Canadian CT Head Rule
Determines need for CT head in patients with minor head injury (GCS 13-15) to identify clinically important brain injury
- Highest activation tier
- Mandatory
- How it is scored
- Scored in code; a stated value is compared only from the structured summary or a supplied value
- Scoring type
- classification
- Care settings
- Emergency department
When it activates
Scribeable activates a calculator from the encounter. The Canadian CT Head Rule can activate when the transcript or pasted chart context documents any of these:
- Minor head injury evaluation
- Head trauma with GCS 13-15
- Concussion assessment
- CT head decision after head injury
- Loss of consciousness after trauma
A coded diagnosis can also activate it. ICD-10 prefixes carried by the registry: S06, S09.
Note-type scope: it activates on notes whose subject resolves to emergency medicine, neurology, hospital medicine. A note that resolves to another subject does not carry it even when the clinician's specialty matches; a note with no resolvable subject (a generic consultation) falls back to the specialty match.
Inputs the note needs
7 inputs. Each is resolved from the transcript, the pasted chart context and charted labs; an input marked "asks you" is requested as a clarification when it is undocumented.
| Input | Type | Unit / options | Guidance |
|---|---|---|---|
| GCS score <15 at 2 hours after injury | exam | GCS <15 measured 2 hours post-injury (Canadian CT Head: HIGH risk — CT indicated). | |
| Suspected open or depressed skull fracture | exam | Suspected open or depressed skull fracture (Canadian CT Head: HIGH risk). | |
| ≥2 episodes of vomiting | symptom | Two or more discrete vomiting episodes (Canadian CT Head: HIGH risk). Asked as: “Have there been 2 or more episodes of vomiting since the injury?” | |
| Age ≥65 years | age | ||
| Retrograde amnesia to event ≥30 minutes | symptom | Retrograde amnesia ≥30 min BEFORE the event (Canadian CT Head: HIGH risk). Asked as: “Is there retrograde amnesia to the event of 30 minutes or more?” | |
| Dangerous mechanism (pedestrian struck, ejected from vehicle, fall >3ft/5 stairs) | history | Pedestrian struck, occupant ejected, or fall >3 ft / 5 stairs (Canadian CT Head: MEDIUM risk). Asked as: “Was the mechanism dangerous — pedestrian struck by a vehicle, ejected from a vehicle, or a fall over 3 feet / 5 stairs?” | |
| Amnesia before impact (anterograde) ≥30 minutes | symptom | Amnesia before impact ≥30 min (Canadian CT Head: MEDIUM risk). Asked as: “Is there amnesia for events before the impact of 30 minutes or more?” |
Scoring
High-risk (need neurosurgical intervention): GCS <15 at 2h, suspected skull fracture, ≥2 vomiting episodes, age ≥65, retrograde amnesia ≥30min. Medium-risk (brain injury on CT): amnesia before impact ≥30min, dangerous mechanism. Score: 0 = no CT needed, 1 = CT indicated (medium risk), 2 = CT indicated (high risk).
Interpretation
Any high-risk criterion: CT required (100% sensitivity for neurosurgical intervention). Medium-risk criteria: CT recommended for brain injury detection. All criteria absent: CT not required. Only applicable to GCS 13-15 with witnessed LOC, definite amnesia, or witnessed disorientation.
Evidence
Sources carried in Scribeable's citation registry for this calculator; guideline version: Stiell IG et al. 2001.
- Stiell IG et al. The Canadian CT Head Rule for patients with minor head injuryStiell et al. (Canadian CT Head) 2001 · 2001 · Level I · link last verified 2026-03-28
How Scribeable handles it in the note
When an encounter activates the Canadian CT Head Rule at the mandatory tier, Scribeable resolves its inputs from the transcript, the pasted chart context and any charted labs, and asks you for a missing input you can supply before the note is finalised. Bedside-exam and separately ordered study values are not requested one input at a time; a calculator that carries a combined clarification question may still put that single question to you.
The score is computed in code from the resolved inputs, not recalled by the language model. A stated Canadian CT Head Rule value is compared against the computed one when the draft's structured summary carries it; a disagreement found there is flagged to the second drafting pass, which is instructed to correct the score and its interpretation, unless Scribeable has supplied the computed value to that pass, in which case the value the draft writes is checked against the supplied one and a detected difference is shown beside the note for you to adjudicate rather than silently rewritten.
Classified as a mandatory rule-out score: a missed result carries acute harm, so the activation filter never approves it on uncertainty.
See it activate on your own encounter
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