Synopsis
Select and interpret CT, angiographic, perfusion and MRI techniques in acute stroke so haemorrhage is excluded quickly, arterial occlusion is found and treatment is not delayed by unnecessary imaging.
- Non-contrast CT is the usual first hyperacute test because it detects haemorrhage quickly and shows large established infarction, although early ischaemic change may be absent.
- Perform brain imaging immediately when reperfusion is considered or when anticoagulation, bleeding tendency, depressed consciousness, progressive symptoms, papilloedema, fever with neck stiffness or severe onset headache applies.
- When none of the immediate criteria applies, NICE still recommends scanning suspected acute stroke as soon as possible and within 24 hours.
Key red flags
Sudden aphasia, neglect, visual-field loss, gaze deviation or unilateral weakness requires immediate stroke assessment even if symptoms fluctuate or partially improve.
Reduced consciousness, severe headache at onset, neck stiffness, papilloedema, anticoagulant use or bleeding tendency increases the need for immediate non-contrast CT.
Brainstem and cerebellar signs can accompany a normal early CT; dysarthria, diplopia, crossed findings or severe truncal ataxia need posterior-circulation evaluation.
Neurological deterioration after initial imaging may represent infarct expansion, oedema, haemorrhagic transformation, re-occlusion or another diagnosis and mandates urgent reassessment.
A technically inadequate CTA, poor bolus or motion artefact cannot safely exclude large-vessel occlusion when the clinical syndrome remains convincing.
Look for contralateral face-arm weakness, aphasia, neglect, gaze deviation or visual-field loss, then inspect the matching arterial territory and proximal vessels.
Diplopia, dysarthria, dysphagia, crossed motor-sensory signs, limb or truncal ataxia and reduced consciousness may localise behind the CT-sensitive supratentorial compartment.
Identify parenchymal, subarachnoid, intraventricular or extra-axial blood because each redirects reperfusion, vascular investigation and specialist management.
Investigation priorities
Exclude intracranial haemorrhage and assess early infarction or a competing structural diagnosis.
Management branches
A patient arrives soon after onset with aphasia and hemiparesis.
- Activate the stroke pathway, document last known well, deficit severity, glucose and relevant anticoagulants while stabilising physiology.
- Perform immediate non-contrast CT and proceed directly to CTA if thrombectomy is being considered.