Incipient Transcalvarial Cerebral Herniation: Underrecognized Complication of Elective Craniotomy

Herniation of the brain through an osseodural defect has been well described in small children as an uncommon occurrence after closed head injury. Pressure from the growing brain has been implicated in progressive enlargement and reshaping of the fracture line. An analogous phenomenon in adults has been observed in the described cases where neurosurgical intervention led to a persistent dural defect. Transcalvarial herniation of the brain through the dural defect resulted in characteristic neurologic and imaging findings producing symptoms disproportionately greater than expected from the extent of the affected brain, accompanied by enlargement of the underlying ventricle and elevation of the bone flap. Disruption of the axonal conduction due to distortion of the axons in the herniated brain is probably responsible for these observations.

A series of 3 cases is described. In all cases, the dural reconstitution at the conclusion of surgery was incomplete. Brain herniation was evident in the postoperative scan. The transcalvarial herniation of the brain was precipitated by either a seizure and resultant brain swelling or persistently raised intracranial tension from a tumor residual. In 2 cases, surgical reexploration resulted in improvement in the neurologic symptoms.

In symptomatic patients with transcalvarial herniation of the brain, identified on imaging, the neurologic syndrome is quite characteristic. Recognition of this condition and prompt treatment lead to lasting neurologic improvement.