Multimodal Localization and Surgery for Epileptic Spasms of Focal Origin

A Review

Taylor J. Abel, MD; Emma Losito, MD; George M. Ibrahim, MD, PhD; Eishi Asano, MD, PhD; James T. Rutka, MD, PhD

Disclosures

Neurosurg Focus. 2018;45(3):e4 

In This Article

Abstract and Introduction

Abstract

Epileptic spasms (ES) are a common manifestation of intractable epilepsy in early life and can lead to devastating neurodevelopmental consequences. Epilepsy surgery for ES is challenging because of inherent difficulties in localizing the epileptogenic zone in affected infants and children. However, recent clinical series of resective neurosurgery for ES suggest that not only is surgery a viable option for appropriately selected patients, but postoperative seizure outcomes can be similar to those achieved in other types of focal epilepsy. Increased awareness of ES as a potentially focal epilepsy, along with advances in neuroimaging and invasive monitoring technologies, have led to the ability to surgically treat many patients with ES who were previously not considered surgical candidates. In this study, the authors review the current state of epilepsy surgery for ES. Specifically, they address how advances in neuroimaging and invasive monitoring have facilitated patient selection, presurgical evaluation, and ultimately, resection planning.

Introduction

EPILEPTIC spasms (ES) are a common seizure semiology in young children, characterized by jerking movements that are brief and can occur in clusters.[25,36] ES usually occur in children at 3–12 months of life, and in such cases are identified as infantile spasms (IS), but they can also occur after the 1st year of life.[42]Typically, although not uniformly, patients with ES develop other seizure semiologies, such as tonic, tonic-clonic, or focal seizures, by age 3–5 years.[21] ES can have devastating consequences and are often associated with developmental regression.[28] First-line medical therapy typically consists of either adrenocorticotropic hormone (ACTH) or vigabatrin.[2,28,44] Yet, many patients fail these treatment modalities as well as other antiepileptic medications, and continue to have ES and progressive neurodevelopmental regression. In such cases of drug-resistant ES, epilepsy surgery should be considered early in the disease course.[18] In appropriately selected children (i.e., those with ES of focal or hemispheric origin), resective epilepsy surgery can play a crucial role in achieving seizure freedom[8] and can provide outcomes similar to those achieved with other forms of medically intractable focal epilepsy.[13]

Identification of the epileptogenic zone (EZ) in ES patients can be challenging, which makes preoperative evaluation in children with drug-resistant ES uniquely difficult. ES semiology often has little lateralizing and no localizing value.[36] Identification of a focal lesion on MRI facilitates presurgical workup, but in ES the EZ often extends beyond the identifiable lesion.[15] Furthermore, a large proportion of children with ES have no identifiable lesion and must be evaluated further using other imaging modalities.[8,18,30] In both MRI-positive and MRI-negative ES cases, presurgical evaluation often includes either interictal fluorodeoxyglucose PET (FDG-PET)[18,20] or magnetoencephalography (MEG)[41] to facilitate identification of the EZ. Ultimately, given that the EZ is often ambiguous after thorough imaging workup, many children require invasive recordings via either subdural grid electrodes[4,30] or stereoelectroencephalography (SEEG)[8] to delineate the margins and extent of the EZ. Surgical strategies for ES are tailored to the extent of the localized EZ but often involve either multilobar resection or hemispherotomy.

In this article, we review the current state of epilepsy surgery for ES. Specifically, we address how advances in neuroimaging and invasive monitoring have facilitated patient selection, presurgical evaluation, and ultimately, resection planning. In this review, we demonstrate that while challenging, resective epilepsy surgery is a viable treatment strategy for select patients with drug-resistant ES.

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