Bedside interpretation: ECG, CXR, CT and labs

CT head: when to scan and how to read it

Reviewed Nov 2026·4 references
New· views rounded down, updated weekly

Indications after head injury, a systematic read (blood, cisterns, brain, ventricles, bone), and early stroke and herniation signs.

Definition
Non-contrast CT is the first-line brain imaging in the ICU for trauma, sudden neurological deterioration, suspected stroke and before LP when indicated. Read systematically: Blood, Cisterns, Brain, Ventricles, Bone ('Blood Can Be Very Bad').

At the bedside

Timed steps
  1. 1

    Head injury - scan within 1 h (NICE)

    ≤ 1 h

    GCS < 13 on initial assessment, GCS < 15 at 2 h, suspected open or depressed skull fracture, signs of basal skull fracture, post-traumatic seizure, focal deficit, more than 1 episode of vomiting.

  2. 2

    Anticoagulated patients

    ≤ 8 h

    Head injury on anticoagulants: CT within 8 h even without other risk factors (sooner if other criteria).

  3. 3

    Blood

    Hyperdense (acute blood 50-100 HU): extradural (lentiform, crosses no sutures), subdural (crescentic, crosses sutures), subarachnoid (in sulci/cisterns), intraparenchymal, intraventricular.

  4. 4

    Cisterns

    Effaced basal cisterns (perimesencephalic) suggest raised ICP and herniation risk.

  5. 5

    Brain

    Grey-white differentiation loss, insular ribbon sign, hyperdense MCA sign (early ischaemia); midline shift; oedema.

  6. 6

    Ventricles

    Hydrocephalus (temporal horn dilatation), effacement from mass effect, intraventricular blood.

  7. 7

    Bone

    Fractures on bone windows; air in the cranium (pneumocephalus) suggests open or basal fracture.

  8. 8

    Stroke

    Non-contrast CT excludes haemorrhage before thrombolysis; ASPECTS scores early MCA ischaemia; CT angiography for large-vessel occlusion if thrombectomy is possible.

CT patterns and action

FindingMeaningAction
Lentiform extra-axial bleedExtradural haematomaUrgent neurosurgery
Crescentic extra-axial bleedSubdural haematomaNeurosurgery if thick, shift, or deteriorating
Blood in basal cisternsSubarachnoid haemorrhageCT angiogram; neurosurgery/neurointervention
Effaced cisterns, midline shift > 5 mmRaised ICP / herniation riskICP measures (raised-icp module)
Hyperdense MCA signAcute MCA thrombusStroke pathway (CTA, thrombolysis/thrombectomy)
Red flag · call your senior now
Falling GCS with a new dilated pupil: treat as herniation (osmotherapy, brief hyperventilation) and arrange immediate CT and neurosurgery.
Pitfall
Reading only the brain window - always review bone and subdural windows.
Pitfall
A normal early CT does not exclude ischaemic stroke, diffuse axonal injury or encephalitis.
Pearl
Isodense subacute subdurals (about 1-3 weeks) are easily missed - look for sulcal effacement and midline shift.

Calculators for this topic

Glasgow Coma Scale

Eye + Verbal + Motor (3-15). Record components, e.g. E3 V4 M5.

References

  1. 1

    National Institute for Health and Care Excellence. Head injury: assessment and early management (NG232). London: NICE; 2023.

  2. 2

    Stiell IG, Wells GA, Vandemheen K, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet 2001;357:1391-6.

  3. 3

    Powers WJ, Rabinstein AA, Ackerson T, et al. Guidelines for the early management of patients with acute ischemic stroke: 2019 update to the 2018 guidelines. Stroke 2019;50:e344-418.

  4. 4

    Farkas J. The Internet Book of Critical Care (IBCC). EMCrit Project; continuously updated.

Test yourself

Module quiz · score 70% to complete the module

Previous

Chest X-ray in the ICU: lines, tubes and lung patterns

Next

Liver tests, coagulation and cardiac biomarkers

Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.