Hemiconvulsion–hemiplegia syndrome in a patient with severe myoclonic epilepsy in infancy

Summary

We report a 2-year-old girl who had repeated febrile or afebrile seizures since infancy. Prolonged left/right hemiconvulsions and myoclonus of the eyelids/extremities with generalization to tonic–clonic seizures, were refractory to antiepileptic agents. At age 1 year and 4 months, she contracted rotavirus infection, and developed status epilepticus with persistent right hemiclonic seizures. Left unilateral brain edema with subsequent emergence of cortical laminar necrosis and white matter lesions, and progressive atrophy of the left cerebral hemisphere were noted during this period. She showed residual right hemiparesis and mild intellectual disability, and had generalized/eyelid myoclonia and hot water epilepsy after a 5-month seizure-free period. Analysis for SCN1A, the gene encoding the neuronal voltage-gated Na⁺ channel α1 subunit revealed a nonsense mutation, R1892X. These indicate the potential risk in patients with severe myoclonic epilepsy in infancy (SMEI) to develop hemiconvulsion–hemiplegia (HH) syndrome. SCN1A mutations may need to be further explored in patients with HH syndrome without features of SMEI.