What are the differential diagnoses for headache, emphasizing the red‑flag conditions that must never be missed?

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Differential Diagnoses for Headache with Never-Miss Red Flags

When evaluating headache, systematically screen for life-threatening secondary causes using the SNNOOP10 framework before diagnosing primary headache disorders, as missing conditions like subarachnoid hemorrhage, meningitis, or temporal arteritis can result in death or permanent disability. 1, 2

Primary Headache Differentials

Migraine (Most Disabling Primary Headache)

  • Unilateral, pulsating pain of moderate-to-severe intensity lasting 4-72 hours
  • Aggravated by routine physical activity
  • Associated symptoms: photophobia, phonophobia, nausea, vomiting
  • Note: Bilateral pain occurs in ~40% of cases 1
  • Migraine with aura: Visual fortification spectra or unilateral paresthesia preceding headache (affects 1/3 of migraine patients) 1

Tension-Type Headache (Most Common Primary Headache)

  • Bilateral, pressing/tightening quality
  • Mild-to-moderate intensity
  • NOT aggravated by routine activity
  • Lacks nausea, vomiting, photophobia, and phonophobia (may have one but not both) 3, 1

Cluster Headache (Rare but Distinctive)

  • Strictly unilateral, severe-to-very severe intensity
  • Short duration: 15-180 minutes
  • Ipsilateral autonomic features: lacrimation, nasal congestion, ptosis, miosis, eyelid edema
  • Frequency: 1-8 attacks per day during cluster periods 3, 1

Never-Miss Secondary Headaches: RED FLAGS (SNNOOP10)

These require immediate evaluation and neuroimaging 1, 2, 4:

S - Systemic symptoms/signs

  • Fever → suspect meningitis, encephalitis
  • Weight loss → malignancy, temporal arteritis
  • HIV/immunosuppression → opportunistic infections, CNS lymphoma

N - Neoplasm history

  • Known cancer → brain metastases (most common: lung, breast, melanoma)

N - Neurologic deficit

  • Focal signs (weakness, sensory loss, visual field defects)
  • Decreased consciousness
  • Impaired memory or personality change → mass lesion, encephalitis

O - Onset sudden/abrupt

  • Thunderclap headache (peak intensity within seconds) → subarachnoid hemorrhage until proven otherwise
  • Requires immediate non-contrast CT head followed by lumbar puncture if CT negative 4

O - Older age (>50-65 years)

  • Temporal arteritis/Giant cell arteritis → jaw claudication, scalp tenderness, elevated ESR/CRP
  • Higher risk for intracranial mass lesions 5

P - Pattern change or recent onset

  • Progressive worsening → intracranial hypertension, mass lesion
  • Change in established headache pattern → new secondary cause

P - Positional headache

  • Worse when lying down → intracranial hypertension, mass
  • Worse when upright → CSF leak, intracranial hypotension

P - Precipitated by Valsalva

  • Sneezing, coughing, exercise → Chiari malformation, mass lesion 1

P - Papilledema

  • With focal signs → mass lesion, venous sinus thrombosis
  • Without focal signs → idiopathic intracranial hypertension

P - Progressive headache

  • Steadily worsening over weeks → mass lesion, subdural hematoma

Additional Critical Red Flags:

  • Pregnancy/puerperium → preeclampsia, cerebral venous thrombosis, reversible cerebral vasoconstriction syndrome 2, 5
  • Painful eye with autonomic features → acute angle-closure glaucoma (requires immediate ophthalmology evaluation)
  • Post-traumatic → subdural hematoma, epidural hematoma 1
  • Neck stiffness → meningitis, subarachnoid hemorrhage 1

Diagnostic Approach Algorithm

Step 1: Screen for ANY red flags using SNNOOP10

  • If present → Immediate neuroimaging (non-contrast CT for acute/emergent; MRI for subacute) 3, 4
  • If absent → Proceed to Step 2

Step 2: Perform thorough neurologic examination

  • If abnormal → Neuroimaging required
  • If normal → Proceed to Step 3

Step 3: Apply diagnostic criteria for primary headaches 3, 1

  • Duration, location, quality, intensity, aggravating factors
  • Associated symptoms (nausea, photophobia, phonophobia)
  • Aura presence/absence

Step 4: Consider medication-overuse headache (MOH)

  • ≥15 headache days/month with regular overuse of acute medications for >3 months
  • Non-opioid analgesics ≥15 days/month OR other acute medications ≥10 days/month 1

Critical Pitfalls to Avoid

  1. Never assume bilateral headache excludes migraine (40% are bilateral) 1
  2. Never skip neuroimaging with thunderclap headache even if examination is normal 4
  3. Never diagnose "sinus headache" without imaging confirmation—most are migraines 4
  4. Never miss temporal arteritis in patients >50 with new headache (check ESR/CRP urgently) 1
  5. Preexisting primary headache does NOT exclude secondary headache—pattern change is a red flag 6
  6. Atypical aura (prolonged, motor symptoms) suggests stroke/TIA, not migraine 1

When Neuroimaging is NOT Indicated

Primary headache with ALL of the following 3, 1:

  • Normal neurologic examination
  • No red flags present
  • Typical features of migraine or tension-type headache
  • Stable pattern over time

References

1
Guideline

diagnosis and management of migraine in ten steps.

Nature Reviews Neurology, 2021

3
Guideline

management of the acute migraine headache.

American family physician, 2002

4
Research

Acute Headache in Adults: A Diagnostic Approach.

American family physician, 2022

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.