Epilepsy is a debilitating neurological disorder affecting approximately 1 % of the world's population. Drug-resistant focal epilepsies are potentially surgically remediable. Although epilepsy surgery is dramatically underutilized among medically refractory patients, there is an expanding collection of evidence supporting its efficacy which may soon compel a paradigm shift. Of note is that a recent randomized controlled trial demonstrated that early resection leads to considerably better seizure outcomes than continued medical therapy in patients with pharmacoresistant temporal lobe epilepsy. In the present review, we provide a timely update of seizure freedom rates and predictors in resective epilepsy surgery, organized by the distinct pathological entities most commonly observed. Class I evidence, meta-analyses, and individual observational case series are considered, including the experiences of both our institution and others. Overall, resective epilepsy surgery leads to seizure freedom in approximately two thirds of patients with intractable temporal lobe epilepsy and about one half of individuals with focal neocortical epilepsy, although only the former observation is supported by class I evidence. Two common modifiable predictors of postoperative seizure freedom are early operative intervention and, in the case of a discrete lesion, gross total resection. Evidence-based practice guidelines recommend that epilepsy patients who continue to have seizures after trialing two or more medication regimens should be referred to a comprehensive epilepsy center for multidisciplinary evaluation, including surgical consideration.

In approximately 30 % of patients with epilepsy, seizures are refractory to medical therapy, leading to significant morbidity and increased mortality. Substantial evidence has demonstrated the benefit of surgical resection in patients with drug-resistant focal epilepsy, and in the present journal, we recently reviewed seizure outcomes in resective epilepsy surgery. However, not all patients are candidates for or amenable to open surgical resection for epilepsy. Fortunately, several nonresective surgical options are now available at various epilepsy centers, including novel therapies which have been pioneered in recent years. Ablative procedures such as stereotactic laser ablation and stereotactic radiosurgery offer minimally invasive alternatives to open surgery with relatively favorable seizure outcomes, particularly in patients with mesial temporal lobe epilepsy. For certain individuals who are not candidates for ablation or resection, palliative neuromodulation procedures such as vagus nerve stimulation, deep brain stimulation, or responsive neurostimulation may result in a significant decrease in seizure frequency and improved quality of life. Finally, disconnection procedures such as multiple subpial transections and corpus callosotomy continue to play a role in select patients with an eloquent epileptogenic zone or intractable atonic seizures, respectively. Overall, open surgical resection remains the gold standard treatment for drug-resistant epilepsy, although it is significantly underutilized. While nonresective epilepsy procedures have not replaced the need for resection, there is hope that these additional surgical options will increase the number of patients who receive treatment for this devastating disorder-particularly individuals who are not candidates for or who have failed resection.

Surgery can be a highly effective treatment for medically refractory temporal lobe epilepsy (TLE). The emergence of minimally invasive resective and nonresective treatment options has led to interest in epilepsy surgery among patients and providers. Nevertheless, not all procedures are appropriate for all patients, and it is critical to consider seizure outcomes with each of these approaches, as seizure freedom is the greatest predictor of patient quality of life. Standard anterior temporal lobectomy (ATL) remains the gold standard in the treatment of TLE, with seizure freedom resulting in 60-80% of patients. It is currently the only resective epilepsy surgery supported by randomized controlled trials and offers the best protection against lateral temporal seizure onset. Selective amygdalohippocampectomy techniques preserve the lateral cortex and temporal stem to varying degrees and can result in favorable rates of seizure freedom but the risk of recurrent seizures appears slightly greater than with ATL, and it is not clear whether neuropsychological outcomes are improved with selective approaches. Stereotactic radiosurgery presents an opportunity to avoid surgery altogether, with seizure outcomes now under investigation. Stereotactic laser thermo-ablation allows destruction of the mesial temporal structures with low complication rates and minimal recovery time, and outcomes are also under study. Finally, while neuromodulatory devices such as responsive neurostimulation, vagus nerve stimulation, and deep brain stimulation have a role in the treatment of certain patients, these remain palliative procedures for those who are not candidates for resection or ablation, as complete seizure freedom rates are low. Further development and investigation of both established and novel strategies for the surgical treatment of TLE will be critical moving forward, given the significant burden of this disease.

Seizures are common in patients with brain tumors, and epilepsy can significantly impact patient quality of life. Therefore, a thorough understanding of rates and predictors of seizures, and the likelihood of seizure freedom after resection, is critical in the treatment of brain tumors. Among all tumor types, seizures are most common with glioneuronal tumors (70-80%), particularly in patients with frontotemporal or insular lesions. Seizures are also common in individuals with glioma, with the highest rates of epilepsy (60-75%) observed in patients with low-grade gliomas located in superficial cortical or insular regions. Approximately 20-50% of patients with meningioma and 20-35% of those with brain metastases also suffer from seizures. After tumor resection, approximately 60-90% are rendered seizure-free, with most favorable seizure outcomes seen in individuals with glioneuronal tumors. Gross total resection, earlier surgical therapy, and a lack of generalized seizures are common predictors of a favorable seizure outcome. With regard to anticonvulsant medication selection, evidence-based guidelines for the treatment of focal epilepsy should be followed, and individual patient factors should also be considered, including patient age, sex, organ dysfunction, comorbidity, or cotherapy. As concomitant chemotherapy commonly forms an essential part of glioma treatment, enzyme-inducing anticonvulsants should be avoided when possible. Seizure freedom is the ultimate goal in the treatment of brain tumor patients with epilepsy, given the adverse effects of seizures on quality of life.

BACKGROUND/AIMS:Interventional MRI (iMRI) allows real-time confirmation of electrode and microcatheter location in anesthetized patients; however, MRI-compatible pneumatic compression devices (PCD) to reduce the periprocedural venous thromboembolism (VTE) risk are not commercially available. Given the paucity of literature on VTE following iMRI surgery, better characterizing patients suffering this complication and the incidence of this event following iMRI procedures is pivotal for defining best surgical practices. We aim to investigate the incidence of postoperative VTE in iMRI procedures without the use of PCD. METHODS:Medical records and operative times of patients were retrospectively reviewed. Patient demographics and mean surgical durations were reported with statistical comparisons via ANOVA and the 2-tailed Student t test, an α of 0.05, and the Bonferroni correction. Patients experiencing postoperative VTE underwent an in-depth chart review. RESULTS:Two out of two hundred ten (0.95%) iMRI procedures resulted in postoperative VTE events. There were statistically significant differences in procedure times between unilateral electrode (157.5 ± 5.7 min), bilateral electrode (193.6 ± 2.9 min), and bilateral gene therapy procedures (467.3 ± 26.5 min). Both patients had longer-than-average operative times for their respective procedures. CONCLUSIONS:The incidence of postoperative VTE is low following iMRI procedures, even without the use of PCD during surgery.

Epilepsy surgery is under-utilized, but recent studies reach conflicting conclusions regarding whether epilepsy surgery rates are currently declining, increasing, or remaining steady. However, data in these prior studies are biased toward high-volume epilepsy centers, or originate from sources that do not disaggregate various procedure types. All major epilepsy surgery procedures were extracted from the Centers for Medicare and Medicaid Services Part B National Summary Data File and the American College of Surgeons National Surgical Quality Improvement Program. Procedure rates, trends, and complications were analyzed, and patient-level predictors of postoperative adverse events were identified. Between 2000-2013, 6200 cases of epilepsy surgery were identified. Temporal lobectomy was the most common procedure (59% of cases), and most did not utilize electrocorticography (63-64%). Neither temporal nor extratemporal lobe epilepsy surgery rates changed significantly during the study period, suggesting no change in utilization. Adverse events, including major and minor complications, occurred in 15.3% of temporal lobectomies and 55.6% of hemispherectomies. Our findings suggest stagnant rates of both temporal and extratemporal lobe epilepsy surgery across U.S. surgical centers over the past decade. This finding contrasts with prior reports suggesting a recent dramatic decline in temporal lobectomy rates at high-volume epilepsy centers. We also observed higher rates of adverse events when both low- and high-volume centers were examined together, as compared to reports from high-volume centers alone. This is consistent with the presence of a volume-outcome relationship in epilepsy surgery.

Atonic seizures are debilitating and poorly controlled with antiepileptic medications. Two surgical options are primarily used to treat medically refractory atonic seizures: corpus callosotomy (CC) and vagus nerve stimulation (VNS). However, given the uncertainty regarding relative efficacy and surgical complications, the best approach for affected patients is unclear. The PubMed database was queried for all articles describing the treatment of atonic seizures and drop attacks with either corpus callosotomy or VNS. Rates of seizure freedom, >50% reduction in seizure frequency, and complications were compared across the two patient groups. Patients were significantly more likely to achieve a >50% reduction in seizure frequency with CC versus VNS (85.6% versus 57.6%; RR: 1.5; 95% CI: 1.1-2.1). Adverse events were more common with VNS, though typically mild (e.g., 22% hoarseness and voice changes), compared with CC, where the most common complication was the disconnection syndrome (13.2%). Both CC and VNS are well tolerated for the treatment of refractory atonic seizures. Existing studies suggest that CC is potentially more effective than VNS in reducing seizure frequency, though a direct study comparing these techniques is required before a definitive conclusion can be reached.

Objective

Corpus callosotomy is a palliative surgery for drug-resistant epilepsy that reduces the severity and frequency of generalized seizures by disconnecting the two cerebral hemispheres. Unlike with resection, seizure outcomes remain poorly understood. The authors systematically reviewed the literature and performed a meta-analysis to investigate rates and predictors of complete seizure freedom and freedom from drop attacks after corpus callosotomy.

Methods

PubMed, Web of Science, and Scopus were queried for primary studies examining seizure outcomes after corpus callosotomy published over 30 years. Rates of complete seizure freedom or drop attack freedom were recorded. Variables showing a potential relationship to seizure outcome on preliminary analysis were subjected to formal meta-analysis.

Results

The authors identified 1742 eligible patients from 58 included studies. Overall, the rates of complete seizure freedom and drop attack freedom after corpus callosotomy were 18.8% and 55.3%, respectively. Complete seizure freedom was significantly predicted by the presence of infantile spasms (OR 3.86, 95% CI 1.13-13.23), normal MRI findings (OR 4.63, 95% CI 1.75-12.25), and shorter epilepsy duration (OR 2.57, 95% CI 1.23-5.38). Freedom from drop attacks was predicted by complete over partial callosotomy (OR 2.90, 95% CI 1.07-7.83) and idiopathic over known epilepsy etiology (OR 2.84, 95% CI 1.35-5.99).

Conclusions

The authors report the first systematic review and meta-analysis of seizure outcomes in both adults and children after corpus callosotomy for epilepsy. Approximately one-half of patients become free from drop attacks, and one-fifth achieve complete seizure freedom after surgery. Some predictors of favorable outcome differ from those in resective epilepsy surgery.

Introduction

Deep brain stimulation (DBS) is an established therapy for movement disorders, and is under active investigation for other neurologic and psychiatric indications. While many studies describe outcomes and complications related to stimulation therapies, the majority of these are from large academic centers, and results may differ from those in general neurosurgical practice.

Methods

Using data from both the Centers for Medicare and Medicaid Services (CMS) and the National Surgical Quality Improvement Program (NSQIP), we identified all DBS procedures related to primary placement, revision, or removal of intracranial electrodes. Cases of cortical stimulation and stimulation for epilepsy were excluded.

Results

Over 28,000 cases of DBS electrode placement, revision, and removal were identified during the years 2004-2013. In the Medicare dataset, 15.2% and of these procedures were for intracranial electrode revision or removal, compared to 34.0% in the NSQIP dataset. In NSQIP, significant predictors of revision and removal were decreased age (odds ratio (OR) of 0.96; 95% CI: 0.94, 0.98) and higher ASA classification (OR 2.41; 95% CI: 1.22, 4.75). Up to 48.5% of revisions may have been due to improper targeting or lack of therapeutic effect.

Conclusion

Data from multiple North American databases suggest that intracranial neurostimulation therapies have a rate of revision and removal higher than previously reported, between 15.2 and 34.0%. While there are many limitations to registry-based studies, there is a clear need to better track and understand the true prevalence and nature of such failures as they occur in the wider surgical community.

Invasive electrocorticography (ECoG) is used in patients when it is difficult to localize epileptogenic foci for potential surgical resection. As MR neuroimaging has improved over the past decade, we hypothesized the utilization of ECoG diminishing over time. Using the USA Nationwide Inpatient Sample, we collected demographic and complication data on patients receiving ECoG over the years 1988-2008 and compared this to patients with medically refractory epilepsy during the same time period. A total of 695 cases using extraoperative ECoG were identified, corresponding to 3528 cases nationwide and accounting for 1.1% of patients with refractory epilepsy from 1988-2008. African Americans were less likely to receive ECoG than whites, as were patients with government insurance in comparison to those with private insurance. Large, urban, and academic hospitals were significantly more likely to perform ECoG than smaller, rural, and private practice institutions. The most frequent complication was cerebrospinal fluid leak (11.7%) and only one death was reported from the entire cohort, corresponding to an estimated six patients nationally. Invasive ECoG is a relatively safe procedure offered to a growing number of patients with refractory epilepsy each year. However, these data suggest the presence of demographic disparities in those patients receiving ECoG, possibly reflecting barriers due to race and socioeconomic status. Among patients with nonlocalized seizures, ECoG often represents their only hope for surgical treatment. We therefore must further examine the indications and efficacy of ECoG, and more work must be done to understand if and why ECoG is preferentially performed in select socioeconomic groups.