Advances in pediatric epilepsy neuroimaging

Abstract

Epilepsy is a chronic brain disorder defined by recurrent seizures. Onset may occur early in life, and in fact most often occurs in childhood. The diagnosis and management of childhood epilepsy is more challenging than in adults, in part because of the rich diversity of underlying etiologies ranging from early cerebral anoxia, infection, metabolic disorders, developmental brain malformations, to those also found in young adulthood including hippocampal sclerosis, vascular malformations, primary brain neoplasms, and traumatic brain injury. Neuroimaging plays an important role in identifying the specific underlying pathology and in guiding treatment, and also provides information necessary for etiologic diagnosis, such as in various epilepsy syndromes, and hence prognosis for the affected child and family. Magnetic resonance imaging (MRI) is themost important noninvasive imaging modality, and is mandated in the pre-surgical evaluation of children with epilepsy together with electroencephalography (EEG). Several series have documented that complete lesional resection is the best predictor for favorable postsurgical outcomes. While structural MRI provides exquisite anatomic delineation because of its high spatial resolution and intrinsic soft tissue contrast, it also has its limitations. For instance, MRI may fail to identify subtle lesions that account for up to 20–30% of refractory partial epilepsy, often related to subtle focal cortical dysplasia with microdysgenesis only revealed on histopathology. The identification of these lesions may be possible with other imaging modalities such as positron emission tomography (PET) or, in some instances, diffusion tensor imaging. In addition, in multifocal or diffuse diseases (such as in tuberous sclerosis), even though structural abnormalities can be sensitively depicted by MRI, it may be difficult to determine which of the lesions are epileptogenic and therefore targeted for surgical intervention. In such cases, additional information afforded by advanced MRI or physiologic imaging techniques including diffusion weighted imaging (DWI), MR spectroscopy, and single photon emission computed tomography (SPECT) or PET may be useful. Pre-surgical localization of these lesions, surgical planning and predicting outcome is therefore best accomplished by a multi-modality approach, incorporating structural, functional and physiologic techniques (including functional MRI [fMRI], and magnetoencephalography [MEG]) in addition to the EEG. To date, many of the advanced physiological and functional imaging modalities have not been extensively validated in the evaluation of childhood epilepsy, and they therefore are not part of routine pre-surgical evaluation of such patients in many institutions. They do, however, hold immense promise. For example, incorporation of fMRI may allow refinement of surgical resection *Corresponding author: Doris D.M. Lin, MD, PhD, Division of Neuroradiology, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 600 North Wolfe Street, Phipps B-100, Baltimore, MD 21287, USA. Tel.: +1 443 287 3079; Fax: +1 410 614 1213; E-mail: ddmlin@JHMI.edu. Journal of Pediatric Epilepsy 2 (2013) 1–2 DOI 10.3233/PEP-13045 IOS Press 1