Head injury in adults

ACR AC Head Trauma (2021); NICE NG232 (2023); Canadian CT Head Rule

Whether to scan is decided by a validated clinical decision rule, not by the request form. Once the rule is satisfied the study is an immediate unenhanced CT, and MRI has no place in the acute assessment.

Blunt head injury presenting to the emergency department, most often with a Glasgow Coma Scale of 13 to 15, where the question is whether an intracranial injury needs neurosurgical intervention or observation.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

GCS

Anticoagulated or on antiplatelets

Moves the threshold for imaging head injury further than any other single item of history.

Focal neurological deficit

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Accept as requested

CT Head — Unenhanced

CT Head

What we'd amend, and why

Everything that needs action in the first hours is dense on an unenhanced scan: extradural and subdural haematoma, contusion, subarachnoid and intraventricular blood, and the fractures and pneumocephalus that accompany them. It takes seconds, needs no cannula, and works in an agitated or intubated patient. Contrast adds nothing and degrades the assessment of acute blood, and MRI — although more sensitive for diffuse axonal injury — is too slow, too motion-sensitive and too poor at acute fracture to serve as the emergency study.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwayadult — Adults
rulerule-paeds-dose — Child-sized technique and contrast dose; checked by Radiographer at the scanner

Decision support only. Local protocol takes precedence.

Handled at the scanner(1)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

Child-sized technique and contrast dose
Confirm that a size- or weight-based protocol is selected — child-sized kV and mAs against size-based diagnostic reference ranges — and that contrast volume is calculated by weight rather than taken from an adult default. Weight-based iodinated contrast volumes of roughly 1.5–2.0 mL/kg are widely used in paediatric CT.
Radiographer at the scannerAt the scanner
Flags back if: No paediatric or size-based protocol exists on the scanner for the requested examination, or the requested coverage or number of phases exceeds what the clinical question needs — for example a multiphase study where a single phase answers it, or whole-body coverage for a focal question.

Worth asking the referrer (1)

None of these hold the request up. They sharpen the protocol or the plan that follows.

Which agent is the patient on — an anticoagulant (warfarin or a direct oral anticoagulant), an antiplatelet, or both?
The NICE NG232 within-eight-hours rule is written for anticoagulants and bleeding disorders, not for antiplatelet monotherapy. Answering it separates the patient who should be scanned despite a normal examination from the one who would be scanned only by the general decision rule. It does not block: where the answer is unknown and the patient is elderly and has hit their head, scan.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

Depressed conscious level or a focal deficit — CT within the hour

Role	Study & protocol	Why this answers the question
First line	CT Head CT Head — Unenhanced usually appropriate	These are the highest-risk features in NG232 and they carry a one-hour target rather than a general urgency: a Glasgow Coma Scale of 12 or less on arrival, or a focal neurological deficit, in a patient who has hit their head. The study is unchanged — unenhanced CT shows extradural and subdural haematoma, contusion, subarachnoid and intraventricular blood and the fractures that go with them — and what changes is that nothing may be queued in front of it. A patient at 8 or less is intubated first and scanned immediately afterwards; the airway is the only thing that legitimately precedes the scanner, and a pregnancy test is not.
Second line	CT Cervical Spine CT Cervical Spine — Unenhanced, Thin Section	A patient with a depressed conscious level cannot be cleared clinically by any rule, so the collar stays until the cervical spine has been imaged — and doing it in the same visit avoids a second transfer and the truncated cervicothoracic junction that separate studies produce.

On an anticoagulant — the injury itself is the indication

Role	Study & protocol	Why this answers the question
First line	CT Head CT Head — Unenhanced usually appropriate	NG232 handles anticoagulation as its own pathway precisely because these patients bleed without any of the classic features: a fully alert patient with no amnesia, no vomiting and a trivial mechanism still warrants a scan, within eight hours of the injury, and this is the commonest reason an otherwise unremarkable examination is imaged. Read the population precisely, because this fact cannot. The recommendation is for ANTICOAGULANT treatment — warfarin or a direct oral anticoagulant — and for bleeding disorders. Antiplatelet monotherapy is not the same thing: aspirin or clopidogrel alone in an alert patient with no other risk feature is not by itself an NG232 indication, and scanning that group wholesale is the over-flagging failure this library treats as equal to the under-flagging one. Dual antiplatelet therapy, or any antiplatelet with a second risk feature, sits much closer to the anticoagulated case and is reasonably scanned. Two failure modes sit either side of this arm and the card treats them as equal — scanning outside any rule in an alert patient with no risk factors, and not scanning the anticoagulated patient who has none of the classic features and is at genuine risk. A normal initial scan is also less final here than elsewhere: delayed haemorrhage is the reason repeat imaging exists in this group.
Second line	CT Cervical Spine CT Cervical Spine — Unenhanced, Thin Section	Added in the same attendance where the collar cannot be removed clinically. The reasoning is the same as on the main pathway; anticoagulation changes the head threshold, not the cervical one.

Adults

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	CT Head CT Head — Unenhanced usually appropriate	Everything that needs action in the first hours is dense on an unenhanced scan: extradural and subdural haematoma, contusion, subarachnoid and intraventricular blood, and the fractures and pneumocephalus that accompany them. It takes seconds, needs no cannula, and works in an agitated or intubated patient. Contrast adds nothing and degrades the assessment of acute blood, and MRI — although more sensitive for diffuse axonal injury — is too slow, too motion-sensitive and too poor at acute fracture to serve as the emergency study.
Second line	CT Cervical Spine CT Cervical Spine — Unenhanced, Thin Section	Head injury and cervical spine injury travel together, and a patient who cannot be cleared clinically needs both. Acquiring them in the same visit avoids a second transfer of a patient in a collar and avoids the incomplete cervicothoracic junction that plagues separate studies.

Pitfalls

Requesting MRI acutely. It delays the answer, tolerates trauma patients poorly and is worse than CT for acute fracture and hyperacute blood.
Scanning outside any decision rule in a fully alert patient with no risk features, and simultaneously failing to scan the anticoagulated patient who has none of the classic features but is at genuine risk.
Missing a thin subdural collection layered along the falx or tentorium by reviewing only on brain windows.
Failing to image the cervical spine in the same attendance when the collar cannot be removed clinically.
Treating an initial normal scan as the end of the matter in a deteriorating or anticoagulated patient; delayed haemorrhage is the reason repeat imaging exists.
Reading the anticoagulation arm across to antiplatelet monotherapy. The NG232 within-eight-hours rule is written for anticoagulants and bleeding disorders; aspirin or clopidogrel alone, in an alert patient with no other risk feature, is not by itself an indication, and treating "on blood thinners" as one indiscriminate category scans a very large number of well people. Dual antiplatelet therapy is the case that does behave like anticoagulation.
Reporting a head CT in a patient over 65 with a fall and forgetting the neck. Elderly falls produce odontoid fractures with little or no neck pain, and NEXUS and the Canadian rule both treat age as a reason not to clear the spine clinically.

Priors — what to pull first

A recent prior scan turns the question from presence into interval change, which is a much easier and much more useful comparison in an anticoagulated patient.
Pre-existing atrophy widens the subdural space and both predisposes to and conceals small collections.

What makes a good request

The Canadian CT Head Rule and NICE NG232 both aim at the same target — identifying the small subgroup with an injury needing intervention — and both rely on high-risk features rather than on the presence of loss of consciousness alone.
NICE NG232 asks for a scan within one hour for the highest-risk features, which include a Glasgow Coma Scale of 12 or less on arrival, a score below 15 at two hours, suspected open or depressed skull fracture, signs of a basal skull fracture, post-traumatic seizure, a focal neurological deficit and repeated vomiting.
Anticoagulation is handled as its own pathway in NG232 and is the commonest reason a patient with an otherwise unremarkable examination is scanned. The recommendation is specific: a patient having ANTICOAGULANT treatment — a vitamin K antagonist or a direct oral anticoagulant — or with a bleeding disorder, who has sustained a head injury with no other indication for CT, has a scan within eight hours.
Antiplatelet monotherapy is not the same recommendation and the distinction matters in both directions. Aspirin or clopidogrel alone, in an alert patient with no other risk feature, is not by itself an NG232 indication for a scan; treating it as one images a very large population for very little, which is the over-flagging failure this library treats as equal to under-flagging. Dual antiplatelet therapy, or an antiplatelet combined with any other risk feature, is a different and much stronger case. Say which agent the patient is on rather than writing "on blood thinners".
A request should state the mechanism, the Glasgow Coma Scale now and on arrival, whether there was loss of consciousness or amnesia, and which antithrombotic agent if any. Those facts are the decision rule.

Scoring this once it is done

The classification and risk tools this question ends in.

Canadian CT Head Rule (CCHR)Marshall CT Classification (TBI)Rotterdam CT Score (TBI)NEXUS Cervical Spine Criteria PECARN Pediatric Head Injury Rule

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

CT Head — Unenhanced CT Cervical Spine — Unenhanced, Thin Section

Confirm locally

CT Head — Unenhanced: timings are typical — confirm against local protocol.
Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.