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Rapid Reference Guide to Serious Headaches

Clinical Indicators/
Red Flags
Secondary Headache Diagnoses
Initial investigations
Nature of Headache
‘Thunderclap’ headache: severe pain maximal within 1-2 minutes.
Subarachnoid haemorrhage (SAH) or intracerebral haemorrhage (ICH). Other differentials include arterial dissection and venous thrombosis.
If no bleed or aneurysm, most common diagnosis is Reversible Cerebral Vasoconstriction Syndrome (RCVS).
CTB, consider CTA for thunderclap headaches*.
LP at 12 hours if CT normal but concern for missed SAH.
(NB CTA is useful for non-bleed differentials, does not diagnose SAH).
Consult for any positive investigations or concerns, consider RCVS follow-up.
*Indications for vascular imaging include multiple or recurrent episodes, presence of any additional red flags (e.g. persistence, physiological compromise, neurological deficit, vascular or thrombotic risks) and informed patient request. MRI/ MR angiography may be an option depending on availability. Consider risk of false-positive or incidental findings.
Persistent or progressive pain, or failure to respond to treatment.
Cerebral venous thrombosis: may have thrombotic risk or facial infection
CTB only 30% sensitive for thrombosis. CTV preferred to MRV.
Pressure/ postural headache: strain/ cough/ supine/ standing.
High intracranial pressure: Idiopathic intracranial hypertension (IIH), Chiari malformation, hypertensive encephalopathy
Low pressure: post LP, spontaneous
Fundoscopy required if suspicion of raised ICP.
CTB (may be normal) and CTV to exclude venous thrombosis.
Consult re LP/ further imaging.
Low pressure: Variable
Associated features
Associated focal deficit,
Confusion/ personality change/ seizure.
Associated neck pain, especially if any deficit.
Fever, neck stiffness.
Space-occupying lesion: may have subtle neurological deficit
Pituitary apoplexy: visual symptoms common, CT often normal.
CTB, consider contrast.
Stroke: use local imaging protocol and Clinical Business Rule.
Consult re further imaging/ investigations e.g. MRI.
Carotid, vertebral or aortic dissection (may be history of mild neck strain eg coughing, look for subtle posterior circulation deficits)
Meningitis. Consider risk of partially treated- e.g. recent antibiotics.
Not all are infective.
LP especially if risk of bacterial, unless contraindications
Treat first if any suspicion of bacterial and delay to LP.
PCR blood and CSF for N. meningitidis.
CTB prior to LP only if papilloedema on fundoscopy, reduced LOC or focal deficit.
Encephalitis, cerebral abscess, other CNS infection, vasculitis. Presume if confusion and/or focal deficit.
CTB consider contrast: LP if CTB normal unless contraindications.
MRI as inpatient.
Patient Risk Factors
Immune compromise/ Intoxication/ advanced age/ pregnancy/ post-partum/ history of malignancy/ thrombotic or haemorrhagic risk/ concerning family hx
Higher overall risk of dangerous secondary headache and/or occult trauma
Pregnancy: consult re CTB with shielding vs MRI.
Giant Cell Arteritis: age over 50, tender temporal pulses
Acute Glaucoma: consider especially in elderly, myopia.
Intraocular pressure >20mmHg

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