Where, [SP.sub.posterior cranial fossa] is the total number of points hitting the components of posterior cranial fossa and [SP.sub.intracranial cavity] is the total number of points hitting sectioned surface of intracranial cavity including all parts.
Brain parenchyma herniations with surrounding CSF into the DVS and/or calvarium have a prevalence of 0.32% and were encountered more frequently in posterior inferior parts of the intracranial cavity .
The authors of one such case report proposed that radiation resulted in the destruction of a tumor invading the base of the skull that then created a defect through which air entered the intracranial cavity resulting in pneumocephalus .
STAGE FEATURES: A Disease confined to the nasal cavity B Disease confined to the nasal cavity and paranasal sinuses C Disease beyond the nasal cavity and paranasal sinuses, including involvement of cribriform plate, base of skull, orbit or intracranial cavity D With metastasis to cervical lymph nodes or distant metastasis.
(3,10) Cholesteatomas were described in 3 cases with heterotopic brain tissue, which suggests that glial choristomas can be caused by local destruction of bony segments subsequent to cholesteatoma, meningitis, or otitis media and that the cholesteatomas can occasionally expand into the intracranial cavity. (3) However, other authors have reported none of these predisposing factors, which perhaps separates these true lesions from the glial variants of acquired encephaloceles.