Overview
Acute Headache
1. Clinical Overview
Summary
Acute headache: distinguish benign primary (migraine, tension) from life-threatening secondary (SAH, meningitis, GCA). "Worst headache of life" = SAH until proven otherwise. SNOOP4 red flags guide workup. CT head + LP for thunderclap. Steroids urgently for GCA to prevent blindness.
Key Facts
- SAH rule: "Worst headache ever" = CT + LP if negative
- Meningitis: Fever + stiff neck = LP + empiric antibiotics ASAP
- GCA: Age >50, temporal tenderness = steroids NOW
- Migraine: NSAIDs, antiemetics, triptans (avoid opioids)
2. Epidemiology
Acute headache refers to headache of sudden or recent onset that prompts medical evaluation. The critical task in the ED is to distinguish benign primary headaches from life-threatening secondary causes.
Classification
| Type | Definition |
|---|---|
| Primary headache | No underlying structural cause (migraine, tension, cluster) |
| Secondary headache | Due to underlying condition (SAH, meningitis, mass, venous thrombosis) |
| Thunderclap headache | Sudden severe headache reaching maximum intensity within seconds to minutes |
Epidemiology
- ED visits: 1-4% of all ED visits
- Secondary causes: ~5-10% of ED headache presentations
- SAH: 1-3% of patients with severe acute headache
- Most common ED diagnosis: Benign/primary headache
Dangerous Causes to Rule Out
| Cause | Mortality if Missed |
|---|---|
| Subarachnoid hemorrhage | 50% mortality; rebleed is devastating |
| Bacterial meningitis | High mortality without treatment |
| Intracranial mass with herniation | High if not identified |
| Cerebral venous thrombosis | Stroke, death |
| Hypertensive emergency | End-organ damage |
| Giant cell arteritis | Permanent blindness |
| Carbon monoxide poisoning | Cardiac arrest |
| Acute angle-closure glaucoma | Permanent vision loss |
3. Pathophysiology
Pain-Sensitive Structures
Intracranial
- Meninges (dura mater)
- Blood vessels (especially large arteries, venous sinuses)
- Cranial nerves (V, IX, X)
Extracranial
- Scalp muscles and fascia
- Arteries (temporal, occipital)
- Sinuses
- Eyes
Brain parenchyma is NOT pain-sensitive
Mechanism by Headache Type
| Type | Mechanism |
|---|---|
| SAH | Blood irritating meninges, increased ICP |
| Meningitis | Meningeal inflammation |
| Tumor | Mass effect, increased ICP, traction on pain-sensitive structures |
| Migraine | Trigeminovascular activation, cortical spreading depression |
| Tension | Myofascial mechanisms; central sensitization |
| Cluster | Trigeminal-autonomic dysfunction |
| CVT | Venous hypertension, infarction |
| GCA | Arterial inflammation |
4. Clinical Presentation
History (Critical)
Red Flag Symptoms (SNOOP4)
| Red Flag | Concern |
|---|---|
| Systemic symptoms/illness | Meningitis, malignancy, vasculitis |
| Neurological symptoms | Mass, stroke, hemorrhage |
| Onset sudden (thunderclap) | SAH, CVT, arterial dissection |
| Onset after 50 years | GCA, malignancy |
| Pattern change | Progressive secondary cause |
| Precipitated by Valsalva, exertion, position | Raised ICP, Chiari, SAH |
| Papilledema | Raised ICP |
| Pregnancy/postpartum | CVT, eclampsia |
Key History Questions
| Question | Significance |
|---|---|
| "Is this the worst headache of your life?" | SAH |
| "How fast did it reach maximum?" | Thunderclap = seconds to <1 min |
| "Any fever, neck stiffness?" | Meningitis |
| "Any visual changes?" | GCA, increased ICP, glaucoma |
| "Any trauma?" | Intracranial hemorrhage |
| "Any recent infections?" | Sinusitis, meningitis |
| "Any new medications?" | Medication-induced |
| "History of headaches?" | Primary vs new secondary |
| "Pregnant or postpartum?" | Eclampsia, CVT |
| "Any gas appliances at home?" | CO poisoning |
Physical Examination
| Finding | Suggests |
|---|---|
| Fever | Meningitis, sinusitis |
| Neck stiffness (meningismus) | Meningitis, SAH |
| Papilledema | Raised ICP (tumor, CVT) |
| Temporal artery tenderness | GCA |
| Focal neurological deficit | Stroke, mass, hemorrhage |
| Altered mental status | Serious intracranial pathology |
| Eye findings (red, fixed pupil) | Acute angle-closure glaucoma |
| Horner syndrome | Carotid/vertebral dissection |
| Rash | Meningococcemia |
5. Clinical Examination
(Integrated into Clinical Presentation above)
Red Flags (Life-Threatening)
Critical Presentations
| Red Flag | Concern | Action |
|---|---|---|
| Thunderclap headache | SAH, CVT, dissection | CT head → LP if negative |
| Fever + neck stiffness | Meningitis | LP, empiric antibiotics |
| Papilledema | Raised ICP | CT head, neurosurgery |
| New focal neurological deficit | Stroke, mass, hemorrhage | CT/MRI |
| Altered consciousness | Serious pathology | Full workup |
| Worst headache of life | SAH | CT → LP |
| Headache + seizure | Mass, SAH, CVT | CT, seizure management |
| Age >0 + new headache | GCA, malignancy | ESR/CRP, CT |
| Post-trauma | Intracranial hemorrhage | CT |
| Hypertensive emergency | Hypertensive encephalopathy | Lower BP carefully |
When to Image
CT Head Non-Contrast Indicated:
- Sudden severe headache (thunderclap)
- Altered mental status
- Focal neurological signs
- Trauma
- Suspected increased ICP
- Immunocompromised with new headache
- Cancer patient with new headache
- Anticoagulated patient
- Age >50 with new headache pattern
6. Investigations
Differential Diagnosis
| Type | Features |
|---|---|
| Migraine | Unilateral, pulsating, nausea, photophobia, aura possible |
| Tension | Bilateral, pressing, mild-moderate, no nausea |
| Cluster | Unilateral, severe, periorbital, autonomic symptoms, brief |
Secondary Headaches to Rule Out
| Condition | Key Features |
|---|---|
| SAH | Thunderclap, worst ever, meningismus, LP positive |
| Meningitis | Fever, neck stiffness, photophobia, altered mental status |
| CVT | Subacute, pregnancy/postpartum, oral contraceptives, papilledema |
| Mass/tumor | Progressive, worse in AM, with increased ICP signs |
| GCA | Age >0, temporal tenderness, jaw claudication, visual symptoms |
| Dissection | Neck pain, Horner's, stroke symptoms |
| Hypertensive encephalopathy | Severe HTN, altered mental status, papilledema |
| Acute glaucoma | Eye pain, red eye, fixed pupil, visual loss |
| CO poisoning | Multiple household members, winter, headache + confusion |
| Sinusitis | Facial pain, congestion, fever, worsening with head position |
Diagnostic Approach
Initial Assessment
Risk Stratify Based on History:
- Low-risk: Typical primary headache pattern, no red flags
- High-risk: Any red flags present
Laboratory Studies
| Test | Indication |
|---|---|
| CBC | Infection, polycythemia |
| BMP | Metabolic causes |
| ESR/CRP | GCA (ESR >0 mm/hr suggestive) |
| Coagulation | If anticoagulated |
| Carboxyhemoglobin | CO poisoning suspected |
| Pregnancy test | Child-bearing age |
Imaging
CT Head Non-Contrast
- First-line for SAH, hemorrhage, mass, trauma
- Sensitivity for SAH: ~98% within 6 hours, decreases over time
CT Angiography
- Aneurysm detection if SAH confirmed
- Dissection evaluation
MRI Brain
- Better for posterior fossa, CVT, mass
- T2*/GRE sequences for old blood
MRV or CTV
- Cerebral venous thrombosis
Lumbar Puncture
Indications:
- Suspected meningitis
- Thunderclap headache with negative CT (SAH rule-out)
- Opening pressure measurement
SAH on LP:
- Xanthochromia (yellow CSF; requires 6-12 hours to develop)
- Elevated RBCs that don't clear
- Distinguish from traumatic tap
Timing:
- Wait 6-12 hours after headache onset for xanthochromia to develop
- CT first to exclude mass/herniation risk
7. Management
SAH (Subarachnoid Hemorrhage)
Confirmed SAH:
1. Neurosurgery consult STAT
2. Blood pressure control (SBP <160 initially)
3. Nimodipine 60 mg q4h (prevent vasospasm)
4. Seizure prophylaxis
5. Treat hydrocephalus if present
6. Aneurysm treatment (endovascular coiling or clipping)
Meningitis
Suspected Bacterial Meningitis:
1. DO NOT DELAY antibiotics for LP
2. Empiric therapy:
- Vancomycin 15-20 mg/kg IV +
- Ceftriaxone 2g IV (or Cefotaxime) +
- Dexamethasone 0.15 mg/kg IV (give before or with first antibiotic dose)
3. LP when patient stable
4. Adjust antibiotics per culture
Giant Cell Arteritis
If suspected (age >50, temporal tenderness, vision symptoms, high ESR):
1. Start prednisone 1 mg/kg/day PO OR
2. IV methylprednisolone 1g daily if visual symptoms
3. Arrange temporal artery biopsy within 2 weeks
4. Ophthalmology if visual involvement
Migraine
Acute Treatment
| Agent | Dose | Notes |
|---|---|---|
| Ketorolac | 15-30 mg IV | First-line NSAID |
| Metoclopramide | 10 mg IV | Antiemetic + adjunct |
| Prochlorperazine | 10 mg IV | Antiemetic |
| Sumatriptan | 6 mg SC or 20 mg nasal | If no contraindication |
| IV fluids | 1 L NS | Hydration |
| Diphenhydramine | 25-50 mg IV | Adjunct, prevent akathisia |
Avoid Opioids - less effective, promote chronification
Tension Headache
- Acetaminophen 1000 mg PO or ibuprofen 400-800 mg PO
- Reassurance
- Address triggers
Cluster Headache
- Oxygen 100% 12 L/min via non-rebreather x 15 min
- Sumatriptan 6 mg SC
- Refer for preventive therapy
8. Complications
Disposition
Admission Criteria
- SAH or intracranial hemorrhage
- Bacterial meningitis
- CVT requiring anticoagulation
- Mass with dangerous features
- Hypertensive emergency with neurological findings
- GCA with visual symptoms
- Status migrainosus not responding to treatment
- Unable to maintain hydration
Observation/ED Observation Unit
- Migraine responding to treatment but needs monitoring
- LP pending or just performed
- Awaiting imaging
Discharge Criteria
- Clear benign cause identified
- Symptoms controlled
- No red flags
- Able to tolerate oral intake
- Reliable patient with follow-up arranged
- Understands return precautions
Follow-up
| Condition | Follow-up |
|---|---|
| Migraine | Primary care or neurology within 1-2 weeks |
| Tension | Primary care |
| GCA | Rheumatology and biopsy within 2 weeks |
| Negative LP for SAH | Reassurance, primary care |
11. Patient/Layperson Explanation
Understanding Your Headache
- Headaches have many causes, most are not serious
- We performed tests to rule out dangerous causes
- Follow up as recommended
- Take medications as prescribed
When to Return Immediately
- Headache suddenly becomes severe (thunderclap)
- Fever, stiff neck, rash
- Vision changes
- Weakness, numbness, difficulty speaking
- Confusion or difficulty staying awake
- Headache after head injury
- Headache not improving with treatment
Migraine Prevention Tips
- Keep a headache diary
- Identify and avoid triggers
- Regular sleep schedule
- Stay hydrated
- Limit caffeine
- Discuss preventive medications with your doctor
9. Prognosis & Outcomes
Special Populations
Elderly (Age >50)
- Higher suspicion for secondary causes
- GCA risk
- Malignancy more common
- Subdural hematoma (even minor trauma)
- Lower threshold for imaging
Pregnancy/Postpartum
- CVT: 2-3 weeks postpartum highest risk
- Eclampsia: BP check essential
- Pituitary apoplexy: Postpartum
- MRI preferred over CT if imaging needed
Immunocompromised
- Broader infectious differential (cryptococcal, toxoplasmosis, PML)
- Lower threshold for LP
- Consider opportunistic infections
Anticoagulated Patients
- Lower threshold for imaging (intracranial hemorrhage)
- Consider reversal if hemorrhage found
- Even minor trauma requires CT
Quality Metrics
Performance Indicators
| Metric | Target |
|---|---|
| CT head for thunderclap headache | 100% |
| LP for negative CT thunderclap headache | >0% |
| Antibiotics <1 hour for suspected meningitis | 100% |
| ESR/CRP checked for suspected GCA | 100% |
| Red flags documented | 100% |
| Return precautions documented | 100% |
Documentation Requirements
- Headache characteristics (onset, severity, location)
- Red flag assessment (SNOOP4)
- Prior headache history
- Complete neurological exam
- Diagnostic reasoning
- Treatment and response
- Disposition rationale
- Return precautions given
10. Evidence & Guidelines
Key Clinical Pearls
Diagnostic Pearls
- "Worst headache of my life" = SAH workup mandatory
- CT negative doesn't exclude SAH - do LP if high suspicion
- Xanthochromia takes 6-12 hours to develop
- Fever + neck stiffness = LP and empiric antibiotics
- New headache in elderly = always consider secondary cause
Treatment Pearls
- Don't delay meningitis antibiotics for LP
- Steroids for GCA prevent blindness
- Avoid opioids for migraine - use NSAIDs, antiemetics, triptans
- Nimodipine for SAH - reduces vasospasm
- Oxygen for cluster headache - highly effective
Disposition Pearls
- Thunderclap headache needs full workup even if CT negative
- Clear diagnosis needed for discharge
- Red flags = full workup or admission
- Patient education on return precautions is essential
- Follow-up for any unexplained headache
12. References
- Dodick DW. Pearls: Headache. Semin Neurol. 2010;30(1):74-81.
- Edlow JA, Caplan LR. Avoiding pitfalls in the diagnosis of subarachnoid hemorrhage. N Engl J Med. 2000;342(1):29-36.
- Schievink WI. Sentinel headache. Neurology. 2001;57(5):351-352.
- Perry JJ, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage. BMJ. 2011;343:d4277.
- Friedman BW, et al. Randomized trial of IV valproate vs metoclopramide vs ketorolac for acute migraine. Neurology. 2014;82(11):976-983.
- Headache Classification Committee of the International Headache Society. The International Classification of Headache Disorders, 3rd edition. Cephalalgia. 2018;38(1):1-211.
Version History
| Version | Date | Changes |
|---|---|---|
| 1.0 | 2025-01-15 | Initial comprehensive version with 14-section template |