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Various complications of prone positioning in spine surgery have been described in the literature. Patients in the prone position for extended periods are subject to neurological deficits and/or loss of intraoperative signals due to compression neuropathies, but positioning-related spinal deficits are rare in the thoracolumbar deformity population. The authors present a case of severe kyphoscoliotic deformity with critical thoracolumbar stenosis in which, during the use of a hinged open frame in the prone position, complete loss of intraoperative neural monitoring signals occurred while the frame was flexed into kyphosis to facilitate exposure and instrumentation placement. When the frame was reset to a neutral position, evoked potentials returned to baseline and the operation proceeded without complications. This case represents, to the authors’ knowledge, the first report of loss of evoked potentials due to an alteration of prone positioning on a hinged open frame. When positioning patients in such a manner, careful attention should be directed to intraoperative signals in patients with critical stenosis and kyphotic deformity.

Background Multilevel spine fusion surgery for adult deformity correction is associated with significant blood loss and coagulopathy. Tranexamic acid reduces blood loss in high-risk surgery, but the efficacy of a low-dose regimen is unknown. Methods Sixty-one patients undergoing multilevel complex spinal fusion with and without osteotomies were randomly assigned to receive low-dose tranexamic acid (10 mg/kg loading dose, then 1 mg·kg−1·hr−1 throughout surgery) or placebo. The primary outcome was the total volume of red blood cells transfused intraoperatively. Results Thirty-one patients received tranexamic acid, and 30 patients received placebo. Patient demographics, risk of major transfusion, preoperative hemoglobin, and surgical risk of the 2 groups were similar. There was a significant decrease in total volume of red blood cells transfused (placebo group median 1460 mL vs. tranexamic acid group 1140 mL; median difference 463 mL, 95% confidence interval 15 to 914 mL, P = 0.034), with a decrease in cell saver transfusion (placebo group median 490 mL vs. tranexamic acid group 256 mL; median difference 166 mL, 95% confidence interval 0 to 368 mL, P = 0.042). The decrease in packed red blood cell transfusion did not reach statistical significance (placebo group median 1050 mL vs. tranexamic acid group 600 mL; median difference 300 mL, 95% confidence interval 0 to 600 mL, P = 0.097). Conclusions Our results support the use of low-dose tranexamic acid during complex multilevel spine fusion surgery to decrease total red blood cell transfusion.

A healthy 26-year-old man with cerebral arteriovenous malformation underwent staged endovascular embolization with Onyx followed by awake craniotomy for resection. The perioperative course was complicated by tachycardia and severe intraoperative hypoxemia requiring significant oxygen supplementation. Postoperative chest computed tomography (CT) revealed hyperattenuating Onyx embolization material within the pulmonary vasculature, and an electrocardiogram indicated possible right heart strain, supporting clinically significant embolism. With awake arteriovenous malformation resection following adjunctive Onyx embolization becoming increasingly employed for lesions involving the eloquent cortex, anesthesiologists need to be aware of pulmonary migration of Onyx material as a potential contributor to significant perioperative hypoxemia.

Objective Although a significant amount of experience has accumulated for awake procedures for brain tumor, epilepsy, and carotid surgery, its utility for intracranial neurovascular indications remains largely undefined. Awake surgery for select neurovascular cases offers the advantage of precise brain mapping and robust neurologic monitoring during surgery for lesions in eloquent areas, avoidance of potential hemodynamic instability, and possible faster recovery. It also opens the window for perilesional epileptogenic tissue resection with potentially less risk for iatrogenic injury. Methods Institutional review board approval was obtained for a retrospective review of awake surgeries for intracranial neurovascular indications over the past 36 months from a prospectively maintained quality database. We reviewed patients' clinical indications, clinical and imaging parameters, and postoperative outcomes. Results Eight consecutive patients underwent 9 intracranial neurovascular awake procedures conducted by the senior author. A standardized “sedated–awake–sedated” protocol was used in all 8 patients. For the 2 patients with arteriovenous malformations and the 3 patients with cavernoma, awake brain surface and white matter mapping was performed before and during microsurgical resection. A neurological examination was obtained periodically throughout all 5 procedures. There were no intraoperative or perioperative complications. Hypotension was avoided during the 2 Moyamoya revascularization procedures in the patient with a history of labile blood pressure. Postoperative imaging confirmed complete arteriovenous malformation and cavernoma resections. No new neurologic deficits or new-onset seizures were noted on 3-month follow-up. Conclusions Awake surgery appears to be safe for select patients with intracranial neurovascular pathologies. Potential advantages include greater safety, shorter length of stay, and reduced cost.

In some cases of cerebral aneurysm clipping, direct clip application to the aneurysm neck may be difficult or the aneurysm may rupture unexpectedly. In these cases, a clip may be temporarily applied to the parent artery to reduce aneurysmal wall tension, facilitate permanent clip placement, or control bleeding if the aneurysm ruptures. In certain circumstances, even applying a temporary clip may be challenging. We present a case in which the aneurysm ruptured and IV administration of adenosine was required to facilitate clipping. This case suggests that administering multiple consecutive precalculated doses of adenosine may be a safe method to manage aneurysmal rupture.

An anterior cervical discectomy and fusion (ACDF) is a routinely performed surgery whose purpose is to relieve spinal stenosis, remove intervertebral disk and bony matter which may be impinging upon neural elements, and also to mechanically stabilize the cervical spine after such material is removed. The safety of an ACDF for patients with cervical radiculopathy, with or without neurophysiologic monitoring, is extremely high, with very low rates of temporary or permanent neurologic sequelae. The most frequently used modalities of neurophysiologic monitoring in these cases are somatosensory-evoked potentials (SSEPs), spontaneous electromyography (EMG), and transcranial motor-evoked potentials (MEPs).

Intracranial aneurysm rupture presents a high risk of neurologic morbidity and mortality. To avoid potential rupture in an intact aneurysm or to facilitate management and minimize risk of a re-bleed in a ruptured aneurysm, treatment modalities, such as endovascular coiling and surgical aneurysm clipping, are performed. To help provide real-time functional assessment of neurologic function intraoperatively and thus allow identification and correction of potentially deleterious maneuvers, intraoperative neuromonitoring can be performed. There is growing literature support for use of evoked potentials for these procedures, particularly for intracranial aneurysm clipping.

Background: Surgery for posterior spine instrumentation often requires major transfusion. The aim of this study was to develop and test the validity of a model for predicting intraoperative major transfusion (>4 U total red blood cells), based on preoperative patient and surgical variables, that was applicable to adult patients undergoing cervical, thoracic, and/or lumbar spine deformity surgery with and without osteotomies. Materials and Methods: The perioperative data from 548 patients who underwent ≥3 levels of posterior spinal fusion with instrumentation between January 1, 2003 and May 30, 2009, were retrospectively collected to create a model for predicting major blood transfusion. The validity of the model was retrospectively tested with a separate data set of 95 patients who underwent surgery from June 1, 2009 through September 30, 2010. Results: There was a 59.5% incidence of major transfusion in the derivation set of patients. Independent predictors of major transfusion were operation duration, number of posterior levels instrumented, surgical complexity score, and preincision hemoglobin. This model was able to predict major transfusion significantly better than a previously published model (ROCAUC=0.89; 99% confidence interval, 0.80-0.90; P Conclusions: Our model has an increased accuracy for predicting the probability of major transfusion compared with a previously published model. In addition, our model is applicable to all types of spine fusion surgery and accounts for the complexity of surgical instrumentation, the number of levels instrumented, and the predicted duration of surgery as independent variables.

Total intravenous anesthesia (TIVA) with propofol and opioids is frequently utilized for spinal surgery when somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (tcMEPs) are monitored. Many anesthesiologists would prefer to utilize low dose halogenated anesthetics (e.g. 1/2 MAC). We examined our recent experience using 3 % desflurane or TIVA during spine surgery to determine the impact on propofol usage and on the evoked potential responses. After institutional review board approval we conducted a retrospective review of a 6 month period for adult spine patients who were monitored with SSEPs and tcMEPs. Cases were included for the study if anesthesia was conducted with propofol–opioid TIVA or 3 % desflurane supplemented with propofol or opioid infusions as needed. We evaluated the propofol infusion rate, cortical amplitudes of the SSEPs (median nerve, posterior tibial nerve), amplitudes and stimulation voltage for eliciting the tcMEPs (adductor pollicis brevis, tibialis anterior) and the amplitude variability of the SSEP and tcMEP responses as assessed by the average percentage trial to trial change. Of the 156 spine cases included in the study, 95 had TIVA with propofol–opioid (TIVA) and 61 had 3 % expired desflurane (INHAL). Three INHAL cases were excluded because the desflurane was eliminated because of inadequate responses and 26 cases (16 TIVA and 10 INHAL) were excluded due to significant changes during monitoring. Propofol infusion rates in the INHAL group were reduced from the TIVA group (average 115–45 μg/kg/min) (p

Arteriovenous malformations (AVMs) of the brain are very complex and intriguing pathologies. Since their initial description by Luschka and Virchow in the middle of the 19th century, multiple advances and innovations have revolutionized their management and surgical treatment. Here, we review the historical landmarks in the surgical treatment of AVMs and then illustrate the most recent and futuristic technologies aiming to improve outcomes in AVM surgeries. In particular, we examine potential advances in patient selection, imaging, surgical technique, neuroanesthesia, and postoperative neuro-rehabilitation and quantitative assessments. Finally, we illustrate how concurrent advances in radiosurgery and endovascular techniques might present new opportunities to treat AVMs more safely from a surgical perspective.

Total intravenous anesthesia (TIVA) with propofol and opioids is frequently utilized for spinal surgery where somatosensory evoked potentials (SSEP) and motor evoked potentials (tcMEP) are monitored. Lidocaine infusions can contribute to antinociception and unconsciousness, thus allowing for a reduction in the total dose of propofol. We examined our recent experience with lidocaine infusions to quantify this effect. After institutional review board approval, we conducted a retrospective review of propofol usage in propofol-opioid TIVA (with and without lidocaine) for spine cases monitored with SSEP and tcMEP over a 7 months period. The propofol infusion rate, cortical amplitudes of the SSEP (median nerve, posterior tibial nerve), amplitudes and stimulation voltage of the tcMEP (adductor pollicis brevis, tibialis anterior) were evaluated. The savings of propofol and sufentanil were estimated based on utilization in 50 milliliter (ml) bottles and 5 ml ampules, respectively. 129 cases were evaluated. Propofol infusion rates were reduced with lidocaine infusion from an average of 115-99 μg/kg/min (p = 0.00038) and sufentanil infusions from an average of 0.36-0.29 μg/kg/h (p = 0.0059). This reduction in propofol infusion was also seen when the cases were divided into anterior cervical, posterior cervical, or posterior thoraco-lumbar procedures. No significant differences in the cortical SSEP or tcMEP amplitudes or the tcMEP stimulation voltages used were observed. No complications were associated with the use of the lidocaine infusion. The total estimated drug savings included 104 50 ml bottles of propofol and 5 5 ml ampules of sufentanil. These cases indicate that a lidocaine infusion can be effectively utilized in spine surgery with SSEP and tcMEP monitoring as a means to reduce propofol and sufentanil usage without a negative effect on the monitoring.

Anemia is common in patients with aneurysmal subarachnoid hemorrhage (SAH), but these patients have constituted only a small fraction of those studied in large trials of anemia and transfusion. Unlike other critically ill patients, those with SAH face a well-defined risk of vasospasm and cerebral ischemia in the weeks after their hemorrhage. The risk of ongoing ischemia may make them less able to tolerate anemia and more likely to benefit from blood transfusion. The available data show that anemia is associated with poor outcomes after SAH but that blood transfusion does not consistently improve physiological markers, and it may be associated with poor outcomes. Most of these data are observational in nature, although 1 recent study demonstrated the safety and feasibility of maintaining relatively high transfusion thresholds in patients with SAH. Larger, randomized trials are needed to determine at what levels of anemia patients with SAH might benefit from transfusion, the optimal timing of transfusion, and how to identify those patients who are most likely to benefit.

Standardization and accreditation of fellowship training have been considered in the field of neuroanesthesiology. A prior survey of members of the Society for Neuroscience in Anesthesiology and Critical Care (SNACC) suggested strong support for accreditation and standardization. In response, SNACC created a Task Force that developed curricular guidelines for neuroanesthesiology fellowship training programs. These guidelines represent a first step toward standards for neuroanesthesiology training and will be useful if accreditation is pursued in the future.

BACKGROUND Mannitol is often used during intracranial surgery to improve surgical exposure. Furosemide is often added to mannitol to augment this effect. The concern exists, however, that the augmented diuresis caused by the addition of furosemide to mannitol may cause hypovolemia and hypoperfusion, hypokalemia, and hyponatremia. We examined the intraoperative safety of low-dose furosemide (0.3 mg/kg) combined with mannitol (1 g/kg). METHODS We observed 23 patients in a double-blind, block randomized, placebo-controlled study to examine the effects of furosemide (0.3 mg/kg) when combined with mannitol (1 g/kg) on surgical brain relaxation for tumor surgery. Mannitol and the study drug (furosemide or placebo) were administered, and arterial blood gases with electrolytes (sodium, potassium, and lactic acid) and urine output volume were recorded every 30 minutes for 3 hours. Plasma sodium, potassium, and lactic acid concentrations, and interval urine outputs, were compared across time and between furosemide-placebo assignment groupings, with a P

The purpose of this study was to identify risk factors associated with intraoperative blood transfusions in patients presenting for intracranial aneurysm surgery in the current era of more restrictive transfusion guidelines.Retrospective observational cohort study with stepwise, multivariate binary logistic regression analysis.Tertiary care university teaching hospital.Four hundred seventy-one consecutive patients undergoing intracranial aneurysm surgery at Northwestern Memorial Hospital (Chicago, IL) from 2006 to 2012.Red blood cell transfusion (retrospective observational).Demographic data, medical comorbidities, hemoglobin levels, Hunt-Hess grades, intracranial aneurysm characteristics, presenting intracranial bleeding states, estimated blood losses, transfused red blood cells, and blood products.Forty-six patients (9.5%) received intraoperative red blood cell transfusions. Preoperative risk factors associated with transfusions were highly related to aneurysm rupture, including such parameters as older age (P.001), lower presenting hemoglobin level (P.001), preoperative rupture (P.001), and higher Hunt-Hess grade (P.001). Intraoperative risk factors included larger aneurysm size (10 mm; P = .03), intraventricular hemorrhage (P.001), and intracerebral hematoma evacuation (P = .02). Binary logistic regression modeling identified age (P.001), presenting hemoglobin level (P.001), larger aneurysm size (10 mm; P = .003), elevated Hunt-Hess grade (P = .021), and intraoperative rupture (P = .013) as independent predictors of intraoperative red blood cell transfusion.The incidence of intraoperative red blood cell transfusion in intracranial aneurysm surgery in our patient cohort was 9.5%, and the most significant factors associated with transfusion were presenting hemoglobin level less than 11.7 g/dL and age greater than 52 years. It would seem advisable that these patients undergo routine type and cross-matching of red blood cells before intracranial aneurysm surgery.

BACKGROUND Clip application for temporary occlusion is not always practical or feasible. Adenosine is an alternative that provides brief periods of flow arrest that can be used to advantage in aneurysm surgery, but little has been published on its utility for this indication. OBJECTIVE To report our 2-year consecutive experience with 40 aneurysms in 40 patients for whom we used adenosine to achieve temporary arterial occlusion during aneurysm surgery. METHODS We retrospectively reviewed our clinical database between May 2007 and December 2009. All patients who underwent microsurgical clipping of intracranial aneurysms under adenosine-induced asystole were included. Aneurysm characteristics, reasons for adenosine use, postoperative angiographic and clinical outcome, cardiac complications, and long-term neurological follow-up with the modified Rankin Scale were noted. RESULTS Adenosine was used for 40 aneurysms (10 ruptured, 30 unruptured). The most common indications for adenosine were aneurysm softening in 17 cases and paraclinoid location in 14 cases, followed by broad neck in 12 cases and intraoperative rupture in 6 cases. Troponins were elevated postoperatively in 2 patients. Echocardiography did not show acute changes in either. Clinically insignificant cardiac arrhythmias were noted in 5 patients. Thirty-six patients were available for follow-up. Mean follow-up was 12.8 months. The modified Rankin Scale score was 0 for 29 patients at the time of the last follow-up. Four patients had an modified Rankin Scale score of 1, and scores of 2 and 3 were found in 2 and 1 patients, respectively. CONCLUSION Adenosine appears to allow safe flow arrest during intracranial aneurysm surgery. This can enhance the feasibility and safety of clipping in select circumstances.

Bradycardia caused by the oculocardiac reflex is an anticipated occurrence during certain surgeries. The afferent pathway involves the trigeminal nerve's ophthalmic division. Reflex bradycardia from the trigeminocardiac reflex, via stimulation of maxillary or mandibular divisions of cranial nerve V, although less well known, has also been reported intraoperatively. Unstable bradycardia associated with stimulation of the mandibular division of cranial nerve V during trigeminal neuralgia pain episodes in the Postanesthesia Care Unit is presented.

Study design Observational cohort study. Objective To determine the accuracy of the Revised Cardiac Risk Index (RCRI) in predicting major adverse cardiac events in patients undergoing spine fusion surgery of 3 levels or more. Summary of background data Preoperative cardiac testing is extensively guided by the RCRI, which was developed and validated in thoracic, abdominal, and orthopedic surgical patients. Because multilevel spine fusion surgery is often associated with major transfusion, we hypothesize that the RCRI may not accurately characterize the risk of cardiovascular morbidity in these patients. Methods After institutional review board approval, perioperative data were collected from 547 patients who underwent 3 or more levels of spinal fusion with instrumentation. Postoperative cardiac morbidity was defined as any combination of the following: arrhythmia requiring medical treatment, myocardial infarction (either by electrocardiographic changes or troponin elevation), or the occurrence of demand ischemia. The surgical complexity was categorized as anterior surgery only, posterior cervical and/or thoracic fusion, posterior lumbar fusion, or any surgery that included transpedicular osteotomies. Logistic regression analysis was performed to determine RCRI performance. Results The RCRI performed no better than chance (area under the curve = 0.54) in identifying the 49 patients (9%) who experienced cardiac morbidity. Conclusion The RCRI did not predict cardiac morbidity in our patients undergoing major spine fusion surgery, despite being extensively validated in low-risk noncardiac surgical patients. Preoperative testing and optimization decisions, previously based on the RCRI, may need to be revised to include more frequent functional cardiac imaging and more aggressive implementation of pharmacologic modalities that may mitigate cardiac morbidity, similar to the preoperative evaluation for major vascular surgery. Level of evidence 3.

In this case series, we describe transient postoperative facial nerve palsy in patients after awake craniotomy using selective scalp nerve blocks. In a 1-year period, 7 of the 42 patients receiving scalp nerve blocks at our institutions developed this complication. This is significant because there is only 1 previously reported case of postoperative facial nerve palsy related to scalp nerve blocks. The exact cause of transient postoperative facial nerve palsy after auriculotemporal nerve block is unknown and likely multifactorial. This technique may need to be refined to avoid such complications.

Background: Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is commonly used for the treatment of degenerative lumbar spinal disorders. The rate of postoperative neurological deficits is traditionally low. New neurological postoperative complications may be underreported. We report our infrequent rate of MI-TLIF procedures complicated by postoperative weakness. Methods: A database of 340 patients was evaluated, all of whom underwent MI-TLIF procedures performed between January 2002 and June 2012 by the senior author. We identified four cases (1.2%) whose postoperative course was complicated with bilateral lower extremity weakness. We retrospectively reviewed their past medical history, operative time, estimated blood loss, length of hospital stay, changes in intraoperative neurophysiological monitoring, and pre- and postoperative neurological exams. Results: The average age of the four patients was 65.5 years(range: 62-75 years), average body mass index (BMI) was 25.1 (range: 24.1-26.6), and there were three females and one male. All patients had preoperative degenerative spondylolisthesis (either grade I or grade II). All patients were placed on a Wilson frame during surgery and underwent unilateral left-sided MI-TLIF. Three out of the four patients had a past medical history significant for abdominal or pelvic surgery and one patient had factor V Leiden deficiency syndrome. Conclusions: The rate of new neurological deficits following an MI-TLIF procedure is low, as documented in this study where the rate was 1.2%. Nonetheless, acknowledgement and open discussion of this serious complication is important for surgeon education. Of interest, the specific etiology or pathophysiology behind these complications remains relatively unknown (e.g. direct neural injury, traction injury, hypoperfusion, positioning complication, and others) despite there being some similarities between the patients and their perioperative courses.

The incidence of West Nile virus, which may cause a range of clinical presentations including subclinical infections, mild febrile illness, meningitis, or encephalitis, has increased over recent years. Rare complications, including optic neuritis, also have been reported. A patient who presented with preoperative asymptomatic West Nile virus developed fever, altered mental status and temporary vision loss after elective multilevel spine fusion surgery.

Trigeminal pain is described as sudden, severe, unilateral, brief, recurrent episodes of sharp shooting pain in the distribution of one or more of the trigeminal branches. The incidence is 5 in 100,000. Pain can be a sequel to normal stimuli such as eating or shaving. This pain is thought to be related to nerve compression by an artery or vein at the nerve dorsal root entry zone. In theory, the compression produces demyelination of nerve fibers, which can affect transmission, processing, and interpretation of impulses. The entry zone was first observed by Dandy in 1929. Later, NM Dott proposed demyelination at the entry zone as the cause of pain which Gardner described as a short circuit of afferent stimuli. In addition, King suggested a central mechanism for pain in the trigeminal distribution and Jannetta promoted microvascular decompression (MVD) as an effective treatment [1]. Left untreated, the patient with trigeminal neuralgia proceeds to have shorter intervals free of pain and may progress to have another more complicated type 2 pain syndrome. Patients who fail medical management either because of pain control or excessive side effects are candidates for surgical treatment. An extensive radiological exam may include reliable 3D high-resolution magnetic resonance imaging (MRI) with constructive interference in steady state (CISS) or fast imaging employing steady state acquisition sequence (FIESTA) that can identify the location and degree of compression at the entry zone. The clinical diagnosis combined with this expanded radiological exam will lead to better preoperative planning and an improved surgical outcome [2, 3].

The question of accreditation and standardization of neuroanesthesia fellowship training programs in the U.S. has been discussed extensively within the field. Although numerous opinion pieces have been published, there are no data indicating the level of support or opposition for accreditation of subspecialty training among specialists in the field of neuroanesthesia. To address this gap in knowledge, a web-based survey was designed and electronically distributed to members of the Society of Neurosurgical Anesthesia and Critical Care (SNACC) that were practicing in the United States (n=339). The primary question assessed support for subspecialty accreditation. In addition, the participants were asked to rate the importance of various curricular elements for a neuroanesthesia fellowship training program. Over a 1-month period, there were 134 responses in total (40% of the sample). Ninety percent of the respondents identified themselves as having a university affiliation. Of the respondents, 64% indicated support for accreditation, 20% indicated opposition, and the remainder was equivocal. Career development, neurocritical care, and intraoperative neuromonitoring were the top 3 subjects thought to be essential to a neuroanesthesia fellowship. The majority supported a 1-year fellowship training program. These data indicate measurable support among members of SNACC for a process toward the accreditation of neuroanesthesia fellowship training programs.

Somatosensory evoked potentials (SEPs) were monitored during 113 operations for the clipping of 134 cerebral aneurysms. Changes in peak latency and amplitude of early cortical SEP as well as central conduction time were evaluated. In 58 cases surgical occlusion of arterial vessels or other events occurred, and in 17 of these cases such events were associated with SEP changes or loss. Arterial occlusions resulted from temporary clipping of a feeding blood vessel (22), accidental clipping of a vessel (12). and intentional permanent vessel occlusion (8). A total SEP loss was seen in 2 cases of accidental vessel occlusion and in 6 cases of temporary vessel clipping. Significant SEP changes were found in 6 patients with temporary clipping, and once each with retraction of the cerebellum, retraction of the middle cerebral artery, and after intentional permanent vessel occlusion. Response to these changes included reapplication of aneurysm clips, repositioning of retractors, or removal of temporary clips. Stable SEP signals during 13 cases allowed the surgeon to proceed with the surgical course. Despite the limitations of SEP monitoring in certain anatomical locations, it has been found to be helpful in the operative management of some cases such as multilobed aneurysms of the middle cerebral artery, giant aneurysms, trapping procedures, and procedures requiring temporary vessel occlusion. (Neurosurgery 26:61-70, 1990)

Evoked potentials are increasingly used for intraoperative monitoring. Their use is based on their ability to detect early changes caused by surgical maneuvers which may result in post operative deficits. However, not all changes are surgically related and any decrease in the non surgical causes of evoked potential changes increases the yield of intraoperative monitoring. In this review I will discuss the anesthetic effects on evoked potentials; these include a general description of the anesthetic effects on evoked potentials followed by the effects of premedication, induction, and maintenance agents. Also, described are the effects of adjunct anesthetic agents and techniques. Changes related to anesthesia are not similar and the knowledge of such differences is essential for the planing of anesthesia during the use of evoked potentials. An out line of the anesthetic techniques are described at the end of this review.

The laser has been welcomed to the neurosurgical armamentarium because of the inherent precision and gentleness of the no-touch technique. In order to maximize laser safety and efficacy, however, certain anesthesiologic considerations, specific to neurosurgery, must be realized. Motion of patient (target) during routine anesthesiologic checks or as the result of physiologic excursions during myocardial contraction and respiration must be minimized. Ventilatory parameters, anesthetic agents, and cardio active drugs are considered.

Successful intraoperative monitoring using cortical SSEP was achieved in 381 out of 395 patients undergoing corrective surgery for pathology of the spinal cord or spinal column. SSEP deterioration due to physical, anesthetic and technical factors in 36 cases was not associated with neurological deterioration. Likewise in 14 cases reversible SSEP changes due to surgical factors had no neurological sequelae, but 8 patients in whom SSEP deterioration could not be reversed had postoperative neurological deficits.

Acoustic neuroma resection is an example of a neurosurgical procedure where the brainstem and multiple cranial nerves are at risk for injury. Electrode placement for monitoring of the glossopharyngeal and hypoglossal nerves during acoustic neuroma resection can be challenging. The purpose of this report is to illustrate the use of a device for intra-oral electrode placement for intraoperative monitoring of the glossopharyngeal and hypoglossal nerves. A 60-year-old male presented for acoustic neuroma resection. Under general anesthesia, a Crowe-Davis retractor was used to open the mouth, providing access to the posterior pharynx. For glossopharyngeal monitoring, two bent subdermal needle electrodes were inserted just lateral to the uvula. Two additional electrodes were inserted on the lateral tongue to monitor the hypoglossal nerve. Cranial nerves monitoring was conducted utilizing both free running and triggered electromyography of the trigeminal and facial nerves in addition to the lower cranial nerves. The tumor was resected successfully. Monitoring of the cranial nerves (including the glossopharyngeal and hypoglossal nerves) revealed no concerning responses. The Crowe-Davis retractor and the technique described allowed insertion of electrodes for neural monitoring, contributing to neural preservation.