Gamma Knife Surgery in Mesial Temporal Lobe Epilepsy: A Prospective Multicenter Study

Innovative minimally invasive options to treat drug-resistant epilepsies

Despite the regular discovery of new molecules, one-third of epileptic patients are resistant to antiepileptic drugs. Only a few can benefit from resective surgery, the current gold standard. Although effective in 50-70% of cases, this therapy remains risky, costly, and can be associated with long-term cognitive or neurological side effects. In addition, patients are increasingly reluctant to have a craniotomy, emphasizing the need for new less invasive therapies for focal drug-resistant epilepsies. Here, we review different minimally invasive approaches already in use in the clinic or under preclinical development to treat drug-resistant epilepsies. Localized thermolesion of the epileptogenic zone has been developed in the clinic using high-frequency thermo-coagulations or magnetic resonance imaging-guided laser or ultrasounds. Although less invasive, they have not yet significantly improved the outcomes when compared with resective surgery. Radiosurgery techniques have been used in the clinic for the last 20years and have proven efficiency. However, their efficacy is not better than resective surgery, and various side effects have been reported as well as the potential risk of sudden unexpected death associated with epilepsy. Recently, a new strategy of radiosurgery has emerged using synchrotron-generated X-ray microbeams: microbeam radiation therapy (MRT). The low divergence and high-flux of the synchrotron beams and the unique tolerance to MRT by healthy brain tissues, allows a precise targeting of specific brain regions with minimal invasiveness and limited behavioral or functional consequences in animals. Antiepileptic effects over several months have been recorded in animal models, and histological and synaptic tracing analysis suggest a reduction of neuronal connectivity as a mechanism of action. The possibility of transferring this approach to epileptic patients is discussed in this review.

A Potential Risk of Radiation-Induced Cavernous Malformations Following Adjuvant Gamma Knife Radiosurgery for Mesial Temporal Lobe Epilepsy

OBJECTIVE

Several clinical studies have explored the feasibility and efficacy of radiosurgical treatment for mesial temporal lobe epilepsy, but the long-term safety of this treatment has not been fully characterized. This study aims to report and describe radiation-induced cavernous malformation as a delayed complication of radiosurgery in epilepsy patients.

METHODS

The series includes 20 patients with mesial temporal lobe epilepsy who underwent Gamma Knife radiosurgery (GKRS). The majority received a prescribed isodose of 24 Gy as an adjuvant treatment after anterior temporal lobectomy.

RESULTS

In this series, we identified radiation-induced cavernous malformation in three patients, resulting in a cumulative incidence of 18.4% (95% confidence interval, 6.3% to 47.0%) at an 8-year follow-up. These late sequelae of vascular malformation occurred between 6.9 and 7.6 years after GKRS, manifesting later than other delayed radiation-induced changes, such as radiation necrosis. Neurological symptoms attributed to intracranial hypertension were present in those three cases involving cavernous malformation. Of these, two cases, which initially exhibited an insufficient response to radiosurgery, ultimately demonstrated seizure remission following the successful microsurgical resection of the cavernous malformation.

CONCLUSION

All things considered, the development of radiation-induced cavernous malformation is not uncommon in this population and should be acknowledged as a potential long-term complication. Microsurgical resection of cavernous malformation can be preferentially considered in cases where the initial seizure outcome after GKRS is unsatisfactory.

Epilepsy

GKNS has been introduced as an alternative to microsurgery for the treatment of certain types of focal epilepsy. It was first noted that epilepsy associated with AVMs often improved before the obliteration of the vascular lesion. It was subsequently shown that the treatment could be effective in mesial temporal lobe epilepsy (MTLE) producing remission in around 60% of patients, provided the treatment was carried out as originally designed. GKNS has also been useful in the treatment of gelastic epilepsy associated with hypothalamic hamartomas.

Corpus Callosotomy in the Modern Era: Origins, Efficacy, Technical Variations, Complications, and Indications

Corpus callosotomy is among the oldest surgeries performed for drug-resistant epilepsy (DRE). First performed in 1940, various studies have since assessed its outcomes in various patient populations in addition to describing different extents of sectioning and emerging technologies (i.e. endoscopic, laser interstitial thermal therapy, and radiosurgery). In order to capture the current state and offer a reappraisal, we comprehensively review corpus callosotomy's origins, efficacy for various seizure types, technical variations, complications, and indications and compare the procedure to vagus nerve stimulation therapy which has similar indications. We consider corpus callosotomy to be a safe and efficacious procedure that should be considered by clinicians when appropriate. Furthermore, it can also play an important role in treating patients with DRE in low-to-middle-income countries where resources are limited.

Surgery procedures in temporal lobe epilepsies

Temporal lobe epilepsy (TLE) is the most common cause of refractory epilepsy amenable for surgical treatment and seizure control. Surgery for TLE is a safe and effective strategy. The seizure-free rate after surgical resection in patients with mesial or neocortical TLE is about 70%. Resective surgery has an advantage over stereotactic radiosurgery in terms of seizure outcomes for mesial TLE patients. Both techniques have similar results for safety, cognitive outcomes, and associated costs. Stereotactic radiosurgery should therefore be seen as an alternative to open surgery for patients with contraindications for or with reluctance to undergo open surgery. Laser interstitial thermal therapy (LITT) has also shown promising results as a curative technique in mesial TLE but needs to be more deeply evaluated. Brain-responsive stimulation represents a palliative treatment option for patients with unilateral or bilateral MTLE who are not candidates for temporal lobectomy or who have failed a prior mesial temporal lobe resection. Overall, despite the expansion of innovative techniques in recent years, resective surgery remains the reference treatment for TLE and should be proposed as the first-line surgical modality. In the future, ultrasound therapies could become a credible therapeutic option for refractory TLE patients.

Resective, Ablative and Radiosurgical Interventions for Drug Resistant Mesial Temporal Lobe Epilepsy: A Systematic Review and Meta-Analysis of Outcomes

Objectives: One-third of individuals with focal epilepsy do not achieve seizure freedom despite best medical therapy. Mesial temporal lobe epilepsy (MTLE) is the most common form of drug resistant focal epilepsy. Surgery may lead to long-term seizure remission if the epileptogenic zone can be defined and safely removed or disconnected. We compare published outcomes following open surgical techniques, radiosurgery (SRS), laser interstitial thermal therapy (LITT) and radiofrequency ablation (RF-TC). Methods: PRISMA systematic review was performed through structured searches of PubMed, Embase and Cochrane databases. Inclusion criteria encompassed studies of MTLE reporting seizure-free outcomes in ≥10 patients with ≥12 months follow-up. Due to variability in open surgical approaches, only comparative studies were included to minimize the risk of bias. Random effects meta-analysis was performed to calculate effects sizes and a pooled estimate of the probability of seizure freedom per person-year. A mixed effects linear regression model was performed to compare effect sizes between interventions. Results: From 1,801 screened articles, 41 articles were included in the quantitative analysis. Open surgery included anterior temporal lobe resection as well as transcortical and trans-sylvian selective amygdalohippocampectomy. The pooled seizure-free rate per person-year was 0.72 (95% CI 0.66-0.79) with trans-sylvian selective amygdalohippocampectomy, 0.59 (95% CI 0.53-0.65) with LITT, 0.70 (95% CI 0.64-0.77) with anterior temporal lobe resection, 0.60 (95% CI 0.49-0.73) with transcortical selective amygdalohippocampectomy, 0.38 (95% CI 0.14-1.00) with RF-TC and 0.50 (95% CI 0.34-0.73) with SRS. Follow up duration and study sizes were limited with LITT and RF-TC. A mixed-effects linear regression model suggests significant differences between interventions, with LITT, ATLR and SAH demonstrating the largest effects estimates and RF-TC the lowest. Conclusions: Overall, novel "minimally invasive" approaches are still comparatively less efficacious than open surgery. LITT shows promising seizure effectiveness, however follow-up durations are shorter for minimally invasive approaches so the durability of the outcomes cannot yet be assessed. Secondary outcome measures such as Neurological complications, neuropsychological outcome and interventional morbidity are poorly reported but are important considerations when deciding on first-line treatments.

A Systematic Review of Minimally Invasive Procedures for Mesial Temporal Lobe Epilepsy: Too Minimal, Too Fast?

BACKGROUND

Cortico-amygdalohippocampectomy (CAH) is effective for mesial temporal lobe epilepsy (mTLE). Concerns regarding surgical morbidity have generated enthusiasm for more minimally invasive interventions. A careful analysis of current data is warranted before widespread adoption of these techniques.

OBJECTIVE

To systematically review the use of laser interstitial thermal therapy (LITT), stereotactic radiosurgery (SRS), radiofrequency thermocoagulation (RF-TC), and focused ultrasound for mTLE.

METHODS

Major online databases were searched for prospective observational studies, randomized clinical trials, and retrospective studies (>50 patients), including mTLE patients. Outcomes of interest were seizure freedom (Engel I), complications and re-operation rates, and neuropsychological and quality-of-life (QoL) data.

RESULTS

Nineteen publications were identified. At ≥6 mo postoperatively, LITT (9/19) Engel I outcomes ranged from 52% to 80%. SRS (3/19) has a latency period (52%-67%, 24-36 mo postoperatively) and the radiosurgery vs. open surgery for epilepsy (ROSE) trial reported inferiority of SRS compared to CAH. RF-TC (7/19) demonstrated variable seizure freedom rates (0%-79%) and high re-operation rates (0%-90%). Twelve studies reported neuropsychological outcomes but QoL (4/19) was not widely reported, and few studies (3/19) assessed both. Study quality ranged from fair to good.

CONCLUSION

Based on nonrandomized data, LITT has compelling evidence of efficacy; however, comparisons to surgical resection are lacking. SRS has a latency period and is inferior to CAH (ROSE trial). RF-TC is a less resource-intensive alternative to LITT; however, comparisons of efficacy are limited. Additional studies are needed before minimally invasive procedures can supplant standard surgery.

Radiosurgical Corpus Callosotomy: A Review of Literature

BACKGROUND

Microsurgical callosotomy is a procedure still under debate and to best a palliative treatment for drug-resistant epilepsy. Unlike microsurgery, radiosurgical callosotomy is an underpracticed treatment option, with no definite account of its safety and outcome profile.

OBJECTIVE

To evaluate the safety, efficacy, and complication profile of radiosurgical callosotomy in the literature.

METHODS

PubMed, SCOPUS, Web of Science, and ResearchGate were reviewed for radiosurgery and callosotomy in the English language following PRISMA guidelines. The patient profile, radiosurgical parameters (dose and isodose), target volume, extent of radiosurgery (anterior third, half, or posterior third callosotomy), and seizure outcome were evaluated. We evaluated the role of radiosurgery as a primary or secondary treatment modality after microsurgery. A literature review was performed to identify the evidence of radiosurgery.

RESULTS

We identified 7 studies detailing 12 patients of mean age 22.8 years (range, 4-58 years) and a mean of 18.9 years of illness (range, 5-37 years). Five series performed Gamma Knife radiosurgery and 2 performed LINAC radiosurgery. The spectrum of seizures ranged from atonic seizures/drop attack (83%), generalized tonic-clonic seizures (75%), complex partial seizures (67%), absence seizures (50%), myoclonic seizures (33%), to focal seizures (16%). Four patients suffered from Lennox-Gastaut syndrome. The average seizure frequency in 11 patients was 297/month (range, 20/day to 15/month). Three patients became free of drop attacks and 2 free of generalized tonic-clonic seizures, and 1 became completely seizure free. The remaining patients continued to have seizures, albeit at a lower frequency. Complex partial seizures and myoclonic seizures were the least responsive seizure types to radiosurgical corpus callosotomy. All patients tolerated the procedure well. After radiosurgery, 3 patients developed symptomatic edema. The symptoms (headache, nausea, hemiparesis, and transient neurologic deficits) were controlled with a short course of steroids. Two patients needed redo radiosurgery (at the same target in 1 patient and complementary middle third callosotomy to previous anterior third callosotomy in another patient). There were no long-term complications.

CONCLUSIONS

Radiosurgery is a viable alternative to microsurgical callosotomy both as a primary and as a secondary treatment modality. It has a specific advantage of better neuropsychological outcomes with comparable seizure control. The neurosurgical community should adopt a more liberal approach with this indication.

Completion Corpus Callosotomy with Stereotactic Radiosurgery for Drug-Resistant, Intractable Epilepsy

BACKGROUND

Stereotactic radiosurgery (SRS) offers a noninvasive technique for division of the corpus callosum, which can confer improved seizure control to patients suffering from frequent atonic seizures due to rapid interhemispheric generalization. This noninvasive approach is well-suited for use in a palliative intervention for improved seizure control in this patient population. To our knowledge, this is the first report of radiosurgical completion corpus callosotomy in an adult in the United States.

CASE DESCRIPTION

A 20-year-old ambidextrous nonverbal man with a history of refractory generalized epilepsy status post open anterior corpus callosotomy at age 10 years, Lennox-Gastaut syndrome, and autism presented after 2 years of incremental, progressive deterioration in seizure control and behavior including 1 year. The family decided to pursue SRS corpus callosotomy. Under general anesthesia, a volume of interest encompassing a full midsagittal plane of the corpus callosum was defined to deliver 60 Gy to the 50% isodose line fully encompassing the target. Gamma Knife was used with 2 isocenters at 90° and 1 at 110° and isodose lines of 60, 20, and 12 Gy. Treatment was carried out without difficulty or complications while the patient remained under close monitoring. The patient was discharged the next day with a 2-week taper of dexamethasone.

CONCLUSIONS

Eight months postradiosurgical corpus callosotomy, the patient is free of atonic seizures and is ambulatory. In carefully selected cases and with protective radiosurgical planning, SRS for completion corpus callosotomy represents an effective option for refractory seizure control.

Magnetic resonance-guided focused ultrasound for ablation of mesial temporal epilepsy circuits: modeling and theoretical feasibility of a novel noninvasive approach

OBJECTIVE

The authors tested the feasibility of magnetic resonance-guided focused ultrasound (MRgFUS) ablation of mesial temporal lobe epilepsy (MTLE) seizure circuits. Up to one-third of patients with mesial temporal sclerosis (MTS) suffer from medically refractory epilepsy requiring surgery. Because current options such as open resection, laser ablation, and Gamma Knife radiosurgery pose potential risks, such as infection, hemorrhage, and ionizing radiation, and because they often produce visual or neuropsychological deficits, the authors developed a noninvasive MRgFUS ablation strategy for mesial temporal disconnection to mitigate these risks.

METHODS

The authors retrospectively reviewed 3-T MRI scans obtained with diffusion tensor imaging (DTI). The study group included 10 patients with essential tremor (ET) who underwent pretreatment CT and MRI prior to MRgFUS, and 2 patients with MTS who underwent MRI. Fiber tracking of the fornix-fimbria pathway and inferior optic radiations was performed, ablation sites mimicking targets of open posterior hippocampal disconnection were modeled, and theoretical MRgFUS surgical plans were devised. Distances between the targets and optic radiations were measured, helmet angulations were prescribed, and the numbers of available MRgFUS array elements were calculated.

RESULTS

Tractograms of fornix-fimbria and optic radiations were generated in all ET and MTS patients successfully. Of the 10 patients with both the CT and MRI data necessary for the analysis, 8 patients had adequate elements available to target the ablation site. A margin (mean 8.5 mm, range 6.5-9.8 mm) of separation was maintained between the target lesion and optic radiations.

CONCLUSIONS

MRgFUS offers a noninvasive option for seizure tract disruption. DTI identifies fornix-fimbria and optic radiations to localize optimal ablation targets and critical surrounding structures, minimizing risk of postoperative visual field deficits. This theoretical modeling study provides the necessary groundwork for future clinical trials to apply this novel neurosurgical technique to patients with refractory MTLE and surgical contraindications, multiple prior surgeries, or other factors favoring noninvasive treatment.

[Functional stereotactic radiosurgery: Indications and perspectives]

Stereotactic radiosurgery (SRS) is a non-invasive technique that enables to create brain focal lesions with a high precision and localization. Thus, functional brain disorders can be treated by SRS in case of pharmacoresistance or inoperability. To date, treatment of trigeminal neuralgia is the most described and known indication. Other indications will be developed in the future like movement disorders, refractory epilepsy, obsessive compulsive disorder and severe depression. We present here a review of actual and future indications of functional brain SRS with their level of evidence. All these SRS treatments have to be strictly conducted by trained teams with an excellent collaboration between radiation physicists, medical physicists, neurosurgeons, neurologists, psychiatrists and probably neuroradiologists.

Stereotactic Gamma Ray Radiosurgery to the Centromedian and Parafascicular Complex of the Thalamus for Trigeminal Neuralgia and Other Complex Pain Syndromes

Introduction We report our initial series of patients treated with radiosurgery to the Centromedian (CM) and Parafascicular (Pfc) Complex (CM-Pf) of the contralateral thalamus mainly for trigeminal neuralgia that had failed most known forms of conventional treatments. The coordinates were co-registered to a three-dimensional atlas of the thalamus in order to have a better comprehension of isodose curves distribution. Methods A fully automated rotating gamma ray unit was used to deliver a high dose of radiation (140 Gy) using a 4-mm collimator to the CM-Pf of the contralateral thalamus in 14 patients suffering from refractory trigeminal pain and other complex pain syndromes. The best stereotactic coordinates were plotted in a thalamic three-dimensional atlas space along with isodose curves corresponding to 50% of the dose prescription and the dose gradient. Results From November 2016 to July 2019, 14 patients experiencing severe forms of different pain syndromes were treated, and 10 were eligible for follow-up evaluation. Pain deriving from trigeminal neuralgia was present in the majority (80%) of patients and from other complex pain syndromes in the rest (20%). Median follow-up was 384 days (range: 30-994). The Visual Analogue Scale (VAS) score before treatment was 9 (range: 7-10) and standardized to 10. Before treatment, all the patients had a Barrow Neurological Institute Pain Scale (BNI) of 5 (V). The median years suffering from pain was 4.5 years (range: 1-15), the number of procedures including radiosurgery to the trigeminal nerve before thalamotomy was four (range: 1-10). Most patients (90%) reported some form of relief, the average VAS at the time of response was 3.5 (range: 0-9), and the average time to response was 67.3 days (range: 2-210). The neuromodulation effect of radiation was seen in 60% of patients. The average BNI score at response was 2.7 (range: 1-5). The final VAS score at last follow-up was 5.5 (range: 0-10) in six patients. In four patients (40%), the procedure had failed with a final BNI of IV, and V, three patients (30%) had excellent response (BNI of I), and three patients (30%) had worthwhile results with BNI of IIIa and IIIb. The total success rate (BNI of I to IIIb) was 60%, and the number of patients experiencing more than 50% of pain reduction at final follow-up was five (50%). Excluding both patients that were treated for pain outside of trigeminal neuralgia, 75% of the patients responded. The best coordinates on average were X: 5.5 mm from the thalamic border, Y: 3.7 mm anterior to the posterior commissure, and Z: 3.7 mm from the intercomissural line. There were no complications to report. Conclusion Radiosurgery to the CM-Pf of the thalamus was demonstrated to be a safe and relatively effective alternative to treat refractory trigeminal neuralgia. Further studies are needed to optimize target dimensions based on the three-dimensional studies of isodose curves as well as coordinates. Longer follow-up is necessary to evaluate recurrence rates that could not be reached.

"Laser and the Tuber": thermal dynamic and volumetric factors influencing seizure outcomes in pediatric subjects with tuberous sclerosis undergoing stereoencephalography-directed laser ablation of tubers

PURPOSE

Tuberous sclerosis (TSC) is a well-known cause of medically refractory epilepsy (MRE). Stereoencephalography-directed magnetic resonance-guided laser interstitial thermal therapy (SEEG-directed MRgLITT) is an emerging minimally invasive technique that appears aptly suited for the surgical management of TSC. Our aims are to present our experiences with patients who had undergone SEEG-directed MRgLITT to identify and treat cortical tubers responsible for clinical seizures and to perform an in-depth analysis of volumetric and thermal dynamic factors that may be related to seizure outcomes.

METHODS

We studied all pediatric patients with MRE due to TSC who underwent SEEG-directed MRgLITT, investigating seizure outcomes in relation to thermal dynamic and volumetric factors.

RESULTS

Eight cortical tubers from three pediatric patients were analyzed. Two of three patients had Engel I outcomes at last follow-up (median 18 months). Average A/T (ablation volume/tuber volume) ratio for Engel I outcomes was 1.28 (variance, 0.16) and 0.84 (variance, < 0.01) for all other outcomes (P = 0.035). There was a moderate positive correlation when comparing ablation energy to ablation volume (R² = 0.65) in cortical tuber tissue. When the calcified tuber is excluded, the correlation is stronger (R² = 0.77). Thus, the calculated energy needed to ablate 1 cm³ of cortical tuber tissue is 1263.6 J (calcified tuber) or 1089.5 J (non-calcified tuber).

CONCLUSIONS

SEEG-directed MRgLITT appears to be a safe and effective technique in the management of pediatric patients with MRE due to TSC. The A/T ratio may be a useful indicator in predicting seizure outcomes.

Neuromodulation beyond neurostimulation for epilepsy: scope for focused ultrasound

Introduction: Epilepsy is one of the most common neurological disorders and is often difficult to control with medication. Intractable epilepsy often results in compromised quality of life (QOL), neurologic morbidity and even mortality. In carefully selected cases, resective surgery offers the best potential for cure or seizure control. However, a large proportion of patients are not suitable for resective epilepsy surgery. Neuromodulation techniques are increasingly being used to treat such refractory cases. Recently, the FDA approved Magnetic Resonance-guided Focused Ultrasound (MRgFUS) for essential tremor and this novel technology is also being explored in several other neuropsychiatric conditions and neurological disorders, including epilepsy. Area covered: While the literature is scant and scattered, the pertinent literature of the MRgFUS is reviewed with an emphasis on research relevant to its application for epilepsy. Expert opinion: Limited preliminary clinical experiences and research studies with MRgFUS ablation or neuromodulation for epilepsy have shown promising results; however, this procedure remains experimental requiring further investigations. Safe and reversible opening of the blood-brain barrier (BBB) with MRgFUS adds an additional therapeutic avenue by allowing targeted delivery of neurotherapeutics in neurological disorders, potentially including epilepsy. Ongoing clinical trials and research coupled with technological advancements contribute to strengthening the MRgFUS epilepsy field. MRgFUS could be the future technology of choice for 'ablation' or 'sononeuromodulation', and/or a 'targeted therapeutics' for epilepsy.

Epilepsy diagnosis and management of children in Kenya: review of current literature

Introduction: The growing impact of non-communicable diseases in low- to middle-income countries makes epilepsy a key research priority. We evaluated peer-reviewed published literature on childhood epilepsy specific to Kenya to identify knowledge gaps and inform future priorities. Methodology: A literature search utilizing the terms "epilepsy" OR "seizure" as exploded subject headings AND "Kenya" was conducted. Relevant databases were searched, generating 908 articles. After initial screening to remove duplications, irrelevant articles, and publications older than 15 years, 154 papers remained for full-article review, which identified 35 publications containing relevant information. Data were extracted from these reports on epidemiology, etiology, clinical features, management, and outcomes. Results: The estimated prevalence of lifetime epilepsy in children was 21-41 per 1,000, while the incidence of active convulsive epilepsy was 39-187 cases per 100,000 children per year. The incidence of acute seizures was 312-879 per 100,000 children per year and neonatal seizures 3,950 per 100,000 live births per year. Common risk factors for both epilepsy and acute seizures included adverse perinatal events, meningitis, malaria, febrile seizures, and family history of epilepsy. Electroencephalography abnormalities were documented in 20%-41% and neurocognitive comorbidities in more than half. Mortality in children admitted with acute seizures was 3%-6%, and neurological sequelae were identified in 31% following convulsive status epilepticus. Only 7%-29% children with epilepsy were on antiseizure medication. Conclusion: Active convulsive epilepsy is a common condition among Kenyan children, remains largely untreated, and leads to extremely poor outcomes. The high proportion of epilepsy attributable to preventable causes, in particular neonatal morbidity, contributes significantly to the lifetime burden of the condition. This review reaffirms the ongoing need for better public awareness of epilepsy as a treatable disease and for national-level action that targets both prevention and management.

Visual field defects after radiosurgery versus temporal lobectomy for mesial temporal lobe epilepsy: Findings of the ROSE trial

PURPOSE

Stereotactic radiosurgery (SRS) may be an alternative to anterior temporal lobectomy (ATL) for mesial temporal lobe epilepsy (MTLE). Visual field defects (VFD) occur in 9-100% of patients following open surgery for MTLE. Postoperative VFD after minimally invasive versus open surgery may differ.

METHODS

This prospective trial randomized patients with unilateral hippocampal sclerosis and concordant video-EEG findings to SRS versus ATL. Humphries perimetry was obtained at 24 m after surgery. VFD ratios (VFDR = proportion of missing homonymous hemifield with 0 = no VFD, 0.5 = complete superior quadrantanopsia) quantified VFD. Regressions of VFDR were evaluated against treatment arm and covariates. MRI evaluated effects of volume changes on VFDR. The relationships of VFDR with seizure remission and driving status 3 years after surgery were evaluated.

RESULTS

No patients reported visual changes or had abnormal bedside examinations, but 49 of 54 (91%) of patients experienced VFD on formal perimetry. Neither incidence nor severity of VFDR differed significantly by treatment arm. VFDR severity was not associated with seizure remission or driving status.

CONCLUSION

The nature of VFD was consistent with lesions of the optic radiations. Effective surgery (defined by seizure remission) of the mesial temporal lobe results in about a 90% incidence of typical VFD regardless of method.

Magnetic Resonance-Guided Focused Ultrasound in Neurosurgery: Taking Lessons from the Past to Inform the Future

Magnetic resonance-guided focused ultrasound (MRgFUS) is a new emerging neurosurgical procedure applied in a wide range of clinical fields. It can generate high-intensity energy at the focal zone in deep body areas without requiring incision of soft tissues. Although the effectiveness of the focused ultrasound technique had not been recognized because of the skull being a main barrier in the transmission of acoustic energy, the development of hemispheric distribution of ultrasound transducer phased arrays has solved this issue and enabled the performance of true transcranial procedures. Advanced imaging technologies such as magnetic resonance thermometry could enhance the safety of MRgFUS. The current clinical applications of MRgFUS in neurosurgery involve stereotactic ablative treatments for patients with essential tremor, Parkinson's disease, obsessive-compulsive disorder, major depressive disorder, or neuropathic pain. Other potential treatment candidates being examined in ongoing clinical trials include brain tumors, Alzheimer's disease, and epilepsy, based on MRgFUS abilities of thermal ablation and opening the blood-brain barrier. With the development of ultrasound technology to overcome the limitations, MRgFUS is gradually expanding the therapeutic field for intractable neurological disorders and serving as a trail for a promising future in noninvasive and safe neurosurgical care.

Radiosurgery versus open surgery for mesial temporal lobe epilepsy: The randomized, controlled ROSE trial

OBJECTIVE

To compare stereotactic radiosurgery (SRS) versus anterior temporal lobectomy (ATL) for patients with pharmacoresistant unilateral mesial temporal lobe epilepsy (MTLE).

METHODS

This randomized, single-blinded, controlled trial recruited adults eligible for open surgery among 14 centers in the USA, UK, and India. Treatment was either SRS at 24 Gy to the 50% isodose targeting mesial structures, or standardized ATL. Outcomes were seizure remission (absence of disabling seizures between 25 and 36 months), verbal memory (VM), and quality of life (QOL) at 36-month follow-up.

RESULTS

A total of 58 patients (31 in SRS, 27 in ATL) were treated. Sixteen (52%) SRS and 21 (78%) ATL patients achieved seizure remission (difference between ATL and SRS = 26%, upper 1-sided 95% confidence interval = 46%, P value at the 15% noninferiority margin = .82). Mean VM changes from baseline for 21 English-speaking, dominant-hemisphere patients did not differ between groups; consistent worsening occurred in 36% of SRS and 57% of ATL patients. QOL improved with seizure remission. Adverse events were anticipated cerebral edema and related symptoms for some SRS patients, and cerebritis, subdural hematoma, and others for ATL patients.

SIGNIFICANCE

These data suggest that ATL has an advantage over SRS in terms of proportion of seizure remission, and both SRS and ATL appear to have effectiveness and reasonable safety as treatments for MTLE. SRS is an alternative to ATL for patients with contraindications for or with reluctance to undergo open surgery.

Cognition in epilepsy: current clinical issues of interest

PURPOSE OF REVIEW

This review provides an update and summary of recent neuropsychological findings in epilepsy focusing on three major clinical topics among the many developments in the field. We will critically outline the current state with regard to cognition in new-onset epilepsies, social cognition in epilepsy, and the long-term outcome of epilepsy surgery and the cognitive outcomes of superselective surgical procedures.

RECENT FINDINGS

Current studies indicate that neuropsychological impairments are prevalent already at the onset of epilepsy and even before, social cognition (i.e., emotion recognition and theory of mind) is impaired in different epilepsy populations, the long-term outcome of epilepsy surgery is mostly characterized by a stable or even improved cognitive status, and superselective epilepsy surgeries are associated with a promising neuropsychological outcome.

SUMMARY

The high prevalence of cognitive deficits around epilepsy onset challenges the assumption that epilepsy is the major cause of cognitive problems and calls for early neuropsychological diagnostics. Social cognition seems to be a relevant domain that is not yet routinely considered in epilepsy. The cognitive long-term outcome of epilepsy surgery is mostly positive. Stereotactic thermocoagulation and gamma knife surgery appear to be cognitively safe procedures.

Surgical treatment for refractory epilepsy

The goal of any epilepsy surgery is to improve patient's quality of life by achieving seizure freedom or by reducing the frequency of severely debilitating seizures. To achieve this goal, non-invasive and invasive diagnostic methods must precisely delineate the epileptogenic zone (EZ), which is defined as the area that needs to be resected to obtain seizure freedom. At the same time, the correct identification of eloquent brain areas is inevitable to avoid new neurological deficits from surgery. In recent years, the technical advances in diagnostics have enabled us to achieve these goals in an increasing number of cases. As a consequence, and with new surgical treatment options available, the number of patients who might benefit from epilepsy surgery is constantly increasing. Especially in pediatric epilepsy, early surgical intervention is becoming frequently advocated as it has been shown to improve cognitive and behavioral outcome. Specialized epilepsy centers and multidisciplinary teams are required to provide adequate care and treatment. The goal of this review is to describe important diseases that are accessible to epilepsy surgery and to give an overview of current diagnostic methods. The focus lies on established as well as novel techniques in epilepsy surgery. The presurgical work-up and patient selection is outlined.

Neuropsychologist's (re-)view: Resective versus ablative amygdalohippocampectomies

Pharmacoresistant mesial temporal lobe epilepsy (mTLE) represents the major indication for epilepsy surgery. Since epilepsy surgery is an elective treatment option, preserving cognition is a high priority. Given the essential role of temporomesial structures in declarative long-term memory formation, surgical treatment for mTLE is primarily associated with a risk of material-specific memory decline, but other cognitive domains may be affected as well. The major determinants for the neuropsychological outcome are the functional integrity of surgically affected tissues, the functional reserve capacities of the remnant brain, the postoperative seizure outcome, as well as the quantitative and qualitative changes of antiepileptic drugs. Anterior temporal lobectomy has long been the standard procedure for treating mTLE. However, if an exclusive mesial pathology is present, then functional non-pathological tissues of the temporal pole and neocortex are sacrificed. As a result, more selective or tailored surgical approaches have been developed which strive towards minimizing iatrogenic effects. However, whether or not these approaches are equipotential with regard to seizure control is still a matter of debate. The quality of the presurgical diagnostics could also be decisive. Selective surgery should indeed be selective in terms of preventing evitable collateral cortical damage along the approach. Invasivity and risks of collateral damage associated with "open" selective resective surgery are further minimized by stereotactic ablative surgery via thermocoagulation, or eventually even eliminated by gamma knife surgery. From a neuropsychological point of view, this development is consequent and desirable, but no clear scientific evidence of a superior cognitive outcome after radiosurgery or thermocoagulation currently exists. The studies that are available contain significant methodological limitations. Thus, randomized head-to-head cognitive outcome studies of competing selective procedures are needed, which should meet the minimum requirements for study design and neuropsychological evaluations. Finally, none of the surgical treatment variants can systematically prevent memory decline when the hippocampus is targeted.

New Techniques and Progress in Epilepsy Surgery

While open surgical resection for medically refractory epilepsy remains the gold standard in current neurosurgical practice, modern techniques have targeted areas for improvement over open surgical resection. This review focuses on how a variety of these new techniques are attempting to address these various limitations. Stereotactic electroencephalography offers the possibility of localizing deep epileptic foci, improving upon subdural grid placement which limits localization to neocortical regions. Laser interstitial thermal therapy (LITT) and stereotactic radiosurgery can minimally or non-invasively ablate specific regions of interest, with near real-time feedback for laser interstitial thermal therapy. Finally, neurostimulation offers the possibility of seizure reduction without needing to ablate or resect any tissue. However, because these techniques are still being evaluated in current practice, there are no evidence-based guidelines for their use, and more research is required to fully evaluate their proper role in the current management of medically refractory epilepsy.

Stereotactic radiosurgery for the treatment of mesial temporal lobe epilepsy

OBJECTIVES

Stereotactic radiosurgery (RS) is a potential option for some patients with temporal lobe epilepsy (TLE). The aim of this meta-analysis was to determine the pooled seizure-free rate and the time interval to seizure cessation in patients with lesions in the mesial temporal lobe, and who were eligible for either stereotactic or gamma knife RS.

MATERIALS & METHODS

We searched the Medline, Cochrane, EMBASE, and Google Scholar databases using combinations of the following terms: RS, stereotactic radiosurgery, gamma knife, and TLE.

RESULTS

We screened 103 articles and selected 13 for inclusion in the meta-analysis. Significant study heterogeneity was detected; however, the included studies displayed an acceptable level of quality. We show that approximately half of the patients were seizure free over a follow-up period that ranged from 6 months to 9 years [pooled estimate: 50.9% (95% confidence interval: 0.381-0.636)], with an average of 14 months to seizure cessation [pooled estimate: 14.08 months (95% confidence interval: 11.95-12.22 months)]. Nine of 13 included studies reported data for adverse events (AEs), which included visual field deficits and headache (the two most common AEs), verbal memory impairment, psychosis, psychogenic non-epileptic seizures, and dysphasia. Patients in the individual studies experienced AEs at rates that ranged from 8%, for non-epileptic seizures, to 85%, for headache.

CONCLUSION

Our findings indicate that RS may have similar or slightly less efficacy in some patients compared with invasive surgery. Randomized controlled trials of both treatment regimens should be undertaken to generate an evidence base for patient decision-making.

History and Technical Approaches and Considerations for Ablative Surgery for Epilepsy

The history of epilepsy surgery is generally noted to have begun in 1886 with Victor Horsley's first report of craniotomies for posttraumatic epilepsy. With increased understanding of brain function and development of electroencephalographic methods, nonlesional epilepsy began to be treated with resection in the 1950s. Methodological improvements and increased understanding of pathophysiology followed, and the advent of stereotaxy and ablative technology in the 1960s and 1970s heralded a new era of minimally invasive, targeted procedures for lesional and nonlesional epilepsy. Current techniques combine stereotactic methods, improved ablative technologies, and electroencephalographic methods for a multidisciplinary approach to the neurosurgical treatment of epilepsy.

Seizure outcomes in nonresective epilepsy surgery: an update

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.

Current and Emerging Surgical Therapies for Severe Pediatric Epilepsies

The use of epilepsy surgery in various medically resistant epilepsies is well established. For patients with intractable pediatric epilepsy, the role of intracranial electrodes, resective surgery, hemispherectomy, corpus callosotomy, neurostimulation, and multiple subpial transections continues to be very effective in select cases. Newer treatment and diagnostic methods include laser thermal ablation, minimally invasive surgeries, stereo electroencephalography, electrocorticography, and other emerging techniques. This article will review the established and emerging surgical therapies for severe pediatric epilepsies, their respective indications and overall efficacy.

Fractionated Stereotactic Gamma Knife Radiosurgery for Medial Temporal Lobe Epilepsy: A Case Report

An 18-year-old left-handed male harbored intractable medial temporal lobe epilepsy (MTLE) underwent fractionated gamma knife surgery (GKS) instead of open surgery, considering the mental retardation and diffuse cerebral dysfunction. GKS treatment parameters were: target volume, 8.8 cm³; total marginal dose, 24 Gy in 3 fractionations at the 50% isodose line. The patient has been free from seizures since 9 months after GKS, with notable improvement in cognitive outcome. Fractionated GKS could be considered as a safe tool for seizure control and neuropsychological improvement in patients with MTLE.

Transcranial magnetic resonance-guided focused ultrasound for temporal lobe epilepsy: a laboratory feasibility study

OBJECTIVE In appropriate candidates, the treatment of medication-refractory mesial temporal lobe epilepsy (MTLE) is primarily surgical. Traditional anterior temporal lobectomy yields seizure-free rates of 60%-70% and possibly higher. The field of magnetic resonance-guided focused ultrasound (MRgFUS) is an evolving field in neurosurgery. There is potential to treat MTLE with MRgFUS; however, it has appeared that the temporal lobe structures were beyond the existing treatment envelope of currently available clinical systems. The purpose of this study was to determine whether lesional temperatures can be achieved in the target tissue and to assess potential safety concerns. METHODS Cadaveric skulls with tissue-mimicking gels were used as phantom targets. An ablative volume was then mapped out for a "virtual temporal lobectomy." These data were then used to create a target volume on the InSightec ExAblate Neuro system. The target was the amygdala, uncus, anterior 20 mm of hippocampus, and adjacent parahippocampal gyrus. This volume was approximately 5cm³. Thermocouples were placed on critical skull base structures to monitor skull base heating. RESULTS Adequate focusing of the ultrasound energy was possible in the temporal lobe structures. Using clinically relevant ultrasound parameters (power 900 W, duration 10 sec, frequency 650 kHz), ablative temperatures were not achieved (maximum temperature 46.1°C). Increasing sonication duration to 30 sec demonstrated lesional temperatures in the mesial temporal lobe structures of interest (up to 60.5°C). Heating of the skull base of up to 24.7°C occurred with 30-sec sonications. CONCLUSIONS MRgFUS thermal ablation of the mesial temporal lobe structures relevant in temporal lobe epilepsy is feasible in a laboratory model. Longer sonications were required to achieve temperatures that would create permanent lesions in brain tissue. Heating of the skull base occurred with longer sonications. Blocking algorithms would be required to restrict ultrasound beams causing skull base heating. In the future, MRgFUS may present a minimally invasive, non-ionizing treatment of MTLE.

Laser interstitial thermal therapy for medically intractable mesial temporal lobe epilepsy

OBJECTIVE

To describe mesial temporal lobe ablated volumes, verbal memory, and surgical outcomes in patients with medically intractable mesial temporal lobe epilepsy (mTLE) treated with magnetic resonance imaging (MRI)-guided stereotactic laser interstitial thermal therapy (LiTT).

METHODS

We prospectively tracked seizure outcome in 20 patients at Thomas Jefferson University Hospital with drug-resistant mTLE who underwent MRI-guided LiTT from December 2011 to December 2014. Surgical outcome was assessed at 6 months, 1 year, 2 years, and at the most recent visit. Volume-based analysis of ablated mesial temporal structures was conducted in 17 patients with mesial temporal sclerosis (MTS) and results were compared between the seizure-free and not seizure-free groups.

RESULTS

Following LiTT, proportions of patients who were free of seizures impairing consciousness (including those with auras only) are as follows: 8 of 15 patients (53%, 95% confidence interval [CI] 30.1-75.2%) after 6 months, 4 of 11 patients (36.4%, 95% CI 14.9-64.8%) after 1 year, 3 of 5 patients (60%, 95% CI 22.9-88.4%) at 2-year follow-up. Median follow-up was 13.4 months after LiTT (range 1.3 months to 3.2 years). Seizure outcome after LiTT suggests an all or none response. Four patients had anterior temporal lobectomy (ATL) after LiTT; three are seizure-free. There were no differences in total ablated volume of the amygdalohippocampus complex or individual volumes of hippocampus, amygdala, entorhinal cortex, parahippocampal gyrus, and fusiform gyrus between seizure-free and non-seizure-free patients. Contextual verbal memory performance was preserved after LiTT, although decline in noncontextual memory task scores were noted.

SIGNIFICANCE

We conclude that MRI-guided stereotactic LiTT is a safe alternative to ATL in patients with medically intractable mTLE. Individualized assessment is warranted to determine whether the reduced odds of seizure freedom are worth the reduction in risk, discomfort, and recovery time. Larger prospective studies are needed to confirm our preliminary findings, and to define optimal ablation volume and ideal structures for ablation.

Radiosurgery for Medial Temporal Lobe Epilepsy Resulting from Mesial Temporal Sclerosis

Medial temporal lobe epilepsy associated with mesial temporal sclerosis (MTS) is perhaps the most well-defined epilepsy syndrome that is responsive to structural interventions such as surgery. Several minimally invasive techniques have arisen that provide additional options for the treatment of MTS while potentially avoiding many of open surgery's associated risks. By evading these risks, they also open up treatment options to patients who otherwise are poor surgical candidates. Radiosurgery is one of the most intensively studied of these alternatives and has found a growing role in the treatment of medial temporal lobe epilepsy.

Gamma Knife radiosurgery for recurrent or residual seizures after anterior temporal lobectomy in mesial temporal lobe epilepsy patients with hippocampal sclerosis: long-term follow-up results of more than 4 years

OBJECT

Gamma Knife radiosurgery (GKRS) has proven efficacy in the treatment of drug-resistant mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) and is comparable to conventional resective surgery. It may be effective as an alternative treatment to reoperation after failed temporal lobe surgery in patients with MTLE-HS. The purpose of this study was to investigate the efficacy of GKRS in patients with unilateral MTLE-HS who did not achieve seizure control or had recurrent seizures after anterior temporal lobectomy (ATL).

METHODS

Twelve patients (8 males; mean age 35.50 ± 9.90 years) with MTLE-HS who underwent GKRS after failed ATL (Engel Classes III-IV) were included. GKRS targets included the remnant tissue or adjacent regions of the previously performed ATL with a marginal dose of 24-25 Gy at the 50% isodose line in all patients. Final seizure outcome was assessed using Engel's modified criteria during the final 2 years preceding data analysis. A comparison between signal changes on follow-up MRI and clinical outcome was performed.

RESULTS

All patients were followed up for at least 4 years with a mean duration of 6.18 ± 1.77 years (range 4-8.8 years) after GKRS. At the final assessment, 6 of 12 patients were classified as seizure free (Engel Class Ia, n = 3; Ic, n = 2; and Id, n = 1) and 6 patients were classified as not seizure free (Engel Class II, n = 1; III, n = 2; and IV, n = 3). Neither initial nor late MRI signal changes after GKRS statistically correlated with surgical outcome. Clinical seizure outcome did not differ significantly with initial or late MRI changes after GKRS.

CONCLUSIONS

GKRS can be considered an alternative option when the patients with MTLE-HS who had recurrent or residual seizures after ATL refuse a second operation.

Minimally invasive surgical approaches for temporal lobe epilepsy

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.

Real-time magnetic resonance-guided stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy

BACKGROUND

Open surgery effectively treats mesial temporal lobe epilepsy, but carries the risk of neurocognitive deficits, which may be reduced with minimally invasive alternatives.

OBJECTIVE

To describe technical and clinical outcomes of stereotactic laser amygdalohippocampotomy with real-time magnetic resonance thermal imaging guidance.

METHODS

With patients under general anesthesia and using standard stereotactic methods, 13 adult patients with intractable mesial temporal lobe epilepsy (with and without mesial temporal sclerosis [MTS]) prospectively underwent insertion of a saline-cooled fiberoptic laser applicator in amygdalohippocampal structures from an occipital trajectory. Computer-controlled laser ablation was performed during continuous magnetic resonance thermal imaging followed by confirmatory contrast-enhanced anatomic imaging and volumetric reconstruction. Clinical outcomes were determined from seizure diaries.

RESULTS

A mean 60% volume of the amygdalohippocampal complex was ablated in 13 patients (9 with MTS) undergoing 15 procedures. Median hospitalization was 1 day. With follow-up ranging from 5 to 26 months (median, 14 months), 77% (10/13) of patients achieved meaningful seizure reduction, of whom 54% (7/13) were free of disabling seizures. Of patients with preoperative MTS, 67% (6/9) achieved seizure freedom. All recurrences were observed before 6 months. Variances in ablation volume and length did not account for individual clinical outcomes. Although no complications of laser therapy itself were observed, 1 significant complication, a visual field defect, resulted from deviated insertion of a stereotactic aligning rod, which was corrected before ablation.

CONCLUSION

Real-time magnetic resonance-guided stereotactic laser amygdalohippocampotomy is a technically novel, safe, and effective alternative to open surgery. Further evaluation with larger cohorts over time is warranted.

Minimally invasive techniques for epilepsy surgery: stereotactic radiosurgery and other technologies

Minimally invasive surgical techniques for the treatment of medically intractable epilepsy, which have been developed by neurosurgeons and epileptologists almost simultaneously with standard open epilepsy surgery, provide benefits in the traditional realms of safety and efficacy and the more recently appreciated realms of patient acceptance and costs. In this review, the authors discuss the shortcomings of the gold standard of open epilepsy surgery and summarize the techniques developed to provide minimally invasive alternatives. These minimally invasive techniques include stereotactic radiosurgery using the Gamma Knife, stereotactic radiofrequency thermocoagulation, laser-induced thermal therapy, and MRI-guided focused ultrasound ablation.

Advances in epilepsy surgery

This review summarises exciting recent and forthcoming advances that will impact on the surgical management of epilepsy in the near future. This does not cover the current accepted diagnostic methodologies or surgical treatments that are routinely practiced today. The content of this review was derived from a PubMed literature search, using the key words 'Epilepsy Surgery', 'Neuromodulation', 'Neuroablation', 'Advances', between 2010 and November 2013.