Hemimegalencephaly With Diffuse Cortical Malformation in a Child With Drug-Resistant Infantile Epileptic Spasms: A Case Report.

Hemimegalencephaly is a rare congenital malformation of cortical development involving hamartomatous overgrowth of part or all of one cerebral hemisphere. It commonly presents during infancy with early-onset, drug-resistant seizures, developmental impairment, and contralateral motor deficits. Infantile epileptic spasms may be an initial manifestation. Brain magnetic resonance imaging (MRI) is central to diagnosis and surgical planning. We report the case of an 11-month-old boy with West syndrome and severe developmental delay whose epileptic spasms persisted despite treatment with vigabatrin, sodium valproate, and levetiracetam. Brain MRI demonstrated marked asymmetric enlargement of the left cerebral hemisphere, diffuse cortical thickening, blurring of the gray-white matter differentiation, enlargement and morphological distortion of the left lateral ventricle, shallow sulcation, and extensive pachygyria with areas approaching an agyric appearance. The right cerebral hemisphere was structurally preserved. These findings were consistent with left hemimegalencephaly associated with an extensive malformation of cortical development. An anterior corpus callosotomy was performed as a palliative disconnective procedure; however, the epileptic spasms persisted, and the patient was subsequently referred for evaluation of definitive left hemispherotomy. This case illustrates the characteristic MRI appearance of hemimegalencephaly with diffuse cortical malformation and highlights the limitations of anterior corpus callosotomy when the epileptogenic substrate involves an entire malformed hemisphere. It also emphasizes the role of imaging in guiding escalation to definitive hemispheric disconnection when seizures remain drug-resistant.