to scan or not to scan

Monday, September 10, 2012

Brandon McCarthy was minding his own business, standing on the mound throwing fastballs for the Oakland As, when one of his pitches was lined back, hitting him in the head and knocking him down. When the dust settled, Mr. McCarthy was in the operating room having his skull drilled open to evacuate an epidural hematoma. With all the attention being given to football players and concussion, it’s easy to forget that other sports carry head injury risk as well. The skill in caring for the head injured patients is deciding who need to be rushed to the hospital and who can be treated on the sideline and sent home. As it turns out, it isn’t as easy as it seems.

The body has a few significant design flaws including the bones that make up the skull. The temporal bone just above the ear is very thin and the middle meningeal artery runs in a groove carved into the inner part of the bone. The skull is an enclosed box and usually there is no room for anything else except for the brain. If a direct blow, like getting hit by a line drive, breaks the bone across that middle meningeal groove, the artery can tear and start bleeding into the space between the brain and the skull. With no room for the blood, the hematoma or clot located in the epidural space starts to enlarge, pushing on the brain, squashing it and eventually turning it off. The bridging veins that cross from the bones of the skull to the surface of the brain are another design flaw. When the skull is hit or shaken, these fragile veins can tear and leak blood into the subdural space, where again there is no room for a growing clot and the brain can turn off if enough bleeding occurs.

Decision making is when the patient is in coma after getting hit in the head. A CT scan is needed to define the injuries that are causing the brain to fail. It’s a lot harder to know what to do if the patient is awake and smiling at you, complaining of pain only where they were hit. Not everybody who hits their head needs a visit to the ER for a CT scan, but it’s not always clear cut deciding who that one person is that needs the emergency full court press. There are a variety of guidelines like the Ottawa roles or the New Orleans rules that try to answer one specific question. Is it safe to send a patient home who was hit in the head but is now normal? The criteria are based on common sense. You need a CT if you have an abnormal neurologic exam, if you a fractured skull on physical exam, if you persistently vomit and if you’ve lost a significant amount of memory. However, the guidelines weren’t made for the playing field. You need a CT scan if you had a major force applied to your body, like a pedestrian getting hit by a car or falling from a height. But does that equal a wide receiver getting hit by a safety or two outfielders colliding chasing a fly ball? And to make decision making harder, the guidelines apply only to people aged 16 to 65 and cannot be used if the patient is taking anti-coagulation or blood thinning medicines.

The classic description of an epidural hematoma, that type of blood clot suffered by Mr. McCarthy, describes getting hit in the temple with or without loss of consciousness and then having a lucent interval before falling unconscious into a coma. The description makes sense; the patient should be awake until the bleeding causes enough pressure to affect brain function. It is in that lucent interval that the diagnosis needs to be made and the offending blood clot removed. The patient who is awake and undergoes surgery has a better outcome than the patient who is in coma. But the lucent interval is only helpful in retrospect, like instant replay. One can only know that a lucent interval has occurred if the victim eventually goes into coma. If the victim never decompensates, then the lucent interval will technically last forever and the doctor has to decide whether the victim’s normal appearance is really normal or if it’s a cruel trick of nature to hide a life threatening condition.

The elite athlete tends to endure more x-rays, CT scans and MRIs than the civilian population. Sometimes the tests are appropriately ordered and other times, we can only wonder why they were done. In the real world, the use of technology costs both in dollars and radiation to the patient and the explosion of scans are coming under increasing scrutiny. It takes a stroke of a pen or click of a mouse to order a head CT but it may take significant effort and many minutes to explain to a patient and their family why a test isn’t necessary. But nobody ever said that doing the right thing was easy.

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