Hemimegalencephaly

  • Etiology: Partial or complete hamartomatous overgrowth of entire or a portion of a cerebral hemisphere due to defective stem cells with abnormal proliferation and migration and organization
  • Imaging:
    — Unilateral generalized or focal enlargement of cerebral hemisphere and ventricle
    — Dysmyelination
    — Thick cortical ribbon
    — Cortical dysplasia
    — Pachygyria
    — Polymicrogyria
    — Heterotopia
    — Ipsilateral advanced myelination
  • DDX:
  • Complications:
  • Treatment:
  • Clinical:
    — Often have hemihypertrophy of ipsilateral body
    — Associated with neurofibromatosis Type 1 and tuberous sclerosis and epidermal nevus syndrome and Proteus syndrome and Klippel-Trenauny syndrome and hypomelanosis of Ito

Radiology Cases of Hemimegalencephaly

MRI of hemimegalencephaly
Axial T2 MRI of the brain shows the left cerebral hemisphere to have diffusely thickening of the cortical ribbon and a decreased amount of white matter.