SJRH ER Dept Guideline – CT Imaging in Minor Head Injury
Implemented November 2014
Minor head injury describes patients who have suffered blunt trauma to the head, and have any of a witnessed loss of consciousness, definite amnesia, or disorientation with an initial Glasgow Coma Score of 13-15.
The current guideline applies to minor head injury in adult patients 17 years of age and older. It does NOT apply to patients with an obvious open skull fracture, or to those on anticoagulants or who have bleeding disorders.
Concussion, a term common in sports medicine, has been used almost interchangeably with mild TBI and minor head injury to describe a patient who sustains a traumatic force to the head resulting in a transient alteration in cognitive abilities, motor function, or level of consciousness. Fewer than 10% of patients with sports-related concussion sustain a loss of consciousness, and sports concussion is defined by the clinical presence of a rapid-onset, short-lived impairment of neurologic function that resolves spontaneously. It is important to appreciate that concussion is not the same as minor head injury; the current guideline applies to minor head injury as defined in bold above.
The major causes of minor head injury are falls, motor-vehicle accidents, nonintentional strike by/against an object, and assaults. According to the best evidence we have, approximately 10% of patients with minor head injury will have an intracranial injury (ICI) identified on CT and < 1% of patients will require neurosurgical intervention. ICIs include subarachnoid hemorrhage (SAH), subdural or epidural hematomas (SDH, EDH), cerebral contusions, intraparenchymal hemorrhages, cerebral edema and petechial hemorrhages.
KEY FACTORS ON HISTORY
In terms of history, it is important to ascertain whether or not a minor head injury, according to the definition above, has occurred. That is, whether the patient lost consciousness, had amnesia or became confused because of the head injury. From there, key factors associated with a risk of increased ICI should be ascertained.
Vomiting more than once is associated with higher risk of ICI, as is a post-traumatic seizure. Finally, amnesia of more than 30 minutes before impact is also associated with ICI in patients with minor head trauma. Therefore, these questions should be specifically asked.
Furthermore, patients aged greater than 64 have consistently been shown to be at higher risk of ICI following minor head injury. Those ≥ 75 years of age have the highest rates of minor head injury-related hospitalizations and death, a trend thought to be due to cerebral atrophy and fragile, less-elastic bridging veins. Of
note, elderly patients with ICI often have fewer clinical clues, and several studies have shown that the majority of elderly patients with mild ICI who require neurosurgical intervention do not even have a history of loss of consciousness. Thus, it is imperative to maintain a low threshold for CT use in elderly patients with mild head injury.
Patients with a history of brain surgery are also at increased risk for ICI with minor head injury, though evidence does not suggest how to best incorporate this into a scanning rule. Also, those with a persistent headache after minor head injury warrant particular clinical attention though, again, there is insufficient evidence to support automatic head CTs in this patient population.
In terms of mechanism of injury, those associated with an increased risk of ICI include the following:
pedestrian being struck by a motor vehicle
occupant ejected from a motor vehicle
fall from an elevation of > 3 feet (0.9 m) or 5 stairs.
Of note, drug or alcohol use, with either chronic or current intoxication, is associated with ICI in patients with minor head trauma, though a clear role as an independent predictor of outcome has not been determined. The CDC/ACEP guidelines include intoxication as an indication for CT, although the best evidence to date shows that it is probably safe to closely observe an otherwise asymptomatic patient who rapidly sobers.
Anticoagulant or antiplatelet use, hemophilia, or platelet disorders are associated with increased risk of immediate and delayed ICI as well. Note, though, that most decision rules, as well as this guideline exclude these patients. That said, Warfarin (Coumadin®, Jantoven®) is the most common and the most studied anticoagulant in patients with mild head injury. There is strong evidence to support the use of immediate CT on all patients with minor head trauma taking warfarin. Several studies have found aspirin and clopidogrel (Plavix®) to be associated with increased risk of ICI. Again, patients on antiplatelet agents should undergo CT after mild head injury. Unfortunately, about 50% of hemophiliacs with mild head injury who harbor an ICI will initially be asymptomatic, and no validated clinical decision rules exist to guide CT use in these patients. At present, patients with bleeding disorders should probably undergo CT after mild TBI. Unfortunately, there is insufficient evidence to address the impact of Dabigatran (Pradaxa®) use on patients with minor head injury. That said, it would be wise for clinicians to maintain a very low threshold for imaging this particular population as well.
KEY FACTORS ON PHYSICAL EXAM
In minor head injury, there is an inverse relationship between GCS score and the incidence of positive findings on CT. In fact, the rate of ICI and need for
neurosurgical intervention doubles when the GCS drops from 15 to 14. For this reason, both the NICE Head Injury Guideline and Canadian CT Head Rules advocate for CT if GCS remains less than 15 at 2 hours after the initial injury. Again, the current guideline excludes patients with GCS <13, though it would be prudent to scan these individuals in very early course, as their risk of ICI is particularly high.
Skull fractures are associated with specific patterns of ICI. For example, fractures that cross the meningeal artery are often associated with epidural hematomas, while those that cross a dural sinus can cause subdural hematoma and thrombosis. Fractures through the base of the skull and carotid canal can cause carotid artery dissection and are associated with damage to cranial nerves. Finally, basilar skull fractures are frequently associated with dural tears and cerebrospinal fluid leaks. Because of this, the current guideline recommends emergent CT if an open or depressed skull fracture is suspected, or if there are any signs of basal skull fracture (for instance, Battle’s sign, hemotympanum, CSF oto/rhinorrhea, or Raccoon eyes).
IMAGING IN MINOR HEAD INJURY
Noncontrast CT is both highly sensitive and specific for the detection of fractures, contusions, epidural and subdural bleeds, and subarachnoid hemorrhages. It is the diagnostic imaging modality of choice in patients with minor head injury in whom an ICI is possible. A CT interpreted as normal in a neurologically intact person with a normal mental status allows for safe discharge with appropriate instructions and avoids prolonged observation or admission.
Of note, radiation exposure from head CT is relatively small. It is inversely related to age.
To date, over 20 clinical decision rules for guiding CT use in the ED have been published; importantly, the Canadian CT Head Rule stands out due to its high sensitivity (99%-100%) in repeated external validations.
DISPOSITION OF PATIENTS WHO HAVE EXPERIENCED MINOR HEAD TRAUMA
Discuss with a neurosurgeon the care of all patients with new abnormalities on imaging.
Those patients who meet this guideline’s criteria and have a negative CT scan may be discharged home if their CT scan is negative and their GCS is 15. Delayed ICI in those meeting the Canadian CT Head Rules Inclusion Criteria with a negative CT is exceedingly rare. Patients with continued symptoms such as short-term memory deficits or repeated vomiting should be considered for admission for further observation, repeat CT, or MRI. Also, if their GCS has not returned to 15, consideration for admission should be given. If the clinician has concerns such as a CSF leak, other injuries, suspicion of abuse, or discharge to an unsafe environment, then it would be prudent to admit the patient.
Although beyond the scope of the current guideline, patients taking anticoagulants or antiplatelet agents, and those with a bleeding disorder do require more careful dispositioning, due to the higher potential for delayed ICI. If not admitted, they must be discharged with a reliable adult who can monitor for new or worsening symptoms.
Remember that patients frequently cannot recall verbal physician instructions on discharge. Because cognitive function is frequently compromised after mild TBI, clear, written instructions should be provided to patients and their family members.
KEY ARTICLES
ACEP. Clinical Policy: Neuroimaging and decision-making in adult mild traumatic brain injury in the Acute setting. December 2008. Last accessed 15 May 2014. http://www.acep.org/MobileArticle.aspx?id=48423&coll_id=618&parentid=740
CDC. Updated mild traumatic brain injury management guidelines for adults. 2008. Last accessed May 15 2014. http://www.cdc.gov/concussion/HeadsUp/clinicians_guide.html
Haydel (2012). Management of Mild Traumatic Brain Injury in the Emergency Department. September 2012 V 14(9) Emergency Medicine Practice (ebmedicine.net).
Jagoda AS, Bazarian JJ, Bruns JJ Jr, et al. Clinical policy: neuroimaging and decisionmaking in adult mild traumatic brain injury in the acute setting. Ann Emerg Med. 2008;52:714-748. (Position statement)
National Institute for Health and Care Excellence (NICE). Head Injury: Triage, assessment, investigation and early management of head injury in children, young people and Adults. January 2014. Last accessed 15 May 2014 guidance.nice.org.uk/cg176.
Smith-Bindman R, Lipson J, Marcus R, et al. Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med. 2009;169(22):2078-2086. (Retrospective; 1119
patients)
Steill et al. (2001) The Canadian CT Head Rule for patients with minor head injury. Lancet 357(9266): 1391-6. (Prospective; 3121 patients)
