The 'mushroom' shape of the gyri and their parasagittal location are typical features of so-called ulegyria.  'Ule' is derived from Latin and means 'scarred'. The lesions are often bilateral and sometimes predominantly unilateral. Diagnostic criteria are atrophic thinning of the cortex, especially at the deep portion with sparing of the apex which causes the mushroom shape. Underlying white matter abnormalities on T2 and FLAIR sequences are mostly seen.

They are the result of hypoxic-ischemic encephalopathy due to perinatal asphyxia and are typical for full-term infants. They are often associated with pharmacoresistant seizures and surgery may give better outcomes.