Learning Radiology xray montage

Leptomeningeal Cyst
Growing Fracture

  • Sometimes called a “growing fracture”
  • Age
    • Usually <3 years
  • Incidence
    • Rare - <1% of pediatric skull fractures
  • Clinical findings
    • Usually detected by parents who note a soft, cystic mass developing on skull of child

  • Pathogenesis

    • Skull fracture with dural tear leads to herniation of pia and arachnoid layers (leptomeninges) through the dural tear
    • Cerebrospinal fluid pulsations lead to progressive erosion of skull around the fracture site
    • Margins of the fracture will still be apparent months after injury and there will be greater diastasis of the fracture as time goes on than when first injured

  • Imaging findings

    • Angular, linear lytic lesion in the skull with scalloped margins
    • Brain extrusion may occur shortly after the fracture in neonates and young infants leading to focal dilatation of the lateral ventricle near the growing fracture
    • MRI
      • Cyst isointense with CSF and communicating with subarachnoid space
      • Area of encephalomalacia underlying fracture (frequent)
      • Intracranial tissue extending between edges of bone

  • Treatment

    • Surgical repair of the dura and resection of the cyst


Leptomeningeal Cyst

Left lateral radiograph of the skull reveals a sharply marginated, angular, linear lucency in the posterior parietal-occipital region at the site of a previous linear skull fracture. This is the characteristic appearance of a leptomeningeal cyst.