Table 3. Summary of North American Clinical Decision Rules for Obtaining CTH after Blunt Head Trauma.

CTH: computed tomography of the head, GCS: Glasgow Coma Scale

Canadian CT Head Rule (CCHR)	New Orleans Criteria (NOC)	National Emergency X-Radiography Utilization Study (NEXUS)
GCS 13-15 AND witnessed loss of consciousness, amnesia, or confusion AND 1 of the following:	GCS 15 AND 1 of the following:	Any of the following:
High risk criteria:	-   Headache	Evidence of skull fracture
-   GCS < 15 at 2 hours after injury	-   Vomiting	- Scalp hematoma
-   Suspected skull fracture (open or depressed)	-   Age > 60 years	- Neurologic deficit
-   Any sign of basal skull fracture	-   Drug/alcohol intoxication	- Abnormal level of alertness
-   2+ episodes of vomiting	-   Persistent anterograde amnesia	- Abnormal behavior
-   Age > 65 years	-   Visible trauma above the clavicle	- Persistent vomiting
Medium risk criteria:	-   Seizure	- Coagulopathy
-   Amnesia before impact of 30+ minutes		- Age ≥ 65 years
Dangerous mechanism (pedestrian struck by a motor vehicle, an occupant ejected from a motor vehicle, or a fall from an elevation of 3 or more feet or 5 stairs)