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A 77-year-old male presented with a history of severe lower back pain for 10 years with radiculopathy, positive claudication type symptoms in his calf with walking, and severe "burning" in his legs bilaterally with walking. Magnetic resonance imaging (MRI) revealed lumbar stenosis at the L3-L4 and L4-L5 levels. During the direct or extreme lateral interbody fusion (DLIF/XLIF) procedure, bilateral posterior tibial, femoral, and ulnar nerve somatosensory evoked potentials (SSEPs) were recorded with good morphology of waveforms observed. Spontaneous electromyography (S-EMG) and triggered electromyography (T-EMG) were recorded from cremaster and ipsilateral leg muscles. A left lateral retroperitoneal transpsoas approach was used to access the anterior disc space for complete discectomy, distraction, and interbody fusion. T-EMG ranging from 0.05 to 55.0 mA with duration of 200 µsec was used for identification of the genitofemoral nerve using a monopolar stimulator during the approach. The genitofemoral nerve (L1-L2) was identified, and the guidewire was redirected away from the nerve. Post-operatively, the patient reported complete pain relief and displayed no complications from the procedure. Intraoperative SSEPs, S-EMG, and T-EMG were utilized effectively to guide the surgeon's approach in this DLIF, thereby preventing any post-operative neurological deficits such as damage to the genitofemoral nerve that could lead to groin pain. [ABSTRACT FROM AUTHOR]

A 38-year-old female with a history of nausea, vomiting, headache, and neck pain underwent suboccipital craniectomy and CI laminectomy for resection of a cervical-medullary junction hemangioblastoma. Posterior tibial nerve somatosensory evoked potentials (SSEPs), median nerve SSEPs, and transcranial electrical motor evoked potentials (TCeMEPs) from arm and leg muscles were recorded bilaterally during the surgical procedure. Total intravenous anesthesia (TIVA) was used for anesthesia. Neuromuscular blockade levels were monitored with train of four (TOF). At the end of resection, left upper median nerve SSEP responses were lost. Postoperative sensory exam revealed a profound lack of fine touch and proprioception in the left arm, with intact motor strength. Magnetic resonance imaging (MRI) revealed no evidence of hemorrhage or edema. The patient slowly regained some sensory function over the next several days before being discharged home. At the time of discharge the patient continued to have markedly decreased sensation in the left arm, but was otherwise intact. In this case, SSEP was an effective method to predict sensory loss in one extremity in the presence of intact TCeMEP responses. [ABSTRACT FROM AUTHOR]

Somatosensory evoked potentials (SEPs) are used to assess the functional status of somatosensory pathways during surgical procedures and can help protect patients' neurological integrity intraoperatively. This is a position statement on intraoperative SEP monitoring from the American Society of Neurophysiological Monitoring (ASNM) and updates prior ASNM position statements on SEPs from the years 2005 and 2010. This position statement is endorsed by ASNM and serves as an educational service to the neurophysiological community on the recommended use of SEPs as a neurophysiological monitoring tool. It presents the rationale for SEP utilization and its clinical applications. It also covers the relevant anatomy, technical methodology for setup and signal acquisition, signal interpretation, anesthesia and physiological considerations, and documentation and credentialing requirements to optimize SEP monitoring to aid in protecting the nervous system during surgery., (© 2024. The Author(s).)

Intracranial lesions, particularly in the language-eloquent areas of the brain, can affect one's speaking ability. Despite advances in surgery, the excision of these lesions can be challenging. Intraoperative neurophysiological monitoring (IONM) during awake craniotomies can help identify language-eloquent areas and minimize postoperative impairments. Preoperative language testing is performed to establish a baseline before intraoperative language testing. This involves subjecting patients to predetermined tasks in the operating room to evaluate their phonological, semantic, and syntactic capabilities. The current state and future directions of intraoperative language testing procedures are discussed in this paper. The most common intraoperative tasks are counting and picture naming. However, some experts recommend utilizing more nuanced tasks that involve regions affected by infrequently occurring tumor patterns. Low-frequency bipolar Penfield stimulation is optimal for language mapping. Exception cases are discussed where awake craniotomies are not feasible. When dealing with multilingual patients, the patient's age of learning and skill level can be accounted for in terms of making informed task choices and mapping techniques to avoid any damage to language areas., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Kabir et al.)

Today, it seems prudent to reconsider how ultrasound technology can be used for providing intraoperative neurophysiologic monitoring that will result in better patient outcomes and decreased length and cost of hospitalization. An extensive and rapidly growing literature suggests that the essential hemodynamic information provided by transcranial Doppler (TCD) ultrasonography neuromonitoring (TCDNM) would provide effective monitoring modality for improving outcomes after different types of vascular, neurosurgical, orthopedic, cardiovascular, and cardiothoracic surgeries and some endovascular interventional or diagnostic procedures, like cardiac catheterization or cerebral angiography. Understanding, avoiding, and preventing peri- or postoperative complications, including neurological deficits following abovementioned surgeries, endovascular intervention, or diagnostic procedures, represents an area of great public and economic benefit for society, especially considering the aging population. The American Society of Neurophysiologic Monitoring and American Society of Neuroimaging Guidelines Committees formed a joint task force and developed updated guidelines to assist in the use of TCDNM in the surgical and intensive care settings. Specifically, these guidelines define (1) the objectives of TCD monitoring; (2) the responsibilities and behaviors of the neurosonographer during monitoring; (3) instrumentation and acquisition parameters; (4) safety considerations; (5) contemporary rationale for TCDNM; (6) TCDNM perspectives; and (7) major recommendations., (© 2022 American Society of Neuroimaging.)

Parkinson's disease (PD) is a neurological disorder in which nigrostriatal pathways involving the basal ganglia experience a decrease in neural activity regarding dopaminergic neurons. PD symptoms, such as muscle stiffness and involuntary tremors, have an adverse impact on the daily lives of those affected. Current medical treatments seek to decrease the severity of these symptoms. Deep brain stimulation (DBS) has become the preferred safe, and reliable treatment approach. DBS involves implanting microelectrodes into subcortical areas that produce electrical impulses directly to high populations of dopaminergic neurons. The most common targets are the subthalamic nucleus (STN), and the basal ganglia's globus pallidus pars interna (GPi). Research studies suggest that DBS of the STN may cause a significant reduction in the daily dose of L-DOPA compared to DBS of the GPi. DBS of the STN has suggested that there may be sweet spots within the STN that provide hyper-direct cortical connectivity pathways to the primary motor cortex (M1), supplementary motor area (SMA), and prefrontal cortex (PFC). In addition, the pedunculopontine nucleus (PPN) may be a new target for DBS that helps treat locomotion problems associated with gait and posture. Both microelectrode recording (MER) and magnetic resonance imaging (MRI) are used to ensure electrode placement accuracy. Using MER, stimulation of the STN at high frequencies (140<) decreased oscillatory neuronal firing by 67%. This paper investigates methods of intraoperative neuromonitoring during DBS as a form of PD treatment., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Fejeran et al.)

Patients with untreated carotid artery stenosis remain at high risk for stroke. Carotid endarterectomy (CEA) is a surgical procedure for the treatment of symptomatic and severe asymptomatic carotid stenosis. A small percentage of patients who do not have good collateral circulation are at high risk of cerebral ischemia during the cross-clamping of the carotid artery. Aspects of CEA, such as cross-clamping and routine shunting, can also carry the risk of perioperative stroke through dislodgement of emboli causing thrombosis, therefore, selective shunting is highly recommended during the CEA procedure. A multimodality approach of intraoperative neurophysiological monitoring (IONM) techniques such as somatosensory evoked potential (SSEP) and electroencephalography (EEG) can be used to monitor cerebral perfusion throughout the duration of the surgery and to predict the need for a selective shunt after cross-clamping. Additional use of transcranial Doppler (TCD) in the multimodality approach can aid in visualizing the cerebral blood flow and detecting any microemboli that may also cause a stroke. A multimodality IONM approach has been reported as more sensitive and specific for predicting and minimizing any postoperative neurological deficits., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Jahangiri et al.)

Intraoperative neurophysiological monitoring (IONM) techniques continue to prove useful as an adjunct in select surgeries for reducing the incidence of various postoperative deficits in motor function through the monitoring of motor evoked potentials (MEPs). The Penfield and Taniguchi methods of direct electrical cortical stimulation (DECS) stand in contrast to each other. Penfield's method uses lower-frequency stimulation over a longer duration, while Taniguchi's method uses a relatively higher frequency over a short duration. DECS motor mapping is considered suitable for tumor resections, aneurysm surgeries, arteriovenous malformation, and epilepsy surgeries. While subcortical motor mapping works efficiently with both methods, it aligns with Taniguchi's method more effectively. Taniguchi's method has a lower risk of seizures relative to Penfield's method. While only cortical neurons are excited in Penfield's stimulation technique, Taniguchi's technique excites the whole corticospinal tract (CST), so it can be used for mapping in a stand-alone fashion. The Penfield technique remains the method of choice for language mapping. In all motor mapping, Train-of-Four (TOF) stimulation during the surgical procedure ensures that the patient's muscles are not unduly relaxed., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Jahangiri et al.)

Introduction Intraoperative neurophysiological monitoring (IONM) helps in better patient outcomes by minimizing risks related to the functional status of the nervous system during surgical procedures. An IONM alert to the surgical team during the surgery can help them identify the cause and take immediate corrective action. IONM confers possible benefits, including improved surgical morbidity and mortality, better patient care, minimal neurological deficits, reduced hospital stay, medical costs, and litigation risk. In addition, a highly skilled IONM team will make a better patient outcome. Methods We retrospectively reviewed 62 consecutive patients who underwent intracranial and spinal neurosurgical procedures. Multimodality IONM was utilized, including somatosensory evoked potentials, transcranial electrical motor evoked potential, spontaneous and triggered electromyography, electroencephalography, electrocorticography, cortical sensory mapping, and direct electrical cortical stimulation. Of a total of 62 patients, two patients revealed neurotonic EMG discharges during IONM, and most patients woke up without any new neurological deficit. Results Sixty-two patients were included, ranging from age 5 to 77 years (mean 43.5 years), with 54.8% men and 45.2% female. Multimodality IONM was used in all patients. Two EMG alerts were recorded during IONM, during a brain tumor resection, and right acetabular hip surgery with postoperative right foot drop. Conclusion Multimodality IONM is the gold standard of care for any surgical services and is used as real-time monitoring of functional integrity of neural structures at risk. If utilized by trained and expert teams, numerous surgeries may benefit from multimodality intraoperative neurophysiologic monitoring., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2021, Ali et al.)

Lateral lumbar interbody fusion procedures are performed with multimodality neuromonitoring of the femoral nerve to prevent lumbosacral plexus and peripheral nerve injury from positioning, dilation, retraction, and hardware implantation. The integrity of the femoral nerve can be continuously assessed during these procedures by Somatosensory Evoked Potentials of the Saphenous nerve (Sn-SSEPs). Sn-SSEPs are technically challenging to acquire and necessitate advanced troubleshooting skills with a more rigid anesthetic regimen and physiological parameters. We performed a retrospective analysis of Sn-SSEP data for 100 consecutive lateral lumbar surgeries where the stimulation electrodes were placed distally below the knee and medial to the tibia bone (i.e., DSn-SSEPs). Monitorable baseline responses were present in 87% of patients after the exclusion of fourteen cases where the tibial nerve SSEP was absent, quadriceps transcranial electrical motor evoked potentials (TCeMEPs) were absent or not utilized. Sex, age, body mass index (BMI), diagnosis, mean arterial pressure (MAP), inhalational anesthetic levels, reliability of ulnar and posterior tibial nerve SSEPs, and the reliability of femoral nerve innervated quadriceps TCeMEPs were evaluated but were not of statistically significant consequence between cases where the DSn-SSEP was present or absent in this study. We found the utilization of DSn-SSEPs to be a valuable adjunct to femoral nerve monitoring. Stimulation electrode placement is easy to palpate with clear anatomical borders. Significant muscle artifact and patient movement from stimulation do not affect waveform morphology, allowing for continuous and reliable monitoring. We recommend including DSn-SSEPs to optimize recordings during lateral lumbar procedures.

Awake craniotomy with intraoperative neurophysiological language mapping (INLM) is an established procedure for patients undergoing surgery to resection tumors in the language cortex area. INLM and continuous neurophysiological monitoring allow assessment of the language function, which is not possible under general anesthesia. INLM of the brain areas provides a helpful tool to the operating surgeon in reducing the risks associated with tumor resection in the motor and language cortex. We present a literature review and the technical method used for INLM by utilizing direct electrical cortical stimulation. We also report the usefulness of INLM for evaluation of the language function during resection of cortical tumors, epilepsy foci, and arteriovenous malformations (AVMs) located near language areas. First, the central sulcus is identified by sensory mapping, followed by the motor cortex's identification by direct electrical cortical stimulation (DECS). Neurological assessment of the patient is done by auditory and visual feedback. The patient is asked to repeat numbers, days, words, sentences, read words, and name pictures during cortical stimulation. DECS may cause a slurring or speech arrest. Electrocorticography (ECoG) is also performed during cortical stimulation to identify any after-discharges. Examination of the patient occurs immediately after surgery, and then 24 hours, one week, six months, and 12 months postoperatively. Bipolar DECS for motor mapping with ECoG can safely and reliably be utilized to identify essential language areas with minimizing permanent language deficits and maximizing the extent of tumor resection., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2021, Jahangiri et al.)

The resection of brain tumors located within or near the eloquent tissue has a higher risk of postoperative neurological deficits. The primary concerns include loss of sensory and motor functions in the contralateral face, upper and lower extremities, as well as speech deficits. Intraoperative neurophysiological monitoring (IONM) techniques are performed routinely for the identification and preservation of the functional integrity of the eloquent brain areas during neurosurgical procedures. The IONM modalities involve sensory, motor, and language mapping, which helps in the identification of the boundaries of these areas during surgical resection. Cortical motor Mapping (CmM) technique is considered as a gold-standard technique for mapping of the brain. We present the intraoperative CmM technique, including anesthesia recommendations, types of electrodes, as well as stimulation and recording parameters for successful monitoring., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2020, Jahangiri et al.)

Introduction: The purpose of this study is to identify the advancing role of Intraoperative Neurophysiological Monitoring (IONM) in detecting and preventing nerve injuries during shoulder surgery procedures. Methods: We performed a retrospective analysis of IONM data from ten shoulder procedures. The patients consisted of nine females and one male with ages ranging from 67 to 81 years (median: 74 years). IONM modalities utilized were bilateral Somatosensory Evoked Potentials (SSEP), Transcranial Motor Evoked Potentials (TCeMEP), ipsilateral Electromyogram (EMG) from upper extremity muscles and Train of four (TOF) recordings. Results: A decrease in signals was noted in three patients (30%). Only upper SSEP amplitude decreased in one patient; both upper extremity SSEP and TCeMEP decreased in two patients. Only one patient had poor baseline radial nerve SSEP that improved during the surgery. We performed spontaneous EMG (s-EMG) in all ten patients and successfully recorded triggered (t-EMG) in seven patients (71.4%). In one patient, SSEP and TCeMEP did not improve, and the patient woke up with deficits. Conclusions: In this small series, we were able to identify real-time impending nerve injury. The use of IONM alerted and may have prevented intraoperative nerve injury in 30% of the patients in this series. In one patient, SSEP and TCeMEP did not recover even after the intervention due to severe blood loss. The patient woke up with sensory and motor deficits. The utilization of multimodality IONM can be helpful due to signal changes, therefore minimizing the frequency of nerve injury and deficits.

Intraoperative sensory cortical mapping is a reliable and safe method for the functional localization of the central sulcus (CS). It is utilized during neurosurgical procedures performed near eloquent brain tissue. It helps in identifying the somatosensory cortex and CS, hence preventing any postoperative neurological deficits. When executed properly, this method can identify the somatosensory cortex for both the upper and lower limbs by locating the CS. This technical report outlines the benefits of cortical sensory mapping (CsM) and detailed methodology. With the help of a properly trained intraoperative neuromonitoring staff who can accurately interpret the signals being monitored, CsM can help in injury prevention during brain surgeries., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2020, Jahangiri et al.)

Introduction: Bowel and bladder function are at risk during tumor resection and other surgeries of the conus, cauda equina, and nerve roots. This study demonstrates the ability to acquire triggered electromyography (t-EMG) from the external urethral sphincter (EUS) muscles by utilizing a urethral catheter with an electrode attached., Methods: A retrospective analysis of neurophysiological monitoring data from two medical centers was performed. Seven intradural tumors and three tethered cord release surgeries that used urethral sphincter electrodes to record t-EMG were included in the analysis. The patients consisted of five females and five males with ages ranging from eight months to 67 years (median: 49 years). Our neuromonitoring paradigm included upper and lower extremity somatosensory evoked potentials (SSEPs) and transcranial electrical motor evoked potentials (TCeMEPs), as well as spontaneous and triggered electromyography (EMG) from the external anal sphincter (EAS), EUS muscles and lower extremity muscles bilaterally. A catheter with urethral electrodes attached was used for recording spontaneous electromyography (s-EMG), t-EMG, and TCeMEPs from the skeletal muscle of the EUS. Train of four (TOF) was also recorded from the abductor hallucis muscle as well for monitoring the level of muscle relaxant., Results: We were able to successfully record t-EMG responses from the EUS muscles in all patients (100%). It is worthy to note that only one patient presented preoperatively with bladder incontinence, urgency, and frequency. Almost immediately in the postoperative phase, the patient's frequency and urgency improved, and the bladder function normalized within two weeks of having the tumor removed., Conclusions: In this small series, we were able to acquire t-EMG in 100% of patients when recorded from the EUS using a urethral catheter with electrodes built into it. T-EMGs can be attempted in surgeries that put the function of the pelvic floor at risk. More study is needed to establish better statistical methods, better modality efficacy, and a better understanding of intraoperative countermeasures that may be employed when an alert is encountered to prevent impending neurological sequelae., Competing Interests: The authors have declared that no competing interests exist.

The American Society of Neurophysiological Monitoring (ASNM) was founded in 1989 as the American Society of Evoked Potential Monitoring. From the beginning, the Society has been made up of physicians, doctoral degree holders, Technologists, and all those interested in furthering the profession. The Society changed its name to the ASNM and held its first Annual Meeting in 1990. It remains the largest worldwide organization dedicated solely to the scientifically-based advancement of intraoperative neurophysiology. The primary goal of the ASNM is to assure the quality of patient care during procedures monitoring the nervous system. This goal is accomplished primarily through programs in education, advocacy of basic and clinical research, and publication of guidelines, among other endeavors. The ASNM is committed to the development of medically sound and clinically relevant guidelines for the performance of intraoperative neurophysiology. Guidelines are formulated based on exhaustive literature review, recruitment of expert opinion, and broad consensus among ASNM membership. Input is likewise sought from sister societies and related constituencies. Adherence to a literature-based, formalized process characterizes the construction of all ASNM guidelines. The guidelines covering the Professional Practice of intraoperative neurophysiological monitoring were initially published January 24th, 2013, and subsequently that document has undergone review and revision to accommodate broad inter- and intra-societal feedback. This current version of the ASNM Professional Practice Guideline was fully approved for publication according to ASNM bylaws on February 22nd, 2018, and thus overwrites and supersedes the initial guideline.

Bowel and bladder function are at risk during tumor resection of the conus, cauda equina, and nerve roots. This study demonstrates the ability to acquire transcranial electrical motor evoked potentials (TCeMEPs) from the urethral sphincter muscles (USMEPs) by utilizing a urethral catheter with an embedded electrode. A retrospective analysis of intraoperative neurophysiological monitoring (IONM) data from nine intradural tumors, four tethered cord releases, and two spinal stenosis procedures was performed (n = 15). The cohort included seven females and eight males (median age: 38.91 years). A catheter with embedded urethral electrodes was used for recording TCeMEPs and spontaneous electromyograph (s-EMG) from the external urethral sphincter (EUS). USMEPs were obtained in 14 patients (93%). The reliability of TCeMEP from the external anal sphincter (EAS) was variable across all patients. In patient 7, the TCeMEP recordings from the urethral sphincter were not present before incision; however, following the resection of the tumor, the USMEP recordings were obtained and remained stable for the remainder of the procedure. Patient 7 had subsequent improvement in bladder function postoperatively. Patient 4 exhibited a 50% increase in the amplitude of the USMEP following tumor resection and exhibited improved bladder function as well postoperatively. In this small series, we were able to acquire consistent and reliable MEPs when recorded from the urethral sphincters. More study is needed to establish a better understanding of the value added by this modality. USMEPs can be attempted in surgeries that put the function of the pelvic floor at risk.

Arthroscopic hip surgery is performed routinely for the treatment of various hip disorders. Leg traction during labral tear repair, femoroplasty, and acetabuloplasty for hip stabilization can stretch the peripheral nerves. This may cause temporary or permanent nerve injury. This study illustrates the benefit of utilizing multimodality Intraoperative Neurophysiological Monitoring (IONM) during hip surgical procedures. We performed a retrospective review of 10 arthroscopic hip surgeries with neurophysiological monitoring at one medical center. The patients consisted of six females and four males (mean age: 48.9 years). The procedures were equally divided into left and right-sided procedures. IONM setup included posterior tibial, peroneal, and femoral or saphenous nerve somatosensory evoked potentials (SSEPs), transcranial electrical motor evoked potentials (TCeMEP), train of four (TOF), and electromyography (EMG) from the lower extremities. All patients exhibited changes in IONM data during the surgical procedure. Changes in the latency and amplitude or loss of the lower SSEPs on the surgical side occurred in 36% of the monitorable SSEPs. The surgeon instructed the team to reduce the leg lengthening by removing traction when changes were observed. The SSEPs exhibited a full recovery in 75% of the affected lower extremity SSEPs. In the two instances of nonrecovery, the SSEP responses remained increased in latency or decreased in amplitude at closing, but the waveform was intact. There were five instances of complete loss of the waveform (four in the ipsilateral leg, and one in the contralateral leg) with recovery after traction was reduced. TCeMEP changes occurred in 53% of the ipsilateral lower muscles monitored. Many of the TCeMEP changes were attributed to ischemia of the feet and could not be resolved intraoperatively. Multimodality IONM can be a beneficial and protective tool during surgical procedures involving hip and acetabular areas. Early identification of changes in evoked potentials during hip arthroscopy surgeries can minimize post-operative neurological deficits due to peripheral nerve injury and leg ischemia., Competing Interests: The authors have declared that no competing interests exist.

Intraoperative neurophysiological monitoring (IONM) consists of a group of neurodiagnostic techniques that assess the nervous system's functional integrity during surgical operations. A retrospective analysis of a pediatric female patient was conducted who underwent 12 operations for the correction of scoliosis, tethered cord, and split spinal cord wherein IONM played an important role. From age 3 to 6, she underwent six procedures including a release of the tethered cord, resection of the filum terminale, removal of a T11-T12 bony spur, release of L3 adhesions, repair of subcutaneous meningocele, and correction of scoliosis with a vertical expandable prosthetic titanium rod (VEPTR) technique without the use of IONM. However, a multimodality IONM protocol with somatosensory evoked potentials, transcranial electrical motor evoked potentials (TCeMEP), and an electromyogram was utilized during the later procedures. At age 6 (the seventh procedure), a VEPTR expansion was performed, with loss and recovery of the lower extremity motor evoked potentials. The postoperative magnetic resonance imaging (MRI) showed a partial split cord malformation with retethering of the spinal cord. We repaired her split cord malformation and tethered cord while employing IONM. Using IONM for her operation was crucial because a sudden significant loss of TCeMEP resulted in a cancellation of the procedure; the MRI showed a thick remnant attached to the spinal cord. If the procedure was performed without IONM, we could have missed the underlying pathology, an error that may have resulted in paraplegia. We strongly recommend using IONM during high-risk surgical procedures to help significantly reduce the risk of permanent postoperative complications.

This case illustrates the benefits of utilizing intraoperative neurophysiological monitoring (IONM) for preventing injury to sensory/motor pathways of the spinal cord during a cordotomy procedure to relieve pain. Cordotomy has been used effectively in the treatment of visceral pain but comes with a high risk of damaging motor and sensory pathways due to close proximity of lesion. The subject is a 47-year-old female with a pancoast tumor of the left lung, left brachialplexopathy, and severe neuropathic pain syndrome, refractory to medical therapy. A palliative cordotomy procedure was elected for pain control. Baseline bilateral posterior tibial and median nerve somatosensory evoked potentials (SSEP) were present except in the left upper extremity. Transcranial electric motor evoked potential (TCeMEP) baselines were present in all extremities except the left upper. Total intravenous anesthesia was used. The spine was exposed at C2-C3 and a right single anterolateral cordotomy was performed with an immediate drop in TCeMEPs (70-80% amplitude reduction) in the right upper and right lower extremities. The surgeon decided to stop the cordotomy at that point. Postoperatively, the patient had no sensory or motor deficit. In this patient, TCeMEPs were used effectively to guide the surgeon in preventing damage to the spinal cord that could lead to motor deficits.

Pedicle screw placement has a high risk of damaging the motor and sensory pathways due to the close proximity to the spinal cord and nerve roots. Early detection and prevention of injury can be achieved by utilizing Somatosensory Evoked Potentials (SSEP) and Transcranial electrical Motor Evoked Potentials (TCeMEP) during a scoliosis surgery. A 19-year-old female presented for correction of scoliosis. After intubation, electrodes were placed for upper and lower SSEPs, EMGs and TCeMEPs. Total intravenous anesthesia was used. Baseline SSEP and TCeMEP responses were present in all limbs. Eight pedicle screws were placed. After placing the last screw, TCeMEP signals were lost bilaterally in lower extremities. Surgery was paused. After removing all the screws TCeMEP responses returned to baseline in left lower limb but remained absent in right lower limb. A wake-up test was performed which was positive in her right leg. Blood pressure was increased and bolus of steroids was given. There was no improvement in right lower limb TCeMEP responses. Surgeon was advised to stop the surgery and proceed for MRI and follow-up. SSEP signals remained stable in all four-extremities. The surgical correction was cancelled. MRI revealed intramedullary spinal cord ischemic changes at T11. After extubation, patient was unable to move her right lower extremity with flaccid paralysis. She also complained about severe burning in her left lower extremity. The patient was taken for rehabilitation exercises. One week post-op, she was moving hip flexors and two weeks later had afull motor function, bilaterally. Real-time IONM was useful in early identification of spinal cord injury. Significant changes were seen in TCeMEP, without any change in SSEP. We highly recommend utilizing continuous TCeMEP and SSEP monitoring during pedicle screw placement for prevention of injury to the spinal cord. In this case, the patient would have been paralyzed post-operatively without the use of IONM.

Introduction: Embolization of a spinal cord arteriovenous malformation (AVM) is considered a high-risk procedure due to the potential risk of spinal cord injury. We present two cases illustrating the benefits of utilizing pharmacologic provocative testing under general anesthesia with continuous neurophysiologic monitoring of somatosensory evoked potentials (SSEPs) and transcranial electrical motor evoked potentials (TCeMEPs) to identify the functional territory of the catheterized vessels prior to embolization., Clinical Presentation: Case #1: A 28-year-old male presented with a progressive right lower leg numbness followed by weakness with impaired sphincter control. The MRI and angiogram of the spine showed an arteriovenous malformation (type 4) (subtype 2). Case #2: A 31-year-old male presented with sudden occipital, neck, right shoulder and back pain. He was neurologically intact. MRI and angiogram showed a predominantly right sided arteriovenous malformation. INTERVENTIONAL PROCEDURE: After intubation, bilateral posterior tibial and median nerve SSEPs were recorded. TCeMEP and electromyogram (EMG) were monitored from upper and lower extremity muscles bilaterally. Total intravenous anesthesia was used with propofol and remifentanil infusion. Neuromuscular blockade was used only for initial intubation. A train of four was maintained during the procedure. Pre-incision baselines were obtained with good morphology of waveforms. Selective spinal Wada tests were performed prior to embolization with lidocaine and propofol. Neurophysiological monitoring was performed for any changes., Results: Complete occlusion of the AVM was achieved. As no changes occurred during provocative testing, all branches were treated with Onyx embolization. At six-month post-operative follow-up, both patients had total relief of symptoms., Conclusion: Multimodality IONM with continuous SSEP, TCeMEP, and EMG monitoring was utilized effectively during provocative testing with lidocaine and propofol. IONM helped in predicting and preventing post-operative neurological deficits due to ischemia to the spinal cord.

Previously intraoperative neurophysiological monitoring (IONM) has not been used along with a computer based navigation system for en bloc resection of a sacral Ewing sarcoma. In order to improve the post-operative neurological outcome of the patient we decided to include IONM in our procedure. A partial or complete resection of a sacral tumor may result in the loss of neurological functions due to close proximity of vascular, neural, and visceral structures. A prolonged two-stage surgical procedure may be a high risk procedure for position related brachial plexus injury. An 18-year-old male presented with left lower extremity weakness, which worsened with gait. His MRI was consistent with a sacral mass causing compression on the left S1 and S2 roots. A surgical resection was planned with anterior and posterior approaches. IONM helped guide the surgical team to prevent damaging the sacral roots on the normal side (right) and position related upper extremity brachial plexus injuries. Our technique involving IONM can be used safely for accurate en bloc removal of a sacral tumor with a safe margin while protecting the neural function and minimizing recurrence. This case report demonstrates that intraoperative neurophysiological monitoring was useful in identifying and reversing impending nerve injury during sacrectomy surgery. Significant changes were seen in ulnar and posterior tibial somatosensory evoked potentials (SSEPs). We recommend that IONM should be considered for safe margin en bloc sacral tumor resection and prevention of injury to the sacral root and brachial plexus.

Previously, intraoperative neurophysiological monitoring was not used routinely during tibial osteotomies. In an attempt to improve the post-operative outcomes and reduce known neurologic complications, we used discrete multimodality recording and stimulation models to identify areas of motor and sensory function in eighteen (18) pediatric patients presenting with Tibia Vara (Blount's Disease). By using both posterior tibial and peroneal nerves somatosensory evoked potentials (SSEPs) with transcranial electrical motor evoked potentials (TCeMEPs) precise status of sensory and motor pathways was possible during surgical correction. Similarly, spontaneous electromyography (s-EMG) and triggered electromyography (t-EMG) were used to more accurately localize nerve irritation. Concerns during tibial and fibular osteotomies included ipsilateral lower limb motor and sensory function, especially peroneal nerve injuries due to the location of the osteotomy at the fibular neck. Surgical interventions consisting of additional fibular resection were made during the index procedures for four patients because of real-time monitoring changes noted as the peroneal nerve was entrapped in three patients at the osteotomy site. In fourth patient, the tourniquet pressure was the cause for loss of ipsilateral SSEPs and TCeMEPs. After appropriate surgical intervention, monitoring parameters began to normalize and postoperatively the patients presented with no neurologic deficit. In this study, the application of multimodality recording and stimulation models were utilized including posterior tibial nerve and peroneal nerve SSEP with lumbar potential (LP) identification to compare with contralateral limb recordings. In addition, by using spontaneous and triggered EMG and TCeMEP, we were able to perform monitoring with a high level of confidence throughout surgery.

We present two cases illustrating the benefit of utilizing intraoperative neurophysiological monitoring (IONM) for prevention of injuries to the lower cranial nerves during fourth ventricle tumor resection surgeries. Multiple cranial nerve nuclei are located on the floor of the fourth ventricle with a high risk of permanent damage. Two male patients (ages 8 and 10 years) presented to the emergency department and had brain magnetic resonance imaging (MRI) scans showing brainstem/fourth ventricle tumors. During surgery, bilateral posterior tibial and median nerve somatosensory evoked potentials (SSEPs); four-limb and cranial nerves transcranial electrical motor evoked potentials (TCeMEPs); brainstem auditory evoked responses (BAERs); and spontaneous electromyography (s-EMG) were recorded. Electromyography (EMG) was monitored bilaterally from cranial nerves V VII, IX, X, XI, and XII. Total intravenous anesthesia was used. Neuromuscular blockade was used only for initial intubation. Pre-incision baselines were obtained with good morphology of waveforms. After exposure the floor of the fourth ventricle was mapped by triggered-EMG (t-EMG) using 0.4 to 1.0 mA. In both patients the tumor was entangled with cranial nerves VII to XII on the floor of the fourth ventricle. The surgeon made the decision not to resect the tumor in one case and limited the resection to 70% of the tumor in the second case on the basis of neurophysiological monitoring. This decision was made to minimize any post-operative neurological deficits due to surgical manipulation of the tumor involving the lower cranial nerves. Intraoperative spontaneous and triggered EMG was effectively utilized in preventing injuries to cranial nerves during surgical procedures. All signals remained stable during the surgical procedure. Postoperatively both patients were well with no additional cranial nerve weakness. At three months follow-up, the patients continued to have no deficits.

Intraoperative neurophysiological monitoring (IONM) is becoming the standard of care for many spinal surgeries, especially those with deformity correction and instrumentation. We reviewed 2069 spine cases with multimodality IONM including somatosensory evoked potentials (SSEP), transcranial electrical motor evoked potentials (TCeMEP), and spontaneous and triggered electromyography (s-EMG and t-EMG) in a University setting over a period of four years to examine perioperative clinical findings when an IONM event was noted and to ascertain how IONM has affected our ability to avoid potential neurological injury during spine surgery. We performed a retrospective analysis of cases from 2006 to 2010 to study the frequency and cause of intraoperative events detected via IONM and the clinical outcome of the patient. There were 32 cases (1.5%) with possible intraoperative events. There were 17 (53%) cases where IONM changes affected the course of the surgery and prevented possible postoperative neurological deficits. Seven cases (41%) were due to deformity correction, five (29%) due to hypotension, four (24%) due to patient positioning, and one (6%) due to a screw requiring repositioning. None of the 17 patients had postoperative motor or sensory deficits. There were four cases with false-positive IONM findings due to correctible technical issues. Three cases required surgical revision due to pedicle screw malposition. In each case, s-EMGs failed to exhibit intraoperative changes but the patient presented with postoperative radiculopathy. We believe that the use of t-EMGs may have prevented these complications. This review reinforces the importance of multimodality IONM for spinal surgery. The incidence of possible events in our series was 1.5%, and several likely postoperative neurologic deficits were avoided by intraoperative intervention.

Background: Traditionally, the dual-radial model, which requires high cortical stimulation intensities and may evoke intraoperative seizures, is used for mapping during resection of lesions within or near the central sulcus., Objective: To examine the potential utility of using the multimodal tangential-radial triphasic model, which may increase the accuracy and reliability of cortical mapping at lower stimulation intensities., Methods: We performed a retrospective review of intracranial neuromonitoring cases at the University of Virginia. The tangential-radial triphasic model used direct electrical cortical stimulation (DECS), electrocorticography, and somatosensory evoked potentials with an additional P25 peak for waveform interpretation, instead of the older dual-radial model with N20 and P30 peaks alone. The central sulcus and sensory cortex were localized by generating multiple sensory maps. DECS with 50-Hz frequency was applied. Electrocorticography was used for detection of afterdischarges., Results: Fifteen consecutive intracranial cases were identified. The patients consisted of 8 males and 7 females ranging in age from 12 to 74 years (median, 53 years). Fourteen patients had an intra-axial cortical mass, and 1 patient had a cortical arteriovenous malformation. The DECS thresholds ranged from 3.7 to 12 mA (median, 6.2 mA). Localization of motor and sensory cortices was accurately performed at low thresholds with bipolar DECS in all patients. Intraoperative seizures occurred in 1 patient (7%), and new permanent postoperative functional deficits occurred in 1 patient (7%)., Conclusion: Our mapping technique appears safe and reliable for resection near the central sulcus. The tangential-radial triphasic model allows for lower stimulation intensities, reducing the risk of intraoperative seizures.

The use of somatosensory evoked potentials (SSEPs) to monitor upper extremity nerves during surgery is becoming more accepted as a valid and useful technique to minimize intraoperative nerve injuries. We present a case illustrating the benefit of utilizing both SSEPs and transcranial electrical motor evoked potentials (TCeMEPs) for preventing position-related injury during surgery. The patient was a 43-year-old male with a history of neck pain, along with numbness and tingling of the upper extremities. While the patient was being draped, upper extremity SSEPs diminished significantly TCeMEP responses in the hands (abductor pollicus brevis-abductor digiti minimi; APB-ADM) vanished shortly after that, followed by the biceps and left deltoid. The surgeons were notified, and the tape on the shoulders was loosened. No improvements were noted in SSEPs nor TCeMEPs due to this intervention, so all tape was removed and the patient's arms were allowed to rest naturally upon the arm boards. Upper extremity TCeMEP responses could then be elicited and SSEPs improved shortly afterward. Surgery was completed with the arms on the arm boards. All signals remained stable for the remaining three hours of the procedure. At two months follow-up, the patient was well with total pain relief and normal upper extremity function when neurological examination was performed. This report demonstrates a case in which intraoperative neurophysiological monitoring was useful in identifying and reversing impending nerve injury during cervical spine surgery. Significant changes were seen in SSEPs as well as TCeMEPs, so we recommend that TCeMEP monitoring be considered as an adjunct to SSEPs for prevention of injury to the brachial plexus.