Abstracts

Hemimegalencephaly (HM) describes a congenital brain hemidysplasia with one substantially malformed hemisphere, often with increased myelination, and enlarged total volume. Most patients with HM/hemidysplasia present in infancy with intractable seizures, often including early infantile spasms (IS). Epilepsia partialis continua (EPC) is frequent, as is hemiparesis and hemianopsia contralateral to the HM. Non-CNS malformations are variable. Treatment of seizures is difficult. Early hemispherectomy is often recommended for seizure control and improved developmental outcome.
We reviewed 6 cases of HM seen in the last decade at CHLA. Neuroradiological and videoEEG were available in all; neuropathologic materials were available for two.
All presented with seizures, often on the day of birth. Serial videoEEG demonstrated evolving seizure patterns. Although first seizures were partial motor, IS appeared in 4, eventually replaced by other seizure types and/or EPC. Early EEGs tended to suggest bilateral discharges; all evolved into strictly unilateral EEG abnormalities. IS were often atypical, with focal components. MRIs demonstrated unilateral cortical and subcortical abnormalities. Two underwent hemispherectomies. One did well, with full seizure control and improved development. One died postoperatively. Two have attained fair seizure control with multiple AEDs. One has persistent EPC involving the hemiparetic hand, which does not add to functional deficits. One recently diagnosed infant has EPC despite multiple anticonvulsants; hemispherectomy is anticipated. Functional MRI suggested motor function in the involved cortex despite clinical hemiparesis.[table1]
In children with cerebral HM/hemidysplasia syndromes, seizure type and pattern is highly variable, but IS are frequently seen in the first year. Seizure control without hemispherectomy is unlikely, but hemispherectomy is not without potential morbidity and mortality.