Seizures in the Contralateral hemisphere in Rasmussen Encephalitis after Disconnective hemispherectomy – True or False lateralizing? (P13-1.010)

Abstract

<h3>Objective:</h3> To describe a case that highlights diagnostic and treatment challenges when seizures recur after disconnective hemispherectomy. <h3>Background:</h3> Recurrence of seizures after hemispheric disconnection warrants careful evaluation to assess candidacy for additional surgery. Interpretation of EEG in the setting of post-hemispheric disconnection poses special challenges. <h3>Design/Methods:</h3> Retrospective chart review and literature search. <h3>Results:</h3> A 10-year-old right-handed girl presented with focal drug-resistant epilepsy from age 7 years. Initially, she had left face/arm motor seizures, but over the years developed other seizure types - myoclonic, generalized tonic-clonic, dialeptic, and atonic head drop. Neurological examination showed no focal motor deficit. Interictal EEG with abundant right frontocentral and secondary bilateral synchronous discharges, while ictally had a diffuse non-localized pattern. Serial MRI brain showed progressive right hemispheric atrophy predominantly around the perisylvian and perirolandic regions. She met the criteria for diagnosis of Rasmussen encephalitis. Due to the poor quality of life from daily seizures, after much contemplation, a right disconnective hemispherectomy was done. Pathology of brain tissue confirmed Rasmussen encephalitis. Her seizures recurred around 4 months post-surgery. Interictal EEG showed abundant independent epileptiform discharges from both hemispheres. Ictal EEG showed ictal patterns over the left hemisphere. Post-operative brain MRI showed no evidence for residual hemispheric disconnection. A possibility of bilateral Rasmussen encephalitis versus a false lateralizing EEG pattern with seizures still arising from the operated hemisphere was considered. She underwent a re-do right anatomic hemispherectomy and has been seizure free since surgery at a 2-year follow-up. Post-op EEG showed no epileptiform abnormalities over the left hemisphere. <h3>Conclusions:</h3> In the post-hemispherectomy setting, both interictal and ictal EEG patterns may be falsely lateralizing, and persistent seizures should raise the suspicion of an incomplete disconnection. Looking for an overt connection on MRI can help, but the lack of one is not always a reliable marker of complete disconnection. <b>Disclosure:</b> Dr. Natteru has nothing to disclose. Dr. Alzahrany has nothing to disclose. William Bingaman has nothing to disclose. Dr. Naduvil Valappil has nothing to disclose.