Extracranial brain herniation

Extracranial or transcalvarial brain herniation refers to herniation of brain tissue external to the calvaria through a skull bone defect, which may be post-traumatic or post-surgical. Unlike encephaloceles, brain herniation is not surrounded by the meninges. 

Craniectomy may be performed to decompress intracranial contents in patients with intracranial hypertension after medical management fails. 

The herniated brain tissue requires surgical reduction as it is at risk of ischemia and venous infarction from occluded cortical veins.