TOOL 2.3: The Canadian Assessment of Tomography for Childhood Head injury 2 (CATCH2) rule

CT of the head is required for children with minor head injury* and any 1 of these findings:

• GCS score < 15 at 2 hours after injury

• Suspected open or depressed skull fracture

• History of worsening headache

• Irritability on examination

• Any sign of basal skull fracture†

• Large, boggy hematoma of the scalp

• Dangerous mechanism of injury‡

• ≥ 4 episodes of vomiting

Note: CT = computed tomography, GCS = Glasgow Coma Scale.

* Minor childhood head injury is defined as injury within the past 24 hours associated with witnessed loss of consciousness, definite amnesia, witnessed disorientation, persistent vomiting (> 1 episode) or persistent irritability (in a child aged < 2 yr) in a patient with a GCS score of 13–15.

† Signs of basal skull fracture include hemotympanum, raccoon eyes, otorrhea or rhinorrhea of the cerebrospinal fluid, and Battle sign.

‡ Dangerous mechanism is a motor vehicle crash, a fall from elevation ≥ 3 ft (≥ 91 cm) or 5 stairs, or a fall from a bicycle with no helmet.

Reprinted from Osmond MH, Klassen TP, Wells GA, et al. Validation and refinement of a clinical decision rule for the use of computed tomography in children with minor head injury in the emergency department. CMAJ.