= “Growing” fracture = loculation of CSF into / through skull

Prevalence: 1% of all pediatric skull fractures

Pathogenesis: skull fracture with dural tear leads to arachnoid herniation into dural defect; CSF pulsations produce fracture diastasis + erosion of bone margins (apparent 2–3 months after injury)

• skull defect with indistinct scalloped margins
• CSF-density cyst adjacent to / in skull, may contain cerebral tissue

MR:

• cyst isointense with CSF + communicating with subarachnoid space
• area of encephalomalacia underlying fracture (frequent)
• intracranial tissue extending between edges of bone