Applying circular posterior-hinged craniotomy to malignant cerebral edemas.

Malignant brain edemas are often fatal, regardless of whether they are treated conservatively with sedation, blood pressure management, mannitol-therapy, hyperventilation and hypothermia, or non-conservatively with routine trepanation. Unfortunately, temporal trepanation may result in significant brain damage through herniation of the cerebrum at the edges of the trepanation openings. In one case of a 26-year-old male with severe head injury, a circular posterior-hinged craniotomy (CPHC) was performed after an ineffective unitemporal trepanation for evacuation of an acute subdural hematoma. This ultimately successful operation prompted experimental and morphologic investigations on a new surgical procedure for lowering intracranial pressure (ICP). In 12 of 15 human cadavers, an experimentally ICP was lowered by a CPHC with between 9-21 mm of frontal elevation of the calvaria. Using computer simulation, the frontal elevations of the calvaria were "virtually" performed on 3D reconstructions from CT scans of skulls, and the intracranial volume gained was measured with a computer software program. The volume increase of the cranial cavity showed a relatively constant relation to the cranial capacity and was increased by 6.0% (+/-0.4%) or 78 cm(3) with a 10 mm elevation and by 12.4% (+/-0.7%) or 160 cm(3) with a 20 mm elevation. There were no significant differences with skulls of different ages or ethnic origin; however, a significant effect of gender (F = 7.074; P < or = 0.013) on the gained volume in percent of the cranial capacity for the 20 mm elevation was observed. This difference can be explained by the inverse relationship between volume increase and cranial capacity (r = -0.507; P < or = 0.004).