Overview
Hemimegalencephaly (HMEG) is a severe malformation of cortical development characterized by unilateral enlargement of a cerebral hemisphere, marked by architectural and cellular abnormalities, often accompanied by intractable epilepsy 13.Diagnosis
Clinical Presentation: Intractable epilepsy, developmental delay 13.
Imaging: MRI reveals unilateral enlargement of the cerebral hemisphere with abnormal cortical architecture 13.
Electroencephalography (EEG): May show burst suppression patterns or specific seizure types like epileptic negative myoclonus in neonates 2.
Histopathology: Neuropathological examination confirms neuronal migration defects, micropolygyria, and cytomegalic neurons 13.Management
First-Line Treatment: Antiepileptic drugs (AEDs) tailored to seizure type; no specific dosing mentioned 2.
Surgical Intervention: Hemispherectomy or focal resection considered for medically refractory epilepsy 1.
Supportive Care: Management of developmental delays and associated neurocutaneous syndromes 1.Special Populations
Pediatrics: Neonatal presentation with Ohtahara syndrome and specific seizure types like epileptic negative myoclonus 2.
Comorbidities: Association with neurocutaneous syndromes such as linear nevus sebaceous syndrome 1.Key Recommendations
Perform MRI and EEG for definitive diagnosis of hemimegalencephaly, identifying characteristic imaging and electrographic features (Evidence: Moderate 12).
Initiate treatment with antiepileptic drugs based on seizure type, with surgical options like hemispherectomy considered for refractory cases (Evidence: Expert opinion 1).
Evaluate for associated neurocutaneous syndromes through dermatological examination, especially in cases with syndromic presentations (Evidence: Moderate 1).References
1 Boer K, Troost D, Spliet WG, Redeker S, Crino PB, Aronica E. A neuropathological study of two autopsy cases of syndromic hemimegalencephaly. Neuropathology and applied neurobiology 2007. link
2 Guzzetta F, Battaglia D, Lettori D, Deodato F, Sani E, Randò T et al.. Epileptic negative myoclonus in a newborn with hemimegalencephaly. Epilepsia 2002. link
3 Dambska M, Wisniewski K, Sher JH. An autopsy case of hemimegalencephaly. Brain & development 1984. link80012-1)