The second common extra-axial form of intracranial hemorrhage is epidural hematoma. The term extra-axial means outside the brain proper, but still inside the skull. Epidural hematoma, abbreviated EDH, can be deadly but need not be. In fact, the usual outcome is complete recovery following emergency surgery to control the source of the hemorrhage.
There is often little or no damage to the underlying brain.
The source of EDH is usually arterial (most commonly the middle meningeal artery for those interested in such things), which means high pressure so that it tends to thwart the body’s efforts to control it. It is sometimes associated with skull fracture.
The bleeding in EDH generally continues until stopped by the surgeon when the vessel is cauterized or tied off. Classically, the patient is fine initially (because there is no damage to the brain with the initial trauma), but begins to fail neurologically (headache, nausea, vomiting, one sided weakness, and finally decreasing arousal) as the size of the hemorrhage increases to put more and more pressure on the brain. This will be fatal if not stopped.
Fortunately, the surgery to control EDH is one of the simplest craniotomies, and indeed is often the first true intracranial operation learned in training. Caught in time, most patients make a complete recovery, with only a scar on the head to show for the trauma.
Interestingly, EDH often results when a moving object (say a baseball bat or a baseball in flight) strikes the stationary head (the baseball catcher or the batter in the case of a pitched ball). The skull is deformed by the moving object, fractures, and begins to bleed. The brain, protected by the skull, is often not injured.
That’s the theory anyway.