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Findings:
Skull Plain Films: 1.5 years post-trauma: large diastatic skull fracture with soft tissue protuberance suggestive of leptomeningeal cyst.

MR: Left parietal defect demonstrating large leptomeningeal cyst and other sequelae of remote trauma. (encephalomalacia, old blood products, ventricular dilatation)

Diagnosis: Left diastatic skull fracture with leptomeningeal cyst.

Discussion: The presence of skull fractures has little prognostic value concerning neurologic damage resulting from trauma. Skull fractures may actually diminish injury to the underlying brain by dispersing the force from trauma. The absence of skull fracture in no way excludes brain injury.

The most common skull fractures are linear and typically in the frontal or parietal region. If nondisplaced, the fracture heals spontaneously without treatment. Infants typically heal in less than 6 months, older children within a year, and adults in 2-3 years.

If skull fractures are associated with tears of the underlying dura, herniation of meninges and brain tissue into the diastatic fracture can occur. This interposition of tissue prevents osteoblasts from migrating, inhibiting fracture healing. CSF pulsation actually results in enlargement of the fracture, with extension of the meninges extracranially, hence, the term "growing fracture" or leptomeningeal cyst.

Leptomeningeal cysts are seen in 0.6% of all fractures, with 90% of these occurring in patients less than 3 years old.

References:
Barkovich AJ. Pediatric neuroimaging, second edition, Raven Press, New York, 1995.

Latchaw RE. MR and CT imaging of the head, neck and spine, Mosby Year Book, St. Louis, 1991.

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