An update on pediatric surgical epilepsy: Part I

INTRODUCTION

Epilepsy is estimated to affect 10.5 million children worldwide.[12] In the early pediatric population, achieving seizure freedom is critical to prevent developmental arrest or regression.[1,13] Nevertheless, these patients often require multiple antiepileptic medications, leading to additive side effects, without adequate seizure control. About 20–40% of children have drug-resistant epilepsy (DRE), persistent seizures refractory to two antiepileptic medications,[3,8] presenting significant social, economic, health, and developmental implications.[14]

Surgical treatment of DRE has been shown to be safer and more efficacious compared to medical management.[11] It is aimed to remove or disconnect the epileptogenic zone (EZ), the minimal amount of cortex to produce seizure freedom,[17] from surrounding normal brain while minimizing morbidity. Conventionally, epilepsy surgery focused on resections or disconnections: lobectomy, hemispherectomy, cortical excision, and corpus callosotomy. Overtime, the armamentarium has grown to include newer, less invasive approaches including neuromodulation and ablative techniques.

With advances in technology, there are now multiple indications for the different types of surgery to address pediatric epilepsy. We describe, in Part I, practices and advances in diagnostic workup and surgical strategies.

SURGICAL INDICATIONS

Surgical indications have evolved overtime to encompass a wider variety of epilepsy types, applying epilepsy surgery to more patients. Table 1 describes the evolution of indications for surgical evaluation in recent years.

Table 1:: Timeline of indications for epilepsy surgery.

SURGICAL PLANNING

Presurgical evaluation identifies the EZ, correlating it with function. Stepwise evaluation should include a detailed clinical history, interictal scalp electroencephalography (EEG), long-term video EEG, high-resolution structural magnetic resonance imaging (MRI), and neuropsychological/ neuropsychiatric assessment[22] and also included magnetoencephalography (MEG), functional MRI (fMRI), interictal positron emission tomography, and ictal single-photon emission computed tomography [Table 2]. Conventionally, the Wada test had been used for cortical stimulation mapping; this may be supplemented or supplanted with fMRI[19] as well as MEG or resting state fMRI.[6]

Table 2:: Presurgical epilepsy evaluation.

Where the EZ cannot be characterized with noninvasive testing, or noninvasive testing yields contradictory results, Phase 2 assessment utilizing intracranial EEG monitoring may be pursued. Implantation of subdural grids and depth electrodes allows more accurate localization of the EZ than scalp EEG. Functional zones may be identified through cortical stimulation mapping. However, invasive electrocorticography may carry a complication rate of up to 20% (e.g., intracranial hematoma).[30]

For those who are not candidates or have failed surgery, vagus nerve stimulation may palliatively reduce seizures by 50–75%.[2,28] Targeted, responsive neuromodulation is also an option, discussed in Part 2.

SURGICAL OPTIONS

Several surgical options exist based on the seizure type, lesion type, size and location, and EZ characteristics. Lesionectomy is favored for singular cortical-based lesions and can be curative. Lobectomy is used for more focal lesions and proven superior in cases of temporal lobe epilepsy over medical management (Class I evidence).[31] Hemispherectomy, reserved for lesions affecting an entire cerebral hemisphere, has evolved to focus on tissue disconnection rather than resection. Corpus callosotomy palliatively prevents synchronization of epileptic activity between hemispheres and is reserved for those most affected by generalized DRE. The clinical application, outcomes, and considerations for each approach are detailed in Table 3.

Table 3:: Open surgical options for drug - resistant epilepsy.

SURGICAL CONSIDERATIONS IN PEDIATRICS

Pediatric epilepsy is more diverse in etiology and semiology with migrational disorders, congenital epileptic syndromes, and extratemporal epileptogenic foci more common in children. Therefore, cortical excisions and hemispherectomies are perhaps more common than temporal lobectomies in the pediatric population versus adults. In addition, DRE impacts neurodevelopment in children. Early surgical intervention limits the time on intolerable medications, minimizes cognitive delays and learning disabilities, and improves psychomotor development.[27] Children brains exhibit greater plasticity versus adults, increasing the potential for rehabilitation following even extensive resective or disconnective procedures.[27]

IDENTIFICATION OF CANDIDATES FOR EPILEPSY SURGERY

It is critical to identify the best candidates for epilepsy surgery. The goals include cure or palliation and may warrant a variety of open versus stereotactic techniques [Figure 1]. With growing technology, there is enhanced ability tailor treatment to individual patients.

Close

Figure 1:: Flowchart demonstrating strategies in the surgical management of drug-resistant epilepsy. The goal of epilepsy surgery can range from curative to palliative, with various available techniques to achieve a range of seizure outcome.

Export to PPT

Despite the growing appreciation for the deleterious developmental and psychosocial effects of pediatric DRE, there are too few surgical referrals,[23] with <1% of patients with DRE referred to epilepsy centers. This may be explained by limited access, cost, and misconceptions regarding who may benefit from evaluation.[25] With continuing innovation in the field of pediatric epilepsy surgery, it is imperative that continued strides be made in patient recruitment and referral to enhance clinical outcomes.

CONCLUSION

Here, we reviewed, summarized, and synthesized important practices and advances in diagnostic workup and surgical strategies of epilepsy surgery. Future increased awareness of the role of epilepsy surgery in children with DRE is critical to increase the breadth of impact.