Acute Headache in Adults

1. Clinical Overview

Summary

Acute headache is one of the most common presentations in emergency departments, representing 2–4% of all visits. [1] The primary clinical challenge is to distinguish common, benign primary headaches (migraine, tension-type) from rare but life-threatening secondary headaches (subarachnoid haemorrhage, meningitis, GCA). [2]

The assessment is anchored by the SNOOP4 red flag mnemonic. [3] The most critical presentation is the thunderclap headache—reaching maximal intensity within 1 minute—which mandates urgent investigation for subarachnoid haemorrhage (SAH) using the Ottawa SAH Rule. [4] While primary headaches account for > 90% of cases, missing a secondary cause carries a high risk of morbidity and mortality. [5]

Key Facts

• The 6-Hour Rule: Non-contrast CT Head is > 98% sensitive for SAH if performed within 6 hours of headache onset. [6]
• The SNOOP4 Mnemonic: Systemic, Neurological, Onset (Sudden), Older (> 50), Pattern change, Postural, Precipitated by Valsalva, Papilloedema/Pregnancy. [3]
• Migraine Prevalence: Affects 1 in 7 people globally; 3:1 female-to-male ratio. [7]
• Xanthochromia: Bilirubin in CSF (detected by spectrophotometry) confirms SAH but takes 12 hours to develop. [8]
• Giant Cell Arteritis (GCA): A "do-not-miss" diagnosis in those > 50 years; start high-dose steroids immediately if suspected to prevent blindness. [9]

Clinical Pearls

The "Thunderclap" Pearl: A "thunderclap" headache is SAH until proven otherwise. Even if the patient is fully conscious and neurologically intact, you MUST investigate if the pain reached peak intensity in less than 60 seconds. [4,10]

The "Fundoscopy" Pearl: Always perform fundoscopy to look for papilloedema (raised ICP) or subhyaloid haemorrhage (SAH). A normal CT does not exclude raised ICP from conditions like Idiopathic Intracranial Hypertension (IIH). [11]

The "Triptan" Tip: Triptans should be taken at the start of the headache phase in migraine, not during the aura phase, to maximize efficacy. [12]

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2. Epidemiology & Risk Factors

Incidence & Distribution

• ED Burden: Headache accounts for approximately 1 in 30 emergency presentations. [1]
• SAH Incidence: Affects ~6–10 per 100,000 person-years; peak age 40–60. [13]
• GCA Incidence: Found in ~20 per 100,000 people over 50 years of age. [9]

Risk Factors

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3. Pathophysiology

1. The Trigeminovascular System

The common final pathway for many headaches is the activation of the trigeminovascular system. Pain-sensing fibres from the Trigeminal nerve (CN V) innervate the meninges and cerebral blood vessels. When stimulated, they release neuropeptides like CGRP (Calcitonin Gene-Related Peptide), causing vasodilation and "sterile inflammation." [15]

2. Migraine: Cortical Spreading Depression (CSD)

Migraine aura is caused by CSD—a wave of neuronal depolarisation followed by depression that spreads across the cortex. This wave triggers the trigeminal nerves, leading to the subsequent headache phase. [16]

3. Subarachnoid Haemorrhage (SAH)

Rupture of an aneurysm (usually at the bifurcations of the Circle of Willis) leads to blood entering the subarachnoid space. This causes an immediate, massive increase in intracranial pressure and chemical irritation of the meninges, resulting in the thunderclap pain. [13,17]

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4. Clinical Presentation

Primary Headache Patterns

• Migraine: Unilateral, throbbing, moderate-severe, associated with nausea, photo/phonophobia. Aggravated by movement. [18]
• Tension-Type: Bilateral, "band-like" pressure, mild-moderate, not aggravated by movement. No nausea. [18]
• Cluster: Strictly unilateral, excruciating periorbital pain. Associated with autonomic features (lacrimation, rhinorrhoea, ptosis) and restlessness. [19]

Red Flags: The SNOOP4 Framework

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5. Investigations

1. Neuroimaging (The "Ottawa" Rule)

• Non-contrast CT Head: 98.7% sensitive if done less than 6 hours from onset by an experienced radiologist. [6,20]
• CT Angiography (CTA): If SAH is confirmed or if RCVS/Dissection is suspected.
• MRI Brain: Superior for posterior fossa lesions, CVST (MRV), and pituitary apoplexy. [21]

2. Lumbar Puncture (LP)

• Timing: Must be performed ≥12 hours after headache onset to allow for bilirubin (xanthochromia) formation. [8,22]
• Findings: Xanthochromia (spectrophotometry) distinguishes SAH from a "traumatic tap."
• Opening Pressure: Essential if IIH or meningitis is suspected.

3. Laboratory Assessment

• ESR/CRP: Mandatory in all patients > 50 years to screen for GCA. [9]
• FBC: Check for leucocytosis (infection) or thrombocytopenia.
• D-dimer: Low utility for CVST, but occasionally used in low-probability cases.

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6. Management: The Headache Algorithm

Management Flowchart (ASCII)

                  [ACUTE SEVERE HEADACHE]
                             |
              +--------------v--------------+
              |    SCREEN FOR RED FLAGS     |
              | (SNOOP4: Thunderclap, GCA)  |
              +--------------+--------------+
                             |
              /--------------+--------------\
      [RED FLAGS PRESENT]              [NO RED FLAGS]
             |                        (Probable Primary)
      +------v------+                 +------v------+
      | URGENT CT   |                 | MIGRAINE /  |
      | (less than 6H Window)|                 | TENSION DX  |
      +------+------+                 +------v------+
             |                               |
      /------+------\                 +------v------+
 [CT POS]        [CT NEG]             | 1. NSAIDs   |
    |               |                 | 2. TRIPTANS |
+---v---+    /------+------\          | 3. ANTIEMETIC|
| SAH!  |    [less than 6H FROM]   [> 6H FROM]  +-------------+
+-------+    [ ONSET  ]   [ ONSET  ]
    |           |               |
+---v---+    +--v---+    +------v------+
| NEURO |    | SAH  |    | LP @ 12 HRS |
| SURG  |    | EXCL*|    | (Xantho)    |
+-------+    +------+    +-------------+
(*If history is non-high risk & CT is high quality)

1. Emergency Management (Secondary)

• Subarachnoid Haemorrhage: Nimodipine 60mg (prevents vasospasm), BP control (less than 160 mmHg), and neurosurgical referral for coiling/clipping. [13,17]
• Meningitis: Immediate IV Ceftriaxone (2g) + Dexamethasone (10mg) if bacterial suspected. [23]
• GCA: Prednisolone 60mg OD (start immediately, biopsy within 2 weeks). [9]

2. Acute Management (Primary)

• Migraine:
  • "First-line: Sumatriptan 50–100mg PO (or 6mg SC) + Naproxen 500mg. [12]"
  • "Antiemetic: Metoclopramide 10mg IV/PO (also helps drug absorption)."
• Cluster:
  • "Gold Standard: 100% Oxygen (12–15 L/min via non-rebreather) for 15 mins. [19]"
  • "Second-line: Sumatriptan 6mg SC."
• Tension: Paracetamol 1g or Ibuprofen 400mg.

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7. Complications

• Vasospasm (SAH): Typically occurs 4–14 days post-bleed; causes delayed cerebral ischaemia. [13]
• Permanent Vision Loss: The primary complication of missed GCA. [9]
• Medication Overuse Headache (MOH): Caused by taking triptans/opioids > 10 days/month or simple analgesics > 15 days/month. [24]
• Status Migrainosus: A migraine attack lasting > 72 hours; often requires IV fluids and parenteral therapy.

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8. Evidence & Landmark Trials

1. Ottawa SAH Rule (PMID: 21646482): Validated clinical decision tool with 100% sensitivity for identifying SAH in neurologically intact patients. [4]
2. Perry et al. (BMJ 2011): Demonstrated that CT Head within 6 hours has near 100% sensitivity for SAH, potentially eliminating the need for LP in early presenters. [6]
3. The CHESS Trial: Evidence for the management of Medication Overuse Headache via withdrawal strategies. [24]
4. REPOSE Trial (PMID: 26038275): Evaluation of Botox for chronic migraine prophylaxis.
5. Cochrane Review (2014): Confirmed high-flow oxygen as a highly effective, side-effect-free treatment for acute cluster headache. [19]

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9. Single Best Answer (SBA) Questions

Question 1

A 45-year-old female presents with a sudden onset, severe headache that reached maximum intensity in 30 seconds while she was lifting a heavy box. She describes it as "being hit by a hammer." She arrives 4 hours after the onset. Her GCS is 15 and there are no focal neurological deficits. A non-contrast CT head performed 5 hours after onset is reported as normal by a consultant radiologist. What is the most appropriate next step?

• A) Perform a Lumbar Puncture immediately
• B) Discharge with migraine advice and safety netting
• C) Perform a Lumbar Puncture in 7 hours
• D) Perform a CT Angiogram of the Circle of Willis
• E) Repeat the non-contrast CT in 24 hours
• Answer: C. According to the 6-hour rule (Perry et al.), a negative CT within 6 hours is extremely sensitive. However, if clinical suspicion is high (thunderclap onset), guidelines still recommend LP. LP must be delayed until 12 hours from onset to allow for xanthochromia development.

Question 2

A 72-year-old woman presents with a new-onset right-sided headache, scalp tenderness when brushing her hair, and pain in her jaw when chewing steak. She has no visual changes. Her ESR is 85 mm/hr. What is the most appropriate immediate management?

• A) Schedule a temporal artery biopsy and wait for the result
• B) Start Prednisolone 60mg OD immediately
• C) Start Aspirin 75mg OD and review in 48 hours
• D) Perform an urgent MRI of the orbits
• E) Start Sumatriptan 50mg for suspected late-onset migraine
• Answer: B. This is a classic presentation of Giant Cell Arteritis (GCA). Treatment with high-dose steroids must start immediately to prevent irreversible blindness. Biopsy can be done up to 2 weeks later.

Question 3

A 28-year-old male presents with strictly right-sided, excruciating stabbing pain around his eye. He is pacing around the room in distress. His right eye is red and watering, and he has a runny nose on that side. This is his third attack today, each lasting 45 minutes. What is the most appropriate acute treatment?

• A) Propranolol 40mg BD
• B) Sumatriptan 100mg PO
• C) 100% High-flow oxygen via non-rebreather mask
• D) Prednisolone 40mg OD taper
• E) Amitriptyline 10mg at night
• Answer: C. The presentation is classic for Cluster Headache (restlessness, autonomic signs, short duration). High-flow oxygen is the gold-standard acute treatment. Sumatriptan should be SC or Nasal, as oral is too slow.

Question 4

Which of the following describes the most common finding on fundoscopy in a patient with a subarachnoid haemorrhage?

• A) Papilloedema
• B) Subhyaloid haemorrhage
• C) Cotton wool spots
• D) Flame-shaped haemorrhages
• E) Neovascularization
• Answer: B. Subhyaloid (preretinal) haemorrhages are seen in ~10–20% of SAH cases (Terson's syndrome) and are highly suggestive of the diagnosis.

Question 5

A 35-year-old woman with a history of migraines presents with a headache she describes as her "usual" migraine but notes it is now occurring 20 days per month. She has been taking over-the-counter co-codamol and ibuprofen daily for the last 3 months. What is the most likely diagnosis?

• A) Status Migrainosus
• B) Chronic Tension-Type Headache
• C) Medication Overuse Headache (MOH)
• D) Idiopathic Intracranial Hypertension
• E) Brain Tumour
• Answer: C. MOH occurs when patients use simple analgesics for > 15 days/month or opioids/triptans for > 10 days/month, leading to a "rebound" chronic headache.

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10. Patient Explanation

"Most headaches are what we call 'primary' headaches, like migraines or tension headaches. These are painful but not dangerous to your health. However, because the brain is so important, we always look for 'red flags'—signs that the headache might be a 'secondary' cause, like a bleed, an infection, or inflammation of the blood vessels.

The most important red flag is a 'thunderclap' headache—one that goes from zero to ten in less than a minute. If you have this, we need to do a brain scan immediately. If you are over 50 and have a new type of headache, or if you have a fever and a stiff neck, these also need urgent checks. For most people, once we’ve ruled out the serious causes, we can focus on the right painkillers and lifestyle changes to manage the pain and get you back to your normal routine."

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11. References

1. Edlow JA, et al. Diagnosis of acute headache in the emergency department. Semin Neurol. 2010. [PMID: 20127598]
2. Hainer BL, et al. Approach to acute headache in adults. Am Fam Physician. 2013. [PMID: 23691456]
3. Dodick DW. Pearls: Headache. Semin Neurol. 2010. [PMID: 20127595]
4. Perry JJ, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013. [PMID: 24065011]
5. Olesen J. International Classification of Headache Disorders. Lancet Neurol. 2018. [PMID: 29656874]
6. Perry JJ, et al. Sensitivity of CT performed within 6 hours of onset of headache for diagnosis of SAH. BMJ. 2011. [PMID: 21768192]
7. GBD 2016 Headache Collaborators. Global, regional, and national burden of migraine and tension-type headache. Lancet Neurol. 2018. [PMID: 30449540]
8. Cruickshank AM, et al. Interpreting CSF xanthochromia: objective spectrophotometry or visual assessment? Ann Clin Biochem. 2005. [PMID: 15949151]
9. Mackie SL, et al. BSR and BHPR guideline for the management of giant cell arteritis. Rheumatology. 2010. [PMID: 20100742]
10. Schwedt TJ, et al. Thunderclap headache. Lancet Neurol. 2006. [PMID: 16781990]
11. Mollan SP, et al. Idiopathic intracranial hypertension. Practical Neurology. 2018.
12. Derry CJ, et al. Sumatriptan (oral route) for acute migraine attacks in adults. Cochrane Database Syst Rev. 2012. [PMID: 22336849]
13. van Gijn J, et al. Subarachnoid haemorrhage. Lancet. 2007. [PMID: 17258671]
14. Ruigrok YM, et al. Familial aneurysmal subarachnoid hemorrhage. Stroke. 2011. [PMID: 21106945]
15. Goadsby PJ, et al. Pathophysiology of Migraine. Annals of Neurology. 2017. [PMID: 28243058]
16. Lauritzen M. Pathophysiology of the migraine aura. The spreading depression theory. Brain. 1994. [PMID: 7953585]
17. Suarez JI, et al. Aneurysmal subarachnoid hemorrhage. N Engl J Med. 2006. [PMID: 16436670]
18. Headache Classification Committee of the International Headache Society (IHS). The International Classification of Headache Disorders, 3rd edition. Cephalalgia. 2018. [PMID: 29368949]
19. Bennett MH, et al. Normobaric and hyperbaric oxygen therapy for migraine and cluster headache. Cochrane Database Syst Rev. 2008. [PMID: 18646121]
20. Dubosh NM, et al. Sensitivity of Early Computed Tomography for Subarachnoid Hemorrhage. Stroke. 2016. [PMID: 26861314]
21. Wardlaw JM, et al. Computed tomography and magnetic resonance imaging in acute headache. BMJ. 1996. [PMID: 8634712]
22. Siddiq F, et al. Xanthochromia in the era of high-resolution computed tomography. Neurocrit Care. 2010. [PMID: 20496101]
23. van de Beek D, et al. Community-acquired bacterial meningitis in adults. N Engl J Med. 2004. [PMID: 15509818]
24. Cousins G, et al. Medication overuse headache. BMJ. 2015. [PMID: 25583162]

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Last Updated: 2026-01-04 | MedVellum Editorial Team | Status: Gold Standard (V4)