Hemispherotomy in Infants with Hemimegalencephaly: Long-Term Seizure and Developmental Outcome in Early Treated Patients

Abstract

Hemimegalencephaly (HME) is a rare brain congenital malformation, consisting in altered neuronal migration and proliferation within one hemisphere, which is responsible for early onset drug-resistant epilepsy. Hemispherotomy is an effective treatment option for patients with HME and drug-resistant epilepsy. Surgical outcome may be variable among different surgical series, and the long-term neuropsychological trajectory has been rarely defined using a standardized neurocognitive test. We report the epileptological and neuropsychological long-term outcomes of four consecutive HME patients, operated on before the age of three years. All patients were seizure-free and drug-free, and the minimum follow-up duration was of five years. Despite the excellent post-surgical seizure outcome, the long-term developmental outcome is quite variable between patients, ranging from mild to severe intellectual disabilities. Patients showed improvement mainly in communication skills, while visuo-perceptive and coordination abilities were more impaired. Epileptological outcome seems to be improved in early treated patients; however, neuropsychological outcome in HME patients may be highly variable despite early surgery.

Keywords: developmental outcome; epilepsy surgery; hemimegalencephaly; hemispherotomy.

Figure 1

(a): MRI of patient 1, showing enlarged right hemisphere, with gray–white matter blurring mainly in the temporo-occipital regions. (b): T2-weighted sequence of patient 2 MRI, showing right enlargement of temporo-occipital regions, with blurring, extending also over the suprasylvian regions. (c): MRI of patient 3, showing enlarged and malformed cortex over the left hemisphere, mainly posteriorly. (d): MRI of patient 4, T2-weighted sequence, showing enlargement and malformation of left hemisphere, mainly temporal region.

Figure 2

(a): Interictal EEG of patient 1, showing sub-continuous poly-sharp waves and slow waves with some flattening over the right posterior perisylvian region. (b): Interictal EEG of patient 3, showing pseudo-periodic paroxystic pattern involving the left hemisphere, characterized by repetitive polyspikes. (c): Patient 3. Focal seizure, characterized by rhythmic theta activity involving the left hemisphere and the vertex, without contralateral diffusion. (d): EEG of patient 4, showing continuous and pseudo-periodic spike–wave complexes over the right centro-temporal derivations, with focal seizure starting from central and temporal regions.

Figure 3

(a): Patient 1 pre- and post-surgical quotients. (b): Patient 2 pre- and post-surgical quotients. (c): Patient 3 post-surgical quotients. (d): Patient 4 post-surgical verbal and performance quotients performed at 3.5, 15, 27, and 48 months after surgery.