. Observed variation differs among muscles studied. It is most apparent in the superficial and deep masseter and least in the temporalis and zygomaticomandibularis. Late cycles of apple and raisin mastication are long and exhibit large gapes but almost no anterior movement. The adductor activity frequently shows a synchronized, pulsatile pattern leading to an unfused tetanus.

Animals↗

PubMed1991

Intramuscular pressure and electromyography in four shoulder muscles.

Estimations of shoulder muscle load are important in biomechanic and ergonomic research. We have studied shoulder muscle load in the trapezius (six subjects), deltoid (six subjects), infraspinatus (eight subjects), and supraspinatus (seven subjects) muscles with simultaneous intramuscular pressure (IMP) and intramuscular bipolar electromyography (EMG) recordings. For imposition of shoulder muscle load, the arm was positioned in abduction or flexion with different hand loads (0, 1, or 2 kg), or isometric force registrations were performed. The microcapillary infusion technique was used for IMP recordings. The IMP in the supra- and infraspinatus muscles were high compared with the trapezius and deltoid muscles in abducted arm positions. In all test situations, IMP and EMG gave a similar description of local muscle load. IMP at maximal voluntary contraction was highest in the supraspinatus and infraspinatus muscles. Both IMP and EMG in all four muscles showed an almost linear correlation to recorded isometric external force. The difference in IMP between shoulder muscles in the same arm position may be due to muscle anatomy, muscle function, and compliance of surrounding tissues. Because a high IMP may impede muscle blood flow, our findings may possibly explain the physiological stress on the rotator cuff muscles as compared with the deltoid and trapezius muscles in work with elevated arms.

Biomechanical Phenomena↗

PubMed2005

Is sphincter electromyography a helpful investigation in the diagnosis of multiple system atrophy? A retrospective study with pathological diagnosis.

Sphincter electromyography (spEMG) is often used as an ancillary test when multiple system atrophy (MSA) is suspected. Our aim was to determine the clinical features associated with spEMG being performed, the influence of the result on the final clinical diagnosis, and its utility as a clinical investigation. A retrospective audit of all cases in the Queen Square Brain Bank between 1989 and 2002 was performed. The clinical features and diagnostic accuracy were compared between patients in whom spEMG was performed and those in whom it was not. From 845 sets of complete clinical records, we identified 37 (4.4%) cases that had been investigated with spEMG. Thirty of these cases had a pathological diagnosis of MSA. Of these 30, 24 had abnormal spEMGs, 5 had a borderline result, and only 1 had a normal spEMG. Sixty-six cases had pathologically proven MSA but no spEMG. Those investigated with spEMG were younger at disease onset (P < 0.001), more frequently male (P = 0.03), and more likely to have had other investigations performed. They had a greater incidence of pyramidal tract signs at final clinical diagnosis, and the final clinical diagnostic accuracy was higher (P = 0.04). Due to the retrospective nature of the study, balanced populations for calculation of sensitivity and specificity were not available. In this selected series of pathologically confirmed cases, investigation with spEMG was one of several factors associated with improved clinical diagnostic accuracy. A normal spEMG is unlikely in pathologically proven MSA, at least in cases with a mean symptom duration of more than 5 years when the test is performed.

Adult↗

PubMed2006

Electromyography patterns of propriospinal myoclonus can be mimicked voluntarily.

In order to investigate the clinical impact of polymyographic evaluation on the diagnosis of propriospinal myoclonus (PSM), we performed electromyography recordings of various truncal muscles in eight healthy volunteers while they mimicked PSM symptoms. Before the experiment, each volunteer learned how to mimic PSM by watching a videotape that showed typical PSM characteristics, i.e., brief symmetric flexion of the trunk. The recorded polymyographic patterns of all volunteers were quite compatible with those found in the previous reports. The present study demonstrates that previously known polymyographic patterns of PSM can be voluntarily mimicked. Additional studies, such as jerk-locked cortical potential, are required to confirm the diagnosis of true PSM.

Adult↗

PubMed1995

Anorectal function in fluctuating (on-off) Parkinson's disease: evaluation by combined anorectal manometry and electromyography.

Anorectal dysfunction and constipation are well recognized in Parkinson's disease and may reflect the direct involvement of the gastrointestinal tract by the primary Parkinson's disease process. We hypothesized, therefore, that anorectal function would alter in parallel with fluctuations in motor function related to on- and off-periods in Parkinson's disease, and employed combined anorectal manometry and electromyography to investigate anorectal function during both on- and off-periods in patients with Parkinson's disease. Manometric recordings revealed a deterioration in voluntary sphincter squeeze during off-periods (squeeze index, on versus off, mean +/- SEM: 46.4 +/- 11.1 versus 29.6 +/- 7.9 mm Hg, p < 0.05); correspondingly, simultaneous electromyographic (EMG) recordings showed poor recruitment of external anal sphincter and puborectalis muscles during off-periods. A hypercontractile ("paradoxical") rectosphincteric reflex response occurred during both on- and off-periods, and was associated with an increase in EMG activity in the external sphincter and/or the puborectalis muscle. These changes in manometric and EMG parameters paralleled changes in overall motor function. These findings provide further support for the involvement of the pelvic floor musculature in the Parkinson's disease process and also provide EMG correlates for some of the manometric abnormalities described in Parkinson's disease.

Age of Onset↗

PubMed1996

Unilateral injection of botulinum toxin in blepharospasm: single fiber electromyography and blink reflex study.

We studied six patients affected with blepharospasm (BSP). We injected botulinum toxin (BTX) around only one eye and saline solution around the other. Clinical rating of BSP was performed. Single fiber electromyography (SFEMG), compound motor action potential (cMAP) at the orbicularis oculi muscle by stimulation of the facial nerve, blink reflex, and blink reflex recovery curve were recorded. All clinical and electrophysiological investigations were carried out before, and 1, 2, and 4 weeks after treatment. Evidence of bilateral clinical benefit was provided. Following therapy, facial cMAP decreased bilaterally and SFEMG revealed statistically significant changes on both sides while the excitability curve of blink reflex remained unmodified. The results confirm that BTX affects merely the neuromuscular junctions. The clinical and neurophysiological effects are present on both sides also for unilateral injection probably because of toxin spreading.

Aged↗

PubMed1997

Validity of long-term electromyography in the quantification of tremor.

We previously developed a method of tremor quantification using long-term electromyography registration of antagonistic forearm muscles that is reliable, sensitive, and specific for pathologic tremors. The present study demonstrates that tremor occurrence as measured by this method correlates well with clinical parameters of tremor in idiopathic Parkinson's disease (PD) and essential tremor (ET) (subscores of the Unified Parkinson's Disease Rating Scale for PD, tremor rating according to Bain et al. for ET). We conclude that the method is a valid and objective means of tremor quantification in PD and ET.

Activities of Daily Living↗

PubMed2002

Electromyography of sternocleidomastoid muscle in ALS: a prospective study.

Needle electromyography (EMG) of the tongue is difficult to perform because of frequent uncontrollable movement. We chose the sternocleidomastoid (SCM) muscle as a possible alternative for assessing the involvement of the rostral neuraxis in amyotrophic lateral sclerosis (ALS). We prospectively studied 21 ALS patients during our initial diagnostic evaluation. EMG parameters that we recorded included the presence of abnormal spontaneous activity, pattern of motor unit potential recruitment, and configuration of motor unit action potentials. For the six patients with bulbar-onset ALS, three had abnormalities in the SCM and three had abnormalities in the tongue. In contrast, for the 15 patients with limb-onset ALS, 9 had abnormalities in the SCM, and only 3 had abnormalities in the tongue. Our results demonstrate the utility of needle EMG of the SCM in the evaluation of ALS. EMG of the SCM carries a similar sensitivity as the tongue in ALS patients with bulbar symptoms, but is more sensitive than the tongue in patients without bulbar symptoms. SCM innervation includes the rostral cervical cord and brainstem, and EMG abnormalities in this muscle support a diffuse involvement, which is unique to ALS.

Action Potentials↗