Intraoperative neuromonitoring as real-time diagnostic for cerebral ischemia in endovascular treatment of ruptured brain aneurysms

OBJECTIVE

To evaluate the diagnostic accuracy of intraoperative neurophysiological monitoring (IONM) during endovascular treatment (EVT) of ruptured intracranial aneurysms (rIA).

METHODS

IONM and clinical data from 323 patients who underwent EVT for rIA from 2014-2019 were retrospectively reviewed. Significant IONM changes and outcomes were evaluated based on visual review of data and clinical documentation.

RESULTS

Of the 323 patients undergoing EVT, significant IONM changes were noted in 30 patients (9.29%) and 46 (14.24%) experienced postprocedural neurological deficits (PPND). 22 out of 30 (73.33%) patients who had significant IONM changes experienced PPND. Univariable analysis showed changes in somatosensory evoked potential (SSEP) and electroencephalogram (EEG) were associated with PPND (p-values: <0.001 and <0.001, retrospectively). Multivariable analysis showed that IONM changes were significantly associated with PPND (Odd ratio (OR) 20.18 (95%CI:7.40-55.03, p-value: <0.001)). Simultaneous changes in both IONM modalities had specificity of 98.9% (95% CI: 97.1%-99.7%). While sensitivity when either modality had a change was 47.8% (95% CI: 33.9%-62.0%) to predict PPND.

CONCLUSIONS

Significant IONM changes during EVT for rIA are associated with an increased risk of PPND.

SIGNIFICANCE

IONM can be used confidently as a real time neurophysiological diagnostic guide for impending neurological deficits during EVT treatment of rIA.

Diagnostic Impact of Monitoring Visual Evoked Potentials to Prevent Visual Complications During Endovascular Treatment for Intracranial Aneurysm

Introduction

The present study aimed to determine the incidence of intraprocedural visual-evoked potential (VEP) changes and to identify correlations with intraprocedural ischemic complications during endovascular treatment in patients with intracranial aneurysm related to visual function.

Methods

This study analyzed data from 104 consecutive patients who underwent endovascular coil embolization to treat intracranial aneurysms related to visual function under VEP and transcranial motor evoked potential (MEP) monitoring. We analyzed associations between significant changes in MEP and VEP, defined as a >50% decrease in amplitude, and both intraprocedural complications and postoperative neurological deficits. Factors associated with postoperative neurological deficits were also assessed.

Results

Treated aneurysms were predominantly located in the internal carotid artery (95%). Five (5%) were located in the posterior cerebral artery (PCA). Significant decreases in intraprocedural VEP occurred in four patients (4%), although one of those four patients did not show concomitant MEP decreases during procedures. Immediate salvage procedures avoided postoperative visual disturbances. All VEP decreases were transient and not associated with postoperative visual impairment. One of three cases who underwent intraoperative balloon occlusion test showed tolerance to balloon occlusion of the proximal PCA under VEP assessment; parent artery occlusion was performed without postoperative visual disturbance in that case.

Conclusion

Although significant VEP decreases occurred 4% during neuro-endovascular aneurysm treatment related to visual function, intraprocedural VEP monitoring identifies ischemic changes associated with visual pathways and facilitates prompt initiation of salvage procedures.

Intraoperative vascular complications during 2278 cerebral endovascular procedures with multimodality IONM: relationship between signal change, complication, intervention and postoperative outcome

BACKGROUND

Intraoperative neuromonitoring (IONM) is often used during cerebral endovascular procedures.

OBJECTIVE

To investigate the relationship between intraoperative vascular complications and IONM signal changes, and the impact of interventions on signal resolution and postoperative outcomes.

METHODS

A series of 2278 cerebral endovascular procedures conducted under general anesthesia and using electroencephalography and somatosensory evoked potential monitoring were retrospectively reviewed. A subset of 763 procedures also included motor evoked potentials (MEPs). IONM alerts were categorized as either a partial attenuation or complete loss of signal. Vascular complications were subcategorized as due to rupture, emboli, instrumentation, or vasospasm. Odds ratios (ORs) for new postoperative motor deficits were calculated and diagnostic accuracy was measured using sensitivity, specificity, and likelihood ratios.

RESULTS

The overall incidence of new postoperative motor deficit was 1.2%; 20.4% in cases with an IONM alert and 0.09% in cases without an alert. Relative to procedures with no alerts, odds of a new deficit increased if there was partial signal attenuation (OR=210.9, 95% CI 44.3 to 1003.5, p<0.0001) and increased further with complete loss of signal (OR=1437.3, 95% CI 297.3 to 6948.2, p<0.0001). Relative to procedures with unresolved alerts, odds of a new deficit decreased if the alert was fully resolved (OR=0.039, 95% CI 0.005 to 0.306, p<0.002). Procedures using MEPs had slightly higher sensitivity (92.3% vs 85.7%) but slightly lower specificity (96.7% vs 98.2%).

CONCLUSIONS

An IONM alert associated with an arterial complication is associated with a dramatic increase in odds of a new postoperative deficit; however, if there is resolution of the alert prior to closure, odds of a new deficit decrease significantly.

Inhaled anesthesia in neurosurgery: Still a role?

In patients undergoing craniotomy, general anesthesia should be addressed to warrant good hypnosis, immobility, and analgesia, to ensure systemic and cerebral physiological status and provide the best possible surgical field. Regarding craniotomies, it is unclear if there are substantial differences in providing general anesthesia using total intravenous anesthesia (TIVA) or balanced anesthesia (BA) accomplished using the third generation halogenates. New evidence highlighted that the last generation of halogenated agents has possible advantages compared with intravenous drugs: rapid induction, minimal absorption and metabolization, reproducible pharmacokinetic, faster recovery, cardioprotective effect, and opioid spare analgesia. This review aims to report evidence related to the use of the latest halogenated agents in patients undergoing craniotomy and to present available clinical evidence on their effects: cerebral and systemic hemodynamic, neurophysiological monitoring, and timing and quality of recovery after anesthesia.

Diagnostic impact of monitoring transcranial motor-evoked potentials to prevent ischemic complications during endovascular treatment for intracranial aneurysms

The present study aimed to determine the incidence of intraprocedural motor-evoked potential (MEP) changes and to correlate them with intraprocedural ischemic complications and postprocedural neurological deficits in patients after endovascular intracranial aneurysm treatment. This study analyzed data from 164 consecutive patients who underwent endovascular coil embolization to treat intracranial aneurysms under transcranial MEP monitoring. We analyzed associations between significant changes in MEP defined as > 50% decrease in amplitude, and intraprocedural complications as well as postoperative neurological deficits. Factors associated with postprocedural neurological deficits were also assessed. The treated aneurysms were predominantly located in the anterior circulation (71%). Fourteen (9%) were located at perforators or branches that supplied the pyramidal tract. Intraprocedural complications developed in eight (5%) patients, and four of eight (50%) patients occurred postprocedural neurological deficits. Significant intraprocedural MEP changes occurred during seven of eight endovascular procedures associated with intraprocedural complications and salvage procedures were performed immediately. Among these changes, four transient MEP changes, recovered within 10 min, were not associated with postprocedural neurological deficits, whereas three permanent MEP changes were associated with postprocedural neurological deficits and mRS ≥ 1 at discharge. Aneurysms located at perforators/branches supplying the pyramidal tract, and permanent intraprocedural MEP changes were associated with postprocedural neurological deficits. We conclude that intraprocedural transcranial MEP monitoring can reliably identify ischemic changes and can initiate prompt salvage procedures during endovascular aneurysm treatment.

Unexpected abnormal intraoperative neurophysiologic monitoring change by multiple spontaneous intracerebral haemorrhage during endovascular coiling

We report a patient with multiple angiographically negative intracerebral haemorrhages, which were recognized by significant changes in intraoperative neurophysiologic monitoring during the coil embolization of a left middle cerebral artery aneurysm.

Neurophysiological Monitoring During Arteriovenous Malformation Embolization

BACKGROUND

Neurophysiological monitoring (NPM) is frequently performed during arteriovenous malformation (AVM) embolization. However, the ability of NPM to predict neurological deficits or improve surgical decision making in this setting has not been studied.

OBJECTIVE

To review our use of NPM during AVM embolization to better define its utility.

METHODS

We retrospectively examined AVM embolization cases from 2004 to 2017. We recorded patient and AVM characteristics as well as outcomes. We then reviewed NPM results from each case, including somatosensory evoked potentials and electroencephalogram. Our primary outcome was postoperative neurological deficit, and secondary outcomes were discharge and 30-d modified Rankin Score (mRS).

RESULTS

There were 173 embolizations in 74 patients. Mean patient age was 40 yr. There were 8 (5%) transient and 2 (1.3%) permanent neurological complications. Among those with neurological complications, 3 had NPM changes during the operation (positive predictive value [PPV] = 50%). This improved to 67% for permanent NPM change. Three patients had NPM changes but did not suffer clinical deficits postoperatively (negative predictive value = 90%). The predictive value of the test was improved for discharge but not 30-d mRS, and the test performance improved dramatically with increased pretest probabilities (likelihood ratio [LR](+) = 14.5, LR(-) = 0.715).

CONCLUSION

We present a large series of AVM embolization operations performed with NPM. The PPV of NPM changes was moderate but improved dramatically with increased pretest probabilities. The rate of permanent neurological complications was among the lowest reported in the literature, suggesting NPM may lead to improved intraoperative decision making.

The Effects of Filter's Class, Cutoff Frequencies, and Independent Component Analysis on the Amplitude of Somatosensory Evoked Potentials Recorded from Healthy Volunteers

Objective: The aim of this study was to investigate the effects of different preprocessing parameters on the amplitude of median nerve somatosensory evoked potentials (SEPs). Methods: Different combinations of two classes of filters (Finite Impulse Response (FIR) and Infinite Impulse Response (IIR)), three cutoff frequency bands (0.5–1000 Hz, 3–1000 Hz, and 30–1000 Hz), and independent component analysis (ICA) were used to preprocess SEPs recorded from 17 healthy volunteers who participated in two sessions of 1000 stimulations of the right median nerve. N30 amplitude was calculated from frontally placed electrode (F3). Results: The epochs classified as artifacts from SEPs filtered with FIR compared to those filtered with IIR were 1% more using automatic and 140% more using semi-automatic methods (both p < 0.001). There were no differences in N30 amplitudes between FIR and IIR filtered SEPs. The N30 amplitude was significantly lower for SEPs filtered with 30–1000 Hz compared to the bandpass frequencies 0.5–1000 Hz and 3–1000 Hz. The N30 amplitude was significantly reduced when SEPs were cleaned with ICA compared to the SEPs from which non-brain components were not removed using ICA. Conclusion: This study suggests that the preprocessing of SEPs should be done carefully and the neuroscience community should come to a consensus regarding SEP preprocessing guidelines, as the preprocessing parameters can affect the outcomes that may influence the interpretations of results, replicability, and comparison of different studies.

Predictive value of neurophysiologic monitoring during neurovascular intervention for postoperative new neurologic deficits

PURPOSE

Forms of intraoperative neurophysiologic monitoring (IONM), including somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs), have been widely used in the field of neurosurgery. This study aimed to evaluate the diagnostic efficacy of IONM in identifying intraoperative events and predicting postoperative neurologic deficits in neurovascular intervention.

METHODS

From January 2013 to December 2016, we retrospectively reviewed patients who underwent neurovascular intervention under general anesthesia with the use of IONM. Associations between significant changes in MEPs or SSEPs which were defined as a decrease more than 50% in amplitude and/or an increase more than 10% in latency and any identifiable intraoperative events and/or postoperative neurologic deficits were determined. The sensitivity and specificity values for both MEPs and SSEPs were calculated.

RESULTS

In total, 578 patients (175 men and 403 women) were included. Their mean age was 59.5 years. SSEP changes occurred in 1% (n = 6), and MEP changes occurred in 1.2% (n = 7). Four patients suffered postoperative neurologic deficits, and identifiable intraoperative events were observed in seven patients. Both SSEP and MEP changes were significantly associated with identifiable intraoperative events and/or postoperative neurologic deficits (p < 0.001, Fisher's exact test). The calculated sensitivity and specificity of MEP monitoring were 50 and 99.5%, respectively. The sensitivity and specificity of SSEP monitoring were both 100%.

CONCLUSION

Intraoperative SSEP monitoring might be a reliable and sensitive method to surveil neurologic complications during neurovascular intervention. Intraoperative MEP monitoring appears to be feasible. However, it is unclear whether MEP monitoring has any additive benefit over SSEP monitoring.