SGEM#266: Old Man Take a Look at the Canadian CT Head Rule I’m a Lot Like You Were

Date: September 10th, 2019 Reference: Fournier et al. Adapting the Canadian CT head rule age criteria for mild traumatic brain injury. Emergency Medicine Journal 2019. Guest Skeptics: Dr. Sarah Berg is a PGY-3 resident in Emergency Medicine at Washington University School of Medicine in St. Louis. She is interested in social determinants of health in the emergency department and health policy. Dr. Ian Holley is also a PGY-3 resident in Emergency Medicine at Washington University School of Medicine in St. Louis.  He is interested in ultrasound and international emergency medicine. Case: It’s a busy night in the emergency department, your next patient is a well appearing 70-year-old man, presenting after a mechanical fall from standing with loss of consciousness.  He is neurologically intact with a Glasgow Coma Scale (GCS) of 15 one hour after the fall.  There are no other external signs of trauma on your exam. He is not on anticoagulation and there is no history of seizures. Background:  Head trauma is an exceedingly common presenting complaint in the emergency department, with approximately 2.5 million emergency department visits in the US in 2014 [1], with the most significant proportion of visits occurring in the elderly ≥75 (1,682/100,000) [1]. Head trauma can result in a spectrum of brain Injuries varying from mild to severe.  In cases of severe injury, the decision to obtain head CT imaging is straight forward.  In mild traumatic brain injury (mTBI), this decision is can be more difficult, as there may be no or minimal evidence of injury on exam.  Traditionally CT imaging was obtained for fear of missing intracranial pathology. In an attempt to improve resource utilization, emergency department length of stay, limit cost and improve outcomes, there have been multiple Clinical Decision Rules (CDRs) created to help guide clinicians in their decision-making process.  Two of the most commonly used rules include the Canadian CT Head Rule (CCHR) and the New Orleans Criteria (NOC); other rules include NEXUS-II, the Neurotraumatology Committee of the World Federation of Neurosurgical Societies, the National Institute of Clinical Excellence guidelines, and the Scandinavian Neurotrauma Committee guideline. We have covered the CCHR on the SGEM with the EM Swami and Dr. Emily Junck back on SGEM#106. It was a classic EM paper published in the Lancet back in 2001 by the Legend of Emergency Medicine, Dr. Ian Stiell. We also discussed three studies that compared CCHR to the NOC. The bottom line was while both rules are highly sensitive for positive CT findings and clinically important brain injuries, the CCHR had higher specificity and may be more clinically applicable given it is designed to predict clinically important brain injuries. The Canadian CT Head Rule [2] is a clinical decision instrument to help you decide if a patient with a mild head injury requires a CT head. Minor head injury was defined as blunt head trauma, resulting in amnesia, loss of consciousness or an altered mental state (confusion or disorientation) with a GCS score ≥13. The CCHR only applies to those patients with minor head injury and is not applicable to non-traumatic cases, GCS less than 13, age less than 16 years, coumadin or bleeding disorder or obvious open skull fractures. The CCHR is the most researched CDR in mTBI [3] and has shown sensitivities and specificities from 99-100% and 48-77% [3].  The use of CDRs such as CCHR, have the ability to reduce the amount of unnecessary head CT imaging obtained in the emergency department [4]. Unfortunately, the CCHR uses age ≥ 65 as a high-risk criterion for obtaining head CT imaging in mTBI.  This is based on the initial validation study which demonstrated an odds ratio (OR) of 4.1 for risk of clinically important brain injury (CIBI) [2].  CIBI is defined, per the CCHR, as “any acute brain finding revealed on CT and which would normally require admission to hospital and neurologi...