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Headache is a frequent presentation to the Emergency Department. Identifying red flags and common features is essential to safe management for serious diagnoses. A clear and detailed history is often overlooked in order to expedite obtaining CT scans. A thorough examination focusing on neurological findings is often as important as the CT scan. The table below gives most of the differentials for acute headache presentations. Click on the active links to get more details. Rapid reference guide to serious headaches here.

Serious Immediate

Serious Urgent


Sub arachnoid haemorrhage (SAH)

Temporal arteritis


Thunderclap headache



Subdural haematoma

Hypertensive emergencies


Cerebral venous sinus thrombosis

Carbon monoxide


Infection - meningoencephalitis

Pseudotumour cerebri



Carotid or vertebral dissection


StrokeReversible cerebral vasoconstriction syndromes

Red flags

Red flags are indicators in the patient history or examination that alert us to potential serious diagnoses. Below is a list of red flags for headache. Any of these findings in the context of a headache should prompt further investigations or consultation. A reasonable attempt to address any underlying cause for the red flag finding/s must be conducted before excluding serious pathologies. The absence of red flag findings does not always exclude serious pathology. Clinicians should adopt a low threshold for investigation or consultation in unusual or atypical presentations.

Always investigate:

  • Worst ever headache

  • Sudden onset headache - 'thunderclap' (especially on exertion)

  • Maximal at onset headache

  • Elderly

  • Warfarin or other anticoagulants

  • Change in level of consciousness

  • Neurological symptoms

  • Long duration

Imaging for Headache and serious neurological presentations

There are two resources to use for imaging pathways, this page on the WA Imaging Pathways provides very clear guidelines for most neurological presentations. The ACEM Diagnostic Imaging Pathways have been developed by the Emergency and Radiology colleges and provide guidance on headache and head trauma patients along with other imaging pathways.

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