When should a blow to the head cause concern? Should stories about head injuries like Ms Richardson’s change anything that we do in a wilderness setting?
1. “I know someone.” Anecdotal stories are not helpful for anyone. They make it nearly impossible to verify cause and effect let alone the details of what really happened. Deriving lessons to be learned from them is accordingly difficult. Ms. Richardson is a case and point. Follow-up stories purported to quote experts who advocated that all people sustaining a blow to the head, whether with or without loss of consciousness, are at significant enough immediate risk to warrant an evaluation by a medical professional. By extension, this means an evacuation if in a remote setting. These ideas are disingenuous and ridiculous and help no one.
2. Our position. We believe that a blow to the head will cause an important brain injury (e.g., ones that require surgery or close hospital observation) only when impaired brain function results. Impaired brain function includes loss of consciousness (LOC), amnesia or at least a brief change in mental status including being stunned, punch drunk; lights on no one home. Dizziness yes; seeing stars, no.
3. Concussion or TBI (traumatic brain injury)? We switched to TBI because it has become current terminology and seemed clinically based (change in brain function implied brain injury). On the other hand, the term concussion is pervasive but it is non-specific and has a variety of definitions.
4. How frequent is unlikely? Ms Richardson developed an acute epidural hematoma (EDH), a collection of blood between the skull and the outer membrane around the brain. The frequency of this happening has been reported in 1 to 10% of all head injuries but it is not clear how head injury is defined or what the origins of these numbers are. More recent studies looking specifically at minor head trauma (LOC but awake on evaluation) of people coming to hospital are probably more helpful. The Canadian Head Rule study reported that 0.5% had EDHs and 0.4% of all patients entered in the study required a neurosurgical procedure.(1) 2% of the patients entered in the New Orleans study had EDHs, 20% of whom required surgery.(2) In each of these studies everyone had an LOC or something that qualified as abnormal brain function. It would be hard to believe that the number of EDHs occurring without abnormal brain function would be higher. And not all EDHs are catastrophic, requiring surgery.
4. Who is at highest risk? Few people who have a TBI but wake up develop any serious sequelae requiring prompt, hospital-based intervention. Who is at the highest risk? Certainly this would include anyone with early signs of increasing intracranial pressure (ICP – persistently abnormal mental state, recurrent vomiting, worsening headache). According to the largest studies previously referenced, other important risk factors include evidence of a skull fracture (e.g., persistent leaking of blood and/or spinal fluid from the ears or nose not attributable to a local injury, large boggy scalp hematoma), high velocity/high mass impact, current use of anticoagulants/antiplatelet drugs, and age in the sixties. Duration of LOC and pupil evaluation in an awake person were not listed as important factors. Injuries to the temple should also heighten one’s concern because its thin-walled structure makes the local arterial blood supply particularly vulnerable. According to several online references (no reliable citations given), 80+% of all EDHs occur following a fracture to the temple.
5. We are at least 2 hours from help. The risk factors listed above should be helpful when a decision to evacuate poses significant risk to the rescuers and additional risk to the patient. But even a prompt evacuation of an EDH may still result in a horrible outcome because one can evolve so quickly. An EDH in the posterior fossa (back of the skull near its base) is particularly devastating because one can present with few signs and proceed catastrophically in minutes.
Bottom line: This is a horribly tragic story. Even if she had developed an EDH without an apparent TBI, it would not be the basis for policies that mandate evacuations for everyone with a blow to the head. Ultimately we know this by reading the literature and seeing real patients on a regular basis. Despite these rare occurrences, we owe it to our students and their clients/patients to address blows to the head rationally. Was there a TBI? If so, the anticipated problem list includes increased ICP. An appropriate plan is one that weighs the risks and benefits including some of the high risk factors list above. If there is no TBI, bleeding and/or increased ICP are not going to develop. In such a case, an urgent evacuation for further evaluation and treatment would not be warranted. Increased ICP, on the other hand, is an emergency. Its signs and symptoms, regardless of the cause, known or not, whether or not diagnosed as a TBI, need to be taken seriously.
If we want to practice and teach medicine, we have to accept the fact that there is no 100% or 0%. In this case, it is a pretty safe bet.
1. Stiell, et al. Comparison of the Canadian CT rule and the New Orleans Criteria in patients with minor head trauma. JAMA 2005;294:1511-1518.
2. Haydel MJ, et al. Indications for computed tomography in patients with minor head injuries. NEJM 2000;343:100-105.
PS This past week there was an article in the New England Journal of Medicine (Vol 360:1588) on the implications of the number of TBIs and subsequent post concussive syndromes being reported in the SW Asian theatre. Among other issues, the author questions the use of mild TBI instead of concussion. This is a subject worthy of more lengthy commentary.