What is the predictive value of intraoperative somatosensory evoked potential monitoring for postoperative neurological deficit in cervical spine surgery?—a meta-analysis

BACKGROUND CONTEXTCervical decompression and fusion surgery remains a mainstay of treatment for a variety of cervical pathologies. Potential intraoperative injury to the spinal cord and nerve roots poses nontrivial risk for consequent postoperative neurologic deficits. Although neuromonitoring with intraoperative somatosensory evoked potentials (SSEPs) is often used in cervical spine surgery, its therapeutic value remains controversial.PURPOSEThe purpose of the present study was to evaluate whether significant SSEP changes can predict postoperative neurologic complications in cervical spine surgery. A subgroup analysis was performed to compare the predictive power of SSEP changes in both anterior and posterior approaches.STUDY DESIGNThe present study was a meta-analysis of the literature from PubMed, Web of Science, and Embase to identify prospective/retrospective studies with outcomes of patients who underwent cervical spine surgeries with intraoperative SSEP monitoring.PATIENT SAMPLEThe total cohort consisted of 7,747 patients who underwent cervical spine surgery with intraoperative SSEP monitoring.METHODSInclusion criteria for study selection were as follows: (1) prospective or retrospective cohort studies, (2) studies conducted in patients undergoing elective cervical spine surgery not due to aneurysm, tumor, or trauma with intraoperative SSEP monitoring, (3) studies that reported postoperative neurologic outcomes, (4) studies conducted with a sample size ≥20 patients, (5) studies with only adult patients ≥18 years of age, (6) studies published in English, (7) studies inclusive of an abstract.OUTCOME MEASURESThe sensitivity, specificity, diagnostic odds ratio (DOR), and likelihood ratios of overall SSEP changes, reversible SSEP changes, irreversible SSEP changes, and SSEP loss for predicting postoperative neurological deficit were calculated.RESULTSThe total rate of postoperative neurological deficits was 2.50% (194/7,747) and the total rate of SSEP changes was 7.36% (570/7,747). The incidence of postoperative neurological deficit in patients with intraoperative SSEP changes was 16.49% (94/570) while only 1.39% (100/7,177) in patients without. All significant intraoperative SSEP changes had a sensitivity of 46.0% and specificity of 96.7% with a DOR of 27.32. Reversible and irreversible SSEP changes had sensitivities of 17.7% and 37.1% and specificities of 97.5% and 99.5%, respectively. The DORs for reversible and irreversible SSEP changes were 9.01 and 167.90, respectively. SSEP loss had a DOR of 51.39, sensitivity of 17.3% and specificity 99.6%. In anterior procedures, SSEP changes had a DOR of 9.60, sensitivity of 34.2%, and specificity of 94.7%. In posterior procedures, SSEP changes had a DOR of 13.27, sensitivity of 42.6%, and specificity of 94.0%.CONCLUSIONSSSEP monitoring is highly specific but weakly sensitive for postoperative neurological deficit following cervical spine surgery. The analysis found that patients with new postoperative neurological deficits were nearly 27 times more likely to have had significant intraoperative SSEP change. Loss of SSEP signals and irreversible SSEP changes seem to indicate a much higher risk of injury than reversible SSEP changes.     

Intraoperative somatosensory evoked potential monitoring during anterior cervical discectomy and fusion in nonmyelopathic patients--a review of 1,039 cases.

BACKGROUND CONTEXT: Intraoperative somatosensory evoked potential (SSEP) monitoring has been shown to reduce the incidence of new postoperative neurological deficits in scoliosis surgery. However, its usefulness during cervical spine surgery remains a subject of debate. PURPOSE: To determine the utility of intraoperative SSEP monitoring in a specific patient population (those with cervical radiculopathy in the absence of myelopathy) who underwent anterior cervical discectomy and fusion (ACDF) surgery. STUDY DESIGN: Retrospective review. PATIENT SAMPLE: A total of 1,039 nonmyelopathic patients who underwent single or multilevel ACDF surgery. The control group (462 patients) did not have intraoperative SSEP monitoring, whereas the monitored group (577 patients) had continuous intraoperative SSEP monitoring performed. OUTCOME MEASURE: A new postoperative neurological deficit. METHODS: SSEP tracings were reviewed for all 577 patients in the monitored group and all significant signal changes were noted. Medical records were reviewed for all 1,039 patients to determine if any new neurological deficits developed in the immediate postoperative period. RESULTS: None of the patients in the control group had any new postoperative neurological deficits. In the monitored group there were six instances of transient SSEP changes (1 due to suspected carotid artery compression; 5 thought to be due to transient hypotension) which resolved with the appropriate intraoperative intervention (repositioning of retractors; raising the arterial blood pressure). Upon waking up from anesthesia, one patient in the monitored group had a new neurological deficit (partial central cord syndrome) despite normal intraoperative SSEP signals. CONCLUSIONS: ACDF appears to be a safe surgical procedure with a low incidence of iatrogenic neurological injury. Transient SSEP signal changes, which improved with intraoperative interventions, were not associated with new postoperative neurological deficits. An intraoperative neurological deficit is possible despite normal SSEP signals.     

The role of multi-modal intra-operative neurophysiological monitoring in corrective surgeries for thoracic tuberculosis with kyphosis

Objective: The aim of this study was to assess the performance and utility of motor evoked potentials (MEP) and somatosensory evoked potentials (SSEP) during corrective surgery for thoracic tuberculosis with kyphosis (TTK).Methods: 68 patients (mean age 31.7 ± 20.3 years) who underwent corrective surgery for TTK from 2012 to 2019 were included in this retrospective study. Patients were neurologicaly evaluated before and after surgery with systematic neurologic examinations. Intraoperative neurophysiological monitoring (IONM) with SSEP and MEP was carried out. A receiver operating characteristic (ROC) curve and area under ROC curve (AUC) were used to identify the diagnostic accuracy of potential recovery.Results: IONM alerting occurred in 12 surgeries (12/68, 17.6%), of which 6 were SSEP alerting, 2 MEP alerting, and 4 combinations of both SSEP and MEP. Among the 12 cases where there was IONM alerting, 3 (25%) had postoperative neurological deficits(PND), whereas one patient had PND without IONM alerting. IONM sensitivity and specificity were 0.75 (95% CI 0.22–0.99) and 0.86 (95% CI 0.74–0.93) respectively. Positive predictive value (PPV) and negative predictive value (NPV) were 0.25 and 0.98 respectively. The AUC of evoked potential recovery in diagnosing PND was 0.884.Conclusion: Our study showed that multi-modal IONM with SSEP and MEP can effectively indicate a potential neural injury and predict PND during TTK corrective surgery.Level of Evidence: Level IV, Therapeutic Study     

Monitoring evoked potentials during spinal surgery in one institution

Purpose

To review the experience of one tertiary care institution with somatosensory evoked potential (SSEP) monitoring during spinal surgery in order to assess the ability to monitor and predict neurological outcome effectively.

Methods

Records of all patients undergoing spinal surgery during 18 mo were retrospectively reviewed. Information from the patient chart included preoperative neurological status, surgical procedure, anaesthetic management, and postoperative neurological outcome. Information regarding the techniques used and interpretation of all SSEP tracings were obtained from evoked potential data sheets completed for each patient. The incidences of clinically important SSEP changes and new postoperative neurological deficits were analysed.

Results

Somatosensory evoked potential monitoringof the lower and upper extremities with non invasive techniques was used in 309 patients undergoing surgery on the cervical (88), thoracic (52), and lumbar spine (169). Thirty seven patients (11%) did not have suitable tracings for interpretation and 17 (5.5%) had baseline tracings described as poor. An intraoperative SSEP change occurred in 16 patients (6%) with SSEP and seven (2.6%) had a new neurological deficit postoperatively. Three persistent deficits were predicted by permanent SSEP change, and one transient deficit by a transient SSEP change. False positive results occurred in 12 patients (4.4%) and false negative results occurred in three (1.1%), with a sensitivity of 57% and a specificity of 95%. The incidence of SSEP changes was greater in the thoracic (18%) than in the cervical (1.2%) or lumbar (5.4%) groups (P < 0.05).

Conclusion

Effective SSEP monitoring was possible despite the many factors which may have interfered with monitoring. More improvements in the techniques and conditions of monitoring are needed to decrease the incidence of false positive and negative results.     

The usefulness of intraoperative neurophysiological monitoring in cervical spine surgery: a retrospective analysis of 200 consecutive patients

The usefulness of intraoperative neurophysiological monitoring (IONM), including somatosensory-evoked potential (SSEP) and transcranial electrical motor-evoked potentials (TcMEPs) in cervical spine surgery still needs to be evaluated. We retrospectively reviewed 200 cervical spine surgery patients from 2008 to 2009 to determine the role of IONM in cervical spine surgery. Total intravenous anesthesia was used for all patients. IONM alerts were defined as a 50% decrease in amplitude, a 10% increase in latency, or a unilateral change for SSEP and an increase in stimulation threshold of more than 100 V for TcMEP. Three patients had SSEP alerts that were related to arm malposition (2 patients) and hypotension (1 patient). Five patients had TcMEP alerts: 4 alerts were caused by hypotension and 1 by bone graft compression of the spinal cord. All alerts were resolved when causative reasons were corrected. There was no postoperative iatrogenic neurological injury. The sensitivities of SSEP and TcMEP alerts for detecting impending neurological injury were 37.5% and 62.5%, respectively. The sensitivity of both SSEP and TcMEP used in combination was 100%. No false-positive and false-negative alerts were identified in either SSEP or TcMEP (100% specificity). The total intravenous anesthesia technique optimizes the detection of SSEP and TcMEP and therefore improves the sensitivity and specificity of IONM. SSEP is sensitive in detecting alerts in possible malposition-induced ischemia or brachial plexus nerve injury. TcMEP specifically detects hypotension-induced spinal functional compromises. Combination use of TcMEP and SSEP enhances the early detection of impeding neurological damage during cervical spine surgery.     

Monitoring of somatosensory evoked potentials during temporary arterial occlusion in cerebral aneurysm surgery

Somatosensory evoked potentials (SSEP) have been used during cerebral aneurysm surgery to monitor the integrity of neural pathways. The purpose of this study was to evaluate the effectiveness of SSEP monitoring as a predictor of neurological outcome during temporary arterial occlusion. In a series of 157 patients monitored, 97 patients had temporary occlusion of the feeding artery. Twenty-three patients developed a SSEP change during temporary occlusion, 15 reversible (recovery of the change after the release of occlusion), and 8 persistent (no recovery) changes. A persistent change predicted a postoperative neurological deficit in each case, whereas, of the 15 patients with reversible changes, only 5 had postoperative deficits. Seventy-four patients had no change on SSEP monitoring but 10 patients did have new neurological deficits postoperatively. The false positive rate was 43% and the false negative rate was 14%. SSEP was a better predictor of neurological deficits in patients with aneurysms of the carotid circulation than of the vertebral-basilar arteries. Despite these limitations, we find SSEP monitoring useful during temporary occlusion in cerebral aneurysm surgery.     

Recording of spinal somatosensory evoked potentials for intraoperative spinal cord monitoring

The authors' experience with intradural and epidural recording of spinal somatosensory evoked potentials (SSEP's) during 26 cases of spinal surgery is described. The techniques of monitoring spinal cord function provided good quality SSEP waveforms in patients both with and without neurological deficits. The SSEP configuration and peak latencies remained stable for up to 5 hours during anesthesia with nitrous oxide, halothane, and fentanyl. Patterns of baseline SSEP's were characteristic of different spinal segments. Distortion and asymmetry of these baseline patterns were seen in several patients with spinal neoplasms. Loss of waveform components during surgery occurred with profound hypotension, overdistraction of the vertebral axis, dorsal midline myelotomy, and removal of intramedullary tumors. Persistent loss of waveform components was associated with an acquired neurological deficit. Fluctuations in the amplitude of the SSEP's were common but were not associated with postoperative neurological deficits. Spinal cord monitoring by means of SSEP recording would appear to be useful during extradural spinal surgery, but there are limitations associated with this technique during some types of intradural surgery.     

Monitoring electrophysiologic function during carotid endarterectomy: a comparison of somatosensory evoked potentials and conventional electroencephalogram

There is no consensus as to the most appropriate monitor for detecting ischemia during carotid endarterectomy. Accordingly, simultaneous 16-channel continuous electroencephalogram (EEG) and somatosensory evoked potential (SSEP) monitoring were performed in 64 normocapnic patients undergoing carotid endarterectomy and anesthetized with isoflurane or halothane-nitrous oxide (supplemented with fentanyl). Recordings were obtained before, during, and for 15 min after cross-clamping of the internal carotid artery. Internal shunt was not used in any patient, regardless of EEG and SSEP changes. Significant amplitude reduction in the cortical component of the primary negative peak (greater than 50%) in SSEP occurred in 6 patients, and an increase in central conduction time (CCT) (greater than 1 ms) occurred in 5 patients. Major EEG changes occurred in 6 patients, 4 of whom also had SSEP changes. Two patients had transient neurologic deficits postoperatively, with both having SSEP changes (amplitude reduction greater than 50%), whereas one had EEG changes. Based on these observations, the relative sensitivity and specificity for EEG and SSEP (amplitude reduction greater than 50%) in detecting postoperative neurologic deficits were 50% and 92% for EEG and 100% and 94% for SSEP, respectively, differences that were not statistically significant. Regarding SSEP, the use of latency change (CCT) as a criterion was associated with a sensitivity of 0% (P = 0.046 from sensitivity of amplitude) and a specificity of 87% (P = 0.17 from specificity of amplitude).(ABSTRACT TRUNCATED AT 250 WORDS)     

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

BackgroundIntraoperative 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%.PurposeOur 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.DesignThis was a retrospective review to analyze the efficacy of SSEP monitoring in the group of pediatric instrumented scoliosis fusion cases.Patient sampleWe 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 measuresMajor outcomes measured were clinically significant postoperative sensory or motor deficits, as well as significant intraoperative SSEP changes.MethodsContinuous 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.ResultsOur 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.ConclusionSSEP 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.     

Somatosensory evoked potential monitoring in the surgical management of acute acetabular fractures

Fifty patients undergoing acute acetabular fracture surgery had intraoperative somatosensory evoked potential (SSEP) monitoring. Group II, the final 38 patients, in addition had independent neurological evaluation preoperatively and postoperatively. Thirteen of 50 patients (26%) had preoperative sciatic nerve involvement. Fourteen of 50 patients (28%) developed significant intraoperative SSEP changes (decreased amplitude, increased latency). When the nerve was involved preoperatively (high-risk group), changes in SSEP occurred in 60% of patients. Iatrogenic sciatic/peroneal neuropraxia occurred in only one patient in the series (2%), and this resolved within 4 months. These results compare favorably to the incidence of 5-18% reported in the literature. We conclude SSEP is feasible and should be used in the operative treatment of acetabular fractures, especially the posterior fracture patterns and for those in the high-risk group.     

Somatosensory evoked potential monitoring during carotid endarterectomy in patients with a stroke.

The aim of our study was to assess the characteristics and feasibility of somatosensory evoked potential (SSEP) monitoring in patients who have had a stroke undergoing carotid endarterectomy. We retrospectively reviewed the medical and SSEP records of 204 patients. The patients were divided into two groups: Stroke (n = 65) and No-Stroke (n = 139). The amplitude and latency of the N20-P25 cortical complex on the ipsilateral side (surgical) were compared with the contralateral side in each group and between groups. Stroke patients showed asymmetry of their cortical waveforms; the ipsilateral N20-P25 baseline amplitude was 1.5 +/- 1.0 microv versus 1.9 +/- 1.2 microv for the contralateral (P = 0.001), for No-Stroke patients 2.0 +/- 1.1 microv versus 2.1 +/- 1.1 microv (P = 0.2). Forty-eight percent of Stroke patients had a ratio (ipsilateral/contralateral amplitude) of <1.0 +/- 0.2 compared with 26% for No-Stroke patients (P = 0.01). There were no differences in latency measurements, in the incidences of significant SSEP changes (four Stroke, six No-Stroke) and immediate postoperative neurological deficits (two Stroke, six No-Stroke) between the two groups. Nine patients (three Stroke, six No-Stroke) had a decrease in ipsilateral N20-P25 amplitude >50% after cross-clamping, and had a shunt inserted. In conclusion, patients with a history of a stroke before surgery had a decrease in the amplitude of the ipsilateral cortical peak. There were no differences in the incidences of SSEP changes or neurological deficits. Implications: Patients who have had a preoperative stroke may show asymmetry of their cortical baseline somatosensory evoked potential waveforms; however, this does not interfere with the ability to use somatosensory evoked potential as a monitor during surgery.     

The value of clinical characteristics and breast-imaging studies in predicting a histopathologic diagnosis of cancer or high-risk lesion in patients with spontaneous nipple discharge

BACKGROUND: The purpose of this study was to determine the utility of breast-imaging studies in identifying cancer and high-risk lesions among patients with spontaneous, single-duct, nipple discharge (SSND). METHODS: The medical records of 168 cases with SSND treated with duct excision between June 1998 and May 2004 were reviewed. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of mammogram, ultrasound, and ductogram in predicting high-risk lesions and cancer were calculated. RESULTS: The sensitivity of mammography was 10%, the specificity 94%, the NPV 88%, and the PPV 18%. Ultrasonography had a sensitivity of 36%, specificity of 68%, PPV of 14%, and NPV of 89%. Ductography had a sensitivity of 75%, specificity of 49%, and NPV and PPV of 93% and 18%, respectively. CONCLUSIONS: Conventional imaging studies do not accurately identify cancer or high-risk lesions in patients with SSND.All patients with SSND should be offered duct excision.     

Operative neurological complications resulting from thoracic and lumbar spine internal fixation

Of 2023 patients treated for acute spinal injuries, 729 sustained acute injuries in thoracic and lumbar regions; 295 surgically treated patients were reviewed for evidence of postoperative neurological complications. Of the 295 patients, 150 were intraoperatively monitored using somatosensory-evoked potentials (SSEP). Six patients (4%) revealed intraoperative deterioration of the SSEP; however, only one of the six revealed a new postoperative neurological deficit (0.7%). The remaining 145 patients were included in the unmonitored or wake-up test group in which ten (6.9%) demonstrated new postoperative deficits. Of the 11 patients with new postoperative neurological deficits, eight patients demonstrated motor weakness, two had radiculopathy, and one had bowel-bladder incontinence. The intraoperative use of SSEP was not able to identify subtle alterations in neurological function; however, due to early warning, SSEP appears capable of preventing profound surgically induced neurological alterations. A new protocol is designed for the management of intraoperative neurological deterioration as detected by SSEP.     

Detection of postoperative neurologic deficits using somatosensory-evoked potentials alone during posterior cervical laminoplasty

Background context

The use of neurophysiologic monitoring during anterior and posterior cervical decompression procedures in patients with spondylotic myelopathy remains controversial. The ideal neurophysiologic monitoring modality of choice is also highly debated.

Purpose

The purpose of this study was to evaluate the utility of neurophysiologic monitoring with only somatosensory-evoked potentials (SSEPs) in a consecutive series of laminoplasty procedures with regard to the detection of new postoperative neurologic deficits.

Study design

Retrospective case series.

Patient sample

Eighty consecutive patients who underwent a posterior cervical laminoplasty were reviewed.

Outcome measures

We analyzed intraoperative SSEP amplitude and latency changes from baseline with regard to the development of new postoperative neurologic deficits.

Methods

We retrospectively reviewed 80 patients who underwent a posterior cervical “open-door” laminoplasty with a standard SSEP neurophysiologic monitoring protocol. Intraoperative SSEP amplitude and latency changes from baseline (“alerts”) were analyzed with regard to the development of new postoperative neurologic deficits.

Results

Baseline SSEP values were obtained in all patients. There were five (6%) procedures that had SSEP alerts. All alerts occurred shortly after the lamina was hinged open. Four patients with SSEP alerts developed new postoperative neurologic deficits, including three unilateral upper extremity motor and sensory deficits and one complete spinal cord injury. In the immediate postoperative period, our experience with SSEP monitoring demonstrated 4 true-positive, 75 true-negative, and 1 false-positive monitoring results.

Conclusions

In this series of laminoplasty procedures, SSEP neurophysiologic monitoring had a high sensitivity and specificity for predicting new neurologic deficits in the early postoperative period. Somatosensory-evoked potentials are an effective tool for spinal cord monitoring when performing a posterior cervical laminoplasty procedure.     

The value of transcranial Doppler in predicting cerebral ischaemia during carotid endarterectomy.

OBJECTIVES: transcranial Doppler (TCD) measurement of middle cerebral artery velocity (MCAV) is an indirect method of assessing cerebral blood flow and therefore predicting patients at risk of stroke during carotid endarterectomy (CEA), and may be used to determine the need for shunting. This study evaluates the accuracy of three accepted TCD criteria in predicting the need for a shunt. DESIGN: prospective study. METHODS: one hundred and twenty consecutive CEA were performed under loco/regional anaesthesia. Patients monitored by TCD and Awake neurological examination were included. Shunts were inserted if there was neurological deterioration. Awake patient monitoring was compared with the three TCD criteria. RESULTS: inadequate TCD recordings were obtained in 16 operations (13%). In the remainder (104 cases), 12 developed symptoms of cerebral ischaemia and required a shunt (12%). Comparisons with the three accepted criteria were as follows: (1) m MCAV <30 cm/s had a sensitivity, specificity, PPV and NPV of 92%, 49%, 19%, and 98%, respectively; (2) clamp/pre-clamp ratio <0.6 had a sensitivity, specificity, PPV and NPV of 92%, 75%, 33% and 99%, respectively; (3) greater than 50% reduction in m MCAV had a sensitivity, specificity, PPV and NPV valves of 83%, 77%, 32% and 97%, respectively. CONCLUSIONS: TCD flow velocities are not a reliable method for detecting cerebral ischaemia and therefore determining the need for a shunt in CEA.     

Intra‐Operative Neurophysiological Monitoring in Patients with Intraspinal Abnormalities Undergoing Posterior Spinal Fusion

ObjectiveTo analyze the intraoperative neurophysiological monitoring (IONM) data of patients with intraspinal abnormalities undergoing posterior spinal fusion and to determine how intraspinal abnormalities influence IONM results.MethodsPatients with severe kyphoscoliosis and intraspinal abnormalities who underwent posterior spinal correction and fusion between September 2015 and January 2019 were retrospectively reviewed. Candidate intraspinal abnormalities included Chiari malformation, syringomyelia, split cord malformation, and tethered cord syndrome. Total intravenous anesthesia was administered, and no muscle relaxant or inhalation anesthesia was used for maintenance. IONM data, including somatosensory evoked potentials (SSEP) and motor evoked potentials (MEP), were recorded. The P37 and N50 latencies and amplitude were recorded for SSEP, whereas only the amplitude was recorded for MEP. The possible high‐risk factors for abnormal IONM results were analyzed.ResultsThe current study included 87 patients (40 men, 47 women) with an average age of 20.2 ± 10.4 years. The etiologies were neuromuscular in 45 patients, idiopathic in four, and congenital in 38. A total of 136 intraspinal abnormalities were detected, including Chiari malformation in 33 patients, syringomyelia in 55, split‐cord malformation in 25, and tethered cord syndrome in 23. Forty patients had one intraspinal abnormality, whereas 47 patients had two or three intraspinal abnormalities. The monitorabilities were 87.4% and 97.7% for the SSEP and MEP, respectively. SSEP alerts were reported in five patients and MEP alerts in four patients, and new neurological deficits were observed in three patients postoperatively. The sensitivity and specificity were 100% and 97.3% for SSEP, and 100% and 98.8% for MEP, respectively. A significant difference in MEP amplitude between the concave and convex sides was observed, while significantly higher SSEP latency was observed on the concave side in patients with preoperative neurological deficits. There were 52 (59.8%) patients with abnormal IONM data. Preoperative neurological deficits (χ² = 7.715, p = 0.005) and more than one intraspinal abnormality (χ² = 9.186, p = 0.004) indicated a higher risk of abnormal IONM data.ConclusionsIONM can be effectively used in patients with intraspinal abnormalities who undergo posterior spinal fusion. Patients with preoperative neurological deficits and more than one intraspinal abnormality have a higher risk of abnormal IONM monitoring.     

Multimodal intraoperative neuromonitoring in corrective surgery for adolescent idiopathic scoliosis: Evaluation of 354 consecutive cases

Background:

Multimodal intraoperative neuromonitoring is recommended during corrective spinal surgery, and has been widely used in surgery for spinal deformity with successful outcomes. Despite successful outcomes of corrective surgery due to increased safety of the patients with the usage of spinal cord monitoring in many large spine centers, this modality has not yet achieved widespread popularity. We report the analysis of prospectively collected intraoperative neurophysiological monitoring data of 354 consecutive patients undergoing corrective surgery for adolescent idiopathic scoliosis (AIS) to establish the efficacy of multimodal neuromonitoring and to evaluate comparative sensitivity and specificity.

Materials and Methods:

The study group consisted of 354 (female = 309; male = 45) patients undergoing spinal deformity corrective surgery between 2004 and 2008. Patients were monitored using electrophysiological methods including somatosensory-evoked potentials and motor-evoked potentials simultaneously.

Results:

Mean age of patients was 13.6 years (±2.3 years). The operative procedures involved were instrumented fusion of the thoracic/lumbar/both curves, Baseline somatosensory-evoked potentials (SSEP) and neurogenic motor-evoked potentials (NMEP) were recorded successfully in all cases. Thirteen cases expressed significant alert to prompt reversal of intervention. All these 13 cases with significant alert had detectable NMEP alerts, whereas significant SSEP alert was detected in 8 cases. Two patients awoke with new neurological deficit (0.56%) and had significant intraoperative SSEP + NMEP alerts. There were no false positives with SSEP (high specificity) but 5 patients with false negatives with SSEP (38%) reduced its sensitivity. There was no false negative with NMEP but 2 of 13 cases were false positive with NMEP (15%). The specificity of SSEP (100%) is higher than NMEP (96%); however, the sensitivity of NMEP (100%) is far better than SSEP (51%). Due to these results, the overall sensitivity, specificity and positive predictive value of combined multimodality neuromonitoring in this adult deformity series was 100, 98.5 and 85%, respectively.

Conclusion:

Neurogenic motor-evoked potential (NMEP) monitoring appears to be superior to conventional SSEP monitoring for identifying evolving spinal cord injury. Used in conjunction, the sensitivity and specificity of combined neuromonitoring may reach up to 100%. Multimodality monitoring with SSEP + NMEP should be the standard of care.     

Evoked potential monitoring during posterior fossa aneurysm surgery: a comparison of two modalities

The purpose of this study was to compare and assess the ability of two different evoked potential (EP) modalities, median nerve somatosensory evoked potentials (SSEP) and brainstem auditory evoked potentials (BAEP) in monitoring for cerebral ischaemia and in predicting neurological outcome during posterior fossa aneurysm surgery. During 70 procedures, patients were monitored with both SSEP and BAEP Temporary occlusion of an artery was used in 52 patients and permanent occlusion in 21 patients. A change was defined as a greater than 50% decrease in amplitude and/or an increase in latency greater than 1 msec of the N20 (cortical waveform) for SSEP monitoring and of the fifth peak for BAEP monitoring. Neurological assessment of the patient was performed immediately on emergence, after 24 hr and at the time of discharge. In total, 14 patients had an SSEP change which predicted a neurological deficit in eight patients (57%). Ten patients had a change in BAEP; six had a neurological deficit (60%). Five patients had a change in both, two had a deficit (40%). The incidence of false negative results (a neurological deficit but no EP change) for both modalities was 20% (SSEP 47%, BAEP 60%). The incidence of false positive results (an EP change but no deficit) was 13% overall (SSEP 11%, BAEP 7%). All patients who had a permanent EP change developed a neurological deficit. We did not find a difference in the ability of SSEP compared with BAEP in predicting neurological deficits but, using both modalities, the incidence of false negative results was decreased. In conclusion, dual modality monitoring should be used whenever possible as neither modality alone was better than the other in detecting cerebral ischaemia and in predicting neurological deficits.     

Is a palpable short saphenous vein a useful clinical sign in varicose vein assessment?

The short saphenous vein (SSV) may be palpable in the popliteal fossa in patients with varicose veins. A prospective study has been carried out to determine the significance of this sign in the presence of primary varicose veins. The SSV was assessed by palpation of the popliteal fossa with the knee slightly flexed. Hand-held Doppler insonation (HHD) was also used in the out-patient clinic. All patients had SSV assessment by duplex scanning. One hundred and sixty legs were examined. In 68 the SSV was palpable; 39 (57%) of these had SSV reflux on duplex examination. When the SSV was not palpable (92 legs), only 1% (1 leg) refluxed on duplex scanning. SSV palpability had a 98% sensitivity, 75% specificity, 57% positive predictive value (PPV), and 99% negative predictive value (NPV). In comparison, HHD had 80% sensitivity, 87% specificity, 67% PPV and 93% NPV. The combined tests had 78% sensitivity, 73% specificity, 76% PPV and 100% NPV. Palpation of the SSV is a valuable part of clinical examination. If the SSV is not palpable, it is unlikely to reflux.     

Surgical Treatment of Solitary Thyroid Nodules Via Fine-Needle Aspiration Biopsy and Frozen-Section Analysis

Background Fine-needle aspiration biopsy (FNAB) and frozen-section analysis of managing solitary thyroid nodules continue to generate considerable controversy. Methods This study was a retrospective review of 619 patients with solitary thyroid nodules who underwent thyroidectomy. Results Of 540 FNABs, 35 (6.5%) were positive for malignancy, 276 (51.1%) were benign, and 229 (42.4%) were suspicious. Only 5.1% were false negative, and 11.4% were false positive. Diagnostic FNAB sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for malignancy were 86.1%, 59.7%, 33.0%, 94.9%, and 64.6%, respectively. Of 569 patients analyzed by frozen section, diagnosis was deferred in 86 (15.1%) patients, and results were positive for malignancy in 92 (16.2%) and benign in 391 (68.7%). No false-positive results were noted, but 2.3% (391) were false negative. Of 86 deferred frozen sections, 11 (12.8%) patients had malignant tumors confirmed by permanent section. Diagnostic frozen-section sensitivity, specificity, PPV, NPV, and accuracy for carcinoma were 82.1%, 100%, 100%, 95.8%, and 96.5%, respectively. Sensitivity, specificity, PPV, NPV, and accuracy for frozen-section analysis for diagnosis of carcinoma in patients with suspicious FNAB were 83.9%, 100%, 100%, 94.9%, and 96.0%, respectively. Conclusions FNAB is a sensitive diagnostic modality in selecting patients who require surgery. Routine use of frozen-section analysis is unwarranted for benign FNAB results. Frozen section is specific and cost-effective in determining the extent of surgery in patients with suspicious or malignant FNABs.