Evoked Muscle Potentials Research Articles

Transcranial electrical evoked muscle potentials for pediatric neurosurgery: scoping review of stimulation techniques and success rates.

The background of this scoping review is that pediatric neurosurgery in the vicinity of motor pathways is associated with the risk of motor tract damage. By measuring transcranial electrical evoked potentials in muscles (electromyogram) or from the spinal cord (epidural D-wave) functional disorders and impending damage can be detected during surgery and countermeasures can be initiated. The objective was to summarize stimulation techniques of transcranial electrical stimulation and the success rate of motor evoked potentials exclusively in children undergoing neurosurgery. The data source was a literature search for reports meeting the suitability criteria (original articles and case series including motor evoked potentials and pediatric neurosurgery). Twenty-four articles meeting suitability criteria were retrieved. The most common primary electrode positions for electrical stimulation were at C3 vs. C4 and C1 vs. C2 according to the 10-20-system of EEG. Single trains of 1 to 9 pulses with voltages from 160 to 900V and pulse durations from 50 to 500µs were applied for voltage-controlled stimulation. Interstimulus intervals ranged from 0.1 to 9.9ms. Signals were filtered with high-pass filters between 1.5 and 300Hz and low-pass filters between 500 and 5000Hz. The overall rate of successful stimulation and measurement was 90.5% (N = 769). A broad range of stimulation parameters was used for transcranial electrical evoked potentials. Measurable potentials were obtained in most patients. Consideration of safety precautions is an important implication to avoid adverse events by application of high voltage to the motor cortex.

Molecular signaling predicts corticospinal axon growth state and muscle response plasticity induced by neuromodulation

Electrical motor cortex stimulation can produce corticospinal system plasticity and enhance motor function after injury. We investigate molecular mechanisms of structural and physiological plasticity following electrical neuromodulation, focusing on identifying molecular predictors, or biomarkers, for durable plasticity. We used two neuromodulation protocols, repetitive multipulse stimulation (rMPS) and patterned intermittent theta burst stimulation (iTBS), incorporating different stimulation durations and follow-up periods. We compared neuromodulation efficacy in promoting corticospinal tract (CST) sprouting, motor cortex muscle evoked potential (MEP) LTP-like plasticity, and their associated molecular underpinnings. Only iTBS produced CST sprouting after short-term neuromodulation (1 d of stimulation; 9-d survival for sprouting expression); both iTBS and rMPS produced sprouting with long-term (10-d) neuromodulation. Significant mTOR signaling activation and phosphatase and tensin homolog (PTEN) protein deactivation predicted axon growth across all neuromodulation conditions that produced significant sprouting. Both neuromodulation protocols, regardless of duration, were effective in producing MEP enhancement. However, persistent LTP-like enhancement of MEPs at 30 d was only produced by long-term iTBS. Statistical modeling suggests that Stat3 signaling is the key mediator of MEP enhancement. Cervical spinal cord injury (SCI) alone did not affect baseline molecular signaling. Whereas iTBS and rMPS after SCI produced strong mTOR activation and PTEN deactivation, only iTBS produced Stat3 activation. Our findings support differential molecular biomarkers for neuromodulation-dependent structural and physiological plasticity and show that motor cortex epidural neuromodulation produces molecular changes in neurons that support axonal growth after SCI. iTBS may be more suitable for repair after SCI because it promotes molecular signaling for both CST growth and MEP plasticity.

Traumatic and iatrogenic sciatic nerve injury in 38 dogs and 10 cats: Clinical and electrodiagnostic findings.

Reports describing sciatic nerve injuries (SNI) and their outcome are scarce in veterinary medicine. Describe the causes of traumatic and iatrogenic SNI and evaluate which clinical and electrodiagnostic findings predict outcome. Thirty-eight dogs and 10 cats with confirmed SNI referred for neurologic and electrodiagnostic evaluation. Clinical and electrodiagnostic examination results, including electromyography (EMG), motor nerve conduction studies, muscle-evoked potential (MEP), F-waves, sensory nerve conduction studies, and cord dorsum potential (CDP), were retrospectively evaluated. Quality of life (QoL) was assessed based on owner interviews. Surgery (42%) and trauma (33%) were the most common causes of SNI; in dogs, 24% were caused by bites from wild boars. Ability to flex and extend the tarsus was significantly associated with positive outcome in dogs. Mean time from onset of clinical signs until electrodiagnostic evaluation was 67 ± 65 (range, 7-300) days and 65 ± 108 (range, 7-365) days for dogs and cats, respectively. A cut-off amplitude of 1.45 mV for compound motor action potentials (CMAP) was predictive of positive outcome in dogs (P = .01), with sensitivity of 58% and specificity of 100%. Clinical motor function predicts recovery better than sensory function. Electrodiagnostic findings also may play a role in predicting the outcome of SNI. Application of the proposed CMAP cut-off amplitude may assist clinicians in shortening the time to reassessment or for earlier suggestion of salvage procedures. Owners perceived a good quality of life (QoL), even in cases of hindlimb amputation.

Electric Epidural Stimulation of the Spinal Cord of the Decerebrated Rat

Decerebrated animals are often used in experimental neurophysiology to study multilevel physiological processes. The model of a decerebrated cat is traditionally used to study locomotion in acute experiments. We wondered if it would be possible to replace it with electrical epidural stimulation of the spinal cord with a decerebrated rat model. On an acute preparation of 16 Wistar rats decerebrated at the precollicular level, the tonic muscles activity, muscles evoked potentials and the possibility of inducing locomotion during electrical epidural stimulation of the spinal cord, were studied. Histological control of the level of decerebration was performed in 10 rats. Quadrupedal walking was induced in five animals, bipedal hindlimb walking – in one animal; the parameters of the evoked locomotion do not depend on the substantia nigra degree of damage. The tonic activity and the amplitude of the sensory component of the evoked potential of the hindlimb muscles (mm. tibialis anterior and gastrocnemius medialis) depend on the rostrocaudal level of decerebration – they are higher when the substantia nigra is damaged. Thus, the model under consideration makes it possible to successfully study muscle tonic activity and evoked muscle potentials; however, the use of this model in the study of controlled locomotion requires additional research.

Intradural extramedullary tumor location in the axial view affects the alert timing of intraoperative neurophysiologic monitoring.

Intraoperative neurophysiologic monitoring (IONM) reportedly helps prevent postoperative neurological complications following high-risk spinal cord surgeries. There are negative and positive reports about using IONM for intradural extramedullary (IDEM) tumors. We investigated factors affecting alerts of IONM in IDEM tumor surgery. We analyzed 39 patients with IDEM tumors who underwent surgery using IONM at our hospital between January 2014 and March 2021. Neurological symptoms were evaluated pre- and postoperatively using the manual muscle test (MMT). All patients were evaluated to ascertain the tumor level and location in the axial view, the operative time, intraoperative bleeding volume, and histological type. Additionally, the intraoperative procedure associated with significant IONM changes in transcranial electrical stimulation muscle-evoked potential was investigated. There were 11 false-positive and 16 true-negative cases. There was one true-positive case and one false-negative case; the monitoring accuracy achieved a sensitivity of 50%, a specificity of 59%, a positive predictive value of 8%, and a negative predictive value of 94%. In the 22 alert cases, if the tumor was located anterolateral in the axial view, alerts were triggered with a significant difference (p = 0.02) during tumor resection. Alerts were generated for fifteen patients during tumor resection; nine (60%) showed waveform improvement by intervention and were classified as rescue cases. Alert is probably triggered during tumor resection for anterolaterally located tumors. Alerts during tumor resection procedures were more likely to be rescued than other procedures in IDEM tumor surgery.

Spinal cord associative plasticity improves forelimb sensorimotor function after cervical injury.

Associative plasticity occurs when two stimuli converge on a common neural target. Previous efforts to promote associative plasticity have targeted cortex, with variable and moderate effects. In addition, the targeted circuits are inferred, rather than tested directly. In contrast, we sought to target the strong convergence between motor and sensory systems in the spinal cord. We developed spinal cord associative plasticity, precisely timed pairing of motor cortex and dorsal spinal cord stimulations, to target this interaction. We tested the hypothesis that properly timed paired stimulation would strengthen the sensorimotor connections in the spinal cord and improve recovery after spinal cord injury. We tested physiological effects of paired stimulation, the pathways that mediate it, and its function in a preclinical trial. Subthreshold spinal cord stimulation strongly augmented motor cortex evoked muscle potentials at the time they were paired, but only when they arrived synchronously in the spinal cord. This paired stimulation effect depended on both cortical descending motor and spinal cord proprioceptive afferents; selective inactivation of either of these pathways fully abrogated the paired stimulation effect. Spinal cord associative plasticity, repetitive pairing of these pathways for 5 or 30 min in awake rats, increased spinal excitability for hours after pairing ended. To apply spinal cord associative plasticity as therapy, we optimized the parameters to promote strong and long-lasting effects. This effect was just as strong in rats with cervical spinal cord injury as in uninjured rats, demonstrating that spared connections after moderate spinal cord injury were sufficient to support plasticity. In a blinded trial, rats received a moderate C4 contusive spinal cord injury. Ten days after injury, they were randomized to 30 min of spinal cord associative plasticity each day for 10 days or sham stimulation. Rats with spinal cord associative plasticity had significantly improved function on the primary outcome measure, a test of dexterity during manipulation of food, at 50 days after spinal cord injury. In addition, rats with spinal cord associative plasticity had persistently stronger responses to cortical and spinal stimulation than sham stimulation rats, indicating a spinal locus of plasticity. After spinal cord associative plasticity, rats had near normalization of H-reflex modulation. The groups had no difference in the rat grimace scale, a measure of pain. We conclude that spinal cord associative plasticity strengthens sensorimotor connections within the spinal cord, resulting in partial recovery of reflex modulation and forelimb function after moderate spinal cord injury. Since both motor cortex and spinal cord stimulation are performed routinely in humans, this approach can be trialled in people with spinal cord injury or other disorders that damage sensorimotor connections and impair dexterity.

Electromyographic Findings in Guillain-Barré Syndrome Patients

Objective: To determine electromyographic findings in Guillain-barré syndrome patients.
 Setting and Duration Study: This is a descriptive cross-sectional study conducted in the Neuromedicine departments of tertiary care Hospital JPMC, from1st February 2020 to 30th July 2021.
 Materials and Methods: GBS was diagnosed according to the diagnostic criteria from the National Institute of Neurological Disorders and Stroke (NINDS) in 1990. All patients gave consent to and underwent electromyographic assessment with a Keypoint evoked muscle potential equipment at admission and 2, 3, and 6 months post disease onset. The records of the patients were anonymized and deidentified before analysis.
 Results: The Age range in this study was from 13 to 70 years with a mean age of 36.58±16.0 years. 63% of patients were of male gender and 37% of patients were female. The frequency of Electromyographic findings were acute demyelinating polyneuropathy in 73% of cases, acute sensorimotor axonal polyneuropathy 14% of cases, acute motor xonal polyneuropathy 12% of cases and acute sensory polyneuropathy 1% case.
 Conclusion: The electromyography plays a role to diagnose GBS but along with this NCV and CSF analysis are also helpful in diagnosis and prognosis prediction.

O2-114 A case report that we could derive muscle evoked potentials (MEPs) by epidural stimulation in spite of the loss of MEPs by transcranial stimulation during lumbar fixation

O2-114 A case report that we could derive muscle evoked potentials (MEPs) by epidural stimulation in spite of the loss of MEPs by transcranial stimulation during lumbar fixation

Muscle-evoked Potentials After Electrical Stimulation to the Brain in Patients Undergoing Spinal Surgery are Less Affected by Anesthetic Fade With Constant-voltage Stimulation Than With Constant-current Stimulation.

A prospective, within-subject study was conducted. We aimed to compare the influence of anesthetic fade under maximum stimulation conditions between constant-current and constant-voltage stimulation techniques. The monitoring of muscle-evoked potentials after electrical stimulation to the brain [Br(E)-MSEP)] is useful for assessing the integrity of spinal cord motor tracts during major spine surgery. Nonetheless, Br(E)-MSEP responses are known to deteriorate over the duration of surgeries performed under general anesthesia. This phenomenon is known as anesthetic fade. We recruited 117 patients undergoing various spinal surgeries from the cervical to the lumbar level. We excluded 29 cases with insufficient data. The decrease rate of the Br(E)-MSEP amplitude for each muscle was examined. Br(E)-MSEP monitoring with constant-current and constant-voltage stimulations at the C3 and C4 electrode positions was applied. Compound muscle action potentials (CMAPs) were bilaterally recorded from the abductor pollicis brevis, deltoid, abductor hallucis, tibialis anterior, gastrocnemius, and quadriceps muscles. We defined the decrease rate as follows: (initial CMAPs-final CMAPs)/initial CMAPs × 100. Differences in the decrease rate were evaluated between stimulators, limbs (upper vs. lower), and operative time group (lowest quartile vs. highest quartile). The overall decrease rate (across all muscles) increased as the operative time increased, and the rate was higher in the lower limbs than in the upper limbs. In addition, the overall decrease rate was lower with constant-voltage stimulation than with constant-current stimulation. Furthermore, the decrease rate for constant-current stimulation was significantly higher than that for constant-voltage stimulation, regardless of the operative time. The CMAP waveform with constant-voltage stimulation is less susceptible to anesthetic fade than that with constant-current stimulation, even during long surgeries. 3.

5 kHz Transcranial Alternating Current Stimulation: Lack of Cortical Excitability Changes When Grouped in a Theta Burst Pattern.

Background: Suprathreshold transcranial single pulse electrical stimulation (tES) is painful and not applicable in a repetitive mode to induce plastic after-effects.Objective: In order to circumvent this pain problem, we applied here a 5 kHz transcranial alternating current stimulation (tACS) theta burst protocol with a field intensity of up to 10 mA to the primary motor cortex (M1). Furthermore, we were interested in finding out whether electrical theta burst stimulation (eTBS) is able to induce lasting after-effects on cortical plasticity.Methods: Three different eTBS protocols were applied at 5 mA in a sham controlled, double blinded cross-over design on the M1 region of seventeen healthy subjects during the first part of the study. The second study part consists of three different eTBS protocols ranging from 5 mA to 10 mA and 1 ms to 5 ms sinusoidal bursts, applied to the M1 region of 14 healthy subjects.Results: We were able to apply all eTBS protocols in a safe manner, with only six subjects reporting mild side effects related to the stimulation. However, no eTBS protocol induced lasting effects on muscle- evoked potential (MEP) amplitudes when compared to sham stimulation. Significant inhibition of MEP amplitude was only seen in the lower intensity protocols as compared to baseline.Conclusion: eTBS is a safe method to apply high frequency tACS with up to 10 mA intensity. Future studies need to explore the parameter space to a larger extent in order to assure efficacy.

The Efficacy of Intraoperative Neurophysiological Monitoring Using Transcranial Electrically Stimulated Muscle-evoked Potentials (TcE-MsEPs) for Predicting Postoperative Segmental Upper Extremity Motor Paresis After Cervical Laminoplasty.

Study Design:Prospective study.Objective:To investigate the efficacy of transcranial electrically stimulated muscle-evoked potentials (TcE-MsEPs) for predicting postoperative segmental upper extremity palsy following cervical laminoplasty.Summary of Background Data:Postoperative segmental upper extremity palsy, especially in the deltoid and biceps (so-called C5 palsy), is the most common complication following cervical laminoplasty. Some papers have reported that postoperative C5 palsy cannot be predicted by TcE-MsEPs, although others have reported that it can be predicted.Methods:This study included 160 consecutive cases that underwent open-door laminoplasty, and TcE-MsEP monitoring was performed in the biceps brachii, triceps brachii, abductor digiti minimi, tibialis anterior, and abductor hallucis. A >50% decrease in the wave amplitude was defined as an alarm point. According to the monitoring alarm, interventions were performed, which include steroid administration, foraminotomies, etc.Results:Postoperative deltoid and biceps palsy occurred in 5 cases. Among the 155 cases without segmental upper extremity palsy, there were no monitoring alarms. Among the 5 deltoid and biceps palsy cases, 3 had significant wave amplitude decreases in the biceps during surgery, and palsy occurred when the patients awoke from anesthesia (acute type). In the other 2 cases in which the palsy occurred 2 days after the operation (delayed type), there were no significant wave decreases. In all of the cases, the palsy was completely resolved within 6 months.Discussion:The majority of C5 palsies have been reported to occur several days after surgery, but some of them have been reported to occur immediately after surgery. Our results demonstrated that TcE-MsEPs can predict the acute type, whereas the delayed type cannot be predicted.Conclusions:A >50% wave amplitude decrease in the biceps is useful to predict acute-type segmental upper extremity palsy. Further examination about the interventions for monitoring alarm will be essential for preventing palsy.

Brain-state dependent non-invasive brain-stimulation with real-time closed-loop simultaneous EEG/TMS

Objective We present initial results using a real-time closed-loop simultaneous EEG/TMS set-up to investigate the impact of the instantaneous state of oscillatory brain activity at the time of a TMS pulse. Methods EEG data is recorded and analyzed in real-time using a signal processing PC system. A TMS pulse is triggered when the recorded EEG signal matches predetermined parameters (spectral power and phase at a given frequency). Results Brain-state dependent stimulation is achieved based on ongoing alpha-band oscillatory EEG activity with an overall latency in the closed-loop set-up below 2.5 ms. The impact of instantaneous brain-state on the variability of TMS-evoked muscle-evoked potentials and EEG responses as well as on the direction and magnitude of TMS-induced plasticity is quantified. Conclusions The instantaneous state of oscillatory brain activity at the time of a TMS pulse is a relevant factor influencing both the responsiveness of the brain to stimulation as well as the induction of plasticity. Key message The brain we stimulate with one pulse is not the same brain that we stimulate with the next pulse. The role of spontaneous oscillatory activity can be investigated with novel stimulation protocols that are time-locked to the instantaneous parameters of the simultaneously recorded EEG signal.

Evaluation of Pharyngeal Function in Dogs with Laryngeal Paralysis Before and After Unilateral Arytenoid Lateralization.

To evaluate pharyngeal and laryngeal function using esophagography, topical pharyngeal/laryngeal sensitivity testing, and electromyography (EMG) in normal and dogs with idiopathic laryngeal paralysis (ILP) before and after unilateral arytenoid lateralization. Prospective controlled cohort study. Dogs with laryngeal paralysis (ILP; n = 8) and age/breed-matched (AB, n = 8) and young breed-matched dogs (B, n = 8) were recruited. Evaluation consisted of esophagography, topical pharyngeal/laryngeal sensitivity testing, and electrodiagnostic testing. Esophagography was performed with liquid and canned phases. Pharyngeal and laryngeal sensitivity was tested by applying a cotton-tipped applicator to the mucosa of pharynx/larynx at anesthetic induction. In all dogs, electrophysiological testing included EMG, direct evoked muscle potentials, motor nerve conduction velocities, and F wave testing. These were performed in the thoracic/pelvic limbs, extrinsic laryngeal muscles, epaxial, and masticatory muscles. Topical pharyngeal and laryngeal sensitivity testing was decreased in LP dogs compared with age-matched healthy control dogs. Esophagram showed dysmotility in the cranial and caudal esophagus. Gastroesophageal reflux was significantly higher in ILP dogs compared with the other 2 groups (P < .03). In all affected dogs, EMG abnormalities were limited to the interosseous muscles of both pelvic and thoracic limbs bilaterally. Dogs with ILP not only have recurrent laryngeal nerve (RLN) and pararecurrent laryngeal nerve (pRLN) dysfunction, but may also have concurrent cranial laryngeal nerve dysfunction.

State of the art: Intraoperative neuromonitoring in spinal deformity surgery.

Application of deformity correction spinal surgery has increased substantially over the past three decades in parallel with improvements in surgical techniques. Intraoperative neuromonitoring (IOM) techniques,including somatosensory evoked potentials (SEPs), muscle evoked potentials (MEPs), and spontaneous electromyography (free-run EMG), have also improved surgical outcome by reducing the risk of iatrogenic neural injury. In this article, we review IOM techniques and their applications in spinal deformity surgery. We also summarize results of selected studies including hundreds of spinal correction surgeries. These studies indicate that multimodal IOM of both motor and sensory responses is superior to either modality alone for reducing the incidence of neural injury during surgery. J. Med. Invest. 62: 103-108, August, 2015.

Dosage effect of rocuronium on intraoperative neuromonitoring in patients undergoing thyroid surgery.

The effect of different concentrations of rocuronium bromide used for anesthesia induction during thyroid surgery on the intraoperative recurrent laryngeal nerve monitoring was evaluated. One hundred patients undergoing thyroid operation were randomized into five groups (20 patients per group). Patients in group I were operated and monitored without the use of rocuronium bromide. Patients in groups II-V were respectively injected with 0.5x, 1x, 1.5x, and 2x ED95 rocuronium bromide intravenously. The time from injecting the rocuronium bromide to the beginning of tube insertion was recorded, the conditions of tracheal intubation were evaluated, and the changes in blood pressure and pulse during the intubation process were monitored. Vagus nerve/recurrent laryngeal nerve evoked muscle potential was monitored using the NIM-Response3.0 nerve electromyography monitor. The amplitude of electromyography signal was recorded every 5 min during 30 min after successful tracheal intubation. The tracheal intubation success rate was 100% in all groups. Compared with group I, intubating condition scores (Cooper scores) in the patients of groups II-V were higher (P < 0.05). The stability of intraoperative neuromonitoring signal amplitude in groups I-III met the monitoring standards. The findings suggest that the use of 0.5x or 1x ED95 rocuronium bromide during the anesthesia induction can improve the tracheal tube conditions without affecting the intraoperative recurrent laryngeal nerve monitoring. The use of 1x ED95 rocuronium bromide induction was associated with the best results.

Effect of rocuronium on transcranial muscle-evoked potentials restored by sugammadex in the patients with cervical myelopthy

Effect of rocuronium on transcranial muscle-evoked potentials restored by sugammadex in the patients with cervical myelopthy

Neuromodulation of evoked muscle potentials induced by epidural spinal-cord stimulation in paralyzed individuals

Epidural stimulation (ES) of the lumbosacral spinal cord has been used to facilitate standing and voluntary movement after clinically motor-complete spinal-cord injury. It seems of importance to examine how the epidurally evoked potentials are modulated in the spinal circuitry and projected to various motor pools. We hypothesized that chronically implanted electrode arrays over the lumbosacral spinal cord can be used to assess functionally spinal circuitry linked to specific motor pools. The purpose of this study was to investigate the functional and topographic organization of compound evoked potentials induced by the stimulation. Three individuals with complete motor paralysis of the lower limbs participated in the study. The evoked potentials to epidural spinal stimulation were investigated after surgery in a supine position and in one participant, during both supine and standing, with body weight load of 60%. The stimulation was delivered with intensity from 0.5 to 10 V at a frequency of 2 Hz. Recruitment curves of evoked potentials in knee and ankle muscles were collected at three localized and two wide-field stimulation configurations. Epidural electrical stimulation of rostral and caudal areas of lumbar spinal cord resulted in a selective topographical recruitment of proximal and distal leg muscles, as revealed by both magnitude and thresholds of the evoked potentials. ES activated both afferent and efferent pathways. The components of neural pathways that can mediate motor-evoked potentials were highly dependent on the stimulation parameters and sensory conditions, suggesting a weight-bearing-induced reorganization of the spinal circuitries.

Palpation- and ultrasound-guided brachial plexus blockade in Hispaniolan Amazon parrots (Amazona ventralis)

ObjectiveTo compare palpation-guided with ultrasound-guided brachial plexus blockade in Hispaniolan Amazon parrots. Study designProspective randomized experimental trial. AnimalsEighteen adult Hispaniolan Amazon parrots (Amazona ventralis) weighing 252–295 g. MethodsAfter induction of anesthesia with isoflurane, parrots received an injection of lidocaine (2 mg kg−1) in a total volume of 0.3 mL at the axillary region. The birds were randomly assigned to equal groups using either palpation or ultrasound as a guide for the brachial plexus block. Nerve evoked muscle potentials (NEMP) were used to monitor effectiveness of brachial plexus block. The palpation-guided group received the local anesthetic at the space between the pectoral muscle, triceps, and supracoracoideus aticimus muscle, at the insertion of the tendons of the caudal coracobrachial muscle, and the caudal scapulohumeral muscle. For the ultrasound-guided group, the brachial plexus and the adjacent vessels were located with B-mode ultrasonography using a 7–15 MHz linear probe. After location, an 8-5 MHz convex transducer was used to guide injections. General anesthesia was discontinued 20 minutes after lidocaine injection and the birds recovered in a padded cage. ResultsBoth techniques decreased the amplitude of NEMP. Statistically significant differences in NEMP amplitudes, were observed within the ultrasound-guided group at 5, 10, 15, and 20 minutes after injection and within the palpation-guided group at 10, 15, and 20 minutes after injection. There was no statistically significant difference between the two groups. No effect on motor function, muscle relaxation or wing droop was observed after brachial plexus block. Conclusions and clinical relevanceThe onset of the brachial plexus block tended to be faster when ultrasonography was used. Brachial plexus injection can be performed in Hispaniolan Amazon parrots and nerve evoked muscle potentials were useful to monitor the effects on nerve conduction in this avian species. Neither technique produced an effective block at the doses of lidocaine used and further study is necessary to develop a useful block for surgical analgesia.

EMG Changes in Thigh and Calf Muscles in Fin Swimming Exercise

Because previous researchers have reported a reduced lactic acid production that accompanies a delayed or an absent ventilatory threshold (VTh) in water-based exercise, we hypothesized that the metaboreflex, activated by muscle acidosis, might be absent in fin swimming. This motor response, delaying the occurrence of fatigue, is characterized by a decreased median frequency (MF) of electromyographic (EMG) power spectrum. Seven healthy subjects performed a maximal fin swimming exercise protocol with simultaneous recordings of surface EMGs in VASTUS MEDIALIS (VM), TIBIALIS ANTERIOR (TA) and GASTROCNEMIUS MEDIALIS (GM). We computed the root mean square (RMS) and MF and recorded the compound evoked muscle potential (M-wave) in VM. We also measured the propulsive force and oxygen uptake (VO (2)), and determined VTh. VTh was absent in 4/7 subjects and measured at 70-90% of VO (2max) in the other three. In the three studied muscles, the global EMG activity (RMS) increased while the MF decreased in proportion of VO (2), the MF changes being significantly higher in VM (-29%) and GM (-39%) than in TA (-19%). Because no M-wave changes were noted, the MF decline was attributed to the recruitment of low-frequency, fatigue-resistant motor units. Our most important finding is the persistence of the metaboreflex even in a situation of reduced muscle acidosis.

Muscle potentials evoked by magnetic stimulation of the sciatic nerve in unilateral sciatic nerve dysfunction

Magnetic stimulation of the sciatic nerve and subsequent recording of the muscle-evoked potential (MEP) was performed in eight dogs and three cats with unilateral sciatic nerve dysfunction. Localisation of the lesion in the sciatic nerve was based on the history, clinical neurological examination and on results of electromyography examination. Aetiology of the sciatic nerve lesion was diverse. A significant difference was found in MEP between the normal and the affected limbs. In addition, absence of conscious pain sensation, absence of voluntary motor function and a poor outcome seemed associated with the inability to evoke an MEP in the affected limb.