Megalencephaly

What it means

Diffuse enlargement of the entire cerebral hemispheres leading to macrocephaly (with or without overlying cortical dysplasia).

Megalencephaly is defined as fronto-occipital diameter above two standard deviations of the mean for the patient's age because of an oversized brain parenchyma. This is different from macrocephaly, which is defined by an enlarged head circumference and therefore accounts also for the size of the extra-axial spaces.

Rare diseases that can present with this8

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Enlarged brain · Macrencephaly