Background: Protrusion of the cortex through a bone flap in the course of surgery is a very serious event and, if it persists, the procedure must be suspended, the cause sought, and the problem resolved.
Case description: We report the case of a 13-year-old boy whose brain underwent sudden swelling during removal of a supratentorial cystic lesion. The operation was suspended at once and an emergency CT scan was performed. It revealed a large contralateral extradural hematoma, which was removed immediately.
Conclusions: We considered the following possible mechanisms of the emergency: bleeding of bone at the site of the supposed piercing by the headrest pin and/or a vacuum mechanism consequent upon removal of the large cystic lesion. Our aims are to emphasize the importance of gauging the thickness of a child's skull before fixing the head in the headrest, especially when chronic intracranial hypertension is present, and the need to suspend the operation for CT scanning in the event of uncontrollable brain swelling.