A Head Injury Can Be Difficult to Diagnose

How Is a Concussion Diagnosed?

Minor head injuries are a routine occurrence. From toddlers falling against tables, kids bumping heads playing ball, to an elderly person falling down, people often lead with their heads when they move about. Usually, a few stars are seen, a headache happens, and all is well. Sometimes it isn't so clear. The person may be knocked out for a few seconds, may vomit, and perhaps may have some loss of memory, but by the time the doctor visits the bedside, everything is back to normal. The diagnosis of a concussion is made.

But now what? What do you do with somebody who acts and appears normal, even though there was a history of a head injury? Who will have bleeding in their brain and who won't? Who needs a CT scan and who just needs to go home?

Less than a generation ago, CT scans didn't exist, and observation was the key to head injury care. If the patient did well, they went home; if not, a neurosurgeon was called in to evaluate the patient. Now, CT scans can be found in even the smallest hospital, but just because the machine is there doesn't mean that it should be used indiscriminately. Putting aside the cost, the radiation risk of an unneeded test is significant.

While scientific studies can provide guidelines as to who needs imaging studies, patients and their families want more than the doctor's opinion; they want the reassurance of hard evidence like an X-ray or CT. Every case needs to be considered individually. However, here are some guidelines that a doctor may use to decide: "To CT or no CT; that is the question.”

The Canadian CT Head Rule states that a CT scan is required if any of the following exist:

Concussions with High Risk for Needing an Operation

  • the person is not fully awake and responsive within 2 hours after injury
  • there is a suspected depressed skull fracture
  • there is a suspected fracture of the base of the skull (bruising of both eyes, blood behind the eardrum, or spinal fluid running from the ears or nose)
  • vomiting occurs more than 2 times
  • the patient is older than 65 years of age

Concussions with Medium Risk for Brain Injury

  • amnesia (loss of memory) of before impact of greater than 30 minutes
  • dangerous mechanism (being hit by a car, being thrown from a car, falling more than 5 stairs)

The New Orleans Criteria state that a CT scan is required with any one of the following findings in a person who is fully awake:

These rules all need to be applied based on the patient's specific situation. Communication among the physician, patient, and family allows the right treatment pathway to be followed while hopefully meeting everyone's expectations.


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Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


Stiell IG, et al. The Canadian CT head rule for patients with minor head injury. Lancet May 5, 2001;357:1391-6.
Stiell, IG, Clement, CM, Rowe, BH, et al. Comparison of the Canadian CT head rule and the New Orleans criteria in patients with minor head injury. JAMA 2005; 294:1511.

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