Spontaneous EMG Activity Research Articles

Allogenic umbilical cord-derived mesenchymal stromal cells improve motor function in prenatal surgical repair of myelomeningocele: An ovine model study.

To investigate the effects of an adjuvant allogenic umbilical cord mesenchymal stromal cell (UC-MSC) patch applied during fetal surgery on motor and sphincter function in the ovine MMC model. MMC defects were surgically created at 75 days of gestation and repaired 14 days later. Ovine MMC model: fetal lambs. We compared lambs that received a UC-MSC patch with a control group of lambs that received an acellular patch. Clinical neurological assessment was performed at 2 and 24 hours of life and included determination of the Sheep Locomotor Rating scale (SLR), which has been validated in the ovine MMC model. Electrophysical examinations, spine scans and histological analyses were also performed. Of the 13 operated lambs, nine were born alive: five had of these had received a UC-MSC patch and four an acellular patch. At 24 hours of life, lambs in the UC-MSC group had a significantly higher score (14 versus 5, P = 0.04). Amyotrophy was significantly more common in the control group (75% versus 0%, P = 0.02). All the lambs in the control group and none of those in the UC-MSC group were incontinent. No significant differences were observed between the UC-MSC and control groups in terms of the presence of spontaneous EMG activity, nerve conduction or spinal evoked potentials. In the microscopic examination, lambs in the UC-MSC group had less fibrosis between the spinal cord and the dermis (mean thickness, 453 versus 3921 μm, P = 0.03) and around the spinal cord (mean thickness, 47 versus 158 μm, P < 0.001). Examination of the spinal cord in the area of the MMC defect showed a higher large neuron density in the UC-MSC group (14.5 versus 5.6 neurons/mm2, P < 0.001). No tumours were observed. Fetal repair of MMC using UC-MSC patches improves motor and sphincter function as well as spinal preservation and reduction of fibrosis.

Combining electromyography and Raman spectroscopy: optical EMG.

Electromyography (EMG) remains a key component of the diagnostic work-up for suspected neuromuscular disease, but it does not provide insight into the molecular composition of muscle which can provide diagnostic information. Raman spectroscopy is an emerging neuromuscular biomarker capable of generating highly specific, molecular fingerprints of tissue. Here, we present "optical EMG," a combination of EMG and Raman spectroscopy, achieved using a single needle. An optical EMG needle was created to collect electrophysiological and Raman spectroscopic data during a single insertion. We tested functionality with in vivo recordings in the SOD1G93A mouse model of amyotrophic lateral sclerosis (ALS), using both transgenic (n = 10) and non-transgenic (NTg, n = 7) mice. Under anesthesia, compound muscle action potentials (CMAPs), spontaneous EMG activity and Raman spectra were recorded from both gastrocnemius muscles with the optical EMG needle. Standard concentric EMG needle recordings were also undertaken. Electrophysiological data were analyzed with standard univariate statistics, Raman data with both univariate and multivariate analyses. A significant difference in CMAP amplitude was observed between SOD1G93A and NTg mice with optical EMG and standard concentric needles (p = .015 and p = .011, respectively). Spontaneous EMG activity (positive sharp waves) was detected in transgenic SOD1G93A mice only. Raman spectra demonstrated peaks associated with key muscle components. Significant differences in molecular composition between SOD1G93A and NTg muscle were identified through the Raman spectra. Optical EMG can provide standard electrophysiological data and molecular Raman data during a single needle insertion and represents a potential biomarker for neuromuscular disease.

WE-225. Comparison of spontaneous EMG activity from two lower facial muscles during microvascular cranial nerve decompression

WE-225. Comparison of spontaneous EMG activity from two lower facial muscles during microvascular cranial nerve decompression

Extramuscular Recording of Spontaneous EMG Activity and Transcranial Electrical Elicited Motor Potentials in Horses: Characteristics of Different Subcutaneous and Surface Electrode Types and Practical Guidelines.

IntroductionAdhesive surface electrodes are worthwhile to explore in detail as alternative to subcutaneous needle electrodes to assess myogenic evoked potentials (MEP) in human and horses. Extramuscular characteristics of both electrode types and different brands are compared in simultaneous recordings by also considering electrode impedances and background noise under not mechanically secured (not taped) and taped conditions.MethodsIn five ataxic and one non-ataxic horses, transcranial electrical MEPs, myographic activity, and noise were simultaneously recorded from subcutaneous needle (three brands) together with pre-gelled surface electrodes (five brands) on four extremities. In three horses, the impedances of four adjacent-placed surface-electrode pairs of different brands were measured and compared. The similarity between needle and surface EMGs was assessed by cross-correlation functions, pairwise comparison of motor latency times (MLT), and amplitudes. The influence of electrode noise and impedance on the signal quality was assessed by a failure rate (FR) function. Geometric means and impedance ranges under not taped and taped conditions were derived for each brand.ResultsHigh coherencies between EMGs of needle-surface pairs degraded to 0.7 at moderate and disappeared at strong noise. MLTs showed sub-millisecond simultaneous differences while sequential variations were several milliseconds. Subcutaneous MEP amplitudes were somewhat lower than epidermal. The impedances of subcutaneous needle electrodes were below 900 Ω and FR = 0. For four brands, the FR for surface electrodes was between 0 and 80% and declined to below 25% after taping. A remaining brand (27G DSN2260 Medtronic) revealed impedances over 100 kΩ and FR = 100% under not taped and taped conditions.ConclusionSubcutaneous needle and surface electrodes yield highly coherent EMGs and TES–MEP signals. When taped and allowing sufficient settling time, adhesive surface-electrode signals may approach the signal quality of subcutaneous needle electrodes but still depend on unpredictable conditions of the skin. The study provides a new valuable practical guidance for selection of extramuscular EMG electrodes. This study on horses shares common principles for the choice of adhesive surface or sc needle electrodes in human applications such as in intraoperative neurophysiological monitoring of motor functions of the brain and spinal cord.

Spastic dystonia in stroke subjects: prevalence and features of the neglected phenomenon of the upper motor neuron syndrome

ObjectiveSpastic dystonia is one of the positive phenomena of the upper motor neuron syndrome (UMNS). It is characterised by the inability to relax a muscle leading to a spontaneous, although stretch-sensitive, tonic contraction. Although spastic dystonia is a recognized cause of muscle hypertonia, its prevalence among hypertonic muscles of stroke subjects has never been investigated. Differently from spasticity, which is an exaggerated stretch reflex, spastic dystonia is viewed as an efferent phenomenon, due to an abnormal central drive to motoneurons. MethodsIn 23 hemiparetic stroke subjects showing increased muscle tone of wrist flexors, surface EMG was used to investigate the presence of spontaneous, stretch-sensitive EMG activity in flexor carpi radialis. ResultsSpontaneous, stretch-sensitive EMG activity was found in 17 subjects. In the remaining 6 subjects, no spontaneous EMG activity was found. ConclusionsThe majority of stroke subjects is affected by spastic dystonia in their hypertonic wrist flexor muscles. Only a minority of subjects is affected by spasticity. SignificanceTo stop spastic dystonia from being the neglected aspect of UMNS, it is essential to link its definition to increased muscle tone, as occurred for spasticity. Recognizing the real phenomena underling muscle hypertonia could improve its management.

Intraoperative neurophysiological monitoring during spinal surgery

Intraoperative neurophysiological monitoring (IOM) is a technique that may contribute to avoiding permanent neurological injury during spine surgery procedure, especially in patients undergoing scoliosis correction. In the last 12 months 26 patients underwent spinal procedures for scoliosis and kyphosis, spinal (cervical or lumbar) stenosis, degenerative disc disease; a patient with posttraumatic L1 fracture and a patient with intradural extramedullary neurinoma were monitored too. TIVA-TCI anesthesia was used in all patients while muscle relaxants were limited only during some patient’s intubation. SEPs (median and tibial nerve) and MEPs (ADM and TA-AH muscles and in cervical surgery also deltoid and ECD muscles) were attempted in all patients. Spontaneous EMG activity was also recorded from multiple muscles. Only in two cases we had significant prolonged alterations of IOM: during a D3 neurinoma surgery we observed the loss of MEPs from a leg with return at normality after a stop and change of neurosurgery procedures; in a decompression/stabilization D10-S1 cortical SEPs and MEPs of right leg slowly reduced progressively until the end of surgery (with a slight transitory paresis). The use of IOM in spine surgery affects positively the neurological outcome so that it has to become a routine procedure.

71. Intraoperative blink reflex monitoring during microvascular decompression for trigeminal neuralgia

Microvascular decompression surgery (MVD) is an established technique for refractory trigeminal neuralgia. In order to reduce the risk of 5°, 7° and 8° cranial nerve lesions, intraoperative monitoring is recommended. To evaluate intraoperative BR modification during MVD surgery. Considering the reflex arc, BR could be useful to monitor sensory part of trigeminal nerve, facial nerve and brainstem function during MVD. We evaluated BR intraoperative modifications in all patients who underwent MVD surgery for trigeminal neuralgia from 2013 to 2016. All the patients underwent surgery with monitoring of BAEPs, EMG free run, BR and direct nerves stimulation. BR was recorded in 14/18 patients. In 12/14 R1 amplitude was stable; these patients didn’t report postoperative facial or trigeminal nerve lesions. In 2/14 we observed intraoperative decrease of R1 amplitude. In one patient, we recorded B and C train at EMG free run; after the operation, he experienced a transient facial palsy. In the other patient, we didn’t record spontaneous pathological EMG activity in facial muscles and we recorded stable amplitude responses after direct nerves stimulation. After the operation, he reported hemifacial hypoesthesia. BR can be an integrative monitoring technique during MVD surgery.

A case of involuntary rhythmic and characteristic tapping sounds during sleep

Abstract Involuntary motor disorders during sleep, such as sleep bruxism (SB) or facio-mandibular myoclonus (FMM), are observed in the oromandibuar area. This feature is repetitive and rhythmic movement produced by short muscle contraction. We report here a case of involuntary repetitive and unusual tapping sounds. The repetitive periodic jaw movement was observed every night but was absent during waking hours. The unusual sounds were confirmed both by audio recorder and the patient's bed partner. Video PSG showed spontaneous myoclonic EMG activity associated with lip movements and characteristic sounds from the patient's mouth. The movements existed in clusters throughout sleep. There are similarities and differences between this case and SB and FMM. The sleep stage and EMG activity in this case were similar to SB and FMM. The EMG burst duration was short as in FMM rather than the longer duration in SB. However, neither the characteristic sounds of grinding or clenching typical of SB nor the clicking sounds typical of FMM were observed. In addition, there was no history of tongue biting, which frequently occurs in SB and FMM. The authors were unable to find any reports regarding treatment for tapping sound, and unfortunately our attempted treatment was ineffective. In this case there was no response to either levetiracetam or clonazepam. Only triazolam reduced the number of episodes but did not result in a complete cure. This is the first reported case of video PSG documented rhythmic tapping sounds might be occurred from patient's oral cavity. We suggest that this case should be viewed as distinct from SB or FMM.

Chemogenetic enhancement of functional recovery after a sciatic nerve injury

Designer receptors exclusively activated by designer drugs (DREADDs) are chemogenetic tools used to modulate neuronal excitability. We hypothesized that activation of excitatory (Gq) DREADD by its designer ligand, clozapine-N-oxide (CNO), would increase the excitability of neurons whose axons have been transected following peripheral nerve injury, and that this increase will lead to an enhanced functional recovery. The lateral gastrocnemius (LG) muscle of adult female Lewis rats was injected unilaterally with AAV9- hsyn- hM3Dq-mCherry (7.6×109 viral genomes/μL) to transduce Gq-DREADD expression in LG neurons. The contralateral LG muscle served as an uninjected control. No significant changes in either spontaneous EMG activity or electrically evoked direct muscle (M) responses were found in either muscle after injection of CNO (1mg/kg, i.p.). The amplitude of monosynaptic H-reflexes in LG was increased after CNO treatment exclusively in muscles previously injected with virus, suggesting that Gq-DREADD activation increased neuronal excitability. After bilateral sciatic nerve transection and repair, additional rats were treated similarly with CNO for up to three days after injury. Electrophysiological data were collected at 2, 4 and 6weeks after injury. Evoked EMG responses were observed as early as 2weeks after injury only in Gq-DREADD expressing virus injected LG muscle. By 4weeks after injury, both M-response and H-reflex amplitudes were significantly greater in muscles previously injected with viral vector than contralateral, uninjected muscles. Increases in the excitability of injured neurons produced by this novel use of Gq-DREADD were sufficient to promote an enhancement in functional recovery after a sciatic nerve injury.

An improved approach for measuring the tonic stretch reflex response of spastic muscles

We propose a new method for detecting the onset of the stretch reflex response for assessment of spasticity based on the Tonic Stretch Reflex Threshold (TSRT). Our strategy relies on a three-stage approach to detect the onset of the reflex EMG activity: (i) Reduction of baseline activity by means of Empirical Mode Decomposition; (ii) Extraction of the complex envelope of the EMG signal by means of Hilbert Transform (HT) and; iii) A double threshold decision rule. Simulated and real EMG data were used to evaluate and compare our method (TSRT-EHD) against three other popular methods described in the literature to assess TSRT (‘Kim’, ‘Ferreira’ and ‘Blanchette’). Four different groups of signals containing simulated evoked stretch reflex EMG activities were generated: groups A and B without spontaneous EMG activity at rest and signal-to-noise ratio (SNR) of 10dB and 20dB respectively; groups C and D with spontaneous EMG activity at rest, as observed frequently in spastic muscles, and SNR of 10dB and 20dB respectively. The results with simulated data showed a significantly higher accuracy of TSRT-EHD for detecting the onset of the reflex EMG activity in groups C and D when compared to the other methods. Analyses using real data from five post stroke spastic subjects demonstrated that the TSRTs generated by each method were dramatically different from one another. Nevertheless, only TSRT-EHD provided valid measures across all subjects.

Acute nerve stretch and the compound motor action potential

In this paper, the acute changes in the compound motor action potential (CMAP) during mechanical stretch were studied in hamster sciatic nerve and compared to the changes that occur during compression.In response to stretch, the nerve physically broke when a mean force of 331 gm (3.3 N) was applied while the CMAP disappeared at an average stretch force of 73 gm (0.73 N). There were 5 primary measures of the CMAP used to describe the changes during the experiment: the normalized peak to peak amplitude, the normalized area under the curve (AUC), the normalized duration, the normalized velocity and the normalized velocity corrected for the additional path length the impulses travel when the nerve is stretched. Each of these measures was shown to contain information not available in the others.During stretch, the earliest change is a reduction in conduction velocity followed at higher stretch forces by declines in the amplitude of the CMAP. This is associated with the appearance of spontaneous EMG activity. With stretch forces < 40 gm (0.40 N), there is evidence of increased excitability since the corrected velocities increase above baseline values. In addition, there is a remarkable increase in the peak to peak amplitude of the CMAP after recovery from stretch < 40 gm, often to 20% above baseline.Multiple means of predicting when a change in the CMAP suggests a significant stretch are discussed and it is clear that a multifactorial approach using both velocity and amplitude parameters is important. In the case of pure compression, it is only the amplitude of the CMAP that is critical in predicting which changes in the CMAP are associated with significant compression.

Sensitivity of MUP parameters in detecting change in early ALS

ObjectivesWe aimed to identify the most appropriate MUP parameter to evaluate reinnervation in very early ALS. MethodsWe studied tibialis anterior (TA), initially of normal strength with normal MUP analysis parameters, in 15 patients with ALS of recent onset. They were studied at the initial diagnostic assessment, and then 3 and 6months later. Spontaneous EMG activity was recorded. Conventional MUP analysis included mean amplitude, mean area, mean duration, mean number of phases, mean number of turns, % polyphasic potentials, mean jitter, % unstable pairs and % pairs with blocking. Non-parametric statistics were utilised in the analysis. ResultsFasciculations were recorded in 72% in TA and increased jitter in 33% at study entry, but without EMG features of denervation. Mean amplitude, mean duration, mean area and the three measures of neuromuscular transmission increased significantly and linearly at each evaluation. Median duration showed the lowest variation and, together with jitter, the largest relative time effect. ConclusionsMean duration and mean jitter are the most effective measures of early reinnervation in a very early affected muscle, in ALS. SignificanceMean MUP duration is a simple and easy measure that should be useful in evaluating reinnervation, for example in a future clinical trial.

Cardiorespiratory coupling of sympathetic outflow in humans: a comparison of respiratory and cardiac modulation of sympathetic nerve activity to skin and muscle

What is the central question of this study?Muscle sympathetic nerve activity (MSNA) is well known to be modulated by the arterial baroreceptors and respiration, but what are the magnitudes of cardiac and respiratory modulation of skin sympathetic nerve activity (SSNA), which primarily subserves thermoregulation?What is the main finding and what is its importance?Using direct microelectrode recordings of MSNA and SSNA in awake humans, we show that the magnitude of respiratory modulation of SSNA is identical to that of MSNA, the primary difference between the two sources of sympathetic outflow being the greater cardiac modulation of MSNA. This emphasises the role of the baroreceptors in entraining sympathetic outflow to muscle. It is well known that microelectrode recordings of skin sympathetic nerve activity (SSNA) in awake human subjects reveal spontaneous bursts of activity with no overt modulation by changes in blood pressure or respiration, in contrast to the clear cardiac and respiratory modulation of muscle sympathetic nerve activity (MSNA). However, cross-correlation analysis has revealed that, like individual muscle vasoconstrictor neurones, the firing of individual cutaneous vasoconstrictor neurones is temporally coupled to both the cardiac and respiratory rhythms during cold-induced cutaneous vasoconstriction, and the same is true of single sudomotor neurones during heat-induced sweating. Here, we used cross-correlation analysis to determine whether SSNA exhibits cardiac and respiratory modulation in thermoneutral conditions and to compare respiratory and cardiac modulation of SSNA with that of MSNA. Oligounitary recordings of spontaneous SSNA (n = 20) and MSNA (n = 18) were obtained during quiet, unrestrained breathing. Respiration was recorded by a strain-gauge transducer around the chest and ECG recorded by surface electrodes. Respiratory and cardiac modulation of SSNA and MSNA were quantified by fitting polynomial equations to the cross-correlation histograms constructed between the sympathetic spikes and respiration or ECG. The amplitude of the respiratory modulation (52.5 ± 3.4%) of SSNA was not significantly different from the amplitude of the cardiac modulation (46.6 ± 3.2%). Both were comparable to the respiratory modulation of MSNA (47.7 ± 4.2%), while cardiac modulation of MSNA was significantly higher (89.8 ± 1.5%). We conclude that SSNA and MSNA share similar levels of respiratory modulation, the primary difference between the two sources of sympathetic outflow being the marked cardiac modulation of MSNA provided by the baroreceptors.

A review of intraoperative monitoring for spinal surgery.

Background:Intraoperative neurophysiologic monitoring (IONM) is a technique that is helpful for assessing the nervous system during spine surgery.Methods:This is a review of the field describing the basic mechanisms behind the techniques of IONM. These include the most often utilized trancranial motor evoked potentials (Tc-MEPs), somatosensory evoked potentials (SSEPs), and stimulated and spontaneous EMG activity. It also describes some of the issues regarding practices and qualifications of practitioners.Results:Although the anatomic pathways responsible for the Tc-MEP and SSEP are well known and these clinical techniques have a high sensitivity and specificity, there is little published data showing that monitoring actually leads to improved patient outcomes. It is evident that IONM has high utility when the risk of injury is high, but may be only marginally helpful when the risk of injury is very low. The monitoring team must be well trained, be able to provide the surgeon feedback in real time, and coordinate activities with those of the surgical and anesthesia teams.Conclusions:Although IONM is a valuable technique that provides sensitive and specific indications of neurologic injury, it does have limitations that must be understood. Maintaining a high quality of practice with appropriately trained personnel is critical.

Is your patient sleeping?

Is your patient sleeping?

Recovery of Electromyographic Activity After Transection and Surgical Repair of the Rat Sciatic Nerve

The recovery of soleus (SOL), gastrocnemius (GAS), and tibialis anterior (TA) electromyographic activity (EMG) after transection and surgical repair of the sciatic nerve was studied in Sprague-Dawley rats using chronically implanted stimulation and recording electrodes. Spontaneous EMG activity in SOL and GAS and direct muscle (M) responses to posterior tibial nerve stimulation persisted for < or =2 days after sciatic nerve transection, but SOL and GAS H-reflexes disappeared immediately. Spontaneous EMG activity began to return 2-3 wk after transection, rose nearly to pretransection levels by 60 days, and persisted for the duration of the study period (120 days). Recovery of stimulus-evoked EMG responses began about 30 days after sciatic nerve transection as multiple small responses with a wide range of latencies. Over time, the latencies of these fractionated responses shortened, their amplitudes increased, and they merged into a distinct short-latency component (the putative M response) and a distinct long-latency component (the putative H-reflex). The extent of recovery of stimulation-evoked EMG was modest: even 100 days after sciatic nerve transection, the responses were still much smaller than those before transection. Similar gradual development of responses to posterior tibial nerve stimulation was also seen in TA, suggesting that some regenerating fibers sent branches into both tibial and common peroneal nerves.

Spontaneous Needle Electromyographic Activity in Myofascial Trigger Points in the Infraspinatus Muscle: A Blinded Assessment

Objective: Myofascial pain syndromes associated with trigger points [TrPs] are an established clinical entity but the structural and functional abnormalities of TrPs are not well under stood. The aim of the study was to conduct a blinded electromyographic investigation of TrPs.Methods: Nineteen young subjects with chronic shoulder and arm pain, who had a TrP [i.e., a tender point with referred pain, producing at least some of the pain complaint] in the infraspinatus muscle, were examined. This point and a nontender control point in the same muscle were code-marked, in order to blind the examiner. Around both points 20 concentric needle electromyographic [EMG] recordings were obtained at rest.Results: More subjects had spontaneous EMG activity at the TrPs than at the control point. The EMG activity was interpreted as end-plate noise or spikes or both. The TrP Root Mean Square amplitudes were significantly higher than at the control points.Conclusion: Our investigation has demonstrated the presence of spont...

Specific processing of the spontaneous EMG. Detection and classification of multiplets using self-organizing neural networks.

To the authors' knowledge, their study is the first approach to a quantitative study of spontaneous EMG. Using the given algorithm, the spontaneous EMG firing that occurs in spasmophilia has been studied on a quantitative basis, and clinical preliminary results have confirmed it as a useful tool to make the diagnostic process more sensitive, and to help in the quantitative analysis concerning clinical correlation with different pathologies. After a classification of the multiplets is performed, the final maps may be used, together with other clinical and paraclinical data, as tools the clinician may rely on in monitoring the patient's status and eventual effects of therapy. In a study on thyroidian pathology with signs of spontaneous EMG activity where 41 subjects were investigated, the program based on the authors' algorithm allowed the dynamic quantitative monitoring of the impact of the modifications of the plasmatic concentration of the thyroidian hormones on the P-Ca metabolism in order to properly initiate and conduct the therapy. The authors' quantitative approach seems promising for further use in clinical practice; it is a distinct noninvasive quantitative EMG examination that can be used by the physician in conjunction with other laboratory and clinical data.

ADAPTATIONS OF RAT PHRENIC MOTONEURONS TO INACTIVITY 130

Morphological and metabolic adaptations of phrenic motoneurons were assessed in response to two weeks of inactivity induced by cervical spinal cord hemisection at C2 level (spinal isolation; SI). The efficacy of SI was verified by the absence of spontaneous inspiratory-related EMG activity in right hemidiaphragm muscle. Phrenic motoneurons on the right side were retrogradely labeled using the fluorescence tracer, fast blue. After two weeks, the cervical cord and a segment of the right mid-costal diaphragm muscle were excised. Labeled phrenic motoneurons were processed using quantitative histochemical techniques for succinate dehydrogenase (SDH) activity. Type II muscle fibers in the diaphragm were identified by immunoreactivity for an anti-fast myosin heavy chain antibody. Nerve terminals on type I and II muscle fibers were then visualized by immunoreactivity for anti-protein gene product (PGP-7.5) and motor endplates were visualized by binding with tetramethlrhodamine α-bungarotoxin. The SDH activity and somal diameter of phrenic motoneurons, and the planner areas of nerve terminals and motor endplates were quantified using a computerized image-processing system. Phrenic motoneuron SDH activity was not significantly different between SI and control animals. Somal diameter of phrenic motoneurons in the SI group was smaller than in controls. In particular, the number of larger phrenic motoneurons (with somal diameters greater than 40μm) decreased in the SI group. These larger motoneurons putatively innervate fast-twitch motor units. The areas of nerve terminals and motor endplates on type II fibers increased in SI animals, while the areas of neuromuscular junctions on type I fiber were unchanged. Based on these results, we conclude that adaptations of phrenic motoneurons to inactivation are restricted to fast-twitch motor units.

Vagal esophagomotor nerve function and esophageal motor performance in dogs with congenital idiopathic megaesophagus

Abstract Objectives To examine the integrity of the vagal efferent innervation to the esophagus and to assess esophageal motor performance in dogs with congenital idiopathic megaesophagus. Design An acute experimental protocol performed in control dogs and dogs with naturally acquired congenital idiopathic megaesophagus under pentobarbitone anesthesia. Animals 4 dogs with congenital idiopathic megaesophagus and 16 control dogs. Procedure Esophageal motor nerve conduction studies were performed by recording evoked compound motor action potentials from the tunica muscularis of the distal thoracic portion of the esophagus in response to supramaximal stimulation of the cervical portion of the vagus nerve at cranial and caudal sites. Subsequently, esophageal motor performance was measured over a wide range of esophageal muscle lengths by recording intraesophageal pressure responses to supramaximal twitch and tetanic stimulation of the cervical portion of the vagus at varying, stepwise amounts of esophageal distention. Results In dogs with congenital idiopathic megaesophagus, no electrophysiologic evidence was found for segmental demyelination or axonal degeneration in cervical vagal motor fibers innervating striated muscle of the thoracic esophagus portion. Nor was spontaneous EMG activity, indicative of esophageal muscle denervation or a primary myopathy, observed. In contrast, esophageal motor performance, which was dependent on esophageal dimensions, was reduced in dogs with congenital idiopathic megaesophagus. Conclusions In dogs with congenital idiopathic megaesophagus, the vagal efferent innervation to the esophagus is likely to be normal, a primary esophageal myopathy is unlikely to be present, and the observed reduction in esophageal motor performance may arise as a secondary consequence of altered esophageal biomechanical properties rather than from a primary neuromuscular abnormality. (Am J Vet Res 1996;57:906–913)