Table 1:

Headache red flags — modified SNOOP4^20,21

	Red flag	Clinical features	Etiologies to exclude
S	Systemic signs, symptoms or disease	Fever, weight loss, HIV, immunosuppression, malignancy, pregnancy or postpartum	Metastatic disease, CNS infection, CVST, RCVS, IIH
N	Neurologic symptoms or signs	Neurologic deficits or atypical or prolonged neurologic symptoms, or both	Neoplastic, inflammatory, infectious or vascular CNS disease
O	Onset (late)	Headache onset after age 50 yr	Neoplastic, inflammatory or infectious CNS disease; giant cell arteritis
O	Onset (sudden)	Thunderclap headache with onset to maximum intensity in < 60 s	Subarachnoid hemorrhage, CVST, RCVS, arterial dissection
P	Papilledema	Optic disc swelling (with or without pulsatile tinnitus, diplopia, transient visual obscuration, weight gain)	Raised intracranial pressure (mass lesion, hemorrhage, edema, CVST, IIH)
P	Postural aggravation	Headache worsened or triggered by standing or lying down	Intracranial hypotension (cerebrospinal fluid leak), intracranial hypertension (IIH, mass lesion)
P	Precipitated by valsalva	Headache triggered by valsalva (coughing, exercise or intercourse)	Chiari malformation, mass lesion (e.g., posterior fossa)
P	Pattern change or progressive	Change in previously stable pattern (loss of headache-free periods) or progressively worsening headache with evolving clinical symptoms	Any secondary cause

Note: CNS = central nervous system, CVST = cerebral venous sinus thrombosis, IIH = idiopathic intracranial hypertension, RCVS = reversible cerebral vasoconstriction syndrome.