Temporal lobe epilepsy and cavernous malformations: surgical strategies and long-term outcomes

Pediatric Intraoperative Neurophysiologic Mapping and Monitoring in Brain Surgery

SUMMARY

Similar to adults, children undergoing brain surgery can significantly benefit from intraoperative neurophysiologic mapping and monitoring. Although young brains present the advantage of increased plasticity, during procedures in close proximity to eloquent regions, the risk of irreversible neurological compromise remains and can be lowered further by these techniques. More so, pathologies specific to the pediatric population, such as neurodevelopmental lesions, often result in medically refractory epilepsy. Thus, their successful surgical treatment also relies on accurate demarcation and resection of the epileptogenic zone, processes in which intraoperative electrocorticography is often employed. However, stemming from the development and maturation of the central and peripheral nervous systems as the child grows, intraoperative neurophysiologic testing in this population poses methodologic and interpretative challenges even to experienced clinical neurophysiologists. For example, it is difficult to perform awake craniotomies and language testing in the majority of pediatric patients. In addition, children may be more prone to intraoperative seizures and exhibit afterdischarges more frequently during functional mapping using electrical cortical stimulation because of high stimulation thresholds needed to depolarize immature cortex. Moreover, choice of anesthetic regimen and doses may be different in pediatric patients, as is the effect of these drugs on immature brain; these factors add additional complexity in terms of interpretation and analysis of neurophysiologic recordings. Below, we are describing the modalities commonly used during intraoperative neurophysiologic testing in pediatric brain surgery, with emphasis on age-specific clinical indications, methodology, and challenges.

Clinical characteristics and long-term outcome of cerebral cavernous malformations-related epilepsy

OBJECTIVE

Cerebral cavernous malformations (CCMs) present variably and epileptic seizures are the most common symptom. The factors contributing to cavernoma-related epilepsy (CRE) and drug resistance remain inconclusive. The outcomes of CRE after different treatment modalities have not yet been fully addressed. This study aimed to characterize the clinical features of patients with CRE and the long-term seizure outcomes of medical and surgical treatment strategies.

METHODS

This was a retrospective cohort of 135 patients with CCM who were diagnosed in 2007~2011 and followed up for 93.6 months on average. The patients were divided into drug-resistant epilepsy (DRE) (n = 29), non-DRE (NDRE) (n = 45), and no epilepsy (NE) (n = 61).

RESULTS

Temporal CCM was the factor most strongly associated with the development of both CRE and DRE. The majority of patients with single temporal CCMs had CRE (86.8%, n = 33) and 50% had DRE, whereas only 14.7% (n = 5) with a non-temporal supratentorial CCM had DRE (P < 0.05). The most common lesion site in the DRE group was the mesiotemporal lobe (50%). Multiple CCMs were more frequently observed in the CRE (29.2%) than the NE (11.5%) group (P < 0.05). In patients with CRE, multiple lesions were associated with a higher rebleeding rate (odds ratio: 11.1), particularly in those with DRE (odds ratio: 15.4). The majority of patients who underwent resective surgery for DRE (76.5%, n = 13) achieved ILAE class I and II seizure outcomes even after a long disease course.

SIGNIFICANCE

Temporal CCM not only predisposes to CRE but is also a major risk factor for drug resistance. The mesiotemporal lobe is the most epileptogenic zone. Multiple CCMs are another risk factor for CRE and increase the rebleeding risk in these patients. Surgical resection could provide beneficial long-term seizure outcomes in patients with DRE.

Intra-operative electrocorticography results and postoperative pathological findings are associated with epileptic outcomes in patients with cerebral cavernous malformations presenting with epilepsy

OBJECTIVES

The purpose of this study was to determine whether intraoperative electrocorticography (ECoG) results and postoperative pathological findings are associated with long-term epileptic outcomes in patients with cerebral cavernous malformations (CCMs).

METHODS AND MATERIALS

To identify all consecutive patients with surgically treated CCM-related epilepsy (CRE) referred to our hospital, our prospectively maintained database of patients with CCM was reviewed (NCT03467295). For these patients, an ECoG-guided extended lesionectomy was performed, in which the CCM, surrounding hemosiderin, and detected epileptic foci were removed. Intraoperative ECoG results and postoperative pathological findings were documented in detail. Engel Class I was defined as a favorable outcome, while Engel Class II-IV was considered an unfavorable outcome. The patients were followed up for at least 2 years. The relationship between ECoG results, postoperative pathological findings, and epileptic outcomes was analyzed.

RESULTS

A total of 522 patients with CCM were reviewed, and 85 patients with epileptic CCM were enrolled in this study. At the last clinical visit, 83.5 % of the patients experienced favorable postoperative outcomes. Multivariate analysis revealed that residual epileptic waves detected by intraoperative ECoG (OR 13.64; Cl 2.13-87.11; p = 0.006) and concomitant focal cortical dysplasia (FCD) (OR 11.37; Cl 1.63-79.27; p = 0.014) were independent factors significantly correlated with long-term epileptic outcomes. Most (61; 93.8 %) of the 65 patients with CRE without FCD achieved favorable outcomes.

CONCLUSION

Residual epileptiform discharges after excision and concomitant FCD may be associated with poorer long-term epileptic outcomes in patients with CRE. Close follow-up and strict administration of oral antiepileptic drugs may be needed for these patients.

Cavernoma-related epilepsy in cavernous malformations located within the temporal lobe: surgical management and seizure outcome

OBJECTIVE

Cavernoma-related epilepsy (CRE) is a frequent symptom in patients with cerebral cavernous malformations (CCMs). Reports on surgical management and seizure outcome of epileptogenic CCM often focus on intracranial cavernoma in general. Therefore, data on CCMs within the temporal lobe are scarce. The authors therefore analyzed their institutional data.

METHODS

From 2003 to 2018, 52 patients suffering from CCMs located within the temporal lobe underwent surgery for CRE at University Hospital Bonn. Information on patient characteristics, preoperative seizure history, preoperative evaluation, surgical strategies, postoperative complications, and seizure outcome was assessed and further analyzed. Seizure outcome was assessed 12 months after surgery according to the International League Against Epilepsy (ILAE) classification and stratified into favorable (ILAE class I) versus unfavorable (ILAE classes II-VI).

RESULTS

Overall, 47 (90%) of 52 patients with CCMs located in the temporal lobe and CRE achieved favorable seizure outcome. Pure lesionectomy was performed in 5 patients, extended lesionectomy with resection of the hemosiderin rim in 38 patients, and anterior temporal lobectomy in 9 patients with temporal lobe CCM. Specifically, 36 patients (69%) suffered from drug-resistant epilepsy (DRE), 3 patients (6%) from chronic CRE, and 13 patients (25%) sustained sporadic CRE. In patients with DRE, favorable seizure outcome was achieved in 32 (89%) of 36 patients. Patients with DRE were significantly older than patients with CCM-associated chronic or sporadic seizures (p = 0.02). Furthermore, patients with DRE more often underwent additional amygdalohippocampectomy following the recommendation of presurgical epileptological evaluation.

CONCLUSIONS

Favorable seizure outcome is achievable in a substantial number of patients with epileptogenic CCM located in the temporal lobe, even if patients suffered from drug-resistant CRE. For adequate counseling and monitoring, patients with CRE should undergo a thorough pre- and postsurgical evaluation in dedicated epilepsy surgery programs.

Treatment of Cerebral Cavernous Malformations Presenting With Seizures: A Systematic Review and Meta-Analysis

Background: Cerebral cavernous malformations (CCMs) presenting with seizures can be treated with neurosurgery or radiosurgery, but the ideal treatment remains unclear. Currently, there is no adequate randomized controlled trial comparing surgical treatment and radiotherapy for epileptogenic CCMs. Therefore, we conducted a systematic review and meta-analysis of available data from published literature to compare the efficacy and safety of neurosurgery and radiosurgery for epileptogenic CCMs. Methods: We performed a comprehensive search of the Ovid MEDLINE, Web of Science, PubMed, China Biological Medicine and China National Knowledge Infrastructure databases for studies published between January 1994 and October 2019. The search terms were as follows: "epilepsy," "seizures," "brain cavernous hemangioma," "cerebral cavernous malformation," "cerebral cavernous hemangioma," "hemangioma, cavernous, central nervous system." Two researchers independently extracted the data and reviewed all the articles. We compared the advantages and disadvantages of the two treatments. Results: A total of 45 studies were included in our analysis. Overall, the seizure control rate was 79% (95% CI: 75-83%) for neurosurgery and 49% (95% CI: 38-59%) for radiosurgery. In the neurosurgery studies, 4.4% of patients experienced permanent morbidity, while no patients in the radiotherapy studies had permanent morbidity. In addition, the results of subgroup analysis showed that ethnicity, CCMs location and average lesion number are likely significant factors influencing the seizure outcome following treatment. Conclusions: The epilepsy control rate after neurosurgery was higher than that after radiosurgery, but neurosurgery also had a relatively higher rate of permanent morbidity.

Continuous ictal discharges with high frequency oscillations confined to the non-sclerotic hippocampus in an epileptic patient with radiation-induced cavernoma in the lateral temporal lobe

Background

Intraoperative electrocorticography (iECoG) recording is recommended for treating cavernoma related epilepsy. However, "interictal" paroxysmal activities are generally recordable but are not always identical to the epileptogenic zone.

Case description

We surgically treated a 15-year-old girl with drug-resistant epilepsy associated with radiation-induced cavernoma in the right lateral temporal lobe. iECoG revealed paroxysmal activities in the cortex around the cavernoma. Additionally, continuous subclinical "ictal" discharges with high-frequency oscillations (HFO), confined to the histologically non-sclerotic hippocampus, were recorded. Following additional hippocampectomy, a good seizure outcome was obtained.

Conclusion

iECoG and HFO analysis revealed high epileptogenicity in the non-sclerotic hippocampus of this patient.

[Surgical treatment of epilepsy in patients with mediobasal temporal cavernous malformations]

OBJECTIVE

Epilepsy is a frequent clinical manifestation of cavernous malformations (CMs) of the mediobasal temporal region (MBTR). Surgical removal of CMs is an excellent technique for treating associated epilepsy and may range from pure lesionectomy to tailored resection of the temporal lobe.

PURPOSE

The study purpose was to determine the optimal surgical management for epilepsy in patients with CMs of the MBTR.

MATERIAL AND METHODS

We retrospectively analyzed the clinical data, neuroimaging findings, surgical techniques, and surgical outcomes in 11 patients with epilepsy and CMs of the MBTR. All patients underwent video-electroencephalography, magnetic resonance imaging, and computed tomography in the pre- and postoperative periods. Nine patients underwent preoperative implantation of foramen ovale electrodes. In all cases, surgery was accompanied by electrocorticography (ECoG).

RESULTS

CMs were located in the anterior MBTR in 7 cases, anterior and middle thirds of the MBTR in 1 case, middle third in 2 cases, and middle and posterior thirds in 1 case. In 8 patients, preoperative monitoring revealed a seizure onset area in the MBTR. These patients underwent cavernomectomy with ECoG-guided resection of the hemosiderin ring and adjacent tissue using the pterional (4 cases) or supracerebellar transtentorial approach (4). In 3 cases, anterior temporal lobectomy with cavernomectomy was additionally used due to spreading of pathological activity to the lateral temporal neocortex. Seizure control after surgery was excellent in 7 patients (class 1 ILAE) and good in 4 (class 2 ILAE).

CONCLUSION

Surgery in patients with epilepsy caused by CMs of the MBTR should be performed based on non-invasive and invasive presurgical evaluation. If the seizure onset area is located in the MBTR, lesionectomy with ECoG-guided resection of the adjacent temporal cortical areas can be performed using the pterional or supracerebellar transtentorial approach. Lateral spread of epileptic activity requires cavernomectomy and anterior temporal lobectomy.

Animal models of status epilepticus and temporal lobe epilepsy: a narrative review

Temporal lobe epilepsy (TLE) is the chronic and pharmacoresistant form of epilepsy observed in humans. The current literature is insufficient in explicating the comprehensive mechanisms underlying its pathogenesis and advancement. Consequently, the development of a suitable animal model mimicking the clinical characteristics is required. Further, the relevance of status epilepticus (SE) to animal models is dubious. SE occurs rarely in people; most epilepsy patients never experience it. The present review summarizes the established animal models of SE and TLE, along with a brief discussion of the animal models that have the distinctiveness and carries the possibility to be developed as effective models for TLE. The review not only covers the basic requirements, mechanisms, and methods of induction of each model but also focuses upon their major limitations and possible modifications for their future use. A detailed discussion on chemical, electrical, and hypoxic/ischemic models as well as a brief explanation on the genetic models, most of which are characterized by development of SE followed by neurodegeneration, is presented.

Surgical Management and Long-Term Seizure Outcome After Surgery for Temporal Lobe Epilepsy Associated with Cerebral Cavernous Malformations

OBJECTIVE

Operative strategies for cerebral cavernous malformation (CCM)-associated temporal lobe epilepsy and timing of surgical intervention continue to be debated. This study aimed to establish an algorithm to evaluate the efficacy of surgical intervention strategies, to maximize positive surgical outcomes and minimize postsurgical neurologic deficits.

METHODS

47 patients having undergone operation for CCM-associated temporal lobe epilepsy were retrospectively reviewed. They had received a diagnostic series for seizure localization, including long-term video electroencephalography (vEEG), high-resolution magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET-CT). In patients with mesial temporal lobe CCMs, the involved structures (amygdala, hippocampus, or parahippocampal gyrus) were resected in addition to the lesions. Patients with neocortical epileptogenic CCM underwent extended lesionectomy guided by intraoperative electrocorticography; further performance of amygdalohippocampectomy depended on the extent of hippocampal epileptogenicity.

RESULTS

The study cohort contained 28 patients with drug-resistant epilepsy (DRE), 12 with chronic epilepsy (CE), and 7 with sporadic seizure (SS). Normal temporal lobe metabolism was seen in 7/7 patients of the SS group. Hypometabolism was found in all patients with chronic disease except for those with posterior inferior and middle temporal gyrus cavernous malformations (CMs). Of the 31 patients with superficial neocortical CCM, 7 had normal PET without hippocampal sclerosis, 14 had ipsilateral temporal lobe hypometabolism without hippocampal sclerosis, and 10 had obvious hippocampal sclerosis and hypometabolism. Seizure freedom in DRE, CE, and SS was 82.1%, 75%, and 100%, respectively. A significant difference was found between lesion laterality and postoperative seizure control; the rate was lower in left-sided cases because of less aggressive resection.

CONCLUSIONS

Our study demonstrates that the data from the presurgical evaluation, particularly regarding CM location, responsiveness to antiepileptic drugs, and temporal lobe metabolism, are crucial parameters for choosing surgical approaches to CCM-associated temporal lobe epilepsy. By this operative strategy, patients may receive maximized seizure control and minimized postsurgical neurologic sequelae.

Epilepsy Treatment: A Futurist View

Advances in epilepsy treatment are occurring at a rapid pace, and it is challenging for us to keep up with the latest in our field. As we struggle to keep up with the literature and concentrate on our own research and clinical work, we often fail to exercise our imagination and envision what our field will be like in future decades. This was the assignment to the speakers for the Presidential Symposium at the 2016 American Epilepsy Society Annual Meeting. I challenged the experts to step outside the frame of their usual daily work to imagine what epilepsy treatment would and should look like for the next generation of epilepsy specialists and their patients. As you will read in the following sections, the speakers truly stepped up to the challenge to look into the crystal ball. The following are summaries of each lecture that describe the current state, existing cutting edge ideas, and some surprising predictions for the future. I am grateful for the tremendous effort these experts put into this challenge and hope they stimulate your imagination so you will work to bring these advances to our patients.

A predicted model for postoperative seizure outcomes after the surgical resection of supratentorial cavernous malformations

To explore a predicted model for postoperative seizure outcomes after the surgical resection of supratentorial cavernous malformations.This study was a retrospective review of consecutive patients with cerebral supratentorial cavernous malformations presenting with seizures. All patients underwent surgical resection of CCMs. Univariate and multivariate analyses were performed to determine the predictive value of the preoperative seizure frequency, seizure type, seizure duration, lesion location, lesion size, and the presence of residual hemosiderin.A total of 43 patients met the inclusion criteria. After a mean follow-up period of 40.95 months, 34 patients who were free from postoperative seizures were classified into Engel class I, and the remaining 9 patients were classified into Engel classes II-IV. A univariate analysis showed that the seizure frequency (χ = 13.440, P = 0.004) and seizure duration (χ = 5.145, P = 0.023) prior to surgery were associated with a worse postoperative seizure prognosis. Other covariates including age at onset, gender, a history of the medications taken, smoking status, family history, lesion characteristics, and the role of hemosiderin were not related to seizure outcomes. Logistic regression results demonstrated that the preoperative seizure frequency was an effective predictor (P = 0.004). The receiver operating characteristic curve indicated that area under the curve for the preoperative seizure frequency test was 0.833 (95% confidence interval 0.709-0.957, P = 0.002).The preoperative seizure frequency was a prognostic factor for postoperative seizure outcomes after surgical resection of supratentorial cavernous malformations. To obtain a favorable prognosis for CCM patients with preoperative seizures, early intervention might be a better choice.