Table 1.

The SNOOP4 mnemonic for excluding red flags (secondary causes of headache)

	Clinical features	Need to exclude
S	Systemic symptoms: fever, chills, myalgia or weight loss	Metastasis and infection
N	Neurological symptoms or deficits	Stroke, mass lesion and encephalitis
O	Older age at onset (>50 years)	Temporal arteritis, glaucoma and mass lesion
O	Onset: thunderclap headache	Bleed
P	Papilloedema	Raised intracranial pressure
P	Positional	Intracranial hypotension
P	Precipitated by Valsalva manoeuvre or exertion	Raised intracranial pressure
P	Progressive headache or substantial pattern change	Any secondary cause

Reproduced with permission from Lee VME, Ang LL, Soon DTL, Ong JJY, Loh VWK. The adult patient with headache. Singapore Med J 2018;59:399–406.