Presentation
Macrocephaly
Patient Data
There is asymmetrical hypertrophy of the left cerebral hemisphere. The left lateral ventricle is enlarged, particularly the occipital horn. The gyri on the left side are overcrowded. Some of them are broad and featureless, especially those in the frontal lobe. The left cerebellar hemisphere is also larger than the right. There is an ectopic band of grey matter in the left deep parietal region separated from the overlying cortex by white matter, giving a double cortex appearance. Note the rightward shift of the falx on account of the enlarged left cerebral hemisphere.
The left cerebral hemisphere is hypertrophied with a contralateral shift of the falx, and the lateral ventricle is enlarged. The gyri of the left cerebral hemisphere are broad and featureless, particularly in the frontal lobe.
Case Discussion
Hemimegalencephaly is a rare genetic disorder characterized by the hamartomatous proliferation of neurons and glial cells of one of the cerebral hemispheres. The involved cerebral hemisphere may have focal or diffuse neuronal migration disorders, including grey matter heterotopia, lissencephaly, and poly-microgyria. There may be abnormal gliosis of white matter which is reflected by abnormal T2 and FLAIR signals. The ipsilateral cerebellar hemisphere or brainstem may be enlarged, termed total hemimegalencephaly.
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