Sinking skin flaps, paradoxical herniation, and external brain tamponade: a review of decompressive craniectomy management.

Decompressive craniectomy is reclaiming a role in neurocritical care. The altered pathophysiology found in a cranium converted from a 'closed' box to an 'open' box' carries benefits and risks. In some craniectomy patients, the forces of atmospheric pressure and gravity overwhelm intracranial pressures, and the brain appears sunken. This can lead to paradoxical herniation and the sinking skin flap syndrome, also called the syndrome of the trephined. At the other polar extreme, external brain tamponade occurs when subgaleal fluid accumulates under pressure and 'pushes' on the brain across the craniectomy defect. The neuro-intensive care team should be prepared to diagnose and treat a spectrum of decompressive craniectomy complications including: cerebral contusions, infections, seizures, intra- and extra-axial hemorrhages and fluid collections, sinking skin flap syndrome or syndrome of the trephined, paradoxical herniation, and external brain tamponade. The treating physicians must set aside the Monro-Kellie doctrine and recognize the new pathophysiologic state of these 'open box' patients.