Current and Emerging Surgical Therapies for Severe Pediatric Epilepsies

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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.

Introduction

Nearly 30% of children with epilepsy have medically intractable seizures.1, 2, 3, 4 They are on multiple antiepileptic medications yet still suffer from seizures and associated debilitating conditions including developmental delay, cognitive decline, behavioral issues, psychosocial difficulties, and even physical injury during seizures. For these children, surgery often provides the best chance at seizure control.

According to the International League Against Epilepsy (ILAE) 2000 Standards, patients are considered medically refractory if they have “persistence of seizures despite adequate trial of anti-epileptic drugs (AEDs) with a minimum of two first-line drugs.”5 Overall, 2.9 million people in the United States alone have active epilepsy, including at least 450,000 children,6, 7 and approximately 800,000 have drug resistant, refractory epilepsy.2

Section snippets

Candidates for Epilepsy Surgery

Any patient with medically refractory epilepsy should be referred to a comprehensive epilepsy center to determine if they are a candidate for surgery. The most important determinant of a successful surgical outcome is good patient selection. Presurgical evaluation would try to determine the patientʼs seizure type and location of onset. The patient would undergo several days of constant electroencephalography (EEG) monitoring so that the epileptologists can study the seizure semiology.

In

Diagnostic Surgeries

When the location and borders of the epileptogenic lesion cannot be adequately determined with extracranial EEG, or if the epileptic focus appears very near to eloquent cortex, intracranial electrodes can provide vital information to determine if resection is safe and to guide the extent of resection. Subdural grids and strips or depth electrodes are placed over or in likely targets, and the patient is monitored in a video monitoring unit. Electrocorticography (ECoG) can determine the location

Resection

Once an epileptogenic focus is found, whether with noninvasive EEG and imaging, or through the use of intracranial electrodes, the patient can proceed to surgery. Temporal lobe resection is the most common procedure for epilepsy, including adult patients, and has a long record showing good rates of seizure freedom in carefully selected patients.

Temporal Lobe Epilepsy

In 2001, Wiebe et al16 published the first randomized controlled trial of anterior temporal lobectomy (ATL) vs. medical management for the treatment of

Corpus Callosotomy

Children who suffer from drop attacks may benefit from a corpus callosotomy in order to interrupt the spread of seizures. A callosotomy is intended as a palliative procedure, but about 75% of patients do notice a significant improvement in seizures.38, 39, 40 For some patients, their seizures change to a partial seizure that does not result in a fall, or they experience improvement in attention or language skills, so quality of life may significantly improve even if seizures persist.39, 40

Vagal Nerve Stimulators

Like the disconnection surgeries, the stimulation surgeries are generally more palliative than curative. Vagal nerve stimulation (VNS) delivers programmable scheduled intermittent electrical stimulation to the vagus nerve, and can be manually triggered to deliver a higher current when a patient is having a seizure to try to abort that seizure. The newest version of the generator (model 106) also offers heart rate detection with an option to provide increased stimulation in response to ictal

High Frequency Oscillations and Single-Pulse Electrical Stimulation

Successful resection of epileptic tissue requires accurate knowledge of the location and borders of that tissue. ECoG via intracranial electrodes monitors for epileptic spikes to determine if tissue should be removed. Recent studies have tried to refine the indicators to more accurately locate epileptic foci.

High frequency oscillations (HFOs) from 80-500 Hz, ictally and interictally, may correlate with epileptogenic zones.57, 58 HFOs may be more specific than spikes and might be able to more

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