Abstracts

Rationale: SCN1A mutation-related seizures are mostly regarded as generalized epileptic syndromes, with variable severity ranging from mild syndromes of febrile seizures and generalized epilepsy with febrile seizures plus (GEFS+), to the severe end of the spectrum such as Dravet syndrome. Recent reports have linked focal seizures to this gene mutation, and reported poor outcome with resective epilepsy surgery. We are reporting a new phenotype of focal seizures in a child with SCN1A mutation and reveiwing pertinent letirature. Methods: Chart review of clinical, laboratory and imaging data, as well as scalp and intracranial stereo depth VEEG recordings. Literature search of SCN1A gene mutation-related focal seizures and surgical evaluations was also conducted. Results: An 8-year-old, right-handed hispanic male with severe cognitive delay presented with a history of medically intractable seizures since the age of 6 months with no history of febriel seiuzres. His seizure were mostly nocturnal stereotyped asymmetric tonic posturing with left arm extension and right arm flexion in a figure 4 shape lasting less than 1.5 minutes, and followed by post ictal left Todd's paralysis. Bain MRI showed mild volume loss of the right mesial hippocampus. PET Scan revealed symmetric decrease of activity in both temporal lobes. Scalp cVEEG showed diffuse background slowing with frequant interictal left central epileptiform sharp-and-wave discharges. Several seizures were captured. The EEG ictal onset  was poorly localizing, however there was a good ictal propagation over the left fronto-cetral region. Phase II VEEG monitoring utilized 12 stereotactic depth electrodes that were implanted in bilateral temporal (amygdala, hippocampus, posterior hippocampus) and bilateral frontal (orbito frontal, anterior cingulate and SMA) lobes. Eleven seizures were captured, five of which had clinical semiology and ICEEG findingd localizing to the left anterior cingulate and left SMA, and six had semiology and ICEEG findings localization to the right anterior cingulate and right SMA. This study proved the presence of bilateral indepandant frontal lobe foci localizing to the SMA bilaterally.The patient was deemed not a good candidate for resective epilepsy surgery. Chromosomal Microarray revealed a 15 kilobase deletion at 2q24.3. The deleted interval involves several coding exons of the SCN1A gene, suggesting a diagnosis of Sodium Channelopathy epileptic encephalopathy. Patient's anti-epileptic Drugs were re-evaluated. He was weaned off Carbamazepine and Lamotrigine, and Valproic Acid was added.Review of literature indentified a few reports of other focal seizures associated with SCN1A gene mutation including Benign Epilepsy of Childhood with Centro Temporal Spikes (BECTS) and Panayiotopoulos Syndrpme. To our knowledge there has been no reports of focal bilateral SMA seizures in patietns with SCN1A mutation. Skjei et al, reported 6 patients with SCN1A mutation and medically intractable focal epilepsy who underwent resective epilepsy surgery (five out of six patients had frontal region resection and one had temporal lobe resection). All patients had poor long term outcome (ILAE class 4 or 5). It is noted that most focal seizures associated with SCN1A mutation were localizing to the frontal lobe. Palliative surgery such as corpus callosotomy and VNS have been reported with good outcome and can be considered in these patients. Conclusions: We report a new phenotype of SCN1A mutation-related seizures manifested as bilateral, independent SMA focal seizures. The presense of SCN1A mutation could predict poor outcome with resective epilepsy surgery. However other palliative surgical proceidures such as Corpus Callosotmy and VNS could be considered. Funding: None