Synonyms: Unilateral megalencephaly
Hemimegalencephaly is a rare cerebral malformation characterized by overgrowth of all or part of a cerebral hemisphere often with ipsilateral severe cortical dysplasia or dysgenesis white matter hypertrophy and dilated lateral ventricle presenting in early infancy with progressive hemiparesis severe psychomotor retardation and intractable seizures. Hemimegalencephaly may be an isolated finding or associated with other syndromes such as angioosteohypertrophic syndrome epidermal nevus syndrome and Ito hypomelanosis (see these terms). Management includes seizure control by antiepileptic medications and early hemispherectomy.
Data from Orphanet are used to provide information on a disease's name, synonym(s), and overview. Reference: Access aggregated data from Orphanet at Orphadata. Orphadata: Free access data from Orphanet. © INSERM 1999. Available on http://www.orphadata.org. Data version February 2026
Newly diagnosed with
Hemimegalencephaly?
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Advocacy Organizations
CLOVES Syndrome Community
The vision of CLOVES Syndrome Community (CSC) is an improved quality of life for those living with CLOVES syndrome. Our mission is to support, educate, empower and improve the lives of those affected by CLOVES syndrome.
COMBINEDBrain Inc
COMBINEDBrain is a consortium for outcome measures and biomarkers for neurodevelopmental disorders. We are collaborating to cure rare, non-verbal brain disorders.
Genetic Epilepsy Team Australia
Collaboration of research and care
Moonshots for Unicorns
Curing single-gene disorders
Pediatric Epilepsy Surgery Alliance
Pediatric Epilepsy Surgery Alliance is the only caregiver-led, science-driven nonprofit organization fully dedicated to the community of children who need neurosurgery to treat their medication-resistant seizures. We enhance the lives of children with drug-resistant epilepsy by empowering their families with research, support services, and impactful programs across the lifespan.
Project CASK
VISION Project CASK believes in a world free of the life limitations and debilitating effects of CASK gene disorders. MISSION To accelerate breakthroughs in research to develop treatments and a cure for CASK gene disorders. VALUES Collaboration. Transparency. Urgency.
Rare Epilepsy Network (REN)
Improving outcomes of people with rare epilepsies through an innovative collaborative infrastructure that drives urgent, patient-centered research, educaiton and advocacy.
Syndromes Without A Name (SWAN) Australia
Provide information, support and advocacy to families caring for a child with an undiagnosed or rare genetic condition.
TNPO2 Foundation
Develop personalized therapeutics for ultra rare genetic neurodevelopmental diseases, especially those arising from mutations in the TNPO2 gene.
Wave of Support, Inc
Empowering those affected by bleeding disorders and other rare disease through advocacy, resources, education, and support
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Clinical Trials
For a list of clinical trials in this disease area, please click here.