Jaime Lopez, MD

All Publications

• Sharps Injuries Related to Subdermal Needles in the Orbicularis Oris During Intraoperative Neurophysiologic Monitoring. Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society Joshi, A., Aissa, Y., Le, S., Cho, S. C., Lee, L., Lopez, J. R. 2021

  Abstract

  PURPOSE: Little is known about the incidence and nature of sharps injuries caused by subdermal intraoperative neurophysiologic monitoring (IONM) needle electrodes. In their institution, the authors observed a series of sharps injuries attributed to placement of needles in the orbicularis oris (OO).METHODS: One large academic institution's sharps injury monitoring database was queried for all reported events over 3 years. The de-identified list was filtered for sharps events occurring in the operating room, and the descriptions of the sharps injuries were individually evaluated. Interventions were performed to attempt to decrease the number of sharps injuries from IONM needles, particularly those placed in OO. Similar data were then collected for 3 months post-intervention.RESULTS: Pre-intervention, 327 sharps injuries were reported over the span of 3 years, of which 13 (4.0%) were attributed to IONM needles not in OO and 5 (1.5%) were attributed to IONM needles in OO. Post-intervention, 41 sharps injuries were reported in 3 months, of which 5 (12.2%) were attributed to IONM needles not in OO and 1 (2.4%) was attributed to needles in OO.CONCLUSIONS: The placement of subdermal needles in the OO presents a disproportionately high risk of sharps injury. Interventions were performed to attempt to decrease the rate of sharps injuries from needles in OO; the post-intervention increase in events was likely skewed by small sample sizes. The implementation of these changes and the ongoing surveillance of injury cases may be important data to help decrease the number of sharps injuries attributed to IONM needles.

  View details for DOI 10.1097/WNP.0000000000000835

  View details for PubMedID 33675313

• Intraoperative Neuromonitoring for Cerebral Arteriovenous Malformation Embolization: A Propensity-Score Matched Retrospective Database Study. Cureus Feng, A. Y., Sussman, E. S., Jin, M. C., Wong, S., Lopez, J., Pulli, B., Heit, J. J., Telischak, N. 2021; 13 (1): e12946

  Abstract

  Introduction The treatment of cerebral arteriovenous malformations (AVMs) may result in neurologic morbidity, particularly when an AVM is located in or adjacent to eloquent brain regions. Intraoperative neurophysiologic monitoring (IONM) may be utilized to reduce the risk of iatrogenic injury during endovascular AVM embolization; however, IONM for endovascular AVM embolization is not ubiquitously the standard of care. Methods Admissions for AVM embolization were assessed from the IBM MarketScan Commercial and Medicare Supplemental databases (IBM Watson Health, Somers, NY). Inclusion criterion for patients was continuous enrollment six months before and after the index encounter. The use of IONM and presence of intracranial hemorrhage (ICH) were noted. Propensity-score matched cohorts with and without IONM were generated to minimize bias between treatment groups (adjusting for age, sex, and comorbidities). Results From 2007 to 2016, there were 16,279 patients diagnosed with cerebral AVM in the MarketScan database. Embolized patients were stratified into IONM and non-IONM cohorts; there were 357 patients in the IONM cohort and 1775 patients in the non-IONM cohort. Provider types were significantly different between cohorts (p<0.005). Unruptured AVMs were significantly more likely to be embolized with adjunctive IONM (17.7%) compared to ruptured AVMs (7.9%) (p<0.005). After balancing for baseline comorbidities, there were 266 patients in the IONM cohort, and 1347 patients in the non-IONM cohort. Among unruptured AVM patients, IONM was linked to a significantly shorter length of stay (2.72 versus 4.92 days; p<0.005), significantly lower rates of complications within 30 days of discharge (0.00% versus 1.88%; p=0.038), and significantly lower total payment ($40,179 versus $50,844; p<0.0001). Conclusion Endovascular embolization for unruptured AVMs performed with adjunctive IONM was associated with shorter length of stay, lower complication rates, and hospitalization costs.

  View details for DOI 10.7759/cureus.12946

  View details for PubMedID 33654622

• Longitudinal alteration of cortical thickness and volume in high-impact sports. NeuroImage Mills, B. D., Goubran, M. n., Parivash, S. N., Dennis, E. L., Rezaii, P. n., Akers, C. n., Bian, W. n., Mitchell, L. A., Boldt, B. n., Douglas, D. n., Sami, S. n., Mouchawar, N. n., Wilson, E. W., DiGiacomo, P. n., Parekh, M. n., Do, H. n., Lopez, J. n., Rosenberg, J. n., Camarillo, D. n., Grant, G. n., Wintermark, M. n., Zeineh, M. n. 2020: 116864

  Abstract

  Collegiate football athletes are subject to repeated head impacts. The purpose of this study was to determine whether this exposure can lead to changes in brain structure. This prospective cohort study was conducted with up to 4 years of follow-up on 63 football (high-impact) and 34 volleyball (control) male collegiate athletes with a total of 315 MRI scans (after exclusions: football n=50, volleyball n= 24, total scans=273) using high-resolution structural imaging. Volumetric and cortical thickness estimates were derived using FreeSurfer 5.3's longitudinal pipeline. A linear mixed-effects model assessed the effect of group (football vs. volleyball), time from baseline MRI, and the interaction between group and time. We confirmed an expected developmental decrement in cortical thickness and volume in our cohort (p<0.001). Superimposed on this, total cortical gray matter volume (p = .03) and cortical thickness within the left hemisphere (p=.04) showed a group by time interaction, indicating less age-related volume reduction and thinning in football compared to volleyball athletes. At the regional level, sport by time interactions on thickness and volume were identified in the left orbitofrontal (p=.001), superior temporal (p=.001), and postcentral regions (p< .001). Additional cortical thickness interactions were found in the left temporal pole (p=.003) and cuneus (p=.005). At the regional level, we also found main effects of sport in football athletes characterized by reduced volume in the right hippocampus (p=.003), right superior parietal cortical gray (p<.001) and white matter (p<.001), and increased volume of the left pallidum (p=.002). Within football, cortical thickness was higher with greater years of prior play (left hemisphere p=.013, right hemisphere p=.005), and any history of concussion was associated with less cortical thinning (left hemisphere p=.010, right hemisphere p=.011). Additionally, both position-associated concussion risk (p=.002) and SCAT scores (p=.023) were associated with less of the expected volume decrement of deep gray structures. This prospective longitudinal study comparing football and volleyball athletes shows divergent age-related trajectories of cortical thinning, possibly reflecting an impact-related alteration of normal cortical development. This warrants future research into the underlying mechanisms of impacts to the head on cortical maturation.

  View details for DOI 10.1016/j.neuroimage.2020.116864

  View details for PubMedID 32360690

• Plasma nitrite as an indicator of cerebral ischemia during extracranial/intracranial bypass surgery in moyamoya patients. Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association Silver, J. H., Jaffe, R. A., López, J. R. 2020; 29 (9): 104830

  Abstract

  Nitric oxide (NO) plays a key role in ischemia and shows potential as a biomarker for ischemia. We measured mixed venous nitrite (NO2-) as a proxy for NO, during controlled cerebral ischemia in patients with moyamoya disease (MMD) during direct extracranial/intracranial (EC/IC) bypass surgery with temporary occlusion of the M4 branch of the middle cerebral artery (MCA) to permit anastomosis with the superficial temporal artery (STA). This small, focal ischemic event is not reliably detected using cerebral oximetry, somatosensory evoked potentials (SSEPs) or electroencephalography (EEG).We enrolled nine adult MMD patients (n=8 female, n=1 male) undergoing direct EC/IC bypass surgery. Nitrite was measured at least one hour prior to MCA occlusion, and before, during and after anastomosis. Cortical function was monitored using either multi-lead EEG and SSEPs, or frontal EEG activity.Mixed venous NO2- was significantly elevated (p<0.05) within 12 min following arterial occlusion vs. baseline. An M4 branch of the MCA was cross clamped for a median duration of 18 (IQR = 5) minutes during anastomosis. One patient with elevated NO2- showed a transient neurologic deficit that resolved 3 days post-operatively.Mixed venous NO2- was significantly elevated shortly following cerebral artery occlusion vs. baseline in a majority of the study subjects, suggesting that NO2- is a potential biomarker for ischemia. Since all patients received identical burst suppression anesthesia and vasopressors, the fact that NO2- was not elevated during cross-clamp in all patients supports the conclusion that the NO2- elevation is likely due to ischemia.

  View details for DOI 10.1016/j.jstrokecerebrovasdis.2020.104830

  View details for PubMedID 32807407

• Longitudinal Changes in Hippocampal Subfield Volume Associated with Collegiate Football JOURNAL OF NEUROTRAUMA Parivash, S. N., Goubran, M., Mills, B. D., Rezaii, P., Thaler, C., Wolman, D., Bian, W., Mitchell, L. A., Boldt, B., Douglas, D., Wilson, E. W., Choi, J., Xie, L., Yushkevich, P. A., DiGiacomo, P., Wongsripuemtet, J., Parekh, M., Fiehler, J., Do, H., Lopez, J., Rosenberg, J., Camarillo, D., Grant, G., Wintermark, M., Zeineh, M. 2019

  View details for DOI 10.1089/neu.2018.6357

  View details for Web of Science ID 000472105100001

• Cerebral Oximetry Fails as a Monitor of Brain Perfusion in Cardiac Surgery: A Case Report A & A PRACTICE McAvoy, J., Jaffe, R., Brock-Utne, J., Lopez, J., Brodt, J. 2019; 12 (12): 441–43

  View details for DOI 10.1213/XAA.0000000000000963

  View details for Web of Science ID 000473709400008

• Superselective methohexital challenge prior to intracranial endovascular embolization JOURNAL OF CLINICAL NEUROSCIENCE Bican, O., Cho, C., Suarez-Roman, A., Viet Nguyen, Lee, L., Le, S., Heit, J., Dodd, R., Lopez, J. 2019; 63: 68–71

  View details for DOI 10.1016/j.jocn.2019.01.051

  View details for Web of Science ID 000466249000013

• Intraoperative Transcranial Motor-evoked Potential Stimulation Does Not Seem to Cause Seizures. Journal of neurosurgical anesthesiology Burbridge, M. A., Nguyen, V. n., Min, J. G., Jaffe, R. A., Ahuja, B. n., Shah, A. D., Lee, L. H., Cho, C. n., Sandoval, B. n., López, J. R. 2019

  Abstract

  Intraoperative neurophysiological monitoring is of critical importance in evaluating the functional integrity of the central nervous system during surgery of the central or peripheral nervous system. In a large recent study, transcranial motor-evoked potentials (TcMEPs) were found to be associated with a 0.7% risk of inducing a seizure as diagnosed by clinical observation and electromyography in patients having general anesthesia with intravenous anesthetics. The gold standard for seizure diagnosis, however, is electroencephalography (EEG). The aim of this single-institution retrospective study is to ascertain the risk of intraoperative seizures detected using EEG during surgeries in adult patients undergoing intraoperative monitoring with TcMEPs.The authors retrospectively reviewed the intraoperative EEG records of 1175 patients anesthetized with a variety of anesthetic agents, including volatile and intravenous anesthetics, to ascertain the rate of EEG-diagnosed seizures attributable to TcMEPs.Our analysis did not reveal a single seizure event attributable to TcMEPs in 1175 patients.The intraoperative use of TcMEPs does not seem to cause seizures.

  View details for DOI 10.1097/ANA.0000000000000671

  View details for PubMedID 31876633

• Novel Mapping Method for the Intraoperative Neurophysiologic Monitoring of Sexual Function During Prostate Surgery JOURNAL OF CLINICAL NEUROPHYSIOLOGY Martin-Palomeque, G., Cabanes-Martinez, L., de Blas Beorlegui, G., Moreno Galera, M., Lopez, J. R., Javier Burgos, F., Regidor Bailly-Bailliere, I. 2018; 35 (6): 463–67

  View details for DOI 10.1097/WNP.0000000000000506

  View details for Web of Science ID 000457849100003

• Positive pharmacologic provocative testing with methohexital during cerebral arteriovenous malformation embolization CLINICAL IMAGING Bican, O., Cho, C., Lee, L., Viet Nguyen, Le, S., Heit, J., Lopez, J. 2018; 51: 155–59

  View details for DOI 10.1016/j.clinimag.2018.02.014

  View details for Web of Science ID 000445321000022

• Intraoperative neurophysiologic monitoring (IONM) changes associated with a case of delayed thalamic infarct: Implications for postoperative management. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia Ghavami, F., Choudhri, O., Marks, M., Lopez, J. R. 2017

  Abstract

  Treatment of cerebral aneurysms poses a risk of cerebral hemorrhage and/or ischemia; these potential sequelae are usually associated with changes in intraoperative neurophysiologic monitoring (IONM) modalities. Our case demonstrates a patient with significant changes in IONM during the treatment of a right posterior cerebral artery aneurysm who did not develop neurologic deficits until three days postoperatively. IONM changes can represent a guide in postoperative patient management and may pose grounds for closer monitoring of patients with IONM changes that do not develop immediate postoperative deficits.

  View details for PubMedID 29066230

• Intraoperative Tonic-Clonic Seizure Under General Anesthesia Captured by Electroencephalography: A Case Report. A & A case reports Burbridge, M. A., Jaffe, R. A., Doufas, A. G., Lopez, J. R. 2017

  Abstract

  We present the case of a 34-year-old man undergoing craniotomy for arteriovenous malformation resection under general anesthesia who suffered a tonic-clonic seizure captured by intraoperative electroencephalograph. The seizure was extinguished with a propofol bolus. This patient had no previous history of seizures, and no precipitating cause was identified. Intraoperative electroencephalographic seizures under general anesthesia have been recorded previously in the literature, but our observation is the first to demonstrate this with overt motor manifestations. We also discuss the differential diagnosis of an intraoperative seizure under general anesthesia and provide guidance to the anesthesiologist who encounters this event.

  View details for DOI 10.1213/XAA.0000000000000509

  View details for PubMedID 28410260

• Large Amplitude Cortical Evoked Potentials in Nonepileptic Patients. Reviving an Old Neurophysiologic Tool to Help Detect CNS Pathology JOURNAL OF CLINICAL NEUROPHYSIOLOGY Martin-Palomeque, G., Castro-Ortiz, A., Pamplona-Valenzuela, P., Saiz-Sepulveda, M. A., Cabanes-Martinez, L., Lopez, J. R. 2017; 34 (1): 84-91

  Abstract

  Although large amplitude evoked potentials (EPs) are typically associated with progressive myoclonic epilepsy patients, giant EPs imply central nervous system (CNS) hyperexcitability and can be seen in various nonepileptic disorders.We performed a retrospective chart review including history, physical examination, imaging and diagnostic studies of nonepileptic patients with large amplitude somatosensory evoked potentials (SSEPs) and visual evoked potentials (VEPs) during 2007 to 2013. Large amplitude EPs were defined as follows: VEPs (N75-P100) >18 μV; and SSEPs (N20-P25) >6.4 μV. Recording montage for VEPs was Oz-Cz and SSEPs C3'/C4'-Fz.Fifty-two patients (33 females, 19 males; age range, 9-90 years) were identified. No CNS pathology was detected in 7 patients. All remaining patients were diagnosed with new CNS disorders including: vascular (37%); myelopathies (13%); demyelinating (11%); space occupying lesions (8.7%); syringomyelia (8.7%); hydrocephalus (6.5%); Vitamin B-12 deficiency (4.3%); multiple system atrophy (4.3%); and toxins (2.2%).This study supports the notion that large amplitude EP implies CNS hyperexcitability and CNS disease. These results confirm the utility of EP studies in patients with suspected CNS pathology.

  View details for DOI 10.1097/WNP.0000000000000326

  View details for Web of Science ID 000390856800014

  View details for PubMedID 27490324

• Intraoperative Tonic-Clonic Seizure Under General Anesthesia Captured by Electroencephalography: A Case Report A and A Case Reports Burbridge, M. A., Jaffe, R. A., Doufas, A. G., Lopez, J. R. 2017: 9–12

  Abstract

  We present the case of a 34-year-old man undergoing craniotomy for arteriovenous malformation resection under general anesthesia who suffered a tonic-clonic seizure captured by intraoperative electroencephalograph. The seizure was extinguished with a propofol bolus. This patient had no previous history of seizures, and no precipitating cause was identified. Intraoperative electroencephalographic seizures under general anesthesia have been recorded previously in the literature, but our observation is the first to demonstrate this with overt motor manifestations. We also discuss the differential diagnosis of an intraoperative seizure under general anesthesia and provide guidance to the anesthesiologist who encounters this event.

  View details for DOI 10.1213/XAA.0000000000000509

• EMG in Pediatric Brachial Plexopathy CLINICAL NEUROPHYSIOLOGY IN PEDIATRICS: A PRACTICAL APPROACH TO NEURODIAGNOSTIC TESTING AND MANAGEMENT Lopez, J. R., Galloway, G. M. 2016: 161–79

  View details for Web of Science ID 000364888000010

• Six Degree-of-Freedom Measurements of Human Mild Traumatic Brain Injury ANNALS OF BIOMEDICAL ENGINEERING Hernandez, F., Wu, L. C., Yip, M. C., Laksari, K., Hoffman, A. R., Lopez, J. R., Grant, G. A., Kleiven, S., Camarillo, D. B. 2015; 43 (8): 1918-1934

  Abstract

  This preliminary study investigated whether direct measurement of head rotation improves prediction of mild traumatic brain injury (mTBI). Although many studies have implicated rotation as a primary cause of mTBI, regulatory safety standards use 3 degree-of-freedom (3DOF) translation-only kinematic criteria to predict injury. Direct 6DOF measurements of human head rotation (3DOF) and translation (3DOF) have not been previously available to examine whether additional DOFs improve injury prediction. We measured head impacts in American football, boxing, and mixed martial arts using 6DOF instrumented mouthguards, and predicted clinician-diagnosed injury using 12 existing kinematic criteria and 6 existing brain finite element (FE) criteria. Among 513 measured impacts were the first two 6DOF measurements of clinically diagnosed mTBI. For this dataset, 6DOF criteria were the most predictive of injury, more than 3DOF translation-only and 3DOF rotation-only criteria. Peak principal strain in the corpus callosum, a 6DOF FE criteria, was the strongest predictor, followed by two criteria that included rotation measurements, peak rotational acceleration magnitude and Head Impact Power (HIP). These results suggest head rotation measurements may improve injury prediction. However, more 6DOF data is needed to confirm this evaluation of existing injury criteria, and to develop new criteria that considers directional sensitivity to injury.

  View details for DOI 10.1007/s10439-014-1212-4

  View details for Web of Science ID 000358249800018

  View details for PubMedCentralID PMC4478276

• Detection of acute femoral artery ischemia during neuroembolization by somatosensory and motor evoked potential monitoring INTERVENTIONAL NEURORADIOLOGY Purger, D., Feroze, A. H., Choudhri, O., Lee, L., Lopez, J., Dodd, R. L. 2015; 21 (3): 397-400

  Abstract

  Neuromonitoring can be used to map out particular neuroanatomical tracts, define physiologic deficits secondary to specific pathology or intervention, or predict postoperative outcome and proves essential in the detection of central and peripheral ischemic events during neurosurgical intervention. Herein, we describe an instance of elective balloon-assisted coiling of a recurrent basilar tip aneurysm in a 61-year-old woman, where intraoperative somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (TcMEPs) were lost in the right lower extremity intraoperatively. We aim to highlight that targeted use of monitoring proves advantageous in both the open surgical and endovascular setting, even in the avoidance of potential iatrogenic peripheral nerve damage and limb ischemia as documented herein. Consideration of the increased risk for peripheral ischemia in the neurointerventional setting is especially imperative in particular populations where blood vessels might be of diminished size, such as in infants, young children, and severely deconditioned adults.

  View details for DOI 10.1177/1591019915583219

  View details for Web of Science ID 000356305000019

  View details for PubMedID 26015519

  View details for PubMedCentralID PMC4757266

• Detection of inferolateral trunk syndrome by neuromonitoring during catheter angiography with provocative testing. Journal of neurointerventional surgery Le, S., Dodd, R., López, J., Nguyen, V., Cho, S. C., Lee, L. 2013; 5 (2)

  Abstract

  It is not uncommon that endovascular balloon test occlusion (BTO) is performed to assess collateral blood flow and risk of injury of permanent occlusion of the internal carotid artery (ICA). This case is the first reported of detection and reversal of the inferolateral trunk (ILT) syndrome in an awake patient during provocative BTO; prompt recognition of the syndrome effectively prevented permanent neurologic deficits.The case of a 42-year-old woman is reported who had a left sphenoid wing meningioma with extension into the cavernous sinus and who underwent awake catheter angiography with provocative BTO of the ICA. Serial examinations by intraoperative monitoring neurologists and neurointerventionalists detected acute progressive left retro-orbital pressure followed by sudden inability to adduct the left eye, or a left medial rectus palsy, indicative of the ILT syndrome which led to immediate balloon deflation and resolution of the deficits. The hypothesis was that hypoperfusion of the ILT, an arterial branch of the ICA which provides blood supply to several cranial nerves (CN) III, CN V1 and CN V2, caused her acute symptoms.Although cerebral ischemia is a well known complication of endovascular procedures, CN ischemia is a rare potential risk. Knowledge of cerebrovascular anatomy and serial examinations prevented neurologic deficits; this case underscores the added utility of examinations by intraoperative monitoring neurologists and interdisciplinary collaboration.

  View details for DOI 10.1136/neurintsurg-2011-010236

  View details for PubMedID 22345146

• Evidence-Based Guideline Update: Intraoperative Spinal Monitoring with Somatosensory and Transcranial Electrical Motor Evoked Potentials JOURNAL OF CLINICAL NEUROPHYSIOLOGY Nuwer, M. R., Emerson, R. G., Galloway, G., Legatt, A. D., Lopez, J., Minahan, R., Yamada, T., Goodin, D. S., Armon, C., Chaudhry, V., Gronseth, G. S., Harden, C. L. 2012; 29 (1): 101-108

  Abstract

  To evaluate whether spinal cord intraoperative monitoring (IOM) with somatosensory and transcranial electrical motor evoked potentials (EPs) predict adverse surgical outcomes.A panel of experts reviewed the results of a comprehensive literature search and identified published studies relevant to the clinical question. These studies were classified according to the evidence-based methodology of the American Academy of Neurology. Objective outcomes of postoperative onset of paraparesis, paraplegia, and quadriplegia were used because no randomized or masked studies were available.Four class I and eight class II studies met inclusion criteria for analysis. The four class I studies and seven of the eight class II studies reached significance in showing that paraparesis, paraplegia, and quadriplegia occurred in the IOM patients with EP changes compared with the IOM group without EP change. All studies were consistent in showing all occurrences of paraparesis, paraplegia, and quadriplegia in the IOM patients with EP changes, with no occurrences of paraparesis, paraplegia, and quadriplegia in patients without EP change. In the class I studies, 16% to 40% of the IOM patients with EP changes developed postoperative-onset paraparesis, paraplegia, or quadriplegia. IOM is established as effective to predict an increased risk of the adverse outcomes of paraparesis, paraplegia, and quadriplegia in spinal surgery (four class I and seven class II studies). Surgeons and other members of the operating team should be alerted to the increased risk of severe adverse neurologic outcomes in patients with important IOM changes (level A).

  View details for DOI 10.1097/WNP.0b013e31824a397e

  View details for Web of Science ID 000300634700015

  View details for PubMedID 22353994

• Evidence-based guideline update: Intraoperative spinal monitoring with somatosensory and transcranial electrical motor evoked potentials Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology and the American Clinical Neurophysiology Society NEUROLOGY Nuwer, M. R., Emerson, R. G., Galloway, G., Legatt, A. D., Lopez, J., Minahan, R., Yamada, T., Goodin, D. S., Armon, C., Chaudhry, V., Gronseth, G. S., Harden, C. L. 2012; 78 (8): 585-589

  Abstract

  To evaluate whether spinal cord intraoperative monitoring (IOM) with somatosensory and transcranial electrical motor evoked potentials (EPs) predicts adverse surgical outcomes.A panel of experts reviewed the results of a comprehensive literature search and identified published studies relevant to the clinical question. These studies were classified according to the evidence-based methodology of the American Academy of Neurology. Objective outcomes of postoperative onset of paraparesis, paraplegia, and quadriplegia were used because no randomized or masked studies were available.Four Class I and 8 Class II studies met inclusion criteria for analysis. The 4 Class I studies and 7 of the 8 Class II studies reached significance in showing that paraparesis, paraplegia, and quadriplegia occurred in the IOM patients with EP changes compared with the IOM group without EP changes. All studies were consistent in showing all occurrences of paraparesis, paraplegia, and quadriplegia in the IOM patients with EP changes, with no occurrences of paraparesis, paraplegia, and quadriplegia in patients without EP changes. In the Class I studies, 16%-40% of the IOM patients with EP changes developed postoperative-onset paraparesis, paraplegia, or quadriplegia. IOM is established as effective to predict an increased risk of the adverse outcomes of paraparesis, paraplegia, and quadriplegia in spinal surgery (4 Class I and 7 Class II studies). Surgeons and other members of the operating team should be alerted to the increased risk of severe adverse neurologic outcomes in patients with important IOM changes (Level A).

  View details for DOI 10.1212/WNL.0b013e318247fa0e

  View details for Web of Science ID 000300638800017

  View details for PubMedID 22351796

• Neurophysiologic Intraoperative Monitoring of the Oculomotor, Trochlear, and Abducens Nerves JOURNAL OF CLINICAL NEUROPHYSIOLOGY Lopez, J. R. 2011; 28 (6): 543-550

  View details for Web of Science ID 000298821700003

  View details for PubMedID 22146351

• Neurophysiologic Intraoperative Monitoring of Pediatric Cerebrovascular Surgery JOURNAL OF CLINICAL NEUROPHYSIOLOGY Lopez, J. R. 2009; 26 (2): 85-94

  Abstract

  The surgical and endovascular treatment of cerebrovascular disorders (CVDs) in children, such as cerebral arteriovenous malformations, cavernous malformations, and moyamoya disease, have become commonplace and routine in many centers. As in the adult population, these procedures carry the risk of intraoperative cerebral ischemia. Therefore, similar strategies used to reduce the risk of cerebral ischemia in adults should be used in children. Unfortunately, there are no published studies on the intraoperative use of available techniques to identify, prevent, or potentially reverse cerebral ischemia. The goal of this article is to review the neurophysiologic techniques that may be useful and applicable in the surgical and endovascular treatment of pediatric CVDs, to describe the rationale and physiologic basis of their utility, to describe our experience in managing these cases, to present some of our results, and finally, to show the clinical utility of these techniques in the intraoperative management of CVDs.

  View details for Web of Science ID 000264960000006

  View details for PubMedID 19279496

• Visual field preservation after curative multi-modality treatment of occipital lobe artemovenous malformations NEUROSURGERY Sinclair, J., Marks, M. P., Levy, R. P., Adler, J. R., Chang, S. D., Lopez, J. R., Do, H. M., Bell-Stephens, T. E., Lim, M., Steinberg, G. K. 2005; 57 (4): 655-666

  Abstract

  Occipital lobe arteriovenous malformations (AVMs) provide challenging management decisions because of their proximity to the visual cortex and optic radiations. Preservation of visual function throughout treatment is the mainstay of therapeutic planning. We reviewed visual field (VF) outcomes of all patients who received curative treatment for occipital AVMs at Stanford University to evaluate the efficacy of different treatment strategies.We conducted a retrospective review of 55 patients with occipital AVMs treated at Stanford University between 1984 and 2003. Clinical presentation, AVM morphology, and treatment modality were correlated with VF function before and after therapeutic intervention.Of 55 patients, 48 (87.3%) underwent multimodality AVM treatment (7 patients < 3 yr from radiosurgery were excluded from final analysis). One patient died from intracerebral hemorrhage 11 months post-radiosurgery, and five patients deferred further treatment. Forty-two patients (87.5%) were cured, with no residual AVM on final angiography. Curative therapeutic modalities used included embolization alone (2 patients), microsurgery alone (6 patients), microsurgery with radiosurgery (1 patient), microsurgery with embolization (23 patients), radiosurgery with embolization (4 patients), and embolization with radiosurgery and microsurgery (6 patients). Mean follow-up was 5.8 years including treatment. VF follow-up was available in all 42 patients. Twenty-eight (66.7%) patients experienced no change in VFs, six (14.3%) patients with previously abnormal VFs improved, and eight (19.0%) patients showed worsening of VFs (although none developed a new homonymous VF deficit). Duration of treatment was related to VF outcome in patients who presented without a history of AVM-related hemorrhage.Occipital AVMs can be safely cured using multimodality strategies with minimal risk to visual function despite the proximity of these lesions to the visual cortex and associated pathways.

  View details for DOI 10.1227/01.NEU.0000175547.05291.85

  View details for PubMedID 16239877

• Wrist hyperextension leads to median nerve conduction block - Implications for intra-arterial catheter placement ANESTHESIOLOGY Chowet, A. L., Lopez, J. R., Brock-Utne, J. G., Jaffe, R. A. 2004; 100 (2): 287-291

  Abstract

  It is common practice to hyperextend the wrist to facilitate insertion of a radial intra-arterial catheter. This position may be maintained for prolonged periods. Although there has been much discussion about optimal patient management to protect the ulnar nerve and brachial plexus, little attention has been paid to the median nerve during wrist hyperextension. The authors report the effects of wrist hyperextension on conduction in the median nerve.Median nerve conduction was studied in 12 awake, healthy volunteers using standard nerve conduction tests consisting of the measurement of compound sensory and motor action potentials, as well as their amplitudes and latencies. With the contralateral hand as a control, the right wrist was placed in hyperextension (angled between 65 and 80 degrees), and compound action potentials were recorded to determine the onset and magnitude of effects. Subsequently, the hand was released from hyperextension and recovery was recorded.In 83% of subjects, hyperextension resulted in a significant decrease in compound sensory action potential amplitudes, sufficient to qualify as conduction block (16.6% of baseline). The average time to conduction block was 43 +/- 13.2 min. All subjects who manifested conduction block showed marked improvement 5 min after release from hyperextension.Wrist hyperextension for arterial line placement and stabilization is likely to result in profound impairment of median nerve function. Although the effects were transient in this study, the results suggest that prolonged hyperextension may be associated with significant changes in median nerve conduction. To minimize the chance for nerve injury, the authors recommend that wrists be returned promptly to the neutral position following arterial line placement.

  View details for Web of Science ID 000188438500015

  View details for PubMedID 14739802

• The use of evoked potentials in intraoperative neurophysiologic monitoring. Physical medicine and rehabilitation clinics of North America López, J. R. 2004; 15 (1): 63-84

  Abstract

  Although not universally adopted, the growing body of literature provides strong evidence of the clinical utility of IOM in a variety of cerebrovascular surgical and endovascular procedures. The Therapeutics and Technology Subcommittee of the American Academy of Neurology and Fisher et al concluded that the following are useful and noninvestigational: 1. EEG, compressed spectral array, and SSEP in CEA and brain surgeries that potentially compromise cerebral blood flow, 2. BAEP and cranial nerve monitoring in surgeries performed in the region of the brainstem or inner ear, 3. SSEP monitoring performed for surgical procedures potentially involving ischemia or mechanical trauma of the spinal cord. They also came to the conclusion that although promising, motor EPs and visual EPs are still investigational. Further investigation, especially in the area of outcomes research and cost-effectiveness, is required before IOM can become standard practice.

  View details for PubMedID 15029899

• Neurophysiological monitoring in the endovascular therapy of aneurysms AMERICAN JOURNAL OF NEURORADIOLOGY Liu, A. Y., Lopez, J. R., Do, H. M., Steinberg, G. K., Cockroft, K., Marks, M. P. 2003; 24 (8): 1520-1527

  Abstract

  Endovascular aneurysm therapy has associated risks of ischemic complications. We undertook this study to evaluate the efficacy of neurophysiological monitoring (NPM) techniques in the detection of ischemic changes that may be seen during endovascular treatment of cerebral aneurysms.Thirty-five patients underwent NPM during endovascular treatment of cerebral aneurysms. The patients underwent a total of 50 endovascular procedures, including balloon test occlusion (19 patients), GDC embolization (22 patients), and permanent vessel occlusion (nine patients). NPM included electroencephalography, somatosensory evoked potentials, and/or brain stem auditory evoked potentials, depending on the location of the aneurysm.NPM changes were seen in nine (26%) of 35 patients and altered the management in five (14%) of 35 patients. In three of the five cases, NPM changes were observed without corresponding neurologic physical examination changes after balloon test occlusion (performed while the patients were under general anesthesia in two cases). In the two other cases in which NPM changes altered management, ischemia was detected at the time of intra-aneurysmal therapy while the patients were under general anesthesia. Overall, 18 of 35 patients underwent a total of 19 balloon test occlusion procedures. Of the 17 remaining patients, 13 underwent aneurysm coiling, two were not treated because of inability to safely place coils, and two were treated for distal aneurysms. Two patients developed transient neurologic deficits without concurrent NPM changes, representing false-negative NPM test results.NPM is a valuable adjunct to endovascular treatment of cerebral aneurysms. Our study suggests that these monitoring techniques may reduce ischemic complications and can be used to help guide therapeutic decisions.

  View details for PubMedID 13679263

• Hyperperfusion syndrome with hemorrhage after angioplasty for middle cerebral artery stenosis AMERICAN JOURNAL OF NEURORADIOLOGY Liu, A. Y., Do, H. M., Albers, G. W., Lopez, J. R., Steinberg, G. K., Marks, M. P. 2001; 22 (8): 1597-1601

  Abstract

  Hyperperfusion syndrome is a well-documented complication of carotid endarterectomy, as well as internal carotid artery angioplasty and stent placement. We report a similar complication after distal intracranial (middle cerebral artery [MCA] M2 segment) angioplasty. To our knowledge, this is the first report of hyperperfusion syndrome after intracranial angioplasty of a distal MCA branch.

  View details for PubMedID 11559514

• AAEM news and comments Muscle & nerve Chang, Lopez, Steinberg 2000; 23 (9): 1450-1451

  View details for PubMedID 10951454

• Reply Muscle & nerve Chang, Lopez, Steinberg 2000; 23 (9): 1446-?

  View details for PubMedID 10951453

• Microsurgical resection of brainstem, thalamic, and basal ganglia angiographically occult vascular malformations NEUROSURGERY Steinberg, G. K., Chang, S. D., Gewirtz, R. J., Lopez, J. R. 2000; 46 (2): 260-270

  Abstract

  To evaluate the clinical results for patients who underwent resection of angiographically occult vascular malformations (AOVMs) of the brainstem, thalamus, or basal ganglia, successfully resected after it exhibited rebleeding and presented to a pial surface.Between January 1990 and May 1998, 56 patients with 57 deep AOVMs underwent 63 operations, at Stanford University Medical Center, to treat AOVMs of the brainstem (42 AOVMs), thalamus (5 AOVMs), or basal ganglia (10 AOVMs). The surgical approach was suboccipital midline (27 operations), far lateral suboccipital (10 operations), transsylvian (9 operations), interhemispheric transcallosal or infracallosal (8 operations), infratentorial supracerebellar (6 operations), or subtemporal (3 operations). Four patients experienced recurrent bleeding from the same lesion after surgical resection, requiring a second operation. One patient required a planned second operation, using a different approach, to completely resect the lesion, and one patient underwent two surgical procedures to resect two separate brainstem AOVMs. One patient initially underwent exploration but not resection of her AOVM, because it did not present to a pial or ependymal surface. The AOVM was successfully resected after it exhibited rebleeding and presented to a pial surface.The immediate outcomes after surgery were unchanged for 31 patients (55%), worsened for 16 (29%), and improved for 9 (16%). The long-term outcomes were unchanged for 24 patients (43%), compared with their presenting grade, worse for 3 (5%), and improved for 29 (52%). Patients who had undergone previous radiotherapy or radiosurgery to treat these lesions experienced more difficult postoperative courses, and radiation necrosis was observed for two patients.AOVMs of the brainstem, thalamus, and basal ganglia can be safely removed, with a long-term neurological morbidity rate of only 5% and a complete lesion resection rate of 93% after the initial planned resection. The use of cranial base surgical approaches and intraoperative electrophysiological monitoring contributes to successful clinical outcomes.

  View details for Web of Science ID 000085191800002

  View details for PubMedID 10690715

• The treatment of giant intracranial arteriovenous malformations using multimodality therapy Chang, S. D., Lopez, J. R., Levy, R. P., Marks, M. P., Steinberg, G. K. LIPPINCOTT WILLIAMS & WILKINS. 2000: 324–24

  View details for Web of Science ID 000084589100304

• Treatment of intracranial arteriovenous malformations in the elderly population Chang, S. D., Lopez, J. R., Marks, M. P., Levy, R. P., Adler, J. R., Steinberg, G. K. LIPPINCOTT WILLIAMS & WILKINS. 2000: 325–25

  View details for Web of Science ID 000084589100308

• Intraoperative electrical stimulation for identification of cranial nerve nuclei 45th Annual Meeting of the American-Association-for-Electrodiagnostic-Medicine Chang, S. D., Lopez, J. R., Steinberg, G. K. JOHN WILEY & SONS INC. 1999: 1538–43

  Abstract

  The purpose of this study was to evaluate the feasibility and usefulness of cranial nerve nuclei monitoring during resection of brainstem cavernous malformations. Eleven patients with brainstem cavernous malformations underwent resection of their malformations utilizing cranial nerve nuclei monitoring. Cranial nerves V and VII were monitored by placing electrodes in muscle groups innervated by these nerves and recording manipulation-induced neurotonic discharges and triggered electromyographic (EMG) activity, after electrical stimulation of the corresponding brainstem nuclei. Seven of 11 procedures (64%) with cranial nerve nuclei monitoring were noted to have cranial nerve nuclei activity corresponding to manipulation of the nuclei. The cavernous malformation was completely resected in 5 of 7 cases with cranial nerve nuclei activity and in all 4 cases without activity. In the remaining 2 cases, the cavernous malformation was not resected due to the proximity of the monitored cranial nerve nuclei to the cavernous malformation and to increasing neurotonic activity as the cavernous malformation was approached. None of the 11 patients had new permanent postoperative deficits corresponding to the cranial nerve nuclei monitored; 1 patient had a transient partial facial palsy lasting 2 days. Preliminary results indicate that cranial nerve nuclei monitoring proves useful in preserving neurologic function and reducing surgical morbidity during resection of brainstem cavernous malformations, particularly indicating when lesion resection places these nuclei at risk.

  View details for Web of Science ID 000083306000008

  View details for PubMedID 10514231

• The usefulness of electrophysiological monitoring during resection of central nervous system vascular malformations. Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association Chang, S. D., Lopez, J. R., Steinberg, G. K. 1999; 8 (6): 412-422

  Abstract

  Goal: The purpose of this study was to evaluate the usefulness of electrophysiological monitoring during the resection of vascular malformations. Methods: Between September 1994 and April 1996, we surgically resected vascular malformations (31 arteriovenous malformations, 22 angiographically occult vascular malformations) from 53 patients (56 procedures) and used intraoperative evoked potential monitoring. Somatosensory evoked potentials (SSEPs) were monitored in 54 procedures (96%), and brain stem auditory evoked potentials (BAEPs) in 17 (30%). The neurological status of the patients was evaluated before and after surgery. Findings: Five of the 54 patients (9%) monitored with SSEPs had SSEP changes (4 transient, 1 persistent) coinciding with new clinical neurological deficits in 4 patients (all transient). In all 4 patients who had transient SSEP changes, the changes resolved with adjustment or removal of clips on feeding vessels (2 patients) or with elevating mean arterial pressure (MAP) (2 patients). Forty-seven patients (91%) had neither SSEP or neurological examination alterations. One of 17 patients (6%) monitored with BAEPs had neurological and persistent BAEP changes, 15 (88%) had neither BAEP or neurological changes, and 1 (6%) had a neurological change despite no change in BAEP (false negative). The sensitivity of SSEP and BAEP for predicting a new postoperative deficit (transient or prolonged) in this series was 86% (6/7); specificity was 98% (55/56). Clinical outcome was excellent in 41 patients, good in 11 and poor in 1 (no patients died) and was largely related to pretreatment grade. Conclusion: SSEPs and BAEPs predict the likelihood of clinical neurological injury during resection of vascular malformations with high sensitivity and specificity and may prove a useful adjunct in treating these lesions.

  View details for PubMedID 17895195

• Embolization of rolandic cortex arteriovenous malformations NEUROSURGERY Paulsen, R. D., Steinberg, G. K., Norbash, A. M., Marcellus, M. L., Lopez, J. R., Marks, M. P. 1999; 44 (3): 479-484

  Abstract

  To evaluate the safety and efficacy of preradiosurgical and presurgical embolization of arteriovenous malformations (AVMs) involving the rolandic cortex.Seventeen consecutive patients with rolandic AVMs seen during a 31-month period (December 1994-July 1997) were evaluated. All patients underwent superselective sodium amobarbital testing to determine any changes in the results of the neurological examinations before undergoing embolization. In 16 of 17 patients (94.1%), somatosensory evoked potentials augmented physical examinations. Patients were embolized with N-butyl cyanoacrylate (Histoacryl; B. Braun, Melsungen, Germany) and iophendylate (Ethiodol; Savage Labs, Melville, NY). Rigid control of the mean arterial pressure (65-75 mm Hg) was maintained in all patients for 24 to 48 hours after embolization.Twenty-three embolization sessions were performed in 17 patients (mean, 1.5 sessions/patient), and a total of 40 feeding arteries were embolized. Two patients were unable to undergo embolization because of positive results of the amobarbital testing despite repeated attempts to reposition a microcatheter in the AVM circulation. In one case, somatosensory evoked potentials and the results of the physical examination were both positive; in the other case, only the somatosensory evoked potentials were used (in a pediatric patient under general anesthesia). All patients with AVMs that were embolized experienced a significant size reduction of their lesions (range, 20-95%; mean, 63%). There were no permanent complications. Four procedures (10% of the procedures, 23% of the patients) resulted in minor transient neurological deficits, with patients' conditions returning to baseline. Thirteen patients subsequently underwent radiosurgery, three underwent surgical resection, and one underwent combined surgery and radiosurgery. Complete obliteration of the lesions has been achieved in four patients to date (three who underwent surgery and one who underwent radiosurgery), with the remainder undergoing further follow-up.When properly evaluated before treatment, rolandic AVMs can be embolized with a high success rate (measured by completed embolization and size reduction) and a low complication rate.

  View details for PubMedID 10069584

• The use of electrophysiological monitoring in the intraoperative management of intracranial aneurysms JOURNAL OF NEUROLOGY NEUROSURGERY AND PSYCHIATRY Lopez, J. R., Chang, S. D., Steinberg, G. K. 1999; 66 (2): 189-196

  Abstract

  Somatosensory evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAEPs) have been increasingly utilised during surgery for intracranial aneurysms to identify cerebral ischaemia. Between July 1994 and April 1996, we surgically treated 70 aneurysms in 49 consecutive patients (58 operations) with the aid of intraoperative evoked potential monitoring. This study sought to evaluate the usefulness of SSEP and BAEP monitoring during intracranial aneurysm surgery.Mean patient age was 51.9 (range 18-79) years. The sizes of the aneurysms were 3-4 mm (15), 5-9 mm (26), 10-14 mm (11), 15-19 mm (seven), 20-24 mm (six), and >25 mm (five). SSEPs were monitored in 58 procedures (100%) and BAEPs in 15 (26%). The neurological status of the patients was evaluated before and after surgery.Thirteen of the 58 procedures (22%) monitored with SSEPs had SSEP changes (12 transient, one persistent); 45 (78%) had no SSEP changes. Three of 15 patients (20%) monitored with BAEPs had changes (two transient, one persistent); 12 (80%) had no BAEP changes. Of the 14 patients with transient SSEP or BAEP changes, these changes resolved with adjustment or removal of aneurysm clips (nine), elevating MAP (four), or retractor adjustment (one). Mean time from precipitating event to electrophysiological change was 8.9 minutes (range 3-32), and the mean time for recovery of potentials in patients with transient changes was 20.2 minutes (range 3-60). Clinical outcome was excellent in 39 patients, good in five, and poor in three (two patients died), and was largely related to pretreatment grade.SSEPs and BAEPs are useful in preventing clinical neurological injury during surgery for intracranial aneurysms and in predicting which patients will have unfavourable outcomes.

  View details for Web of Science ID 000078450800011

  View details for PubMedID 10071098

  View details for PubMedCentralID PMC1736209

• The use of electrophysiologic monitoring during intracranial cerebrovascular surgery: A cost-benefit analysis Chang, S. D., Lopez, J. R., Steinberg, G. K. LIPPINCOTT WILLIAMS & WILKINS. 1999: 257–57

  View details for Web of Science ID 000077934200205

• Evoked potential monitoring and EKG: A case of a serious "cardiac arrhythmia" ANESTHESIOLOGY Diachun, C. A., Brock-Utne, J. G., Lopez, J. R., Ceranski, J. A. 1998; 89 (5): 1270-1272

  View details for Web of Science ID 000076891400033

  View details for PubMedID 9822022

• Cranial nerve nuclei monitoring during resection of brainstem cavernous malformations: Preliminary results Chang, S. D., Lopez, J. R., Steinberg, G. K. LIPPINCOTT WILLIAMS & WILKINS. 1998: 276–76

  View details for Web of Science ID 000071417100075

• The use of electrophysiologic monitoring during resection of arteriovenous malformations and angiographically occult vascular malformations Chang, S. D., Lopez, J. R., Steinberg, G. K. LIPPINCOTT WILLIAMS & WILKINS. 1997: 172–72

  View details for Web of Science ID A1997WB81400222

• Intraoperative neurophysiological monitoring INTERNATIONAL ANESTHESIOLOGY CLINICS Lopez, J. R. 1996; 34 (4): 33-54

  View details for Web of Science ID A1996VV64300004

  View details for PubMedID 8956063

• ENTOMOPIA - A REMARKABLE CASE OF CEREBRAL POLYOPIA NEUROLOGY Lopez, J. R., Adornato, B. T., Hoyt, W. F. 1993; 43 (10): 2145-2146

  View details for Web of Science ID A1993MC70400055

  View details for PubMedID 8413985