[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Clinical exam](https://durgical.com/en/clinical-exam/) › [Nervous system](https://durgical.com/en/clinical-exam/areas/neuro/) › Headache: primary or secondary, and the red flags (SNOOP)

# Headache: primary or secondary, and the red flags (SNOOP)

- Topic

Most headaches are migraine or tension-type, but a few hide a bleed, an infection or raised pressure. These are the warning signs to look for.

Updated Nov 13, 2026

**See it in 3D:** [Dura mater](https://durgical.com/en/anatomy/cranial-dura/) · [Superficial temporal artery](https://durgical.com/en/anatomy/superficial-temporal-artery/)

## Key points

- Thunderclap headache (maximal within about a minute) is subarachnoid hemorrhage until proven otherwise.
- SNOOP: Systemic symptoms, Neurologic signs, Onset sudden, Older age at onset, Pattern change (and positional or Valsalva-provoked headache, papilledema, progression).
- Fever with headache and neck stiffness: meningitis; act fast.
- New headache after 50 with jaw claudication, scalp tenderness or visual symptoms: giant cell arteritis.
- Headache in pregnancy or the puerperium, with seizures or papilledema: think of cerebral venous thrombosis and preeclampsia.
- Frequent use of pain medicines can itself cause daily headache (medication overuse headache).

## What it is

Headache is primary when it is the disease itself (migraine, tension-type, cluster) and secondary when it is a symptom of something else, such as subarachnoid hemorrhage, meningitis or raised intracranial pressure. The bedside task is to find the few secondary headaches among the many primary ones. Red-flag lists such as SNOOP, extended in the literature as SNNOOP10, organize the questions; most patients without red flags need no tests.

## Key facts

- Primary headaches: migraine (unilateral, pulsating, with nausea, light and sound sensitivity, sometimes aura), tension-type (bilateral, pressing, mild to moderate), cluster (short, severe, one eye, with tearing and nasal congestion).
- Onset: sudden and explosive points to vascular causes; days to weeks points to mass, infection or raised pressure; years of a stable pattern points to a primary headache.
- Site and character: where it hurts, whether it throbs or presses, and whether it is always on the same side.
- Triggers and modifiers: worse lying down or in the morning, with coughing or straining (raised pressure); worse standing (low pressure after lumbar puncture).
- Associated symptoms: fever, vomiting, visual loss, diplopia, weakness, confusion, seizures, red painful eye with halos.
- Background: cancer, HIV or immunosuppression, anticoagulants, head trauma, pregnancy, oral contraceptives, family history of migraine.

## Step by step

- Check vital signs, temperature and level of consciousness first.
- Ask: 'Is this a new headache or your usual one? How fast did it reach its worst?'
- Go through the red flags in order (SNOOP), one by one, and write down each answer.
- Characterize the pain: site, quality, intensity, duration, frequency, triggers, and what relieves it.
- Ask about pain medicine use: which ones and how many days a month.
- Examine: neck stiffness, full neurologic exam, fundoscopy for papilledema, temporal arteries, eyes, sinuses, teeth and jaw.
- No red flags and a typical primary pattern: diagnose the primary headache clinically; red flags present: arrange imaging or referral.

## Primary and secondary headaches: typical picture

| Type | Typical picture | Key clue |
| --- | --- | --- |
| [Migraine](https://durgical.com/en/conditions/migraine/) | Recurrent, unilateral, throbbing, hours to days | Nausea, light sensitivity, aura; family history |
| [Tension-type](https://durgical.com/en/conditions/tension-type-headache/) | Bilateral, pressing band, mild to moderate | No nausea or aura; daily activity does not worsen it |
| [Cluster](https://durgical.com/en/conditions/cluster-headache/) | Severe, around one eye, under about three hours | Tearing, red eye and nasal congestion on the same side; restlessness |
| [Subarachnoid hemorrhage](https://durgical.com/en/conditions/subarachnoid-haemorrhage/) | Sudden 'worst ever' headache | Peak within about a minute, vomiting, neck stiffness, fainting |
| [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/) | Headache over hours with fever | Neck stiffness, confusion, rash |
| [Idiopathic intracranial hypertension](https://durgical.com/en/conditions/idiopathic-intracranial-hypertension/) | Daily headache, worse lying down | Young woman with obesity, papilledema, transient visual loss |
| [Giant cell arteritis](https://durgical.com/en/conditions/giant-cell-arteritis/) | New headache after 50 | Jaw claudication, tender temporal artery, visual loss, raised ESR |
| [Cerebral venous thrombosis](https://durgical.com/en/conditions/cerebral-venous-sinus-thrombosis/) | Progressive headache, days | Pregnancy or puerperium, contraceptives, seizures, papilledema |

## Clinical notes

- Thunderclap headache needs urgent brain CT; if CT is normal and suspicion remains, lumbar puncture.
- Fever, headache and altered consciousness or rash: suspected bacterial meningitis is an emergency; treatment should not wait for imaging.
- Headache with focal deficit, confusion or papilledema needs urgent imaging.
- Painful red eye with halos and a mid-dilated pupil suggests acute angle-closure glaucoma.
- Headache in a patient with cancer or HIV: consider metastases, abscess or opportunistic infection.
- Headache after a head injury in an older or anticoagulated patient: rule out subdural hematoma.

## In the lab

- Most primary headaches need no tests.
- Non-contrast brain CT for thunderclap headache or acute deficit; MRI for subacute deficit, change in pattern, cancer or HIV.
- Lumbar puncture when meningitis or subarachnoid hemorrhage with normal CT is suspected, after imaging when indicated.
- ESR and C-reactive protein when giant cell arteritis is suspected; venous imaging when venous thrombosis is suspected.

## Memory aid

One headache you have had for years is a story; a new one is a question.

## Test yourself

Think of the answer, then tap the question to see it.

## What does each letter of SNOOP stand for?

Systemic symptoms or illness, Neurologic signs, Onset sudden, Older age at onset, Pattern change or progression (plus positional, Valsalva-provoked and papilledema).

## Which test comes first in a thunderclap headache?

An urgent non-contrast brain CT; lumbar puncture follows if CT is normal and suspicion of hemorrhage remains.

## Which features separate cluster headache from migraine?

Cluster is shorter, strictly around one eye, with same-side tearing and nasal congestion, and the patient is restless rather than lying still.

## Which diagnosis must be considered in a new headache after 50 with jaw pain on chewing?

Giant cell arteritis, because it can cause sudden permanent visual loss.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/clinical-exam/headache-primary-or-secondary-and-the-red-flags/)

## Connections

## See it in 3D 2

The structures of Durgical's 3D anatomy where it is found.

- [Dura mater](https://durgical.com/en/anatomy/cranial-dura/)
- [Superficial temporal artery](https://durgical.com/en/anatomy/superficial-temporal-artery/)

## Related 7

- [Meningeal signs: neck stiffness, Kernig and Brudzinski](https://durgical.com/en/clinical-exam/meningeal-signs-neck-stiffness-kernig-and-brudzinski/)
- [Meningeal syndrome](https://durgical.com/en/clinical-exam/meningeal-syndrome/)
- [Intracranial hypertension syndrome](https://durgical.com/en/clinical-exam/intracranial-hypertension-syndrome/)
- [Fundoscopy: the optic disc, papilledema and retinopathy](https://durgical.com/en/clinical-exam/fundoscopy-the-optic-disc-papilledema-and-retinopathy/)
- [The neurological examination: order and screening exam](https://durgical.com/en/clinical-exam/the-neurological-examination-order-and-screening-exam/)
- [Analysing a symptom: onset, site, character, radiation and more](https://durgical.com/en/clinical-exam/analysing-a-symptom-onset-site-character-radiation-and-more/)
- [Recognising a stroke: BE-FAST and the NIH Stroke Scale](https://durgical.com/en/clinical-exam/recognising-a-stroke-be-fast-and-the-nih-stroke-scale/)

## Related conditions 8

- [Migraine](https://durgical.com/en/conditions/migraine/)
- [Tension-type headache](https://durgical.com/en/conditions/tension-type-headache/)
- [Cluster headache](https://durgical.com/en/conditions/cluster-headache/)
- [Subarachnoid haemorrhage](https://durgical.com/en/conditions/subarachnoid-haemorrhage/)
- [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/)
- [Idiopathic intracranial hypertension](https://durgical.com/en/conditions/idiopathic-intracranial-hypertension/)
- [Giant cell arteritis](https://durgical.com/en/conditions/giant-cell-arteritis/)
- [Cerebral venous sinus thrombosis](https://durgical.com/en/conditions/cerebral-venous-sinus-thrombosis/)

[← All of the clinical exam](https://durgical.com/en/clinical-exam/)

Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: [Headache](https://medlineplus.gov/ency/article/003024.htm) (MedlinePlus Medical Encyclopedia, U.S. National Library of Medicine, 2025); [Approach to the Patient With Headache](https://www.msdmanuals.com/professional/neurologic-disorders/headache/approach-to-the-patient-with-headache) (MSD Manual Professional Edition, 2025); [Red and orange flags for secondary headaches in clinical practice: SNNOOP10 list](https://pmc.ncbi.nlm.nih.gov/articles/PMC6340385/) (Neurology (Do TP et al.), via PubMed Central, 2019).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/clinical-exam/headache-primary-or-secondary-and-the-red-flags/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/clinical-exam/headache-primary-or-secondary-and-the-red-flags/