Original Article SISCOM in Children with Tuberous Sclerosis Complex-Related Epilepsy Mariam S. Aboian MD, PhD a , Lily C. Wong-Kisiel MD b , Michelle Rank CNMT c , Nicholas M. Wetjen MD d , Elaine C. Wirrell MD b , Robert J. Witte MD c, * a Department of Internal Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire b Division of Child and Adolescent Neurology, Department of Neurology, Mayo Clinic College of Medicine, Rochester, Minnesota c Division of Neuroradiology, Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota d Department of Neurosurgery, Mayo Clinic College of Medicine, Rochester, Minnesota article information Article history: Received 15 December 2010 Accepted 28 March 2011 abstract Identification of a single epileptogenic focus in patients with tuberous sclerosis complex is a challenge. Noninvasive imaging modalities, including subtraction ictal single-photon emission computed tomog- raphy coregistered to magnetic resonance imaging (SISCOM), have been used to determine the dominant epileptogenic focus for surgical resection. We assessed whether complete resection of SISCOM hyper- perfusion abnormality correlates with seizure-free outcome in 6 children with tuberous sclerosis complex-related epilepsy. The median seizure onset age was 4 months (range 1 day to 16 months). The age at surgery ranged from 8 months to 13 years. A dominant SISCOM hyperperfusion focus was iden- tified in 5 patients with multiple tubers. SISCOM provided additional localizing information for epilepsy surgery in 3 patients with nonlocalizing or discordant electrophysiologic and neuroimaging findings. At a minimum of 2 years’ follow-up, 3 patients were free of seizures overall. Freedom from seizures was associated with complete resection of SISCOM abnormality in 2 patients. These findings demonstrate that SISCOM can be useful in identifying the epileptogenic zone and in guiding the location and extent of epilepsy surgery in children with tuberous sclerosis complex and multifocal abnormalities. In children with tuberous sclerosis complex and intractable epilepsy, complete resection of the SISCOM hyper- perfusion abnormality is associated with freedom from seizures. Ó 2011 Elsevier Inc. All rights reserved. Introduction Over 90% of children with tuberous sclerosis complex develop epilepsy at an early age, with over 80% of these progressing to medically refractory epilepsy [1-8]. Seizure-free outcome in chil- dren with tuberous sclerosis complex undergoing epilepsy surgery is reported to be 22-69% [9,10], with more favorable outcomes in patients who have a single tuber on magnetic resonance imaging (MRI), focal preoperative electroencephalographic (EEG) abnor- malities, and focal seizure semiology [9-15]. Tonic seizures and low intellectual quotient have been reported to be negative predictive factors [16]. Identification of a focal epileptogenic region in children with tuberous sclerosis complex is frequently a challenge because of multiple tubers on neuroimaging, multiple seizure semiologies, and nonlocalizing, generalized, or multifocal epileptiform abnor- malities [2,17]. As a result, many patients are offered ketogenic diet or palliative procedures such as corpus callosotomy or vagus nerve stimulation as opposed to focal cortical resection procedures [6,9,12-14,18-20]. Several reports have documented the effective- ness of resection of multiple tubers on seizure outcome [4,21,22]. Novel imaging methods to localize the epileptogenic focus are of increasing importance when MRI and EEG are discordant or non- localizing. Potential modalities reported to be of use include diffusion weighted imaging [23], fluorodeoxyglucose and a-[ 11 C] methyl-L-tryptophan positron emission tomography [24-30], magnetoencephalography [29,31-33], functional MRI [34], and ictal single-photon emission computed tomography [14,35,36]. Jansen et al. suggested that multifocal findings on ictal single-photon emission tomography correlate with negative outcome after epilepsy surgery [16]. Subtraction ictal single-photon emission computed tomography coregistered to MRI (SISCOM) improves the conventional inter- pretation of ictal single-photon emission computed tomography. Intensity differences more than 2 standard deviations between interictal and ictal images are coregistered onto the individual patient’s MRI. This technique produces semiquantitative maps of cerebral perfusion differences between ictal and interictal states and places that information in the context of the patient’s own * Communication should be addressed to: Dr. Witte; Division of Neuroradiology; Department of Radiology; Mayo Clinic Foundation and College of Medicine; 200 First St. SW; Rochester, MN 55905. E-mail address: witte.robert@mayo.edu Contents lists available at ScienceDirect Pediatric Neurology journal homepage: www.elsevier.com/locate/pnu 0887-8994/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.pediatrneurol.2011.05.001 Pediatric Neurology 45 (2011) 83e88