Decide on neuroimaging after a paediatric head injury — OSCE

Candidate brief

You have this station to assess a 3-year-old boy after a fall, decide whether he needs neuroimaging using the validated PECARN prediction rule, and counsel his anxious parent about the radiation risk of a head CT and the reasoning behind your decision. Treat this as a communication and decision-making encounter: take a focused history, apply the rule explicitly, communicate the decision and the safety-net clearly, and demonstrate radiation-aware reasoning. [1] [4]

Key teaching and management objectives

Begin by confirming the clinical state and the mechanism. The child has a Glasgow Coma Scale of 15, is alert and interactive, has not lost consciousness, has not vomited, has no severe headache, and has no signs of a basilar skull fracture. The mechanism is a fall of approximately one metre onto a rubber surface, which is below the severe-mechanism threshold for this age group. [1]

Apply the PECARN prediction rule for the two-years-and-over arm, working through the six predictors in turn: altered mental status (absent); signs of basilar skull fracture (absent); loss of consciousness (absent); severe mechanism of injury (absent); severe headache (absent); and vomiting (absent). Meeting none of the predictors places the child at very low risk of a clinically-important traumatic brain injury, with a negative predictive value well over 99 percent in the derivation cohort. CT is therefore not indicated. Observe briefly and discharge with written head-injury advice, giving the explicit return precautions of persistent or repeated vomiting, worsening headache, increasing drowsiness, a seizure, or any focal neurology. [1]

Counsel the parent about the radiation risk in accurate plain language. A single paediatric head CT carries an effective dose of the order of 1 to 2 mSv, comparable to several months of natural background radiation, and an attributable lifetime cancer risk of the order of one excess cancer per 10,000 scans — a real but very small increase over the background lifetime cancer risk of roughly one in three. Frame it so that the parent understands the scan is more likely to cause harm than to find anything in this child, that the validated rule supports observation over imaging, and that you are making this decision because you take radiation safety seriously — not because you are being casual about the head injury. [2] [3]

State the ALARA principle and its four levers — justification (is any imaging needed), optimisation of the dose (paediatric protocols when CT is needed), substitution of a non-ionising modality (ultrasound or MRI where they answer the question), and limitation of repeat scanning — and explain that applying the PECARN rule to avoid an unnecessary scan is justification in action. [4]

Document the assessment, the application of the rule, the discussion with the parent, the disposition, and the written safety-net advice. [1] [4]

Marking domains

• Application of the PECARN rule (4 marks). Works through the six age-appropriate predictors explicitly; correctly concludes that no predictor is met and CT is not indicated; states the negative predictive value and the role of the rule as a rule-out tool; gives the correct disposition of observe and discharge with advice.
• Radiation-risk counselling (3 marks). States the effective dose and the attributable lifetime cancer risk in plain, accurate language; names the cohort evidence (Brenner, Pearce); frames the risk so that the parent consents to the decision without minimising or exaggerating the risk.
• ALARA and radiation-aware reasoning (2 marks). Names the four levers of ALARA; explains that avoiding an unnecessary scan is justification; demonstrates that the decision is grounded in radiation-aware practice.
• Safety-net and documentation (1 mark). Gives the explicit return precautions of persistent vomiting, worsening headache, drowsiness, seizure, and focal neurology; documents the assessment, the rule, the discussion, and the safety-net. [1] [4]