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Cluster of partial motor seizures heralding the onset of hemimyoclonic subacute sclerosing panencephalitis

Subacute sclerosing panencephalitis (SSPE) is a devastating neurodegenerative disorder of childhood and young adults. It is caused by a persistent infection of the brain by an aberrant measles virus that produces inflammatory changes in the brain, leading to the death of cortical neurons. In developed countries, SSPE is a rare disease because of widespread immunization; however, in developing countries such as India, the incidence of SSPE is still high. SSPE evolves typically in several stages, as described by Jabbour et al., or atypically whereby diagnosis becomes difficult. We report an unusual case of SSPE presenting with hemimyoclonus, heralded by a cluster of partial motor seizures. A 15-year-old girl was referred to our institution with a history of recurrent episodes of abnormal movement involving the right upper and lower limbs for 2 weeks, followed by onset of jerks of the same side for 3 days. She was provisionally diagnosed as having partial epilepsy, and intravenous loading with sodium valproate (30 mg/kg body weight) was given, followed by an equivalent oral dose in two divided dosages. At the time of presentation, the girl was conscious and well oriented to time, place, and person. Quasiperiodic jerks (i.e., slow myoclonus) involving the right upper and lower limbs were observed. Facial muscles and muscles of the axial skeleton were apparently not involved (see Video). The rest of her neurological examination was normal. Her routine biochemistry and hemogram were normal. An EEG was done, which depicted generalized, 70 to 220 lV in amplitude, stereotypic periodic discharges, 800 to 1,500 ms in duration, occurring at an interval of 4 to 9 seconds (Fig. 1). A detailed enquiry into the past did not reveal any suggestion of similar episodes, cognitive decline, behavioral disturbances, medication use or abuse, or febrile illness. She had received measles vaccine at the age of 9 months, and there was no suggestion of measles in childhood. On the basis of the presence of ‘‘slow myoclonus’’ and classical EEG changes, SSPE was suspected and a cerebrospinal fluid study was done. Cerebrospinal fluid was clear and acellular, with normal sugar (76 g/dL; corresponding blood sugar, 104 g/dL) and protein content (36 mg/dL). A particle agglutination test revealed a measles-antibody titer of 1:256 (control, 1:128). Cerebrospinal fluid immunoglobulin M antibodies against herpes simplex virus, varicella zoster, Japanese encephalitis, and dengue virus, as well as serology for human immunodeficiency virus, hepatitis B surface antigen, and hepatitis C virus, were found to be nonreactive. A final diagnosis of SSPE was made. Presently, the patient is receiving 6 million units of intrathecal interferon, on a monthly basis, with sodium valproate and clonazepam. After 4 months of follow-up, she continues to have hemimyoclonus, without any suggestion of cognitive decline or behavioral abnormality. Hemimyoclonus in our patient could be differentiated from epilepsia partialis continua, which is a continuous focal motor seizure confined to a specific body part and usually consists of clonic movements, in contrast to myoclonic jerks of patients with myoclonic epilepsies, which affect the limbs diffusely. In addition to this, the EEG features were bilaterally symmetrical and characteristic of SSPE. Usually, SSPE presents with cognitive and behavioral abnormalities followed by myoclonic jerks and, subsequently, an akinetic-mute state. Uncommonly, SSPE may manifest with different types of seizures, such as generalized-tonic-clonic seizure, complex-partial seizure, and hemimyoclonus. A case with isolated facial twitching has also been described. A recent report describes 2 boys with epilepsia partialis continua with a fulminant -Additional Supporting Information may be found in the online version of this article. *Correspondence to: Hardeep Singh Malhotra, Department of Neurology, Chhatrapati Shahuji Maharaj Medical University, Lucknow 226003, India; drhsmalhotra@gmail.com Relevant conflicts of interest/financial disclosures: Nothing to report. Full financial disclosures and author roles may be found in the online version of this article.