Seizures as Presenting Feature of Subacute Sclerosing Panencephalitis: a Systematic Review of Case Reports and Case Series

Purpose of ReviewIn this systematic review, we reviewed the seizure characteristics, particularly seizure semiology, in patients with SSPE. We also assessed the impact of seizures on the course of SSPE. Four databases were used to gather the information: PubMed, Embase, Scopus, and Google Scholar. The last search was done on May 3, 2023. The PRISMA requirements were adhered to. Protocol was registered to PROSPERO (CRD42023409343). SSPE was identified based on Dyken's criteria. The Joanna Briggs Institute Critical Appraisal tool was used to assess the quality of data.Recent FindingsOur review identified 63 reports containing information on 73 patients. Approximately, 60% of patients had an "acute fulminant" course. Seizure semiology varied among the reported cases, with the majority experiencing generalized tonic-clonic seizures (21; 29%) or focal seizures (25; 34.7%). Other seizure types included absences, febrile seizures, and atonic seizures/drop attacks. Approximately in 10% (7/72) of cases, multiple seizure types were recorded. In the majority, seizures were difficult to control despite the administration of multiple drugs. Five patients presented with status epilepticus that included both convulsive status and non-convulsive status. In a few cases, seizures were recorded after intrathecal interferon-alpha therapy. MRI showed T2/FLAIR periventricular white matter hyperintensity in 30 cases. We noted that approximately 10% of cases were either misdiagnosed or had periodic myoclonus misclassified as myoclonic seizures.Among patients with multiple seizure types, particularly with periodic myoclonus and progressive encephalopathy possibility of SSPE should always be considered. Periodic myoclonus should not be confused with seizures.