The Use of Somatosensory Evoked Potentials to Determine the Relationship Between Patient Positioning and Impending Upper Extremity Nerve Injury During Spine Surgery: A Retrospective Analysis

Detecting and Addressing Secondary Neural Injuries in Cranial Surgery: Case Report

Intraoperative neurophysiological monitoring (IONM) is instrumental in mitigating neurological deficits following cranial and spinal procedures. Despite extensive research on IONM's ability to recognize limb-malposition-related issues, less attention has been given to other secondary neural injuries in cranial surgeries. A comprehensive multimodal neuromonitoring approach was employed during a left frontal craniotomy for tumor resection. The electronic medical record was reviewed in detail in order to describe the patient's clinical course. The patient, a 46-year-old female, underwent craniotomy for excision of a meningioma. Deteriorations in somatosensory evoked potential and transcranial motor evoked potential recordings identified both a mal-positioned limb as well as an infiltrated intravenous (IV) line in the arm contralateral to the surgical site. The IONM findings for the infiltrated IV were initially attributed to potential limb malposition until swelling and blistering of the limb were appreciated and investigated. The timely identification and management of the infiltrated IV and adjustment of limb positioning contributed to the patient's recovery, avoiding fasciotomy, with no postoperative neurological deficits. This case is the first published demonstration of the utility of IONM in detecting IV infiltration. This early recognition facilitated early intervention, saving the patient from a potential fasciotomy and enabling their recovery with no postoperative neurological deficits. The findings from this single case highlight the necessity for vigilant and dynamic application of IONM techniques to enhance patient safety and outcomes in neurosurgical procedures. Further research is needed to explore broader applications and further optimize the detection capabilities of IONM.

Intraoperative somatosensory evoked potential (SEP) monitoring: an updated position statement by the American Society of Neurophysiological Monitoring

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.

Anesthetic Considerations for Patients with Hereditary Neuropathy with Liability to Pressure Palsies: A Narrative Review

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant demyelinating neuropathy characterized by an increased susceptibility to peripheral nerve injury from trauma, compression, or shear forces. Patients with this condition are unique, necessitating distinct considerations for anesthesia and surgical teams. This review describes the etiology, prevalence, clinical presentation, and management of HNPP and presents contemporary evidence and recommendations for optimal care for HNPP patients in the perioperative period. While the incidence of HNPP is reported at 7-16:100,000, this figure may be an underestimation due to underdiagnosis, further complicating medicolegal issues. With the subtle nature of symptoms associated with HNPP, patients with this condition may remain unrecognized during the perioperative period, posing significant risks. Several aspects of caring for this population, including anesthetic choices, intraoperative positioning, and monitoring strategy, may deviate from standard practices. As such, a tailored approach to caring for this unique population, coupled with meticulous preoperative planning, is crucial and requires a multidisciplinary approach.

Unilateral abnormality of initial motor-evoked potential in the upper limb detected during lumbar spine surgery: a case report

BACKGROUND

We present a case with abnormal findings of initial motor-evoked potential (MEP) in the left upper limb after prone positioning during lumbar spine surgery.

CASE PRESENTATION

A 71-year-old man with bilateral lower extremity numbness without a history of preexisting motor weakness underwent L3-5 spinal fenestration. Initial MEP monitoring after prone positioning revealed markedly prolonged latency and lower amplitude in the left abductor pollicis brevis (APB). Because the left upper limb somatosensory-evoked potentials had normal values, a position-related impending peripheral nerve injury located between the neck and the forearm was excluded. Postoperative examination revealed that MEP abnormality in the left APB was caused by carpal tunnel syndrome.

CONCLUSIONS

Abnormal initial MEP from the upper limb was unexpectedly detected after prone positioning during lumbar spine surgery. The condition was caused by preexisting carpal tunnel syndrome.

Case Report: Acute common peroneal nerve injury after posterior lumbar decompression surgery

Spine surgery is a prevalently performed procedure. Some authors have proposed an age-related surge in surgical and general complications. During spine surgery, patients are placed in positions that are not physiologic, would not be tolerated for prolonged periods by the patient in the awake state, and may lead to complications. Understanding these uncommon complications and their etiology is pivotal to prevention and necessary. The patient is a 76-year-old woman referred to the outpatient department of neurosurgery in February 2022 by her physiatrist with a chief complaint of chronic low back pain and numbness over the left leg. Lumbar spine magnetic resonance imaging revealed degenerative disc disease and posterior disc bulging at the levels of L2/3∼L5/S1 with compression of the thecal sac. After receiving anti-inflammatory medication, nerve block and caudal block, her symptoms persisted. She was referred to a neurosurgeon for surgical intervention. We diagnosed spinal stenosis with left L3 and L4 radiculopathy, and elective decompression surgery was scheduled a few days later. We performed discectomies at L2/3 and L3/4 and left unilateral laminectomy at L2 and L3 for bilateral decompression. Following an uneventful surgery, the patient was extubated, and her left leg pain improved, but pain over the right outer calf with drop foot developed. A second lumbar MRI the next day revealed no evidence of recurrent disc herniation or epidural hematoma. Then, she received nerve conduction velocity and needle electromyogram on postoperative day 2, and the studies indicated right common peroneal nerve entrapment neuropathy. After medication with steroids and foot splint use, right leg pain improved. However, weak dorsiflexion of the right ankle persisted. We referred this patient to a physiatrist and OPD for follow-up after discharge. Perioperative peripheral nerve injury (PPNI) is most commonly caused by peripheral nerve ischemia due to abnormal nerve lengthening or pressure and can be exacerbated by systemic hypotension. Any diseases affecting microvasculature and anatomical differences may contribute to nerve injury or render patients more susceptible to nerve injury. Prevention, early detection and intervention are paramount to reducing PPNI and associated adverse outcomes. The use of intraoperative neuromonitoring theoretically allows the surgical team to detect and intervene in impending PPNI during surgery.

Neuromonitoring Identifies Occlusion of Femoral Artery in STA-MCA Bypass Procedure: A Case Report

Intraoperative neurophysiological monitoring (IONM) is a technique used to assess the somatosensory and gross motor systems during surgery. While it is primarily used to detect and prevent surgically induced nervous system trauma, it can also detect and prevent injury to the nervous system that is the result of other causes such as trauma or ischemia that occur outside of the operative field as a result of malpositioning or other problematic physiologic states. We present a case study where a neuromonitoring alert altered the surgical procedure, though the alert was not correlated to the site of surgery. A 69-year-old male with a history of bilateral moyamoya disease and a left middle cerebral artery infarct underwent a right-sided STA-MCA bypass and encephaloduroarteriosynangiosis (EDAS) with multimodal IONM. During the procedure, the patient experienced a loss of motor evoked potential (MEP) recordings in the right lower extremity. Blood pressure was elevated, which temporarily restored the potentials, but they were lost again after the angiography team attempted to place an arterial line in the right femoral artery. The operation was truncated out of concern for left hemispheric ischemia, and it was later discovered that the patient had an acute right external iliac artery occlusion caused by a fresh thrombus in the common femoral artery causing complete paralysis of the limb. This case highlights the importance of heeding IONM alerts and evaluating for systemic causes if the alert is not thought to be of surgical etiology. IONM can detect adverse systemic neurological sequelae that is not necessarily surgically induced.

Agreement between distal and forearm radial arterial pressures in patients undergoing prone spinal surgery: a prospective, self-controlled, observational study

OBJECTIVE

To test agreement and interchangeability between distal (dRA) and forearm radial arterial (RA) pressures (AP) during general anesthesia (GA) for prone spinal surgery.

METHODS

This prospective observational study involved 40 patients scheduled for GA spinal surgery. The right dRA and left forearm RA were cannulated in all patients to continuously measure invasive blood pressures (IBP). We compared the agreement and trending ability of systolic AP (SAP), diastolic AP (DAP), and mean AP (MAP) at each site 15 minutes after tracheal intubation, start of surgery, 30 and 60 minutes after the start of surgery, and after skin suturing.

RESULTS

Paired BP values (n = 184) (37 cases) were analyzed. The bias (standard deviation), limits of agreement, and percentage error were: SAP: 0.19 (3.03), -5.75 to 6.12, and 5.04%; DAP: -0.06 (1.75), -3.50 to 3.38, and 5.10%; and MAP: 0.08 (1.52), -2.90 to 3.05, and 3.54%, respectively. The linear regression coefficients of determination were 0.981, 0.982, and 0.988 for SAPs, DAPs, and MAPs, respectively; four-quadrant plot concordance rates were 95.11%, 92.03%, and 92.66%, respectively.

CONCLUSION

All arterial BPs showed good agreement and trending capabilities for both the dRA and RA. The dRA may be substituted for the RA in IBP monitoring.

Patient Positioning in Spine Surgery: What Spine Surgeons Should Know?

Spine surgery has advanced tremendously over the last decade. The number of spine surgeries performed each year has also been increasing constantly. Unfortunately, the reporting of position-related complications in spine surgery has also been steadily increasing. These complications not only result in significant morbidity for the patient but also raises the risk of litigation for the surgical and anesthetic teams. Fortunately, most position-related complications are avoidable with basic positioning knowledge. Hence, it is critical to be cautious and take all necessary precautions to avoid position-related complications. We discuss the various position-related complications associated with the prone position, which is the most commonly used position in spine surgery, in this narrative review. We also discuss the various methods for avoiding complications. Furthermore, we briefly discuss less commonly used positions in spine surgery, like the lateral and sitting positions.

The value of intraoperative neurophysiological monitoring during positioning in pediatric scoliosis correction: A case report

Introduction

Prone position during posterior spine surgery can represent a potentially risky procedure for the nervous system. Infrequent injuries due to prone positioning consist of subtle spinal cord infarction or myelopathy that can be promptly detected by intraoperative neurophysiological monitoring (IONM), if applied in this phase of surgery. Here, we report a case that stresses the value of IONM even in detecting spinal positioning-related neurological complications during kyphoscoliosis correction.

Case presentation

A 3-year-old child with a severe thoracic kyphoscoliosis with the angle in the tract T5-T6 underwent an early treatment of scoliosis with growing rods. Before instrumentation or the reduction maneuver, lower limb somatosensory and motor responses disappeared. The patient was repositioned with neck and chest in a more protective position and neuromonitoring signals returned to baseline. The surgery could be completed and the patient had no postoperative neurologic or vascular deficits.

Conclusion

Our findings suggest the importance of extending neuromonitoring in the early phases of anesthesia induction and patient positioning during corrective spinal deformity surgery.

Surgical Position of Lateral-Tilted Supine is Suitable for Proximal Humeral Fracture Operations in Geriatric Patients

OBJECTIVE

To report a new surgical position of lateral-tilted supine (LTS) for geriatric proximal humeral fracture operations.

METHODS

Between January 2016 and December 2020, we adopted the LTS position for operations in 65 geriatric patients with proximal humeral fractures.

RESULTS

Sixty-five patients including 25 males and 40 females aged 80.3 ± 8.5 years. The LTS position could be used for almost all proximal humeral fracture surgeries, such as ORIF with plate, suture anchor, and other fixation in 4 patients, open reduction and internal fixation (ORIF) with multiLoc nailing in 48, and shoulder hemiarthroplasty (SHA) in 13. Surgical position setting times were 11.47 ± 2.14 min. The systolic blood pressure changes before and after positioning were 15.07 ± 8.72 mmHg. All of the C-arm X-ray directions, including the cephalic side, contralateral side, and ipsilateral side, can be used in the LTS position surgeries. No surgical complications or no surgical position-related complications were found in these 65 cases.

CONCLUSION

The surgical position of LTS is suitable for geriatric proximal humeral fracture operations.

Single-port transaxillary robotic thyroidectomy (START): 200-cases with two-step retraction method

Background

This study aims to report the results of a pioneering clinical study using the single-port transaxillary robotic thyroidectomy (START) for 200 patients with thyroid tumor and to introduce our novel two-step retraction method.

Methods

START was performed on consecutive 200 patients using the da Vinci Single-Port (SP) robot system from January 2019 to September 2020 at the Yonsei University Health System, Seoul, Korea. The novel two-step retraction technique, in which a 3.5 cm long incision is made along the natural skin crease, was used for the latter 164 patients. The surgical outcome and invasiveness of the SP two-step retraction method were analyzed.

Results

Among the 200 cases who underwent START, 198 were female and 2 were male, with a mean age of 34.7 (range: 13–58 years). Thyroid lobectomy was performed for 177 patients and total thyroidectomy was performed for 23 patients. Ten patients had benign thyroid nodules, whereas the other 190 had thyroid malignancy. The mean body mass index (BMI) was 22.2 ± 3.7 kg/m² (range: 15.9–37.0 kg/m²). All of the operations were performed successfully without any open conversions, and patients were discharged on postoperative day 3 or 4 without significant complication. The mean operative time for thyroid lobectomy with the two-step retraction method was 116.69 ± 23.23 min, which was similar to that in the conventional robotic skin flap method (115.33 ± 17.29 min). We could minimize the extent of the robotic skin flap dissection with the two-step retraction method.

Conclusions

START is a practical surgical method. By employing the new two-step retraction method, we can maximize the cosmetic and functional benefits for patients and reduce the workload fatigue of surgeons by increasing robotic dependency.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00464-021-08837-9.

Evaluation of Safety of Overhead Upper Extremity Positioning During Fenestrated-Branched Endovascular Repair of Thoracoabdominal Aortic Aneurysms

PURPOSE

Peripheral nerve and brachial plexus injury can occur from compression or stretching during positioning for operative procedures. The aim of this study was to evaluate the safety of overhead upper extremity positioning to optimize imaging during fenestrated-branched endovascular aortic repair (FB-EVAR) of pararenal (PRA) and thoracoabdominal aortic aneurysms (TAAAs).

METHODS

Forty-four consecutive patients enrolled in a prospective non-randomized study underwent FB-EVAR with overhead upper extremity positioning. Patients underwent intra-operative neuromonitoring of upper and lower extremities and neurological examination prior to discharge and at 2 months following the procedure. End points were peripheral or brachial plexus nerve injury, quality of lateral projection and cone beam computed tomography (CBCT) and major adverse event (MAEs).

RESULTS

There were 28 (64%) male patients with mean age of 74 ± 8 years treated for 10 PRAs (23%) and 34 (78%) TAAAs. Mean body mass index was 29 ± 7 kg/m², with 17 obese patients (39%). Open surgical upper extremity access was used in 19 patients (43%). Three patients (16%) had access-related complications, all focal brachial artery dissections treated by patch angioplasty. Two patients (5%) developed upper extremity changes in neuromonitoring, which immediately resolved with repositioning of the upper extremity. Technical success was 95%. Lateral projection and rotational CBCT were feasible in all patients with satisfactory imaging quality for catheterization and stenting of the celiac axis and superior mesenteric artery. There was one mortality (2%) at 30 days, and six patients (14%) had MAEs. There were no upper extremity neurological injuries.

CONCLUSION

Overhead upper extremity position allows optimal imaging on lateral projections and rotational CBCT during FB-EVAR. There were no upper extremity neurological injuries in this study.

Development of Sciatic Neuropraxia following Abdominal Surgery in 3 Giant Breed Dogs

This report describes the clinical course of three giant breed dogs (2 Great Danes and 1 Saint Bernard) that developed sciatic neuropraxia following successful surgical management of gastric dilatation and volvulus (GDV). All three patients received physical rehabilitation with varying degrees of success. Two patients died of unrelated causes within a year of their initial presentation. The third case recovered nerve function and is alive with minimal neurologic deficits at the time of publication. This paper is aimed at positing potential causes for this complication and highlighting the importance of proper management of giant-breed dogs during hospitalization. Special attention should be given in regards to intraoperative positioning and postoperative care including frequent walks or changes in positioning, deep kennel bedding, and physical therapy.

Effects of Surgical Positioning on L4-L5 Accessibility and Lumbar Lordosis in Lateral Transpsoas Lumbar Interbody Fusion: A Comparison of Prone and Lateral Decubitus in Asymptomatic Adults

BACKGROUND

Lateral interbody fusion (LIF) is traditionally performed in lateral decubitus on a breaking surgical table to improve L4-L5 access. Prone transpsoas (PTP) LIF may improve sagittal alignment and facilitate single-position circumferential procedures; but may require manipulation of the iliac crest for L4-L5 accessibility.

METHODS

Healthy adult volunteers (n = 41) were positioned as if for surgery in right-lateral decubitus on a radiolucent breaking table, and also prone on a Jackson-style surgical frame atop a custom PTP bolster. Iliac crest distance from the L5 superior endplate, and coronal and sagittal plane alignments were measured from fluororadiographs obtained in each of 5 positions: standard lateral decubitus (LD), prone-hips and spine neutral (PR-NN), prone-hips neutral and spine coronally bent (PR-NCB), prone-hips extended and spine neutral (PR-EN), and prone-hips extended and spine coronally bent (PR-ECB).

RESULTS

L4-L5 accessibility was lowest in prone-neutral and improved in all augmented positional configurations: PR-NN<>PR-EN<LD<PR-ECB<PR-NCB. Coronal bending with the PTP positioner created greater accessibility than that achieved by lateral decubitus breaking (PR-NCB>LD, P = 0.0480). Coronal angulations were greatest in LD, and statistically different from both prone neutral (LD>PR-NN, P < 0.0001) and prone coronally bent (LD>PR-NCB, P < 0.0001). Lordosis was greatest in extended prone positions and lowest in lateral decubitus: PR-EN>PR-ECB>PR-NCB<>PR-NN>LD. All prone positions showed significantly greater lordosis than lateral decubitus (P < 0.001).

CONCLUSIONS

Compared with lateral decubitus, prone positioning provides equivalent or better L4-L5 LIF access around the iliac crest when a positioner is used that enables coronal bending, and improved positional lordosis, which may facilitate segmental correction and achievement of surgical alignment goals.

Prone position surgery for a professional sumo wrestler with thoracic ossification of the posterior longitudinal ligament resulting in intraoperative brachial plexus injury by hypertrophic pectoral muscles

Surgery in the prone position is associated with a variety of complications due to the positioning, including the widely recognized peripheral nerve compression injuries and brachial plexus neuropathy. Previous studies have reported that thin body habitus is a predisposing risk factor for the compressive peripheral nerve injuries due to the prone position surgery. However, prone-position-related brachial plexus injury in patients who are overweight due to hypertrophic muscles have never been reported. Here we report a case of a professional sumo wrestler with severe thoracic ossification of the posterior longitudinal ligament (OPLL). Thoracic OPLL was successfully treated by posterior spinal fusion and decompression surgery. Despite a preoperative simulation and intraoperative inspection of the patient's surgical positioning, he suffered from bilateral upper extremity paralysis immediately after the surgery. Postoperative axillary MRI image revealed a high-intensity area on both sides of his pectoral muscles and axillary fossa, which implied that the pectoral muscles between the ribs and chest pad were pushed out toward the axillary fossa, resulting in compressive brachial plexus injury. His upper extremity motor paralysis was fully recovered in 6 months, but he still has mild tingling sensation even after 12 months of his surgery. In conclusion, overweight patients with hypertrophic muscles pose a risk for brachial plexus entrapment injury by pectoral muscles during prone-position surgery, and therefore it would be more effective to use a wide chest pad to reduce the pressure on the pectoral muscles to prevent it from being pushed out toward the axillary fossa.

Somatosensory evoked potential: Preventing brachial plexus injury in transaxillary robotic surgery

OBJECTIVES/HYPOTHESIS

The potential for brachial plexopathy due to arm positioning is a major concern regarding the robotic transaxillary approach. Intraoperative nerve monitoring via somatosensory evoked potential (SSEP) has been suggested to prevent such injury. In this study, we examined the use of SSEP in detecting imminent brachial plexus traction during robotic transaxillary thyroid and parathyroid surgery.

STUDY DESIGN

Retrospective case series.

METHODS

A analysis was performed for all patients undergoing robotic transaxillary surgery with continuous intraoperative SSEP monitoring at a North American institution between 2015 and 2017. A significant intraoperative SSEP change was defined as a decrease in signal amplitude of >50% or an increase in latency of >10% from baseline established during preoperative positioning.

RESULTS

One hundred thirty-seven robotic transaxillary surgeries using SSEP monitoring were performed on 123 patients. Seven patients (5.1%) developed significant changes, with an average SSEP amplitude reduction of 73% ± 12% recorded at the signals' nadir. Immediate arm repositioning resulted in recovery of signals and complete return to baseline parameters in 14.3 ± 9.2 minutes. There was no difference in age (40.4 ± 9.4 years vs. 44.5 ± 13.4 years; P = .31) or body mass index (27.3 ± 3.7 kg/m² vs. 26.9 ± 6.1 kg/m² ; P = .79) between cases with and without SSEP change. Operative time was shorter for patients with significant SSEP change (131.6 ± 14.7 minutes vs. 146.5 ± 46.7 minutes; P = .048). There were no postoperative positional brachial plexus injuries.

CONCLUSIONS

SSEP is a novel, safe, and reliable tool in detection of position-related brachial plexus neuropathy. Intraoperative monitoring using SSEP can play a vital role in early recognition and prevention of injury during robotic transaxillary thyroid and parathyroid surgery.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:2663-2668, 2019.

The diagnostic accuracy of somatosensory evoked potentials in evaluating neurological deficits during 1057 lumbar interbody fusions

BACKGROUND

Lumbar interbody spinal fusion (LIF) surgeries are performed to treat or prevent back pain in patients with degenerated intervertebral discs and a variety of spinal diseases. However, post-operative neurological complications may ensue. Intraoperative monitoring techniques have been used to predict and potentially reduce the risk of complications.

METHODS

This study examined the diagnostic accuracy of significant changes of somatosensory evoked potentials (SSEPs) to evaluate and predict post-operative neurological deficits after LIF. All patients underwent LIF at UPMC from 2010 to 2012. One thousand fifty-seven patients had pre-operative baseline and continuous intraoperative SSEP monitoring. Statistical analysis was completed using SPSS version 22. No relevant disclosure.

RESULTS

Patient outcomes were not significantly affected by age over 65, gender, obesity, and abnormal baselines. Lower extremity (LE) significant changes in SSEPs and LE loss of responses resulted in a sensitivity/specificity of 0.03/0.99 and 0.03/0.99; they had an AUC of 0.54/0.73 with a 95% confidence interval (CI) of [0.34, 0.74]/[0.29, 1.00].

CONCLUSIONS

Significant SSEP changes during LIF are a very specific but poorly sensitive indicator of perioperative neurological deficits. The odds ratio for LE loss of responses was 29.14 with a 95% CI of 1.79-475.5, so LE SSEP loss of responses can serve as a biomarker of perioperative neurological deficits after LIF.

A Comprehensive Protocol to Prevent Brachial Plexus Injury During Ankylosing Spondylitis Surgery

PURPOSE

This article describes a comprehensive protocol to protect the brachial plexus when performing pedicle subtraction osteotomy for ankylosing spondylitis patients with thoracolumbar kyphosis.

DESIGN

A descriptive study was conducted.

METHODS

Records of 101 cases from October 2013 to December 2016 were retrospectively audited. The protocol included five items: (1) preoperative assessment of motion range and nerve function of limbs and trunks; (2) preoperative positioning according to the assessment results; (3) intra-operative somatosensory evoked potential and blood pressure monitoring; (4) intra-operative repositioning according to the monitoring alarm signals; and (5) postoperative neurological function check.

FINDINGS

Five patients showed impending brachial plexus injury indicators, including two who had a decrease in blood pressure and three who had a decrease in the amplitude of somatosensory evoked potential. After adjustment of position and soft pads, one patient had brachial plexus injury (0.99%) and the recovery time was 2 weeks.

CONCLUSIONS

With this comprehensive strategy, the brachial plexus could be effectively protected during the surgery.

The Significance of Upper Extremity Neuromonitoring Changes During Thoracolumbar Spine Surgery

STUDY DESIGN

This is a retrospective matched-pair cohort study.

OBJECTIVE

To investigate the significance of upper extremity (UE) neuromonitoring changes in patients undergoing thoracolumbar surgery in prone position.

SUMMARY OF BACKGROUND DATA

Peripheral nerve injuries in the UEs due to the prone positioning during prolonged thoracolumbar spinal procedures can cause diminished postsurgical outcomes. Intraoperative neuromonitoring has been utilized to alert the surgeon of the development of such injuries.

MATERIALS AND METHODS

Patients who developed intraoperative ulnar somatosensory-evoked potential (SSEP) signal changes during posterior thoracolumbar surgery were identified and compared with a group of patients who did not develop such signal changes. The patients in 2 groups were pair-matched on the number of vertebral levels undergoing surgery. Data regarding intraoperative attempts to resolve signal changes and outcomes were collected.

RESULTS

In total, 843 patients underwent thoracic, lumbar, or thoracolumbar spine surgeries in the prone position with intraoperative ulnar SSEPs neuromonitoring data available. Of these, 37 patients (4.4%) had intraoperative signal changes in the UEs. An equal number of patients without signal changes were also selected. In each group, 6 patients underwent thoracic, 20 patients underwent lumbar, and 11 patients underwent thoracolumbar procedures. In 8 patients (21.6%), there was no resolution of SSEP signal changes despite intraoperative attempts. The 2 groups were similar with respect to age and comorbidities. There was no significant difference in the mean body mass index (P=0.22). The mean duration of the procedures was 324 minutes in the SSEP signal change patients and 260 minutes in the patients without SSEP signal changes (P=0.03). No patient with UE SSEP changes had a clinically detectable neurological deficit postoperatively.

CONCLUSIONS

UE SSEP signal changes during multilevel posterior thoracolumbar procedures are more likely to occur as the duration of the operation increases. The presence of UE signal changes does not coincide with clinically significant peripheral neuropathies.

LEVEL OF EVIDENCE

Level III.

Use of motor evoked potentials during lateral lumbar interbody fusion reduces postoperative deficits

BACKGROUND CONTEXT

Intraoperative neurophysiological monitoring (IONM) has gained rather widespread acceptance as a method to mitigate risk to the lumbar plexus during lateral lumbar interbody fusion (LLIF) surgery. The most common approach to IONM involves using only electromyography (EMG) monitoring, and the rate of postoperative deficit remains unacceptably high. Other test modalities, such as transcranial electric motor-evoked potentials (tcMEPs) and somatosensory-evoked potentials, may be more suitable for monitoring neural integrity, but they have not been widely adopted during LLIF. Recent studies have begun to examine their utility in monitoring LLIF surgery with favorable results.

PURPOSE

This study aimed to evaluate the efficacy of different IONM paradigms in the prevention of iatrogenic neurologic sequelae during LLIF and to specifically evaluate the utility of including tcMEPs in an IONM strategy for LLIF surgery.

STUDY DESIGN/SETTING

A non-randomized, retrospective analysis of 479 LLIF procedures at a single institution over a 4-year period was conducted. During the study epoch, three different IONM strategies were used for LLIF procedures: (1) surgeon-directed T-EMG monitoring ("SD-EMG"), (2) neurophysiologist-controlled T-EMG monitoring ("NC-EMG"), and (3) neurophysiologist-controlled T-EMG monitoring supplemented with MEP monitoring ("NC-MEP").

PATIENT SAMPLE

The patient population comprised 254 men (53.5%) and 221 women (46.5%). Patient age ranged from a minimum of 21 years to a maximum of 89 years, with a mean of 56.6 years.

OUTCOME MEASURES

Physician-documented physiological measures included manual muscle test grading of hip-flexion, hip-adduction, or knee-extension, as well as hypo- or hyperesthesia of the groin or anterolateral thigh on the surgical side. Self-reported measures included numbness or tingling in the groin or anterolateral thigh on the surgical side.

METHODS

Patient progress notes were reviewed from the postoperative period up to 12 months after surgery. The rates of postoperative sensory-motor deficit consistent with lumbar plexopathy or peripheral nerve palsy on the surgical side were compared between the three cohorts.

RESULTS

Using the dependent measure of neurologic deficit, whether motor or sensory, patients with NC-MEP monitoring had the lowest rate of immediate postoperative deficit (22.3%) compared with NC-EMG monitoring (37.1%) and SD-EMG monitoring (40.4%). This result extended to sensory deficits consistent with lumbar plexopathy (pure motor deficits being excluded); patients with NC-MEP monitoring had the lowest rate (20.5%) compared with NC-EMG monitoring (34.3%) and SD-EMG monitoring (36.9%). Additionally, evaluation of postoperative motor deficits consistent with peripheral nerve palsy (pure sensory deficits being excluded) revealed that the NC-MEP group had the lowest rate (5.7%) of motor deficit compared with the SD-EMG (17.0%) and NC-EMG (17.1%) cohorts. Finally, when assessing only those patients whose last follow-up was greater than or equal to 12 months (n=251), the rate of unresolved motor deficits was significantly lower in the NC-MEP group (0.9%) compared with NC-EMG (6.9%) and SD-EMG (11.0%). A comparison of the NC-MEP versus NC-EMG and SD-EMG groups, both independently and combined, was statistically significant (>95% confidence level) for all analyses.

CONCLUSIONS

The results of the present study indicate that preservation of tcMEPs from the adductor longus, quadriceps, and tibialis anterior muscles are of paramount importance for limiting iatrogenic sensory and motor injuries during LLIF surgery. In this regard, the inclusion of tcMEPs serves to compliment EMG and allows for the periodic, functional assessment of at-risk nerves during these procedures. Thus, tcMEPs appear to be the most effective modality for the prevention of both transient and permanent neurologic injury during LLIF surgery. We propose that the standard paradigm for protecting the nervous system during LLIF be adapted to include tcMEPs.

Risk factors for positioning-related somatosensory evoked potential changes in 3946 spinal surgeries

The goal of this study was to evaluate the risk factors associated with positioning-related SSEP changes (PRSC). The study investigated the association between 18 plausible risk factors and the occurrence of intraoperative PRSC. Risk factors investigated included demographic variables, comorbidities, and procedure related variables. All patients were treated by the University of Pittsburgh Medical Center from 2010 to 2012. We used univariate and multivariate statistical methods. 69 out of the 3946 (1.75%) spinal surgeries resulted in PRSC changes. The risk of PRSC was increased for women (p < 0.001), patients older than 65 years of age (p = 0.01), higher BMI (p < 0.001) patients, smokers (p < 0.001), and patients with hypertension (p < 0.001). No associations were found between PRSC and age greater than 80 years, diabetes mellitus, cardiovascular disease, and peripheral vascular disease. Three surgical situations were associated with PRSC including abnormal baselines (p < 0.001), patients in the "superman" position (p < 0.001), and patients in surgical procedures that extended over 200 min (p = 0.03). Patients with higher BMIs and who are undergoing spinal surgery longer than 200 min, with abnormal baselines, must be positioned with meticulous attention. Gender, hypertension, and smoking were also found to be risk factors from their odds ratios.

Intraoperative Neurophysiologic Monitoring for Degenerative Cervical Myelopathy

Multimodal intraoperative neurophysiologic monitoring is a reliable tool for detecting intraoperative spine injury and is recommended during surgery for degenerative cervical myopathy (DCM). Somatosensory evoked potential (SEP) can be used to monitor spine and peripheral nerve injury during positioning in surgery for DCM. Compensation technique for transcranial evoked muscle action potentials (tcMEPs) should be adopted in intraoperative monitoring during surgery for DCM. Free-running electromyography is a useful real-time monitoring add-on modality in addition to SEP and tcMEP.

Unanticipated Disturbance in Somatosensory Evoked Potentials in a Patient in Park-Bench Position

Perioperative neuropathy is a known complication of malpositioning during anaesthesia. Somatosensory evoked potentials are used for detecting such a complication in selected surgeries. Most reports of intraoperative nerve injuries due to malpositioning are limited to injuries to the peripheral nervous system, and there have been no previously reported cases of somatosensory evoked potential monitoring disturbance attributable to position-related cerebral ischemia in the park-bench position. We present the case of a patient with glioblastoma in the park-bench position whose somatosensory evoked potential waveforms disappeared after head and neck repositioning. A prompt diagnosis of this complication and elimination of the underlying cause led to the return of somatosensory evoked potential waveforms, and there was no relevant neurologic deficit at the end of the surgery.

What Is the Frequency of Intraoperative Alerts During Pediatric Spinal Deformity Surgery Using Current Neuromonitoring Methodology? A Retrospective Study of 218 Surgical Procedures

INTRODUCTION

There is variability in intraoperative neuromonitoring (IONM), anesthetic and surgical techniques for the treatment of pediatric spinal deformity. This study evaluates a series of patients treated at multiple centers utilizing transcranial motor and somatosensory evoked potentials (TcMEP and SSEP) and electromyography (EMG). The frequency of alerts and the intraoperative follow-up is reported.

METHODS

Standard patient demographics and IONM data were collected from a two-month cohort of pediatric spine deformity cases.

RESULTS

Data from 218 scoliosis patients were included from 46 facilities and 72 surgeons. Baseline upper and lower extremity TcMEP data were present in 96.7% and 93.9% patients respectively. Baseline upper and lower SSEPs were present in 99.5% and 95.4% respectively Surgical TCMEP alerts occurred in 19 (8.7%) patients during deformity correction (n = 11), placement of instrumentation (n = 5), decompression (n = 2), and closing (n = 1) with concurrent SSEP alerts occurring in five patients. Nine had TCMEP recovery, eight showed partial recovery and two did not recover. Additional alerts occurred due to: positioning (n = 16), inhalational agent change (n = 4), global physiological change (n = 4) and technical reasons (n = 2). A total of 2164 pedicle screws were tested. Of 197 (9.1%) screws that tested from 6-9 mA, 171 (65.4%) were left unchanged, 10 (51%) removed, eight (4.1%) repositioned with improved threshold, and eight (4.1%) without improvement. Of 26 screws that tested ≤ 5 milliamperes (mA), 17 (65.4%) were left unchanged, five (19.2%) removed, two (7.7%) repositioned with improved threshold, and two (7.7%) without improvement.

CONCLUSIONS

IONM provides data that causes re-evaluation in about 10% of pediatric spinal deformity cases.

Contemporaneous Evaluation of Intraoperative Ulnar and Median Nerve Somatosensory Evoked Potentials for Patient Positioning: A Review of Four Cases

Somatosensory evoked potentials (SSEPs) are a valuable tool for assessing changes in peripheral nerve pathways caused by patient positioning during spinal surgeries. These changes, when left undiagnosed, may lead to postoperative neurological sequelae. Why an upper extremity SSEP attenuates due to positioning is not necessarily clear and can be multifactorial, affecting the peripheral nerves or elements of the brachial plexus. A conduction block can occur at any point along the course of the nerve secondary to entrapment, compression, and ischemia. These mechanisms of injury may be caused by extreme body habitus, the length of the procedure, or the patient's metabolic underpinnings. The goal of neuromonitoring for positional injury is to predict and prevent both peripheral nerve and brachial plexus injuries. Using ulnar and median nerve SSEPs contemporaneously may lead to better identification of compromised structures when an SSEP change to one or both of the nerves occurs. The investigators provide four case reports where intraoperative SSEP assessment of contemporaneous ulnar and median nerves prevented postoperative upper extremity neural deficits.

Intraoperative Neurophysiological Monitoring for Endoscopic Endonasal Approaches to the Skull Base: A Technical Guide

Intraoperative neurophysiological monitoring during endoscopic, endonasal approaches to the skull base is both feasible and safe. Numerous reports have recently emerged from the literature evaluating the efficacy of different neuromonitoring tests during endonasal procedures, making them relatively well-studied. The authors report on a comprehensive, multimodality approach to monitoring the functional integrity of at risk nervous system structures, including the cerebral cortex, brainstem, cranial nerves, corticospinal tract, corticobulbar tract, and the thalamocortical somatosensory system during endonasal surgery of the skull base. The modalities employed include electroencephalography, somatosensory evoked potentials, free-running and electrically triggered electromyography, transcranial electric motor evoked potentials, and auditory evoked potentials. Methodological considerations as well as benefits and limitations are discussed. The authors argue that, while individual modalities have their limitations, multimodality neuromonitoring provides a real-time, comprehensive assessment of nervous system function and allows for safer, more aggressive management of skull base tumors via the endonasal route.

Brachialis syndrome: a rare consequence of patient positioning causing postoperative median neuropathy

BACKGROUND

Poor positioning of patients can result in devastating permanent neurologic deficits. We describe a previously unreported cause of median nerve compression that we have termed the brachialis syndrome, associated with patient positioning that results in permanent median nerve damage.

METHODS

We identified this condition affecting 6 median nerves. All patients underwent surgical decompression of the proximal median nerve at the level of the antecubital fossa.

RESULTS

Five patients presented with symptoms of median nerve compression; 6 affected median nerves manifested brachialis syndrome after a lengthy index surgery. Every patient had a similar presentation characterized by a mixed sensory and motor deficit. Average time to symptom presentation postoperatively was 1 hour. Two patients had delayed time to decompression, one of 25 days and one of 92 days. In the additional patients, the average time to decompression was 19.7 hours. At median nerve decompression, the brachialis was found to have varying degrees of muscle necrosis. In the patients whose decompression was delayed, there was only partial neurologic recovery at follow-up to 1 year. In the patients expeditiously decompressed, full neurologic recovery occurred in 1 to 14 days.

CONCLUSIONS

This is the first description of the brachialis syndrome. During surgery, arms were placed into full extension, compressing the brachialis against the trochlea. The brachialis reliably developed necrosis, resulting in swelling, compressing the median nerve against the lacertus fibrosus. Two patients with delayed decompression had poor neurologic outcomes. This supports modification of patient positioning, postoperative vigilance, and timely surgical management of brachialis syndrome.

Postoperative complications of spine surgery

A variety of surgical approaches are available for the treatment of spine diseases. Complications can arise intraoperatively, in the immediate postoperative period, or in a delayed fashion. These complications may lead to severe or even permanent morbidity if left unrecognized and untreated [1-4]. Here we review a range of complications in the early postoperative period from more benign complications such as postoperative nausea and vomiting (PONV) to more feared complications leading to permanent loss of neurological function or death [5]. Perioperative pain management is covered in a separate review (Chapter 8).

Is the lateral jack-knife position responsible for cases of transient neurapraxia?

OBJECT

The lateral jack-knife position is often used during transpsoas surgery to improve access to the spine. Postoperative neurological signs and symptoms are very common after such procedures, and the mechanism is not adequately understood. The objective of this study is to assess if the lateral jack-knife position alone can cause neurapraxia. This study compares neurological status at baseline and after positioning in the 25° right lateral jack-knife (RLJK) and the right lateral decubitus (RLD) position.

METHODS

Fifty healthy volunteers, ages 21 to 35, were randomly assigned to one of 2 groups: Group A (RLD) and Group B (RLJK). Motor and sensory testing was performed prior to positioning. Subjects were placed in the RLD or RLJK position, according to group assignment, for 60 minutes. Motor testing was performed immediately after this 60-minute period and again 60 minutes thereafter. Sensory testing was performed immediately after the 60-minute period and every 15 minutes thereafter, for a total of 5 times. Motor testing was performed by a physical therapist who was blinded to group assignment. A follow-up call was made 7 days after the positioning sessions.

RESULTS

Motor deficits were observed in the nondependent lower limb in 100% of the subjects in Group B, and no motor deficits were seen in Group A. Statistically significant differences (p < 0.05) were found between the 2 groups with respect to the performance on the 10-repetition maximum test immediately immediately and 60 minutes after positioning. Subjects in Group B had a 10%–70% (average 34.8%) decrease in knee extension strength and 20%–80% (average 43%) decrease in hip flexion strength in the nondependent limb.

Sensory abnormalities were observed in the nondependent lower limb in 98% of the subjects in Group B. Thirty-six percent of the Group B subjects still exhibited sensory deficits after the 60-minute recovery period. No symptoms were reported by any subject during the follow-up calls 7 days after positioning.

CONCLUSIONS

Twenty-five degrees of right lateral jack-knife positioning for 60 minutes results in neurapraxia of the nondependent lower extremity. Our results support the hypothesis that jack-knife positioning alone can cause postoperative neurological symptoms.

Prevention of perioperative limb neuropathies in abdominal free flap breast reconstruction

BACKGROUND AND AIMS

Perioperative peripheral neuropathies are a significant cause of post-operative morbidity in patients undergoing prolonged procedures. The aims of this study were to determine the incidence and possible causes of peripheral neuropathy in patients undergoing abdominal free flap breast reconstruction and to develop methods of ameliorating this problem.

METHODS

A 4-year retrospective study of patients undergoing abdominal free flap breast reconstruction by a single surgeon and anaesthetist was undertaken to determine the incidence and potential causes of perioperative neuropathy. A new positioning protocol was introduced to minimise the stretch on the brachial plexus and to protect peripheral nerves from compression forces. In addition, regular intraoperative physiotherapy was introduced. A prospective study was then conducted on patients managed by the same team to evaluate the effect of this change in practice on the subsequent incidence of peripheral neuropathies.

RESULTS

Over the 4-year retrospective period, 93 consecutive patients underwent abdominal free flap breast reconstruction, six of whom (6.5%) developed a peripheral neuropathy. Following the introduction of the new positioning protocol, prospective data collected on 65 consecutive patients showed no further occurrences of perioperative neuropathy (p = 0.04). There were no significant differences in the characteristics between the two cohorts.

CONCLUSION

Perioperative peripheral neuropathy in abdominal free flap breast reconstruction is a preventable problem. This paper presents a peripheral neuropathy prevention protocol for managing these patients.

Detection of Position-Related Sciatic Nerve Dysfunction by Somatosensory Evoked Potentials During Spinal Surgery

It is well established that intraoperative somatosensory evoked potentials (SSEPs) are sensitive to plexus and peripheral nerve dysfunction related to malpositioning of patients during spinal surgery. While most reports focus on upper extremity nerve or brachial plexus effects, there is very little on detection of sciatic nerve compromise. Recording of the SSEP at the popliteal fossa is a common strategy to aid in troubleshooting stimulus-related problems or distal peripheral tibial nerve failure; yet position-related sciatic nerve effects may not be realized by changes in the popliteal fossa response. Three posterior lumbar surgeries are reviewed in which there was evidence of proximal lower extremity peripheral nerve dysfunction related to positioning. Loss of posterior tibial nerve SSEPs with preservation of the peripheral popliteal fossa response recording occurred in the absence of critical surgical manipulations. Efforts at repositioning and release of tension on the lower limbs promptly resulted in recovey of lost responses. Two of the three cases involved patients in a kneeling position with a tight strap across the posterior thigh. Standard SSEP recordings used in intraoperative neuromonitoring do not specifically localize intraoperative changes to the sciatic nerve; thus, such changes affecting SSEPs above the popliteal fossa mimic iatrogenic changes occurring at the surgical site. These case reports show that when the stage of surgery does not support iatrogenic changes, malpositioning affecting sciatic nerve should be considered, especially for patients placed in a kneeling position on an Andrews frame.

Use of somatosensory evoked potentials to detect and prevent impending brachial plexus injury during surgical positioning for the treatment of supratentorial pathologies

Somatosensory evoked potentials (SSEPs) are widely utilized for the intraoperative detection and prevention of nerve conduction injuries. Their use in identifying position-related injuries to the brachial plexus in patients undergoing supine craniotomies for the treatment of supratentorial pathology is not well documented. This case series describes three instances of unilateral upper extremity SSEP changes in patients positioned for supine craniotomies. In all three cases SSEP responses improved after repositioning. None of the patients exhibited new neurological deficits post-operatively. This case series highlights the importance of vigilant monitoring in the period after final positioning and demonstrates the usefulness of SSEPs as a tool to aid in the early detection and prevention of impending position-related nerve injury.

Somatosensory-evoked potential monitoring during instrumented scoliosis corrective procedures: validity revisited

BACKGROUND

Intraoperative monitoring (IOM) using somatosensory-evoked potentials (SSEPs) plays an important role in reducing iatrogenic neurologic deficits during corrective pediatric idiopathic procedures for scoliosis. However, for unknown reasons, recent reports have cited that the sensitivity of SSEPs to detect neurologic deficits has decreased, in some to be less than 50%. This current trend, which is coincident with the addition of transcranial motor-evoked potentials, is surprising given that SSEPs are robust, reproducible responses that were previously shown to have sensitivity and specificity of >90%.

PURPOSE

Our primary aim was to assess whether SSEPs alone can detect impending neurologic deficits with similar sensitivity and specificity as originally reported. Our secondary aim was to estimate the potential predictive value of adding transcranial motor-evoked potentials to SSEP monitoring in idiopathic scoliosis procedures.

DESIGN

This was a retrospective review to analyze the efficacy of SSEP monitoring in the group of pediatric instrumented scoliosis fusion cases.

PATIENT SAMPLE

We retrospectively reviewed all consecutive cases of patients who underwent idiopathic scoliosis surgery between 1999 and 2009 at Children's Hospital of Pittsburgh. We identified 477 patients who had the surgery with SSEP monitoring alone. Exclusion criteria included any patients with neuromuscular disorders or unreliable SSEP monitoring. Patients who had incomplete neurophysiology data or incomplete postoperative records were also excluded.

OUTCOME MEASURES

Major outcomes measured were clinically significant postoperative sensory or motor deficits, as well as significant intraoperative SSEP changes.

METHODS

Continuous interleaved upper- and lower-extremity SSEPs were obtained throughout the duration of all procedures. We considered a persistent 50% reduction in primary somatosensory cortical amplitude or a prolongation of response latency by >10% from baseline to be significant. Persistent changes represent significant deviation in SSEP amplitude or latency in more than two consecutive averaged trials. Patients were classified into one of four categories with respect to SSEP monitoring: true positive, false positive, true negative, and false negative. The sensitivity, specificity, positive predictive value, and negative predictive value were then calculated accordingly.

RESULTS

Our review of 477 idiopathic scoliosis surgeries monitored using SSEPs alone revealed a new deficit rate of 0.63% with no cases of permanent injury. Sensitivity = 95.0%, specificity = 99.8%, positive predictive value = 95%, negative predictive value = 99.8%. Using evidence-based epidemiologic measures, we calculated that the number needed to treat was 1,587 patients for one intervention to be performed that would have been missed by SSEP monitoring alone. In addition, the number needed to harm, which represents the increase in false positives with the addition of transcranial electrical motor-evoked potentials, was 200.

CONCLUSION

SSEP monitoring alone during idiopathic scoliosis continues to be a highly reliable method for the detection and prevention of iatrogenic injury. Our results confirm the high sensitivity and specificity of SSEP monitoring alone published in earlier literature. As such, we suggest the continued use of SSEP alone in idiopathic scoliosis surgeries. At this time we do not believe there are sufficient data to support the addition of MEP monitoring, although more studies and revised criteria for the use of MEP may provide added value for its use in the future.

Proper Patient Positioning and Complication Prevention in Orthopaedic Surgery

➤ The consequences of improper intraoperative positioning can be profound: it not only may cause substantial morbidity but also may be a major area of litigation, particularly when peripheral nerve injury occurs.➤ The ulnar nerve is most likely to be injured secondary to improper positioning. The elbow should be flexed ≤90° and the forearm placed in a neutral or slightly supinated position intraoperatively to minimize pressure in the cubital tunnel.➤ Pressure-related complications, such as pressure ulcers and alopecia, are best avoided by the use of adequate padding. Cushions on the operating-room table and armrest should be emphasized under osseous prominences.➤ Positioning the head in a non-neutral alignment or arm abduction of ≥90° may result in injury to the brachial plexus.➤ The hemilithotomy position increases intracompartmental pressure in the leg on the uninjured side. The risk of well-leg compartment syndrome can be minimized by avoiding this position if possible.

Modified robotic-assisted thyroidectomy: an initial experience with the retroauricular approach

OBJECTIVES/HYPOTHESIS

New approaches for robotic-assisted thyroidectomy, including the retroauricular approach, were recently described. We have modified the established surgical approach for retroauricular robotic thyroidectomy. Herein, we report our initial experience to identify challenges and limitations of this new surgical approach.

STUDY DESIGN

Prospective case series.

METHODS

This study was performed under institutional review board approval for patients who underwent retroauricular robotic hemithyroidectomy at an academic North American institution. The retroauricular approach was modified by using the space between the two heads of the sternocleidomastoid muscle as our working space. Additionally, selected patients underwent concomitant neck lift surgery with robotic thyroid surgery. Clinical characteristics, total operative time, blood loss, surgical outcomes, and length of hospital stay were evaluated.

RESULTS

Twelve female patients were included in this study. Mean age was 45 ± 4.43 years, and mean body mass index was 28.6 ± 2.15. Mean thyroid nodule size was 1.15 ± 0.26 cm(3). All cases were completed successfully via single retroauricular incision. There was no conversion to an open approach. Four out of 12 patients (33%) underwent additional concomitant neck lift surgery, with a mean total operative time of 156 ± 15.88 minutes. The mean operative time for the remaining eight patients who underwent the robotic approach without additional neck lift surgery was 145.4 ± 10.08 minutes. There were no cases of permanent vocal cord paralysis or permanent hypoparathyroidism. Mean blood loss was 22.4 ± 4.32 mL. Four patients (33%) were discharged home on the same day of surgery, and the remaining eight patients were discharged after an overnight stay.

CONCLUSIONS

Single-incision retroauricular robotic hemithyroidectomy can be a safe and feasible alternative to other remote access techniques. Neck lift surgery can be performed safely in a select group of patients. However, future studies are warranted to further evaluate the benefits and limitations of this novel approach.

Predictive Value of Somatosensory Evoked Potential Monitoring during Resection of Intraparenchymal and Intraventricular Tumors Using an Endoscopic Port

BACKGROUND AND PURPOSE

Intraoperative neurophysiological monitoring (IONM) using upper and lower somatosensory evoked potentials (SSEPs) is an established technique used to predict and prevent neurologic injury during intracranial tumor resections. Endoscopic port surgery (EPS) is a minimally-invasive approach to deep intraparenchymal and intraventricular brain tumors. The authors intended to evaluate the predictive value of SSEP monitoring during resection of intracranial brain tumors using a parallel endoscopic technique.

METHODS

A retrospective review was conducted of patients operated on from 2007-2010 utilizing IONM in whom endoscopic ports were used to remove either intraparenchymal or intraventricular tumors. Cases were eligible for review if an endoscopic port was used to resect an intracranial tumor and the electronic chart included all intraoperative monitoring data as well as pre- and post-operative neurologic exams.

RESULTS

139 EPS cases met criteria for inclusion. Eighty five patients (61%) had intraparenchymal and fifty four (39%) had intraventricular tumors or colloid cysts. SSEP changes were seen in eleven cases (7.9%), being irreversible in three (2.2%) and reversible in eight cases (5.8%). Seven patients (5.0%) with intraparenchymal tumors had SSEP changes which met our criterea for significant changes while there were four (2.9%) with intraventricular (p-value=0.25). Five patients suffered post operative deficits, two reversible and two irreversible SSEP changes. Only one case exhibited post operative hemiparesis with no SSEP changes. The positive predictive value of SSEP was 45.4% and the negative predictive value was 99.2%.

CONCLUSIONS

Based on the high negative and low positive predictive values, the utility of SSEP monitoring for cylindrical port resections may be limited. However, the use of SSEP monitoring can be helpful in reducing the impact of endoscopic port manipulation when the tumor is closer to the somatosensory pathway.

Preventing perioperative peripheral nerve injuries

Peripheral nerve injuries are largely preventable injuries that can result from incorrect patient positioning during surgery. Patients who are diabetic, are extremely thin or obese, use tobacco, or undergo surgery lasting more than four hours are at increased risk for developing these injuries. When peripheral nerve injuries occur, patients may experience numbness, burning, or tingling and may have difficulty getting out of bed, walking, gripping objects, or raising their arms. These symptoms can interrupt activities of daily living and impede recovery. Signs and symptoms of peripheral nerve injury may appear within 24 to 48 hours of surgery or may take as long as a week to appear. Careful attention to body alignment and proper padding of bony prominences when positioning patients for surgery is necessary to prevent peripheral nerve injury. The use of a preoperative assessment tool to identify at-risk patients, collaboration between physical therapy and OR staff members regarding patient positioning, and neurophysiological monitoring can help prevent peripheral nerve injuries.

Somatosensory evoked potentials help prevent positioning-related brachial plexus injury during skull base surgery

OBJECTIVE

Evaluate the use of somatosensory evoked potentials (SSEP) monitoring to detect positioning-related brachial plexus injury during skull base surgery.

STUDY DESIGN

Prospective cohort observational study.

SETTING

University Hospital.

SUBJECTS AND METHODS

Patients undergoing skull base surgery had a focused neurologic exam of the brachial plexus performed before and after surgery. Under stable anesthesia, brachial plexus SSEP values were obtained before and after surgical positioning. Significant SSEP changes required a readjustment of arm or neck positions. SSEPs were assessed every 30 minutes. If changes were noted, position was readjusted and SSEPs were reassessed until surgical completion. Demographic data, neurologic exams, SSEP latency, and amplitude values were recorded. Persistent changes were correlated with postoperative neurologic findings.

RESULTS

Sixty-five patients, 15 to 77 years old, were studied. Six patients (9.2%) developed SSEP amplitude changes after positioning (average amplitude decrease 72.8%). One patient had a significant latency increase. The sensitivity of SSEP for detection of injury was 57%, while specificity was 94.7%. The average body mass index (BMI) of patients with normal and abnormal SSEPs was 28.7 ± 5.6 versus 29.2 ± 8.0, respectively. Average BMI of patients with postoperative symptoms regardless of SSEP findings was 33.8 ± 4.3. Two patients who had persistent SSEP changes after positioning had BMIs of 40.1 and 31.2 kg/m(2), respectively. Improvement in neurologic findings occurred in all patients after surgery.

CONCLUSIONS

This study demonstrates that upper extremity nerve stress can be detected in real time using SSEP and may be of value in protecting patients from nerve injury undergoing lateral skull base surgery.