Invasive Intracranial Monitoring Research Articles

Combination Resective or Ablative Epilepsy Surgery with Neurostimulation for Complex Epilepsy Networks: A Case Series

Introduction: Complex epilepsy networks with multifocal onset zones that overlap with eloquent cortex may benefit from combined surgical approaches. However, limited data exist on outcomes associated with performing these therapies in tandem. In this case series, we report on 6 patients who underwent combination surgery with either resection or laser interstitial thermal therapy (LITT) and neuromodulation with responsive neurostimulation (RNS) or deep brain stimulation (DBS). Methods: We performed a retrospective review of adult patients with medically refractory epilepsy who underwent staged combination epilepsy surgeries during the same admission at our institution. Six cases treated between 2019 and 2023 were identified. All patients underwent a presurgical work-up including invasive intracranial monitoring and underwent a combined approach with either surgical resection, LITT, RNS, or DBS. We extracted data on demographic, clinical, and surgical characteristics. The primary outcome was change in seizure frequency from baseline. Results: The mean age was 42.7 years old (4 female). All patients had at least one epileptogenic zone in the temporal lobe, two in extratemporal neocortex, two in periventricular nodular heterotopia. For the staged combination approach, 3 patients underwent LITT followed by RNS, two underwent resection and RNS, and one received LITT and DBS. The mean reduction in seizure frequency per month at last follow-up was 90%. Postoperatively, 1 patient experienced superior visual field deficits related to LITT, and another had postoperative deep vein thrombosis. Conclusion: All patients experienced at least an 83% reduction in seizures. This case series demonstrates the potential benefits of a combined surgical approach in patients with multifocal seizures and at least one lesion that can be safely resected or ablated. Future prospective studies are warranted.

Derivation, external and clinical validation of a deep learning approach for detecting intracranial hypertension

Increased intracranial pressure (ICP) ≥15 mmHg is associated with adverse neurological outcomes, but needs invasive intracranial monitoring. Using the publicly available MIMIC-III Waveform Database (2000–2013) from Boston, we developed an artificial intelligence-derived biomarker for elevated ICP (aICP) for adult patients. aICP uses routinely collected extracranial waveform data as input, reducing the need for invasive monitoring. We externally validated aICP with an independent dataset from the Mount Sinai Hospital (2020–2022) in New York City. The AUROC, accuracy, sensitivity, and specificity on the external validation dataset were 0.80 (95% CI, 0.80–0.80), 73.8% (95% CI, 72.0–75.6%), 73.5% (95% CI 72.5–74.5%), and 73.0% (95% CI, 72.0–74.0%), respectively. We also present an exploratory analysis showing aICP predictions are associated with clinical phenotypes. A ten-percentile increment was associated with brain malignancy (OR = 1.68; 95% CI, 1.09-2.60), intracerebral hemorrhage (OR = 1.18; 95% CI, 1.07–1.32), and craniotomy (OR = 1.43; 95% CI, 1.12–1.84; P < 0.05 for all).

D.5 Low density scalp electrical source imaging of the ictal onset zone network using source coherence maps

Background: This study investigates the utility of low-density scalp electrical source imaging (LD-ESI) of the Ictal Onset Zone (IOZ) and interictal spike ripple high frequency oscillation (ISRHFO) networks using Source Coherence Maps (SCM) in the surgical evaluation of children with medically refractory epilepsy. Invasive intracranial monitoring, the gold standard for determining epileptogenic zones, has limited spatial sampling. SCM presents a promising new non-invasive diagnostic technique. Methods: This was a retrospective review of 11 patients who underwent focal resections. SCMs were generated using Standardized Low Resolution Electromagnetic Tomography (sLORETA). SCM concordance to resection margins was assessed, noting outcomes at 3 years. Results: For 7/11 cases, ictal SCMs included the resection, and 5/7 achieved seizure freedom, indicating inclusion of the epileptogenic zone. For the 2/7 not seizure-free, the IOZ networks on the SCMs extended beyond resection margins, suggesting the epileptogenic zone also extended beyond the resection. Interictal spike ripple ESI and ISRHFO SCM were performed for 7/11, with 3/7 included in the resection and all 3 seizure-free. Conclusions: These findings may support LD-ESI of the IOZ and ISRHFO network using SCM as promising methods complementary to ictal and interictal ESI in pediatric epilepsy surgical workup, guiding electrode placement for intracranial monitoring to identify the epileptogenic zone.

Non-lesional epilepsy does not necessarily convey poor outcomes after invasive monitoring followed by resection or thermal ablation

ABSTRACT Objective We aimed to compare outcomes including seizure-free status at the last follow-up in adult patients with medically refractory focal epilepsy identified as lesional vs. non-lesional based on their magnetic resonance imaging (MRI) findings who underwent invasive evaluation followed by subsequent resection or thermal ablation (LiTT). Methods We identified 88 adult patients who underwent intracranial monitoring between 2014 and 2021. Of those, 40 received resection or LiTT, and they were dichotomized based on MRI findings, as lesional (N = 28) and non-lesional (N = 12). Patient demographics, seizure characteristics, non-invasive interventions, intracranial monitoring, and surgical variables were compared between the groups. Postsurgical seizure outcome at the last follow-up was rated according to the Engel classification, and postoperative seizure freedom was determined by Kaplan-Meyer survival analysis. Statistical analyses employed Fisher’s exact test to compare categorical variables, while a t-test was used for continuous variables. Results There were no differences in baseline characteristics between groups except for more often noted PET abnormality in the lesional group (p = 0.0003). 64% of the lesional group and 57% of the non-lesional group received surgical resection or LiTT (p = 0.78). At the last follow-up, 78.5% of the patients with lesional MRI findings achieved Engel I outcomes compared to 66.7% of non-lesional patients (p = 0.45). Kaplan-Meier curves did not show a significant difference in seizure-free duration between both groups after surgical intervention (p = 0.49). Significance In our sample, the absence of lesion on brain MRI was not associated with worse seizure outcomes in adult patients who underwent invasive intracranial monitoring followed by resection or thermal ablation.

Groote Schuur Hospital neurosurgical intensive care unit: A 2-year review of admission characteristics.

At Groote Schuur Hospital (GSH), the neurosurgical intensive care unit (NsICU) is a 6-bed unit headed by a specialist neurosurgeon with extensive experience in neurocritical care, working in close collaboration with intensivists from the Division of Critical Care. There is currently no detailed analysis of the demographics, diagnosis and management of patients admitted to the NsICU at GSH. To provide a detailed descriptive analysis of the demographics, diagnosis and management of patients admitted to the NsICU at GSH from 1 January 2020 to 31 December 2021. A retrospective descriptive analysis was done of patients who received treatment in the NsICU from 1 January 2020 to 31 December 2021. A total of 685 patients were admitted to the unit over a 2-year period, with a male preponderance (68.2%). The average age was 42.5 (standard deviation (SD) 17.2) years. The most common neurosurgical diagnoses were traumatic brain injuries (39.6%), brain tumours (22.6%) and aneurysmal subarachnoid haemorrhages (9.9%). Emergency admissions comprised 76.6% of the total and 86.7% of patients were admitted postoperatively. Three hundred and seventy-two patients (54.3%) required mechanical ventilation, 132 (19.3%) required both an intracranial pressure (ICP) monitor and brain tissue oxygenation monitor, 86 (12.5%) needed placement of an external ventricular drain, 50 (7.3%) needed placement of a tracheostomy tube and 16 (2.3%) needed placement of an ICP monitor only. The average duration of stay was 5.5 (1.3) days and NsICU mortality over 2 years was 11.1%. The NsICU at GSH manages predominantly male trauma patients and a significant number of admitted patients require specialised invasive intracranial monitoring. This is the first in-depth analysis of patients managed in a dedicated neurosurgical intensive care unit in South Africa. The work defines the patient population, neurosurgical pathologies and service level requirements that would likely be encountered by teams building a similar service.

Epilepsy Surgery in Young Children With Tuberous Sclerosis Complex: A Novel Hybrid Multimodal Surgical Approach.

Surgery has become integral in treating children with tuberous sclerosis complex (TSC)-related drug-resistant epilepsy (DRE). To describe outcomes of a multimodal diagnostic and therapeutic approach comprising invasive intracranial monitoring and surgical treatment and compare the complementary techniques of open resection and magnetic resonance-guided laser interstitial thermal therapy. Clinical and radiographic data were prospectively collected for pediatric patients undergoing surgical evaluation for TSC-related DRE at our tertiary academic hospital. Seizure freedom, developmental improvement, and Engel class were compared. Thirty-eight patients (20 females) underwent treatment in January 2016 to April 2019. Thirty-five underwent phase II invasive monitoring with intracranial electrodes: 24 stereoencephalography, 9 craniotomy for grid/electrode placement, and 2 grids + stereoencephalography. With the multimodal approach, 33/38 patients (87%) achieved >50% seizure freedom of the targeted seizure type after initial treatment; 6/9 requiring secondary treatment and 2/2 requiring a third treatment achieved >50% freedom. The median Engel class was II at last follow-up (1.65 years), and 55% of patients were Engel class I/II. The mean age was lower for children undergoing open resection (2.4 vs 4.9 years, P = .04). Rates of >50% reduction in seizures (86% open resection vs 88% laser interstitial thermal therapy) and developmental improvement (86% open resection vs 83% magnetic resonance-guided laser interstitial thermal therapy) were similar. This hybrid approach of using both open surgical and minimally invasive techniques is safe and effective in treating DRE secondary to TSC. Clinical trials focused on treatment method with longer follow-up are needed to determine the optimal candidates for each approach and compare the treatment modalities more effectively.

Decision Support Tool to Judiciously Assign High-Frequency Neurologic Examinations in Traumatic Brain Injury

IntroductionTraumatic brain injury (TBI) management includes serial neurologic examinations to assess for changes dictating neurosurgical interventions. We hypothesized hourly examinations are overassigned. We conducted a decision tree analysis to determine an algorithm to judiciously assign hourly examinations. MethodsA retrospective cohort study of 1022 patients with TBI admitted to a Level 1 trauma center from January 1, 2019, to December 31, 2019, was conducted. Patients with penetrating TBI or immediate or planned interventions and those with nonsurvivable injuries were excluded. Patients were stratified by whether they underwent an unplanned intervention (e.g., craniotomy or invasive intracranial monitoring). Univariate analysis identified factors for inclusion in chi-square automatic interaction detection technique, classifying those at risk for unplanned procedures. ResultsA total of 830 patients were included, 287 (35%) were assigned hourly (Q1) examinations, and 17 (2%) had unplanned procedures, with 16 of 17 (94%) on Q1 examinations. Patients requiring unplanned procedures were more likely to have mixed intracranial hemorrhage pattern (82% versus 39%; P = 0.001), midline shift (35% versus 14%; P = 0.023), an initial poor neurologic examination (Glasgow Comas Scale ≤8, 77% versus 14%; P < 0.001), and be intubated (88% versus 17%; P < 0.001). Using chi-square automatic interaction detection, the decision tree demonstrated low-risk (2% misclassification) and excellent discrimination (area under the curve = 0.915, 95% confidence interval 0.844-0.986; P < 0.001) of patients at risk of an unplanned procedure. By following the algorithm, 167 fewer patients could have been assigned Q1 examinations, resulting in an estimated 6012 fewer examinations. ConclusionsUsing a 4-factor algorithm can optimize the assignment of neuro examinations and substantially reduce neuro examination burden without sacrificing patient safety.

Epidural grid, a new methodology of invasive intracranial EEG monitoring: A technical note and experience of a single center

IntroductionSubdural grid monitoring (SDG) has the advantage to provide continuous coverage over a larger area of cortex, direct visualization of electrode location and functional mapping. However, SDG can cause direct irritation of the cortex or postoperative headaches due to cerebrospinal fluid (CSF) leakage. Epidural grid monitoring (EDG) without opening the dura is thought to reduce the possibility of these complications. We report our experience with EDG. MethodsWe described our surgical technique of EDG in invasive intracranial electroencephalography (iEEG) monitoring. A retrospective review of 30 patients who underwent grid placement of iEEG between March 2019 and December 2020 was performed to compare SDG and EDG. ResultsOf the 30 patients, 10 patients underwent SDG and 20 patients underwent EDG. There was no difference in age between SDG and EDG groups (p = 0.13). Also, there was no difference in the number of grid electrodes, craniotomy size, number of electrodes per craniotomy area and postoperative complication rate (p = 0.32, 0.84, 0.58 and 0.40). However, the maximum number of electrodes that have been undermined from the bone margin was much higher in SDG group (SDG 4.6 ± 2.2 vs. EDG 2.0 ± 0.9; p = 0.001). The demand for postoperative analgesics was significantly lower in EDG group (SDG 13.4 ± 9.1 vs. EDG 4.1 ± 4.3; p = 0.012); and the demand for postoperative antiemetics also tended to be low (SDG 4.6 ± 3.6 vs. EDG 1.8 ± 1.6; p = 0.078). ConclusionsThere was no significant difference in craniotomy and electrode insertion between the two groups; however, the EDG group showed less postoperative headache and nausea. Though not in direct contact with the cortex, the quality of the electrophysiological signal received through the electrode in EDG is comparable to that of the SDG. The EDG enables to detect the onset of seizure and delineate the epileptogenic zone sufficiently. Moreover, functional mapping is possible with EDG. Therefore, EDG has the sufficient potential to replace SDG for monitoring of the lateral surface of brain.

Treating the body to prevent brain injury: lessons learned from the coronavirus disease 2019 pandemic.

We aim to provide the current evidence on utility and application of neuromonitoring tools including electroencephalography (EEG), transcranial Doppler (TCD), pupillometry, optic nerve sheath diameter (ONSD), cerebral near-infrared spectroscopy (cNIRS), somatosensory-evoked potentials (SSEPs), and invasive intracranial monitoring in COVID-19. We also provide recent evidence on management strategy of COVID-19-associated neurological complications. Despite the common occurrence of neurological complications, we found limited use of standard neurologic monitoring in patients with COVID-19. No specific EEG pattern was identified in COVID-19. Frontal epileptic discharge was proposed to be a potential marker of COVID-19 encephalopathy. TCD, ONSD, and pupillometry can provide real-time data on intracranial pressure. Additionally, TCD may be useful for detection of acute large vessel occlusions, abnormal cerebral hemodynamics, cerebral emboli, and evolving cerebral edema at bedside. cNIRS was under-utilized in COVID-19 population and there are ongoing studies to investigate whether cerebral oxygenation could be a more useful parameter than peripheral oxygen saturation to guide clinical titration of permissive hypoxemia. Limited data exists on SSEPs and invasive intracranial monitoring. Early recognition using standardized neuromonitoring and timely intervention is important to reduce morbidity and mortality. The management strategy for neurological complications is similar to those without COVID-19.

Peak Systolic Velocity in Middle Cerebral Artery in Patients with Severe Traumatic Brain Injury as an Indicator of Detrimental Rise in Intracranial Pressure

Background Intracranial pressure (ICP) is the major concern for neurosurgeons while treating patients with severe traumatic brain injury, as any troublesome escalation in intracranial pressure heralds feared complications leading to definite morbidity or even mortality.&#x0D; Objective This study focuses on analyzing the correlation between peak systolic velocity in middle cerebral artery derived from transcranial doppler ultrasonographic spectral analysis and intracranial pressure values derived from invasive intracranial pressure monitoring system in a patient with severe traumatic brain injury.&#x0D; Method A prospective observational study was performed using a convenience sample technique including all adult patients with severe traumatic brain injury who had invasive intracranial monitors placed as part of their clinical care. Transcranial doppler ultrasonography was performed with a 2 MHz linear probe of ACUSON X300 ultrasound system while simultaneous intracranial pressure readings were obtained directly from invasive intracranial pressure monitoring. The association between peak systolic velocity in the middle cerebral artery and invasive intracranial pressure was assessed with Pearson’s correlation coefficient.&#x0D; Result One hundred one transcranial doppler ultrasound spectral analysis was performed on 26 individual patients. The mean age of the population involved in this study is 43.57 years ± S.D. 19.95 (range 18-78 years), with male preponderance in a ratio of 5.5:1. Pearson’s correlation coefficient of peak systolic velocity in middle cerebral artery and intracranial pressure was 0.715 (p &lt; 0.000) demonstrating a significant positive correlation. With further evaluation of area under curve characteristics, peak systolic velocity in middle cerebral artery of 39.6 cm/s yielded the most favorable balance of test characteristics to diagnose elevation of intracranial pressure, with a resulting sensitivity of 82.1% and specificity of 84.4%.&#x0D; Conclusion Peak systolic velocity in middle cerebral artery can be explored further as a dependable screening tool to evaluate intracranial pressure among patients with severe traumatic brain injury in settings with unavailability of invasive intracranial pressure monitoring facilities.

Global and intertuberal epileptic networks in tuberous sclerosis based on stereoelectroencephalographic (sEEG) findings: a quantitative EEG analysis in pediatric subjects and surgical implications.

Recent evidence favors a network concept in tuberous sclerosis (TSC) with seizure generation and propagation related to changes in global and regional connectivity between multiple, anatomically distant tubers. Direct exploration of network dynamics in TSC has been made possible through intracranial sampling with stereoelectroencephalography (sEEG). The objective of this study is to define epileptic networks in TSC using quantitative analysis of sEEG recordings. We also discuss the impact of the definition of these epileptic networks on surgical decision-making. Intracranial sEEG recordings were obtained from four pediatric patients who presented with medically refractory epilepsy secondary to TSC and subjected to quantitative signal analysis methods. Cortical connectivity was quantified by calculating pairwise coherence between all contacts and constructing an association matrix. The global coherence, defined as the ratio of the largest eigenvalue to the sum of all the eigenvalues, was calculated for each frequency band (delta, theta, alpha, beta, gamma). Spatial distribution of the connectivity was identified by plotting the leading principal component (product of the largest eigenvalue and its corresponding eigenvector). Four pediatric subjects with TSC underwent invasive intracranial monitoring with sEEG, comprising 31 depth electrodes and 250 contacts, for localization of the epileptogenic focus and guidance of subsequent surgical intervention. Quantitative connectivity analysis revealed a change in global coherence during the ictal period in the beta/low gamma (14-30Hz) and high gamma (31-80Hz) bands. Our results corroborate findings from existing literature, which implicate higher frequencies as a driver of synchrony and desynchrony. Coordinated high-frequency activity in the beta/low gamma and high gamma bands among spatially distant sEEG define the ictal period in TSC. This time-dependent change in global coherence demonstrates evidence for intra-tuberal and inter-tuberal connectivity in TSC. This observation has surgical implications. It suggests that targeting multiple tubers has a higher chance of seizure control as there is a higher chance of disrupting the epileptic network. The use of laser interstitial thermal therapy (LITT) allowed us to target multiple disparately located tubers in a minimally invasive manner with good seizure control outcomes.

Correlation between Invasive Intracranial Pressure Monitoring and Optic Nerve Sheath Diameter in Patients with Traumatic Brain Injury

Background In management of patients with traumatic brain injury, intracranial pressure holds an important place. Any untoward rise in intracranial pressure portends dreaded complications. Hence, any delay in detecting the issue is considered unacceptable.&#x0D; Objective This study focuses on analyzing the correlation between ultrasound derived optic nerve sheath diameter and intracranial pressure values derived from invasive intracranial pressure monitoring system in a neurosurgical patient with severe traumatic brain injury.&#x0D; Method A prospective observational study was performed using a convenience sample technique including all adult patients with traumatic brain injury who had invasive intracranial monitors placed as part of their clinical care. Ocular ultrasound was performed with 5 - 7.5 MHz linear probe of ACUSON X300 ultrasound system while simultaneous intracranial pressure readings were obtained directly from an invasive intracranial pressure monitoring system. The association between optic nerve sheath diameter and invasive intracranial pressure reading was assessed with the Pearson’s correlation coefficient and a receiver operator characteristic curve was created to determine the optimal optic nerve sheath diameter cutoff to detect intracranial pressure &gt; 15 cm H2O.&#x0D; Result One hundred and fifteen ocular ultrasounds were performed on 30 individual patients. The mean age of the population involved in this study is 42.13 years ± 1.89 with male preponderance in the ratio of 6:1. Pearson’s correlation coefficient of optic nerve sheath diameter and intracranial pressure was found to be 0.844 (p &lt; 0.000) demonstrating a significant positive correlation. The area under the receiver operating characteristic curve was found to be 0.961 (95% confidence interval = 0.93 to 0.99). Based on analysis of the receiver operating characteristic curve, optic nerve sheath diameter &gt; 4.85 mm performed best to detect intracranial pressure &gt; 15 cm H2O with a sensitivity of 93.5% and specificity of 83%.&#x0D; Conclusion Optic nerve sheath diameter is a dependable screening tool to evaluate for elevated intracranial pressure among patients with traumatic nerve injury.

Implications of genetic diagnostics in epilepsy surgery candidates: A single-center cohort study.

ObjectiveGenetic causes are increasingly identified in patients with focal epilepsy. These genetic causes may be related to the effectiveness of epilepsy surgery. We aimed to assess the use and yield of genetic testing in a large cohort of patients who were evaluated for epilepsy surgery.MethodsWe performed a retrospective single‐center consecutive cohort study of patients who were evaluated for surgery between 1990 and 2016. Within this cohort, we assessed the use of genetic testing—either before or after presurgical decision‐making. We evaluated genetic results as well as the outcome of presurgical decision‐making and surgery, and compared these end points for different subgroups—especially MRI‐positive vs MRI‐negative patients. Patients with tuberous sclerosis (TSC) and KRIT1 mutations were excluded from analysis.ResultsOf the 2385 epilepsy patients who were evaluated for surgery, 1280 (54%) received surgical treatment in our center. Of the entire cohort, 325 (14%) underwent genetic testing, comprising 156 of 450 MRI‐negative patients (35%) vs 169 of 1935 MRI‐positive patients (9%). A genetic cause of epilepsy was found in 40 of the 325 patients (12%, 2% of the entire cohort), mainly consisting of mutations in ion channel function and synaptic transmission genes, and mTOR pathway gene mutations. Three of the seven patients with mTOR pathway gene mutations underwent surgery; two achieved complete seizure freedom. One of the 17 patients with germline mutations in ion channel function and synaptic transmission genes received resective surgery but was not rendered seizure‐free; two other patients underwent invasive intracranial EEG‐monitoring before being rejected.SignificanceThis study shows that genetic testing is increasingly applied in focal epilepsy patients who are considered for epilepsy surgery. The diagnostic yield of genetic testing is highest in next generation sequencing techniques, and the outcome of genetic testing assists selecting eligible patients for invasive intracranial monitoring and resective surgery.

Global and Intertuberal Epileptic Networks in Tuberous Sclerosis Based on Stereoelectroencephalographic (sEEG) Findings: A Quantitative EEG Analysis in Pediatric Subjects and Surgical Implications

Abstract INTRODUCTION Recent evidence favors a network concept in tuberous sclerosis complex (TSC) with seizure generation and propagation related to changes in global and regional connectivity between multiple, anatomically distant tubers. Direct exploration of network dynamics in TSC has been made possible through intracranial sampling with stereoelectroencephalography (sEEG). The objective of this study is to define epileptic networks in TSC using quantitative analysis of sEEG recordings. METHODS Intracranial sEEG recordings were obtained from pediatric patients who presented with medically refractory epilepsy secondary to TSC and subjected to quantitative signal analysis methods. Cortical connectivity was quantified by calculating pairwise coherence between all contacts and constructing an association matrix. The global coherence, defined as the ratio of the largest eigenvalue to the sum of all the eigenvalues, was calculated for each frequency band (delta, theta, alpha, beta, gamma). Spatial distribution of the connectivity was identified by plotting the leading principal component (product of the largest eigenvalue and its corresponding eigenvector). RESULTS Four pediatric subjects with TSC underwent invasive intracranial monitoring with sEEG, comprising 31 depth electrodes and 250 contacts, for localization of the epileptogenic focus and guidance of subsequent surgical intervention. Quantitative connectivity analysis revealed a sustained increase in global coherence during the ictal period in the beta/low gamma (14-30 Hz) and high gamma (31-80 Hz) bands. Our results corroborate findings from existing literature, which implicate higher frequencies as a driver of synchrony and desynchrony. Late delta activity was noted in the postictal period. CONCLUSION Epileptic networks, characterized by coordinated high frequency activity in the beta/low gamma and high gamma bands define the ictal period in TSC. This time-dependent increase in global coherence demonstrates evidence for intratuberal, intertuberal, and perituberal connectivity in TSC. These findings have surgical implications for targeted laser ablation or surgical resection of tubers.

Approach Angle Affects Accuracy in Robotic Stereoelectroencephalography Lead Placement

One third of patients with epilepsy fail to gain optimal control using antiepileptic drugs. New advances in epilepsy surgery have reshaped some diagnostic and therapeutic modalities into less invasive approaches. To understand the cortical epileptogenic networks, stereoelectroencephalography uses depth electrodes as a tool for invasive intracranial monitoring. These electrodes are now being placed using a robot instead of the traditional Talairach stereotactic grid and frame with comparable accuracy and the advantage of shortened surgical time. Whereas accuracy is important for correct cortical sampling and surgical morbidity, the factors that play a role in the deviation of the electrode's trajectory are not yet understood. The aim of this study was to determine if the angle the planned trajectory makes with the skull impacts the final accuracy of placement. Twenty-five patients with 319 stereotactic trajectories were examined. Skew angle and accuracy measurements were computed based on preoperative and postoperative computed tomography scans fused with trajectories planned using ROSA robot software. Trajectories with a planned angle of >30° (oblique group) had significantly higher radial error (2.05 mm vs. 1.45 mm, P < 0.001) than trajectories with planned angles <30° (orthogonal group). The ROSA robotic system is a powerful tool that increases the speed and efficiency of stereotactic neurosurgery. Care should be taken when planning trajectories to avoid high skew angles. If a high skew angle is unavoidable, care should be taken to ensure a larger margin of safety.

Abstract 147: Individualized Blood Pressure Management After Subarachnoid Hemorrhage Using Real-time Autoregulation Monitoring: A Pilot Study Using NIRS and ICP-derived Limits of Autoregulation

Introduction: Optimal blood pressure (BP) targets in the early stages of aneurysmal subarachnoid hemorrhage (aSAH) prior to occurrence of clinical vasospasm have not been well established. It is unclear which patients are ideal candidates for therapeutic BP manipulation. To determine the association of individualized autoregulation-based BP targets on functional outcome, we continuously measured limits of autoregulation (LA) in SAH patients. Methods: We prospectively enrolled 7 patients with aSAH who underwent multimodality neuromonitoring. Autoregulatory function was continuously measured by interrogating changes in arterial BP and intracranial pressure (ICP) or the near-infrared spectroscopy (NIRS) derived tissue-oxygenation index. Resulting indices of autoregulation were used to identify the BP of individual patients at which autoregulation was best preserved (MAPopt). A time trend of MAPopt with upper and lower limits of autoregulation (ULA, LLA) provided dynamically updated targets for BP control, and percent time within and outside LA was computed for each patient (Fig 1A). Functional outcome was assessed using the modified Rankin Scale (mRS) at discharge and 90 days. Results: Identification of MAPopt was possible in all patients (mean age 59, 3 male, mean WFNS 2.1) with an average monitoring time of 62.8h starting within 24h of SAH. A high degree of correlation was observed between invasive (ICP) and non-invasive (NIRS) modalities for calculation of MAPopt (r=0.91, p=0.01). The median time spent within optimal BP range was 51.4%, and percent time outside LA showed a linear association with worse functional outcomes (Fig 1B). Conclusions: Calculation of personalized autoregulation-based BP targets after SAH is feasible; BP management outside LA may increase the risk for worse functional outcomes. Non-invasive NIRS-based methods could provide a reasonable alternative for patients for whom invasive intracranial monitoring is not indicated.

"Saved by the Bell": Near SUDEP during intracranial EEG monitoring.

Summary SUDEP is the sudden unexpected death of a person with epilepsy, when no structural or toxicological cause of death can be found. The majority of witnessed cases are reported to be preceded by a convulsive seizure and postictal hypoventilation. Here, we report an 8‐year‐old girl with drug‐resistant focal seizures secondary to a focal cortical dysplasia type IIb. While undergoing invasive intracranial monitoring with subdural and depth electrodes, she had a clinical apnea event recorded on video, followed by bradycardia, which required resuscitation. Her intracranial electroencephalogram (EEG) during the event showed diffuse slowing and attenuation of cortical activity, with bradycardia that responded to positive pressure ventilation with oxygen. This near SUDEP event was not preceded by either an electroclinical or electrographic seizure. This is the first report of a witnessed, near‐SUDEP event during intracranial monitoring. It emphasizes the fact that near‐SUDEP can occur without a preceding seizure.

Diagnostic evaluation and surgical management of pediatric insular epilepsy utilizing magnetoencephalography and invasive EEG monitoring

IntroductionThe diagnosis and surgical management of pediatric patients with insular epilepsy is challenging due to variable and indistinct seizure semiology arising within the insular cortex. In addition, surgical approaches are associated with potential morbidity given the regional neurosurgical and vascular anatomy. Our institutional experience in evaluation and surgical management of insular epilepsy patients is presented. Diagnostic evaluation, surgical treatment and seizures outcomes are highlighted. MethodsThe institutional database for all pediatric surgical epilepsy patients was reviewed over a period of 15 years (2000–2015). Study subjects were defined as patients who had undergone surgical resection of the epileptogenic zone involving the insular cortex. Diagnostic imaging, electrophysiological studies and surgical records were assessed. ResultsSix (n = 6) patients with insular epilepsy were identified with a mean follow up of 2.8 years (range: 0.8–6.8 years). Mean age at surgical resection was 9.5 ± 2.5 years (range: 2.5–16 years). Majority of patients (n = 4/6, 67%) underwent more than 1 surgical procedure. Magnetoencephalography (MEG) identified insular cortex involvement presurgically in all cases. MEG cluster localization was useful in guiding invasive EEG monitoring in 5 patients and was concordant with identification of epileptogenic zone through intracranial monitoring in all 5 patients. Surgical resection of the epileptogenic zone, as delineated through MEG spike sources and invasive EEG monitoring, was associated with favorable seizure outcome in 4 of 6 patients (67%; Engel Class I). Cortical dysgenesis was identified on histopathology in 4 cases. ConclusionDiagnostic evaluation through invasive and noninvasive electrophysiological studies is critical to identify pediatric patients with insular epilepsy. Our findings suggest that MEG may help with identifying the epileptogenic zone within the insular cortex, which could be confirmed with invasive intracranial monitoring.

Complications of invasive intracranial pressure monitoring devices in neurocritical care.

Intracranial pressure monitoring devices have become the standard of care for the management of patients with pathologies associated with intracranial hypertension. Given the importance of invasive intracranial monitoring devices in the modern neurointensive care setting, gaining a thorough understanding of the potential complications related to device placement-and misplacement-is crucial. The increased prevalence of intracranial pressure monitoring as a management tool for neurosurgical patients has led to the publication of a plethora of papers regarding their indications and complications. The authors aim to provide a concise review of key contemporary articles in the literature concerning important complications with the hope of elucidating practices that improve outcomes for neurocritically ill patients.

1. Across all the seven seas: Fifty years in neurology, EEG and epilepsies

Since the 1960s, major neuroscience advances have facilitated the development of new antiepilepsy drugs (AEDs) targeting specific neurotransmitter-receptor systems, particularly the GABAergic, the NMDA-receptors and voltage-gated ion channels. In addition to the classical AEDs, carbamazepine and cogeners act at the voltage-gates sodium channels, while ethosuxumide acts at the calcium channel, improving the treatment of partial and generalized seizures. But approximately 30% of partial complex seizures remain refractory to AEDs, leading to novel AEDs: levetiracetam, tiagabine, lacosamide, perampanel and others. The pharmacoresistant epilepsies are typically dyscognitive partial-onset, arising from limbic structures of mesial temporal lobes, better visualised by improved neuroimaging methods eg. MRI and PET. Together with invasive intracranial monitoring in specialized units with long-term recording of multichannelled EEG and videorecording of behaviour, the localization of the seizure-onset zone has allowed targeted excision of the epileptogenic tissue for better outcome. Functional neurosurgical methods include vagal nerve stimulation and deep brain stimulation of selected targets in affected circuits, mapped by new EEG criteria including gamma rhythm, HFOs, ripples and clusters. Novel intervention in refractory epilepsies include the ketogenic diet and variants, neurosteroids, hormones eg. progestins and ACTH. A number of genetic mutations and copy number variants have been linked to epilepsies. It remains to be seen how expanded knowledge of the genetic bases of the epilepsies and epileptic encephalopathies leads to new intervention improving long-term prognosis and quality of life in persons afflicted with this ancient curse of the human condition, ‘The Falling Sickness’ also known as ‘The Sacred Disease’ (Hippocrates). In the words of Sir William Osler: ‘He who studies medicine without books sails an uncharted sea, but he who studies medicine without patients does not go to sea at all’ (‘Aequanimitas’ by Osler), quoted in Herbert Ho Ping Kong, ‘The Art of Medicine: Healing and the Limits of Technology’ (ECW Press, 2014 Toronto).