hemimegalencephaly
Findings
No curated finding names hemimegalencephaly yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
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. Management includes seizure control by antiepileptic medications and early hemispherectomy.
Definition from the Mondo Disease Ontology (MONDO:0020492), read 2026-09-29. CC BY 4.0.
Features
33 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- Hyperintensity of cerebral white matter on MRIHPOHP:0030890
- Very frequent (80% to 99% of cases)
- Interictal EEG abnormalityHPOHP:0025373
- Very frequent (80% to 99% of cases)
- SeizureHPOHP:0001250
- Very frequent (80% to 99% of cases)
- Abnormal skull morphologyHPOHP:0000929
- Frequent (30% to 79% of cases)
- Cranial asymmetryHPOHP:0000267
- Frequent (30% to 79% of cases)
- EEG with burst suppressionHPOHP:0010851
- Frequent (30% to 79% of cases)
Show the remaining 21
- HemihypsarrhythmiaHPOHP:0011215
- Frequent (30% to 79% of cases)
- HemimegalencephalyHPOHP:0007206
- Frequent (30% to 79% of cases)
- PolymicrogyriaHPOHP:0002126
- Frequent (30% to 79% of cases)
- VentriculomegalyHPOHP:0002119
- Frequent (30% to 79% of cases)
- Abnormal neuron morphologyHPOHP:0012757
- Occasional (5% to 29% of cases)
- Atonic seizureHPOHP:0010819
- Occasional (5% to 29% of cases)
Where it sits
Other names
1 name
Resolves to: hemimegalencephaly
- Also called
- unilateral megalencephaly