Imaging of intractable paediatric epilepsy

Page 1 of 10 Review Article Imaging of intractable paediatric epilepsy Authors: Sanjay Prabhu1 Nasreen Mahomed2 Affiliations: 1 Department of Radiology, Boston Children’s Hospital, Harvard Medical School, United States of America Department of Diagnostic Radiology, University of the Witwatersrand, South Africa 2 Correspondence to: Sanjay Prabhu Email: sanjay.prabhu@childrens. harvard.edu Postal address Private Bag X3, University of the Witwatersrand, Johannesburg 2050, South Africa Dates: Received: 01 Sept. 2015 Accepted: 15 Oct. 2015 Published: 09 Dec. 2015 How to cite this article: Prabhu S. & Mahomed N. ‘Imaging of intractable paediatric epilepsy’. S Afr J Rad. 2015;19(2): Art. #936, 10 pages. http://dx.doi. org/10.4102/sajr.v19i2.936 Copyright: © 2015. The Authors. Licensee: AOSIS OpenJournals. This work is licensed under the Creative Commons Attribution License. Approximately 20% of paediatric patients with epilepsy are refractory to medical therapies. In this subgroup of patients, neuroimaging plays an important role in identifying an epileptogenic focus. Successful identification of a structural lesion results in a better outcome following epilepsy surgery. Advances in imaging technologies, methods of epileptogenic region localisation and refinement of clinical evaluation of this group of patients in epilepsy centres have helped to widen the spectrum of children who could potentially benefit from surgical treatment. In this review, we discuss ways to optimise imaging techniques, list typical imaging features of common pathologies that can cause epilepsy, and potential pitfalls to be aware of whilst reviewing imaging studies in this challenging group of patients. The importance of multidisciplinary meetings to analyse and synthesise all the non-invasive data is emphasised. Our objectives are: to describe the four phases of evaluation of children with drug-resistant localisation-related epilepsy; to describe optimal imaging techniques that can help maximise detection of epileptogenic foci; to describe a systematic approach to reviewing magnetic resonance imaging of children with intractable epilepsy; to describe the features of common epileptogenic substrates; to list potential pitfalls whilst reviewing imaging studies in these patients; and to highlight the value of multimodality and interdisciplinary approaches to the management of this group of children. Introduction Approximately 20% of children with epilepsy are refractory to medical therapy, which has a significant adverse effect on patients and their families.1 The term ‘drug-resistant epilepsy’ has been proposed by the International League against Epilepsy (ILAE) to replace terms such as refractory and intractable epilepsy. Neuroimaging plays an important role in identifying epileptogenic foci that can be surgically resected. Advances in neuroimaging, including advances in scanner hardware and software, have allowed improved signal-to-noise ratio and achieve faster scan times and fewer motion artifacts. In addition, use of advanced imaging techniques, including multimodality fusion, has enabled improved lesion detection and localisation. It is important to choose tests based on their potential to further define the epileptogenic region, acknowledge their known strengths and limitations, and weigh the expected clinical benefit and incremental cost-effectiveness. Any additional test should be chosen on the basis of the likelihood that it can change the resection plan or surgical method. It should be pointed out that a review in 2011 by an ILAE panel found no studies that qualified as class 1 evidence, and little class 2 evidence on the utility of diagnostic tests in pre-surgical evaluation of patients with pediatric epilepsy.2 Recommendations provided in the present review are based on the first author’s personal experience of working in paediatric epilepsy groups over the last decade and is similar to consensus recommendations from various ILAE panels.3 Phases in the evaluation of children with epilepsy Phase 1 One must first define the seizure syndrome and ensure that medical therapy is optimised; this includes a detailed history, including pre- and postnatal events, seizure history including the semiology (type of seizure), characteristics of onset and manifestations of the seizures, a full neurological examination, detailed electrophysiology via several electroencephalography (EEG) exams that record interictal and ictal events, and neuroimaging. Read online: Scan this QR code with your smart phone or mobile device to read online. Functional imaging with single-photon emission computed tomography (SPECT) and/or positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and magneto encephalography (MEG) are also used in some cases. Results are discussed at multidisciplinary team meetings involving specialists in neurology, neurosurgery, neurophysiology, neuroradiology and neuropsychology. If the anatomical and functional images are concordant with the http://www.sajr.org.za doi:10.4102/sajr.v19i2.936 Page 2 of 10 seizure semiology and information gathered is considered adequate, surgical resection may be planned. If there is no concordance of data, further testing may be required, such as hospital admission for continuous scalp EEG or video-telemetry to better define the seizure frequency and semiology, particularly if the seizures are predominantly nocturnal or ill-defined on routine EEG. Neuropsychological testing helps to assess baseline performance, the level of neurodevelopment, deficits in various domains including verbal and non-verbal communication, and psychosocial factors. This evaluation helps in documenting the extent of premorbid damage and predicting possible outcomes following epilepsy surgery. Phase 2 Invasive monitoring is used to further lateralise and localise the seizure focus that remains incompletely defined by noninvasive studies in Phase 1 or to determine the location of the seizure focus relative to eloquent cortex. Phase 3 Comprehensive review of the data is done by the epilepsy team, to confirm concordance of findings; and to decide if surgery is the best option (either curative or palliative). Phase 4 The postoperative assessment is routinely performed 6–24 months after the surgical procedure to document the final outcome. Imaging techniques Neuroimaging is recommended when localisationrelated epilepsy is known or suspected, when the epilepsy classification is in doubt, or when an epilepsy syndrome with remote symptomatic cause is suspected. MRI is the modality of first choice. Aims of structural imaging include locating the epileptogenic region, providing a surgical planning map, defining the relation of a focal lesion to eloquent areas, and as a base for functional studies including PET, SPECT, fMRI and MEG. In the last decade, advances in scanner hardware and software have improved the rate of detection of epileptogenic lesions. Wherever (...truncated)