Hole in Skull Relieves Pressure During Deadly Stroke
By William Allstetter
Until recently, physicians could do little for people with a clot in a major artery of the brain. tPA can be used to dissolve the clot, but more than 80 percent of patients arrive in the emergency room too late for this treatment to be effective. Many of these patients arrive in relatively good condition but worsen and die within days due to massive swelling in the brain. Since the fall of 1997, however, P&S neurosurgeons have helped reduce this toll by temporarily removing a section of the skull in a procedure called a craniectomy.
Strokes are the leading cause of disability in the United States and third leading cause of death, behind cancer and heart disease. Major hemispheric infarctions account for 10 percent to 15 percent of all strokes. With the blood supply to either hemisphere severely limited, large portions of tissue are likely to die. But even more dangerous is the swelling that occurs two to five days after the initial stroke. This creates so much pressure that it pushes the brain stem right through the bottom of the skull. Once such herniation occurs, the autonomic functions controlled by the brain stem, such as heartbeat and breathing, cease.
If P&S neurosurgeons see a patient within two days of the initial stroke, before the swelling begins in earnest, they can avoid the deadly pressure build-up by removing a piece of the skull about six inches across. They store the bone in the patients abdomen, if there is room, or in a freezer. The surgeons then slice open the dura, the tough membrane surrounding the brain, and add a patch of substitute dura, which gives the brain room to swell.
The original blockage of the artery still causes damage, sometimes quite significant, to the brain tissue, but the pressure relief provided by the hole in the skull prevents the deadly herniation of the brain stem. And there is some evidence in animal studies that the pressure relief prevents further damage by preventing the collapse of other blood vessels in the brain. In two to three weeks, after the swelling has gone down, surgeons return the excised piece of skull to its proper place.
P&S surgeons had performed 10 craniectomies as of February 1999. Nine of the patients survived. The patient who died was operated on after brain herniation had already begun. Mere survival, however, is not always a positive outcome for patients because the severe disability a stroke can cause leaves about 30 percent to 40 percent of patients unhappy or uncertain that saving their lives was the right choice. Dr. Connolly says that all seven patients who had a craniectomy on the right side of the skull report a good quality of life following the operation. Results for the two patients with strokes on the left side of the brain are less certain. The families are happy, but it is too early to know what the patients think.
We believe this is great for large right-sided strokes, says Dr. Connolly. The big question is should we be doing it for left-sided strokes.
The left side of the brain contains the areas that control both comprehension and production of speech in most people. Strokes on this side can destroy a persons ability to speak and to understand what people say as well as other important cognitive functions. Since the craniectomies on the left side of the brain do not significantly reduce such damage, their value to the patient remains controversial.
Dr. Connolly and Neurological Institute colleagues Drs. Mitchell Elkind, Stephan Mayer, and Gary Bernardini have applied for a grant to study craniectomies for strokes on both sides of the brain. They will assess both survival rates and patient satisfaction with life after the stroke.
Dr. Connolly believes that craniectomy is part of a trend toward more aggressive treatment of cerebral infarctions, which began with the introduction of tPA in the late 1980s. tPA showed that acute stroke could be treated, says Dr. Connolly. That captured the attention of interventionists who began to study other treatments. Neurosurgeons at P&S are also studying other novel therapies, including anticoagulants, anti-inflammatory drugs, anti-oxidants and focal cerebral hypothermia. Dr. Connolly hopes that physicians will one day think of severe strokes in terms similar to that of heart attacks, a potentially deadly condition that can be alleviated by early, aggressive intervention.