The occasional burr hole
Keith MacLellan, MD,
Correspondence to: Dr. Keith MacLellan, PO Box 609, Shawville QC J0X 2Y0
Acknowledgements: Thanks to Dr. William Feindel of the Montreal Neurological Institute for all his sage advice and to the personnel at the McGill Anatomy Laboratory, who point out that this type of article would not be possible without true cadaver specimens (CD-ROMs just would not cut it). Photographs courtesy of Donna Ager.
This paper has been peer reviewed.
© 1998 Society of Rural Physicians of Canada
Every now and again word comes of some doctor in the hinterland who has drilled a hole in a patient's skull to relieve an epidural bleed. One published account by an SRPC member in rural Alberta1 described the evacuation of 400 mL of blood from the cranium of an 8-year-old child after the neurosurgeon in a tertiary centre faxed the instructions. The child had suffered a temporal bone fracture, lacerating the middle meningeal artery and was comatose, with a unilateral dilated pupil which "blew" at the time of admission to the emergency department. The child is now completely normal but would surely have died without the immediate intervention.
This report got me thinking about how lucky the child was that a neurosurgeon was not only located quickly but also had the time to fax a set of instructions promptly. What would I have done in a similar situation if I had been unable to contact someone knowledgeable? Did our hospital have the proper equipment? If not, what could be found in hospital maintenance or at local hardware stores that could be used in a pinch? Here are the results. Post this in your emergency room. If you are in a hurry just read the bold type.
There are 2 clear possibilities: either you have the stuff or you don't. The first lesson I learned was that drilling a hole in the cranium is usually a 2- stage procedure. You use a sharp pointed drill (penetrator) to make a hole in the outer table of the cranium. Once the hole is large enough, you then switch to a blunt-ended burr hole bit to complete the drilling through the skull and minimize the chance of penetrating the dura. As it turns out our hospital had a burr hole bit and drill but did not have a penetrator.
I went to the local hardware stores looking for a penetrator bit with as blunt an end as possible that would drill the initial hole. The best I could find was a Canadian Tire 1/2-inch high-speed steel drill bit (part #54-3032-8, cost $8.49). When I compared this bit (now called an "instrument") with those at the Montreal Neurological Institute, the difference was minimal, except that their instruments were sterile and made of stainless steel. However, the new bit did not fit the brace supplied with the hospital's burr hole drill. Another carpenter's brace (hard to find these days) or a regular carpenter's electric drill were needed. Illustrated in Fig. 1 are the electric drill and the penetrator and the burr hole bit and hand brace beside it. Detail of the 2 bits is shown on the right.
If you do not have a burr hole bit then use the 1/2 -inch penetrator or hardware store bit to drill carefully all the way through the cranium. You are, after all, presuming that there will be a large lake of blood in front of the dura, ensuring some leeway when you go through the cranium. Everything should be sterilized to the best of your abilities, but if you can't use sterilized instruments go ahead anyway and change gloves at each step.
Use your hospital's properly sterilized penetrator and burr hole bits and braces for a formal 2-stage entry through the cranium. If these are not available, use a 1/2-inch steel drill bit for an adult (slightly smaller for a child) and sterilize it as well as possible.
You want to avoid drilling into the orbit or into the temporal artery. One rule for an adult is to drill 2 fingerbreadths above the top of the ear and 2 fingerbreadths anterior to the auditory canal (Fig. 2). Some people will even go 3 fingerbreadths above the ear. Adjust the distances for children. You want to be just above the roof of the zygoma. Plain skull x-ray films in the setting of an epidural hematoma will often show a temporal bone fracture. If it is a depressed fracture, then care must be taken in putting pressure on the drill point.
(1) A sense of historical proportion. Drilling a hole in the head is just the boring (sorry) start to most neurosurgical days. Trephination was practised safely in the Stone Age. So relax.
If there continues to be excessive bleeding through the hole, try packing the wound with a hemostatic agent like Gelfoam. Muscle is a wonderful blood clotter and was used extensively in earlier neurosurgery. In a pinch, cut off a piece of temporalis muscle and stuff it into the hole. If all else fails and transport is delayed, use a bone rongeur and a good light to eat away at the bone until the bleeding branch of the meningeal artery can be found and cauterized. That is probably all the neurosurgeon would do anyway.