Subcortical band heterotopia in a child with new-onset seizures: A case report

Subcortical band heterotopia (SBH), also known as "double cortex" syndrome, is a rare neuronal migration disorder characterized by symmetric bands of heterotopic gray matter located between the cerebral cortex and lateral ventricles. It predominantly affects females and typically presents in childhood or adolescence with epilepsy and variable cognitive or motor impairment. We report a 9-year-old girl with normal antenatal, perinatal, developmental, and academic history who presented with a one‑month history of frequent generalized tonic-clonic seizures accompanied by new onset generalized limb weakness. Neurological examination revealed mild, symmetric weakness with brisk deep tendon reflexes but preserved cranial nerve and sensory function. Routine laboratory tests and electroencephalography were unremarkable. Brain magnetic resonance imaging demonstrated classic features of SBH, including bilateral, well-defined bands of gray matter deep to and paralleling the cortical surface, separated from the overlying cortex by intervening white matter and isointense to normal cortex on all sequences. A diagnosis of SBH was made based on these characteristic imaging findings. The patient was started on phenytoin, reflecting local prescribing practices and formulary availability in resource‑limited settings, resulting in effective seizure control and clinical stability on follow‑up; genetic testing for DCX or other implicated genes was not performed due to resource limitations. This case highlights that SBH can present in a developmentally normal child with new-onset generalized seizures and limb weakness, underscores the crucial role of MRI in diagnosis where genetic testing is unavailable, and emphasizes the importance of early recognition and tailored antiepileptic therapy to optimize long‑term neurological outcomes.