FIGURE 96.19 MRI image showing hemimegalencephaly progression in a 6-month-old child Axial (A ) and coronal (B) T2-weighted magnetic resonance imaging (MRI) images show markedly enlarged left cerebral hemisphere with thickened gyri and smooth surface, consistent with HME The left lateral ventricle and caudate head are deformed White matter is diffusely hypointense compared with the unaffected right cerebral hemisphere, suggesting accentuated myelination C: Intraoperative photograph of the region of HME oriented with the frontal lobe (F) in the top left and the temporal lobe (T) in the lower middle portions of the image Notice the diffuse cortical disorganization of all gyri This child had a monozygotic twin who was normal (Panel A and C: Reprinted with permission from Engel J, Pedley TA, Aicardi J, et al Epilepsy 2nd ed Philadelphia, PA: Lippincott Williams & Wilkins; 2007 Panel B: From Salamon N, Andres M, Chute DJ, et al Contralateral hemimicrencephaly and clinicalpathologic correlations in children with hemimegalencephaly Brain 2006;129:352–365; with permission of the editor of Brain and Oxford University Press.)