Electromyogram Monitoring Research Articles

External Ocular Movement(EOM)Monitoring

The intraoperative monitoring of extraocular motor nerves allows optimal skull base surgery by protecting the cranial nerves. For detecting cranial nerve function, several methods, such as external ocular movement monitoring with an electrooculogram(EOG), electromyogram(EMG), and piezoelectric device sensors, are present. While being valuable and useful, several problems related to its accurate monitoring persist when scanning from inside the tumor, which might be far from the cranial nerves. Here, we described three modalities, free-run EOG monitoring, trigger EMG monitoring, and piezoelectric sensor monitoring for monitoring external ocular movement. Improvement of these processes is essential for appropriately conducting these procedures during neurosurgical operations without harming the extraocular motor nerves.

Evaluation of Triggered Electromyogram Monitoring during Insertion of Percutaneous Pedicle Screws.

Objective: percutaneous pedicle screw (PPS) fixation has been widely used in minimally invasive spine stabilization. Triggered electromyogram (TrEMG) monitoring is performed to prevent PPS misplacement, but is not widely accepted. We have newly developed an insulating tap device to minimize the misplacement of PPS. Methods: TrEMG was measurable in insulation tap devices in 31 cases, and in non-insulating tap devices in 27 cases. Fluoroscopy was used to insert 194 PPS and 154 PPS, respectively. Based on the Rampersaud classification of postoperative computed tomography, we classified PPS insertion into four categories (Grade A as no violation, Grade D as more than 4 mm perforation). Results: Grade A was noted in 168 PPSs (86.6%) and Grade B to D in 26 PPSs in the insulation tap device group, and Grade A was noted in 129 PPSs (83.8%) and Grade B to D in 25 PPSs in the non-insulating tap device group, respectively. At a cutoff value of 11 mA, the sensitivity was 41.4% and the specificity was 98.2%. The sensitivity and specificity of the non-insulating tap device were 4.0% and 99.2%, respectively. Conclusions: The insulation treatment of the tap device has improved the sensitivity of TrEMG. TrEMG using the insulating tap device is one of the methods for safe PPS insertion.

IOT Enabled Wearable Gloves with SEMG Subsystem with Posture Analysis

Abstract: Electromyogram (EMG) is a technique to track the record , analyze and estimate the electrical activity produced by muscles. This technique is used to detect the muscle issues that harm the nerves activity , muscle tissues and identify the location where they are joined together . This paper discusses the implementation of a project which can be considered as a tool for the acquisition of muscle activity, presentation and real-time attainment of EMG signal using a specific EMG sensor. The live EMG reading is recorded using the Wi-Fi- enabled Raspberrypi and then sent to a remote server in our case ThingSpeak server with the help of IoT concepts which helps in the telemetry of the obtained biomedical signals using the cloud. Results are displayed in ThingSpeak. The live recordings are also obtained on the PC using the serial plotter. This project can also help us in monitor and observe the progress of the patient treatment even if the physiotherapist could not come and data can be directly sent to them. Thus, the project aims to develop an EMG monitoring device based on IoT, for analyzing and acquiring EMG signals. Keywords: EMG sensor, Raspberry pi, LCD, ADS1115

Wireless Epidermal Electromyogram Sensing System

Massive efforts to build walking aid platforms for the disabled have been made in line with the needs of the aging society. One of the core technologies that make up these platforms is a realization of the skin-like electronic patch, which is capable of sensing electromyogram (EMG) and delivering feedback information to the soft, lightweight, and wearable exosuits, while maintaining high signal-to-noise ratio reliably in the long term. The main limitations of the conventional EMG sensing platforms include the need to apply foam tape or conductive gel on the surface of the device for adhesion and signal acquisition, and also the bulky size and weight of conventional measuring instruments for EMG, limiting practical use in daily life. Herein, we developed an epidermal EMG electrode integrated with a wireless measuring system. Such the stretchable platform was realized by transfer-printing of the as-prepared EMG electrodes on a SiO2 wafer to a polydimethylsiloxane (PDMS) elastomer substrate. The epidermal EMG patch has skin-like properties owing to its unique mechanical characteristics: i) location on a neutral mechanical plane that enables high flexibility, ii) wavy design that allows for high stretchability. We demonstrated wireless EMG monitoring using our skin-attachable and stretchable EMG patch sensor integrated with the miniaturized wireless system modules.

Application of transcranial electrical stimulation-facial nerve motor evoked potentials in resection of large acoustic neuromas

Objective To discuss the role of transcranial electrical stimulation facial nerve motor evoked potentials (TCE-FNMEP) in resection of large acoustic neuromas. Methods In a retrospective clinical study, 58 patients with large acoustic neuroma were investigated at Department of Neurosurgery, Tianjin HuanHu Hospital form July 2016 to March 2017.All patients were investigated by facial nerve motor evoked potentials elicited by multi-pulse transcranial electrical motor cortex stimulation. For recording, the same electrode set-up was used as for continuous EMG (electromyogram) monitoring of the orbicularis oculi, oris muscles and mentalis. Pre-surgical (dura opening), intraoperative and post-surgical (dura closing) TCE-FNMEP amplitudes and latencies were documented. End (dura closing) to start (dura opening) amplitude ratios were compared to early-term (1 day post surgery) facial nerve function by House-Brackmann (H-B) grading. Results Fifty-one (87.9%, 51/58) patients obtained total tumor resection and 7 (12.1%, 7/58) achieved subtotal resection. All patients had anatomical preservation of facial nerves. There was no death in this series. Reliable TCE-FNMEPs were obtained in all patients. At 1 day post operation, 48 out of 58 case were graded as H-B Ⅰ-Ⅱ, the range of TCE-FNMEP amplitude ratio was 47.6%-100.0%, and the median was 85.4%. Five cases were graded as H-B Ⅲ, the range of TCE-FNMEP amplitude ratio was 43.2%-55.8%, and the median was 45.4%. Three cases were graded as H-B Ⅳ, the range of TCE-FNMEP amplitude ratio was 31.4%-53.2%, and the median was 33.6%. Two cases were graded as H-B Ⅴ-Ⅵ, the range of TCE-FNMEP amplitude ratio was 6.1% and 11.3%, respectively. There was a negative correlation between TCE-FNMEP amplitude ratio and early post-surgical HB grading (r=-0.611, P<0.01). Conclusion TCE-FNMEP seems to be highly reliable in predicting early postoperative facial function in resection of large acoustic neuromas and could be a valid protection technique of facial nerve. Key words: Neuroma, acoustic; Facial nerve; Evoked potentials, motor; Transcranial electrical stimulation

Carework analysis by time study investigation for one minute and electromyogram monitoring : comparison among daycare & dayservice, nursing homes, and hospital(Paper & Abstract September 18th)

Carework analysis by time study investigation for one minute and electromyogram monitoring : comparison among daycare & dayservice, nursing homes, and hospital(Paper & Abstract September 18th)

Detection of G-Induced Loss of Consciousness (G-LOC) prognosis through EMG monitoring on gastrocnemius muscle in flight.

G-Induced Loss of Consciousness (G-LOC) is mainly caused by the sudden acceleration in the direction of +Gz axis from the fighter pilots, and is considered as an emergent situation of which fighter pilots are constantly aware. In order to resist against G-LOC, fighter pilots are subject to run Anti-G straining maneuver (AGSM), which includes L-1 respiration maneuvering and muscular contraction of the whole body. The purpose of this study is to create a G-LOC warning alarm prior to G-LOC by monitoring the Electromyogram (EMG) of the gastrocnemius muscle on the calf, which goes under constant muscular contraction during the AGSM process. EMG data was retrieved from pilots and pilot trainees of the Korean Air Force, during when subjects were under high G-trainings on a human centrifugal simulator. Out of the EMG features, integrated absolute value (IAV), reflecting muscle contraction, and waveform length (WL), reflecting muscle contraction and fatigue, have shown a rapid decay during the alarm phase, 3 seconds before G-LOC, compared to that of a normal phase withstanding G-force. Such results showed consistency amongst pilots and pilot trainees who were under G-LOC. Based on these findings, this study developed an algorithm which can detect G-LOC prognosis during flight, and at the same time, generate warning signals. The probability of G-LOC occurrence is detected through monitoring the decay trend and degree of the IVA and WL value of when the pilot initiates AGSM during sudden acceleration above 6G. Conclusively, this G-LOC prognosis detecting and warning system is a customized, real-time countermeasure which enhanced the accuracy of detecting G-LOC.

Polysomnography using video electroencephalogram, electro-oculogram and electromyogram monitored continuously by telemetry in cynomolgus monkeys

Medication-induced sleep disturbances are a major concern in drug development as a multitude of prescription drugs cause abnormalities at polysomnography. Rodent sleep architecture (nocturnal) differs from larger mammals (diurnal) which present higher translational value. Polysomnography is used in clinical diagnostic but also applicable to cynomolgus monkeys when using telemetry with continuous electroencephalogram (EEG), electro-oculogram (EOG) and electromyogram (EMG) monitoring with video. Sleep stages in cynomolgus monkeys include wake, N1 (somnolence), N2 (includes Spindles and K complexes), N3 (deep sleep with slow waves) and rapid eye movements (REM) and are quantified with automated or manual scoring. Optimal cynomolgus data filters included EOG low pass 5Hz. As observed in humans, cynomolgus present an increased duration of REM sleep the 2nd half of the night. REM sleep was characterized by muscle atonia, high frequency (mostly theta) low amplitude EEG in all animals and EOG activity in most but not all epochs. Total sleep time was 70.3±2.2% of the 12 hour dark cycle. Sleep stages N1, N2, N3 and REM were typically observed in sequence and represented 1.1±0.3%, 65.2±5.3%, 16.0±5.6% and 17.7±2.4% of total sleep time, respectively. Amphetamine (1 and 2 mg/kg, PO) significantly reduced total sleep time and all stages the night of ingestion followed by a rebound during the recovery night. Spectral analysis revealed a significant increase in higher frequency bands after amphetamine. VideoEEG, EOG and EMG by telemetry is a useful non-clinical model to investigate drug induced sleep disturbances. Materials and methods One (1) male Cynomolgus monkey received the following control and test items once by oral gavage within 5 minutes before light off, with a period of at least 2 days between each dose: Reverse osmosis water (0mg/kg) d-amphetamine (2mg/kg) Electroencephalographic, electro-oculographic and electromyographic monitoring was recorded in conscious animals, surgically instrumented with a telemetry transmitter (DSI: D70-EEE), from 1 hour prior to the first dose up to 24 hours following the third dose: Electroencephalograms, electrooculograms and sleep architecture were analyzed using Neuroscore software (DSI). Table 1: Stages of sleep in Cynomolgus monkeys EEG EMG EOG Wake Activated : low amplitude High frequencies Signal +/fast (low amplitude et high frequency) as per activity Signal +/fast (low amplitude et high frequency) as per activity Stage N1 Slowing of EEG (frequency generally theta 4-8 Hz) and amplitude higher than at the Wake Few or no movements Few or no movements Stage N2 Frequency generally theta (4-8 Hz) like N1 but presence spindles (small fast waves of 12-16Hz, duration > 0.5s) and K complexes (slow isolated waves) are needed Few or no movements Few or no movements Stage N3 Slow waves (delta 1-4 Hz) High amplitude (>75μV) Few or no movements Few or no movements Paradoxical Sleep Frequency generally in the theta (4-8 Hz) very regular with low amplitude Weak muscular movement Fast ocular movement Results Table 2: Effects of Amphetamine on sleep architecture in Cynomolgus monkeys Saline Amphetamine Baseline night First night Second night Baseline night First night Second night Wake Mean 20.5% 17.8% 20.0% 20.4% 84.2% 28.3% SD 6.0% 5.0% 5.0% 3.7% 14.5% 9.6% N 1 Mean 0.2% 0.3% 0.2% 0.2% 0.1% 0.1% SD 0.4% 0.6% 0.3% 0.3% 0.1% 0.2% N 2 Mean 55.6% 58.5% 57.0% 55.1% 14.0% 53.6 SD 10.5% 9.7% 10.5% 11.1% 13.8% 12.7% N 3 Mean 8.4% 9.4% 8.2% 10.8% 1.5% 11.5% SD 9.5% 9.7% 9.6% 9.0% 2.3% 9.3% REM Mean 15.2% 14.0% 14.4% 13.8% 0.3% 11.0% SD 3.9% 3.2% 3.2% 2.7% 0.7% 5.5% Fig. 2: Sleep architecture in Cynomolgus monkeys Fig. 1: EOG, EEG and EMG signals during various sleep stages 0 10 20 30 40 50 60 0 5 10 15 20 D u ra ti o n ( m in /h o u r) Zeitgeber time (h) Wake 0 5 10 15 20 0 5 10 15 20 25 30 35 40 D u ra ti o n ( m in /h o u r) Zeitgeber time (h) NREM2 0 5 10 15 20 0 2 4 6 8 10 12 14 16 18 20 A m o u n t o f ti m e ( m in ) Paradoxical (REM) Zeitgeber time (h) 0 5 10 15 20 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 D u ra ti o n ( m in /h o u r) Zeitgeber time (h) NREM1 0 5 10 15 20 0 5 10 15 20 25 D u ra ti o n ( m in /h o u r) Zeitgeber time (h) NREM3

Reprint of “Effects of amphetamine, diazepam and caffeine on polysomnography (EEG, EMG, EOG)-derived variables measured using telemetry in Cynomolgus monkeys”

Introduction: Medication-induced sleep disturbances are a major concern in drug development as a multitude of prescription drugs alter sleep patterns, often negatively. Polysomnography is used in clinical diagnostics but is also applicable to animal models. Rodent sleep architecture (nocturnal) differs from larger diurnal mammals, including humans, increasing the translational potential of non-rodent species to the clinic. This study aimed to characterize the response to pharmacological agents known to affect sleep structure and EEG activity in a non-human primate (Macaca fascicularis) using telemetry-based polysomnography. Methods: Animals were instrumented with telemetry transmitters for continuous electroencephalogram (EEG), electro-oculogram (EOG) and electromyogram (EMG) monitoring combined with video. EEG, EMG and EOG were monitored for 12 to 24h to establish baseline values, followed by administration of pharmacological agents (saline, d-amphetamine, diazepam or caffeine). Results: Amphetamine (0.3 and 1mg/kg, by oral administration (PO)) significantly reduced total sleep time, including the duration of both non-rapid eye movement [NREM] sleep and REM sleep. It also decreased EEG activity in low frequencies (i.e., 4–6Hz) during wakefulness. Diazepam (2mg/kg, PO) did not significantly alter sleep duration, but importantly reduced EEG activity in low frequencies (approximately 2–12Hz) during wakefulness, NREM and REM sleep. Finally, caffeine (10 and 30mg/kg, PO) decreased both NREM and REM sleep duration. In addition, spectral analysis revealed important decreases in low frequency activity (i.e., 1–8Hz) during wakefulness with a parallel increase in high frequency activity (i.e., 20–50Hz) during NREM sleep. Discussion: As these observations are similar to previously reported pharmacological effects in humans, results support that EEG, EOG and EMG monitoring by telemetry in Cynomolgus monkeys represents a useful non-clinical model to investigate and quantify drug-induced sleep disturbances.

Effects of amphetamine, diazepam and caffeine on polysomnography (EEG, EMG, EOG)-derived variables measured using telemetry in Cynomolgus monkeys

Introduction: Medication-induced sleep disturbances are a major concern in drug development as a multitude of prescription drugs alter sleep patterns, often negatively. Polysomnography is used in clinical diagnostics but is also applicable to animal models. Rodent sleep architecture (nocturnal) differs from larger diurnal mammals, including humans, increasing the translational potential of non-rodent species to the clinic. This study aimed to characterize the response to pharmacological agents known to affect sleep structure and EEG activity in a non-human primate (Macaca fascicularis) using telemetry-based polysomnography. Methods: Animals were instrumented with telemetry transmitters for continuous electroencephalogram (EEG), electro-oculogram (EOG) and electromyogram (EMG) monitoring combined with video. EEG, EMG and EOG were monitored for 12 to 24h to establish baseline values, followed by administration of pharmacological agents (saline, d-amphetamine, diazepam or caffeine). Results: Amphetamine (0.3 and 1mg/kg, by oral administration (PO)) significantly reduced total sleep time, including the duration of both non-rapid eye movement [NREM] sleep and REM sleep. It also decreased EEG activity in low frequencies (i.e., 4–6Hz) during wakefulness. Diazepam (2mg/kg, PO) did not significantly alter sleep duration, but importantly reduced EEG activity in low frequencies (approximately 2–12Hz) during wakefulness, NREM and REM sleep. Finally, caffeine (10 and 30mg/kg, PO) decreased both NREM and REM sleep duration. In addition, spectral analysis revealed important decreases in low frequency activity (i.e., 1–8Hz) during wakefulness with a parallel increase in high frequency activity (i.e., 20–50Hz) during NREM sleep. Discussion: As these observations are similar to previously reported pharmacological effects in humans, results support that EEG, EOG and EMG monitoring by telemetry in Cynomolgus monkeys represents a useful non-clinical model to investigate and quantify drug-induced sleep disturbances.

Temperature and fatigue effect on the maximum swimming speed of jack mackerel Trachurus japonicus

Swimming performance of jack mackerel Trachurus japonicus (18.2 ± 0.8 cm fork length (FL), n = 185) was examined in a flume tank by measuring the stride length at low and high tail beat frequencies with electromyogram monitoring and a muscle twitch experiment. Stride length was analyzed by monitoring the tail beat frequency according to the swimming speed at different temperatures of 10, 15 and 22 °C. In the electromyographic observations, the initiation of ordinary muscle activity occurred between 71.4 and 99.6 cm/s, that is 3.7 to 5.3 FL/s, when the tail beat frequency was over 6 Hz. The swimming speeds increased rectilinearly with the tail beat frequency at each water temperature both for the low and high tail beat frequency. Lower stride length was observed at the lowest temperature (10 °C) tested. The forced swimming exercise significantly affected the muscle contraction time to become longer than the control fish, which indicated a reduction of the maximum swimming speed performance.

Efficacy of the Disappearance of Lateral Spread Response before and after Microvascular Decompression for Predicting the Long-Term Results of Hemifacial Spasm Over Two Years

ObjectiveThe purpose of this large prospective study is to assess the association between the disappearance of the lateral spread response (LSR) before and after microvascular decompression (MVD) and clinical long term results over two years following hemifacial spasm (HFS) treatment.MethodsContinuous intra-operative monitoring during MVD was performed in 244 consecutive patients with HFS. Patients with persistent LSR after decompression (n=22, 9.0%), without LSR from the start of the surgery (n=4, 1.7%), and with re-operation (n=15, 6.1%) and follow-up loss (n=4, 1.7%) were excluded. For the statistical analysis, patients were categorized into two groups according to the disappearance of their LSR before or after MVD.ResultsIntra-operatively, the LSR was checked during facial electromyogram monitoring in 199 (81.5%) of the 244 patients. The mean follow-up duration was 40.9±6.9 months (range 25-51 months) in all the patients. Among them, the LSR disappeared after the decompression (Group A) in 128 (64.3%) patients; but in the remaining 71 (35.6%) patients, the LSR disappeared before the decompression (Group B). In the post-operative follow-up visits over more than one year, there were significant differences between the clinical outcomes of the two groups (p<0.05).ConclusionIt was observed that the long-term clinical outcomes of the intra-operative LSR disappearance before and after MVD were correlated. Thus, this factor may be considered a prognostic factor of HFS after MVD.

The Potential Value of the Disappearance of the Lateral Spread Response During Microvascular Decompression for Predicting the Clinical Outcome of Hemifacial Spasms: A Prospective Study

Hemifacial spasm (HFS) is a benign, chronic, involuntary movement of the muscles involved in facial expressions that typically begins in the orbicularis oculi and spreads to the other expression muscles over several years. To clarify the effectiveness of intraoperative electromyogram during microvascular decompression (MVD) for HFS. Two hundred ninety-nine consecutive patients with HFS underwent continuous intraoperative monitoring during MVD. The patients were divided into 2 groups based on whether the lateral spread response (LSR) disappeared before or after decompression In 276 of 299 patients (92.3%), the LSR was observed during intraoperative facial electromyogram monitoring. The mean follow-up period was 17.9 months (range, 12-27 months). Three patients in whom the LSR persisted despite decompression were not included in this study. In 183 of the 273 patients (67%), the LSR disappeared after decompression (group A); in the remaining 90 (33%), the LSR disappeared at dural opening or after drainage of the cerebrospinal fluid before decompression (group B). At the postoperative 3-month and 2-year follow-up visits, there were significant differences in the clinical outcomes between the 2 groups (P<.05). The disappearance of the LSR before and after MVD may predict clinical outcomes. This must be considered together with the disappearance or persistence of LSR after decompression as a prognostic factor for HFS after MVD.

Botulinum Neurotoxin Type A Injections for Vaginismus Secondary to Vulvar Vestibulitis Syndrome

To investigate whether botulinum neurotoxin type A improves vaginismus and study its efficacy with repeated treatments. Outpatients were referred because standard cognitive-behavioral and medical treatment for vaginismus and vulvar vestibular syndrome failed. From this group, we prospectively recruited consecutive women (n=39) whose diagnostic electromyogram (EMG) recordings from the levator ani muscle showed hyperactivity at rest and reduced inhibition during straining. These women were followed for a mean (+/-standard deviation) of 105 (+/-50) weeks. Recruited patients underwent repeated cycles of botulinum neurotoxin type A injected into the levator ani under EMG guidance and EMG monitoring thereafter. At enrollment and 4 weeks after each cycle, women were asked about sexual intercourse; underwent EMG evaluation and examinations to grade vaginal resistance according to Lamont; and completed a visual analog scale (VAS) for pain, the Female Sexual Function Index Scale, a quality-of-life questionnaire (Short-Form 12 Health Survey), and bowel and bladder symptom assessment. At 4 weeks after the first botulinum neurotoxin type A cycle, the primary outcome measures (the possibility of having sexual intercourse, and levator ani EMG hyperactivity) both improved, as did the secondary outcomes, Lamont scores, VAS, Female Sexual Function Index Scales, Short-Form 12 Health Survey, and bowel-bladder symptoms. These benefits persisted through later cycles. When follow-up ended, 63.2% of the patients completely recovered from vaginismus and vulvar vestibular syndrome, 15.4% still needed reinjections (censored), and 15.4% had dropped out. Botulinum neurotoxin type A is an effective treatment option for vaginismus secondary to vulvar vestibular syndrome refractory to standard cognitive-behavioral and medical management. After patients received botulinum neurotoxin type A, their sexual activity improved and reinjections provided sustained benefits. III.

Relationship of Temporal Lobe Seizures to Sleep and Arousal: A Combined Scalp-Intracranial Electrode Study

The role of arousal from sleep in promoting epileptic seizures is controversial. To examine the question of whether seizures precede or follow arousals from sleep, we defined the timing of temporal lobe seizures in relation to sleep and arousal using combined scalp-intracranial electrodes. Retrospective review of 67 sleep-related mesial temporal lobe seizures in 14 subjects. Inpatient epilepsy monitoring laboratory. Subjects with medically refractory mesial temporal lobe seizures undergoing epilepsy surgery evaluations. None Electroencephalographic (EEG) and/or polygraphic recordings and videotapes were independently reviewed to determine intracranial electrode seizure onset times and time of initial arousal from sleep. In 60 seizures in 13 subjects, intracranial ictal onsets always preceded clinical arousals from sleep. Electrographic signs of arousal in the scalp EEG, defined by the presence of sustained alpha or theta activity, either coincided with or followed, but never preceded, intracranial ictal onsets. In seven seizures in one subject with known seizures upon awakening, intracranial ictal onsets always followed clinical arousals and electrographic signs of arousal from sleep. Seven of the 14 subjects had electrooculogram and chin electromyogram monitoring; in these subjects, no seizures occurred during REM sleep with the majority occurring during NREM stage 2 sleep. Most sleep-related temporal lobe seizures occurred during NREM sleep and preceded arousals, supporting the premise that processes involved in the initiation and maintenance of NREM sleep play a greater role in facilitating temporal seizures than those involved in promoting REM sleep and arousal. However, arousal from sleep may provoke seizures in exceptional cases.

Intraoperative electromyogram monitoring of the recurrent laryngeal nerve: experience with an intralaryngeal surface electrode. A method to reduce the risk of recurrent laryngeal nerve injury during thyroid surgery.

A clinical method to localize the recurrent laryngeal nerve intraoperatively in order to minimize the risk of accidental injury is presented. By means of an electrode, the nerve was stimulated by a pulsed contact current. The resulting muscle potential was detected using an electrode placed in the larynx. We applied this technique during the time period between 1 January 1997 and 31 December 1998. In 96 cases of primary thyroid resection, the recurrent nerve was identified 167 times. The patients were operated on for nodular thyroid (n=85), Grave's disease (n=9) and malignant papillary goiter (n=2). Retrospectively, the rate of intraoperative nerve injury, equivalent to the rate of postoperative transient and permanent nerve palsy, was 1.04% in the 96 patients and 0.60% with respect to the 167 nerves at risk. The rate of failure of the method was 7.29%.

Stimulus-evoked EMG monitoring during transpedicular lumbosacral spine instrumentation. Initial clinical results.

The authors developed and evaluated an electrophysiologic method for minimizing the risk of nerve root trauma associated with the placement of pedicle screws during transpedicular lumbosacral fixation in humans. Various methods have been evaluated to reduce the high complication rates associated with lumbosacral transpedicular fixation, but none are without significant limitations or drawbacks. Using a pig model, we previously developed a technique for assessing, by electrophysiologic means, the potential risk associated with placement of a screw at a given site. In this report, the authors describe their experience with this technique in patients. Electromyogram (EMG) was monitored from eight lower extremity muscles bilaterally. Square-wave electrical shocks (200 microseconds, 7 mA) were delivered through the instruments used to form and evaluate each pedicle hole, and through the screw itself if placement was deemed safe. Provided that the instruments used (e.g., awl, tap, probe) do not exit from bone in any direction below the entry point, the resistance of bone to the 7 mA stimulus intensity is high enough such that no nerve roots are stimulated, and the EMG traces remain flat. Conversely if EMG is evoked, it warns of a potential perforation in a pedicle wall or in the anterior body. The authors evaluated this technique in 18 patients in whom a total of 102 screws were placed. Based on results of electrophysiologic and palpatory evaluation, 68% of the screws were placed in a satisfactory manner. Electrophysiologic evidence of a perforation, which could not be confirmed by palpation or visualization, was seen in another 13% of this total. The remaining 19% of screw placements involved sites where a defect was missed originally by palpation alone, but was located based on electrophysiological testing combined with palpation and visualization (11%), and where a perforation was initially palpated (8%). There was no postoperative morbidity associated with malpositioned screws. Our results indicate that the technique is sensitive and, based on early clinical results, reliable in the detection of perforations in pedicle screw placement. Moreover, the method is inexpensive, rapid, and easily implemented into a standard intraoperative monitoring protocol.

Improved Facial Nerve Function in Infratemporal Skull Base Surgery

At the recent meeting of the American Academy of Otolaryngology–Head and Neck Surgery in Washington, DC, John P. Leonetti and coinvestigators, Otologic Medical Group, Los Angeles, Calif, recently reported that facial nerve monitoring during infratemporal skull base surgery would lessen the risk of nerve injury. Their report emphasized the importance of intraoperative nerve monitoring during these procedures. Results in 15 monitored patients were compared with those in 23 unmonitored patients, all of whom required nerve rerouting. Immediate postoperative facial function was normal in 93% of monitored cases but only in 70% of unmonitored cases. More importantly, no patients in the monitored group developed grade V or grade VI weakness, while 48% of unmonitored cases experienced this unfavorable status. Careful rerouting during continuous acoustical facial electromyogram monitoring has resulted in improved preservation of facial nerve function following the infratemporal resection of skull base tumors.

A New Device for Locating the Facial Nerve During Surgery

Richard Prass, MD, PhD, Department of Otolaryngology, and Hans Luders, MD, PhD, Department of Neurology, Cleveland Clinic, have developed an acoustic (loudspeaker) facial nerve electromyogram monitoring system. The use of this monitoring technique has facilitated the dissection of the facial nerve during acoustic neuroma surgery. The stimulus probe is flush-tipped with insulation that reaches to the end. The flush tip prevents widespread electrical current in the presence of cerebrospinal fluid. A reference electrode is placed on the patient's forehead. The recording system consists of bipolar wires placed directly in the facial muscles using a 22-gauge needle. The response is amplified, and an acoustic response is delivered back into the operating room over a loudspeaker for immediate recognition on the part of the operating surgeon. Three types of activity have been identified: burst activity, which results from direct manipulation of the facial nerve; train activity, which results from stretching the nerve;