Headache Red Flags

Quick Answer

One-liner: Headache red flags are clinical features suggesting serious secondary causes (SAH, meningitis, mass lesions, temporal arteritis) requiring urgent investigation to prevent death or permanent neurological injury.

Headache is a common ED presentation (2-4% of all visits), but 1-4% harbour life-threatening pathology. The SNOOP mnemonic systematically identifies red flags: Systemic symptoms, Neurological signs, sudden Onset, Older age (greater than 50 years), Pattern change. Thunderclap headache (maximal in below 1 minute) is SAH until proven otherwise. New headache in patients greater than 50 years mandates ESR/CRP to exclude temporal arteritis (risk of irreversible blindness 15-20%). CT brain detects 98-100% of SAH in first 6 hours but falls to 50% after 1 week—LP is required after negative CT to detect xanthochromia (12 hours to 2 weeks post-bleed).

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ACEM Exam Focus

Primary Exam Relevance

• Anatomy: Circle of Willis aneurysm sites (anterior communicating 30%, posterior communicating 25%, MCA bifurcation 20%); cranial nerve pathways (CN VI palsy in raised ICP, CN III palsy in posterior communicating artery aneurysm); meningeal anatomy (dura, arachnoid, pia; CSF circulation and reabsorption at arachnoid granulations)
• Physiology: Monro-Kellie doctrine (ICP regulation: brain 80%, blood 10%, CSF 10%); cerebral autoregulation (50-150 mmHg MAP); CSF production 20 mL/hour (500 mL/day), volume 150 mL; normal ICP 5-15 mmHg; normal opening pressure LP 10-25 cm H₂O
• Pharmacology: Mannitol 0.25-1 g/kg (osmotic diuretic, reduces ICP within 15-30 min); hypertonic saline 3% 2-5 mL/kg (alternative to mannitol, preferred in hypotension); methylprednisolone 1 g IV daily for temporal arteritis (immediate treatment before biopsy); nimodipine 60 mg Q4H for SAH vasospasm prevention

Fellowship Exam Relevance

• Written: High-yield SAQ topics: SNOOP mnemonic, CT brain indications, LP timing and xanthochromia, thunderclap headache DDx (SAH, RCVS, dissection, CVST), temporal arteritis ESR/CRP thresholds, bacterial meningitis empiric antibiotics (ceftriaxone 2 g + vancomycin 25-30 mg/kg + dexamethasone 10 mg)
• OSCE: Likely scenarios: (1) Take focused headache history from patient with red flags (thunderclap, age greater than 50, focal neurology); (2) Perform LP and interpret CSF results (xanthochromia, cell count, protein, glucose); (3) Breaking bad news to SAH patient and family; (4) Communicate CT brain indications to GP questioning need
• Key domains tested: Medical Expert (recognize red flags, order appropriate investigations), Communicator (explain LP rationale to anxious patient, discuss temporal arteritis steroid treatment and biopsy timing), Leader (prioritize CT vs LP, escalate to neurosurgery for SAH)

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Key Points

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Epidemiology

Australian/NZ Specific

• Australian burden: SAH hospitalisations 1,500-2,000/year; bacterial meningitis 200-300 cases/year (post-vaccination era); temporal arteritis 3,000-5,000 cases/year in greater than 50 population
• Indigenous population: Aboriginal and Torres Strait Islander Australians have 2-3× higher rates of bacterial meningitis (overcrowding, lower vaccination rates in remote areas); Māori and Pacific Islander populations in NZ similarly affected
• Rural/remote: Delayed presentation common (greater than 24 hours from symptom onset to ED arrival in 30-40% of RFDS retrievals for headache); reduced access to CT and neurosurgical services (median retrieval time 4-6 hours)
• Seasonal variation: Bacterial meningitis peaks in winter (June-August); thunderstorm asthma-related headache (Victoria, November-December)

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Pathophysiology

Mechanism

Secondary headaches arise from distinct pathological processes:

Vascular Pathology (SAH, Dissection, CVST, RCVS)

• SAH: Aneurysm rupture → blood in subarachnoid space → meningeal irritation (chemical meningitis), sudden ICP spike, vasospasm (delayed 3-14 days causing ischaemia), hydrocephalus (impaired CSF reabsorption)
• Dissection: Tear in arterial wall (carotid/vertebral) → intramural haematoma → reduced flow (ischaemia) or external compression of pain-sensitive structures (adventitia, periarterial sympathetic plexus)
• CVST: Venous sinus thrombosis → impaired CSF drainage → raised ICP → headache + papilledema; venous infarction → haemorrhage
• RCVS: Reversible multifocal vasoconstriction of cerebral arteries → thunderclap headache (recurrent over 1-4 weeks); mechanisms include sympathetic hyperactivity, endothelial dysfunction, calcium channel dysregulation

Infection (Meningitis, Encephalitis)

• Bacterial meningitis: Bacterial invasion → meningeal inflammation → vasogenic oedema, cytotoxic oedema, vascular thrombosis → raised ICP + headache + fever
• Viral encephalitis: Parenchymal inflammation → oedema → raised ICP; HSV predilection for temporal lobes → seizures + behavioural change
• Abscess: Space-occupying lesion → mass effect + perilesional oedema → raised ICP

Inflammation (Temporal Arteritis, Vasculitis)

• GCA: Granulomatous inflammation of medium/large arteries → intimal hyperplasia → luminal narrowing → ischaemia of ophthalmic artery (blindness), superficial temporal artery (headache, jaw claudication)
• Primary CNS vasculitis: Segmental vessel inflammation → multifocal infarcts

Raised ICP (Mass Lesion, IIH, Hydrocephalus)

• Mass lesion: Tumour, abscess, haematoma → mass effect + perilesional oedema → raised ICP
• IIH: Impaired CSF reabsorption at arachnoid granulations (obesity, medications) → raised ICP → papilledema → optic atrophy (blindness)
• Hydrocephalus: Impaired CSF circulation (obstructive) or reabsorption (communicating) → ventriculomegaly → raised ICP

Hypoxia/Hypercapnia (Carbon Monoxide)

• CO poisoning: CO binds haemoglobin (COHb) → reduced O₂ delivery → tissue hypoxia → cerebral vasodilation → headache; CO also binds myoglobin, cytochrome oxidase → cellular hypoxia

Pathological Progression

Primary Insult → Inflammatory/Vascular/Mass Effect → Raised ICP → Secondary Brain Injury
     ↓                      ↓                             ↓                    ↓
  (Aneurysm rupture)  (Meningeal inflammation)    (Herniation risk)    (Permanent deficit/death)

Why It Matters Clinically

• Time-critical intervention: SAH requires aneurysm securing within 24-72 hours to prevent rebleed (4% in first 24 hours, 15-20% in first 2 weeks); bacterial meningitis mortality increases 15% for each hour delay in antibiotics; temporal arteritis requires steroids within 24 hours to prevent blindness
• Irreversibility: Optic nerve infarction from GCA is irreversible (15-20% risk); brainstem herniation from raised ICP is rapidly fatal
• Diagnostic window: Xanthochromia detectable 12 hours to 2 weeks post-SAH—LP too early or too late misses diagnosis; CSF opening pressure must be measured with patient in lateral decubitus position (sitting falsely elevated)

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Clinical Approach

Recognition

Headache red flags trigger immediate high-acuity assessment:

• Triage category 2: Thunderclap headache, focal neurology, seizure, GCS below 15, fever + headache + neck stiffness
• Triage category 3: New headache age greater than 50, progressive headache, positional headache, immunocompromised patient
• Immediate senior review: Any patient with ≥2 red flags

Initial Assessment

Primary Survey (if applicable)

• A: Airway patency (reduced GCS below 8 requires RSI); vomiting risk aspiration
• B: Respiratory rate, SpO₂ (hypoxia in CO poisoning, hyperventilation in raised ICP, irregular breathing in brainstem compression)
• C: BP (hypertension in raised ICP—Cushing's triad: HTN, bradycardia, irregular respirations; hypotension excludes IIH), HR, CRT, ECG (arrhythmia post-SAH)
• D: GCS, pupils (CN III palsy: dilated, down-and-out in posterior communicating artery aneurysm; bilateral fixed dilated in herniation; bilateral small reactive in pontine haemorrhage), focal neurology
• E: Temperature (fever in meningitis, encephalitis, abscess), rash (petechial in meningococcal sepsis), neck stiffness, Kernig's/Brudzinski's sign

Vital Signs Interpretation

• Cushing's triad (HTN + bradycardia + irregular breathing) = impending herniation
• Fever greater than 38.5°C + headache = meningitis/encephalitis until proven otherwise
• SBP greater than 220 or DBP greater than 120 = hypertensive emergency (posterior reversible encephalopathy syndrome - PRES)
• COHb greater than 10% on ABG = CO poisoning (smokers baseline 3-10%, non-smokers below 3%)

History

Key Questions

SNOOP4 Mnemonic (Expanded Red Flags)

S - Systemic symptoms/signs

• Fever, weight loss, night sweats (infection, malignancy)
• Pregnancy/postpartum (CVST, pre-eclampsia)
• HIV/immunosuppression (opportunistic infection)
• Cancer (metastases, paraneoplastic)

N - Neurological symptoms/signs

• Focal deficit (weakness, numbness, aphasia)
• Seizure
• Altered mental status/confusion
• Papilledema

O - Onset sudden (thunderclap)

• Maximal intensity below 1 minute
• "Worst headache of life"
• Triggered by Valsalva, exertion, coitus

O - Older age (greater than 50 years, or below 5 years in children)

• New headache greater than 50: GCA, mass lesion, subdural
• New headache below 5: mass lesion, hydrocephalus

P - Pattern change

• Increasing frequency/severity
• Change in characteristics (location, quality)
• New associated symptoms
• Refractory to usual treatment (in known primary headache)

SNNOOP10 Mnemonic (Complete Version)

Red Flag Symptoms

Examination

General Inspection

• Appearance: Toxic, diaphoretic (meningitis), drowsy (raised ICP, CO poisoning), writhing in pain (SAH)
• Behaviour: Confusion (encephalitis, meningitis), photophobia (meningitis, SAH), combativeness (hypoxia, encephalitis)
• Rash: Petechiae/purpura (meningococcal sepsis—do NOT delay antibiotics for LP), cherry-red skin (CO poisoning—rare)

Specific Findings

Jolt Accentuation Test

• Patient turns head horizontally 2-3 times/second
• Positive: Headache worsens significantly
• Utility: Sensitivity 97%, specificity 60% for meningitis in febrile patients
• Limitation: Cannot be used if neck stiffness prevents movement

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Risk Stratification

Ottawa SAH Rule

Apply to: Alert patients greater than 15 years with new-onset severe non-traumatic headache reaching maximum intensity in below 1 hour.

Investigate (CT + LP) if ANY of:

1. Age ≥40 years
2. Neck pain or stiffness
3. Witnessed loss of consciousness
4. Onset during exertion
5. Thunderclap headache (instantaneous peak)
6. Limited neck flexion on examination

Performance: 100% sensitivity (95% CI 97.2-100%) for SAH in validation studies [12]

Clinical utility: If ALL criteria absent, SAH can be ruled out without CT/LP (but this is rare - most thunderclap headache patients meet ≥1 criterion)

RCVS2 Score

Purpose: Distinguish RCVS from other causes of thunderclap headache

Interpretation: Score ≥5 = RCVS probable (sensitivity 90%, specificity 99%)

High-Risk vs Low-Risk Stratification

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Investigations

Immediate (Resus Bay)

Standard ED Workup

CT Brain Indications for Headache (ACEM High-Yield)

Immediate CT brain required if ANY of:

1. Thunderclap onset (below 1 minute to peak)
2. Focal neurological deficit (weakness, sensory loss, aphasia, neglect)
3. Seizure (new onset)
4. Altered mental status (GCS below 15)
5. Age greater than 50 years with NEW headache
6. Immunocompromised (HIV, chemotherapy, steroids, transplant)
7. Anticoagulation (warfarin, DOACs, antiplatelets)
8. Papilledema on fundoscopy
9. Head trauma (especially greater than 65 years, anticoagulated)
10. Ventriculoperitoneal shunt in situ

CT Sensitivity for SAH by Time

LP Timing and Technique (ACEM High-Yield)

Contraindications to LP:

• Suspected mass lesion (papilledema, focal signs, seizure) → CT brain FIRST
• Coagulopathy (platelets below 50, INR greater than 1.5) → correct first
• Skin infection at LP site
• Cardiorespiratory compromise (cannot lie flat in lateral decubitus)

LP for Suspected SAH:

• Timing: ≥12 hours post-headache onset (allow xanthochromia to develop from RBC breakdown)
• Position: Lateral decubitus (measure opening pressure before CSF withdrawal)
• Tubes: Send 3-4 tubes (tube 1 and 4 for cell count comparison if traumatic tap suspected)
• Tests: Cell count (RBC, WCC), protein, glucose, xanthochromia (spectrophotometry, NOT visual inspection), Gram stain/culture (if infection suspected)

Xanthochromia vs Traumatic Tap:

• Xanthochromia (yellow CSF): Bilirubin from RBC breakdown; appears 12h post-bleed, peaks 1 week, detectable 2 weeks
• Traumatic tap: RBC decreases from tube 1 to tube 4 (50% reduction suggests traumatic); CSF supernatant clear/colourless; clots in collection tube
• SAH: RBC equal in all tubes; xanthochromia present (12h-2wks); no clotting

ESR/CRP Thresholds for Temporal Arteritis

Clinical pearl: ESR normal in 20% of biopsy-proven GCA (especially in partial arteritis variant)—clinical suspicion trumps labs. Start steroids if high suspicion even with normal ESR.

Advanced/Specialist

Point-of-Care Ultrasound

POCUS applications in headache red flags:

1. Optic nerve sheath diameter (ONSD)

   • Measurement: Transorbital approach, 3 mm behind globe
   • Normal: below 5.0 mm (adults), below 4.5 mm (children)
   • Raised ICP: greater than 5.7 mm (sensitivity 90%, specificity 85%)
   • Use: Bedside raised ICP screening (mass, IIH, CVST)

2. Temporal artery assessment

   • Halo sign: Hypoechoic wall thickening in GCA (sensitivity 68%, specificity 91%)
   • Compression sign: Non-compressible artery
   • Operator-dependent: Requires training

3. Transcranial Doppler (TCD)

   • Vasospasm post-SAH: Elevated MCA velocity greater than 120 cm/s (delayed 3-14 days post-bleed)
   • Not available in most Australian EDs

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Thunderclap Headache Differential Diagnosis

Complete Differential

RCVS (Reversible Cerebral Vasoconstriction Syndrome)

Key features:

• Thunderclap headache (recurrent over 1-4 weeks, average 4 episodes)
• Triggers: Sexual activity, bathing/showering, exertion, emotional stress, Valsalva
• Peak incidence: Women 20-50 years, postpartum period
• Precipitants: Vasoactive drugs (SSRIs, triptans, cannabis, cocaine, phenylephrine, ergots)

Diagnosis:

• CTA/MRA: "String-of-beads" (multifocal segmental vasoconstriction)
• LP: Normal or near-normal (protein below 100 mg/dL, WCC below 10)
• Important: Angiography may be normal in first week—repeat in 1-2 weeks if high suspicion
• Confirmation: Resolution of vasoconstriction on imaging at 3 months

Management:

• Stop precipitants: SSRIs, triptans, cannabis, cocaine, ergots
• Nimodipine 60 mg PO Q4H (reduces headache severity, does not prevent stroke)
• Avoid steroids: May worsen RCVS (unlike PACNS)
• Bed rest: During acute phase (1-4 weeks)
• Analgesia: Paracetamol, opioids (AVOID triptans, NSAIDs may worsen)

Complications: Convexal SAH (22%), PRES (8-38%), ischaemic stroke (4-39%)

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Management

Immediate Management (First 10 minutes)

General approach for ANY headache red flag:

1. STAT senior (consultant) review
2. High-flow O₂ 15 L/min non-rebreather if hypoxic (SpO₂ below 94%) or suspected CO poisoning
3. IV access + bloods (FBC, UEC, coags, BSL, blood cultures if febrile)
4. Analgesia (paracetamol 1 g IV, avoid NSAIDs if SAH suspected)
5. Antiemetic (ondansetron 4-8 mg IV)
6. CT brain non-contrast STAT if ANY indication (see above)
7. Nil by mouth (NBM) pending diagnosis

Condition-Specific Management

Thunderclap Headache (Suspected SAH)

Step 1: Resuscitation

- ABC assessment
- High-flow O₂ if hypoxic
- IV access, bloods (FBC, UEC, coags, group & hold)
- Analgesia (paracetamol 1 g IV ± fentanyl 25-50 mcg IV titrated)
- Antiemetic (ondansetron 4-8 mg IV)
- Keep SBP below 160 mmHg (labetalol 10-20 mg IV boluses, or nicardipine infusion)
- Neurosurgery consult STAT

Step 2: CT brain non-contrast STAT

• Positive (blood in subarachnoid space): CTA brain to identify aneurysm → neurosurgery for aneurysm securing (coiling vs clipping within 24-72h)
• Negative: Proceed to LP (≥12 hours post-headache onset if possible)

Step 3: LP (if CT negative)

• Xanthochromia positive: Treat as SAH → CTA → neurosurgery
• Xanthochromia negative, normal cell count: Consider alternative DDx (RCVS, dissection, primary thunderclap) → CTA/MRA

Step 4: SAH confirmed - prevent complications

• Nimodipine 60 mg PO/NG Q4H for 21 days (prevents vasospasm, improves outcome)
• Maintain euvolaemia (avoid hypotension, which worsens vasospasm; avoid hypovolemia)
• DVT prophylaxis (mechanical compression devices, NOT pharmacological until aneurysm secured)
• Stool softeners (docusate) to avoid Valsalva
• Neurological observations Q1H (GCS, pupils, focal signs)

Bacterial Meningitis (Suspected)

Time-critical - mortality increases 15% per hour delay in antibiotics

Step 1: Immediate empiric antibiotics (do NOT wait for LP)

- Ceftriaxone 2 g IV (50 mg/kg in children)
  + Vancomycin 25-30 mg/kg IV (if age greater than 50, immunocompromised, or recent neurosurgery - covers Listeria, MRSA)
  + Dexamethasone 10 mg IV (0.15 mg/kg in children) BEFORE or WITH first antibiotic dose

Step 2: Blood cultures + bloods

• Draw BEFORE antibiotics if possible (but do NOT delay greater than 5 minutes)
• FBC, UEC, CRP, lactate, coags, blood cultures × 2

Step 3: LP (after antibiotics started)

• Contraindications: Focal signs, papilledema, GCS below 12, coagulopathy → give antibiotics, do CT brain first
• Opening pressure: Measure in lateral decubitus (normal 10-25 cm H₂O)
• CSF tests: Cell count (WCC, RBC, differential), protein, glucose (paired with serum), Gram stain, culture, PCR (meningococcus, pneumococcus, HSV if encephalitis suspected)

Step 4: Supportive care

• Fluids: 0.9% saline to maintain euvolaemia (avoid fluid overload, which worsens cerebral oedema)
• Steroids: Dexamethasone 10 mg IV Q6H for 4 days (reduces mortality in pneumococcal meningitis)
• Notify public health if meningococcal (notifiable disease; close contacts require chemoprophylaxis - rifampicin 600 mg BD for 2 days or ciprofloxacin 500 mg single dose)

Temporal Arteritis (Suspected)

Time-critical - irreversible blindness in 15-20% if untreated

Step 1: Immediate steroids (do NOT wait for biopsy)

- Methylprednisolone 1 g IV daily for 3 days (if visual symptoms)
  OR
- Prednisolone 1 mg/kg PO (40-60 mg) daily (if no visual symptoms)

Step 2: Investigations

• ESR, CRP, FBC: Thrombocytosis (platelets greater than 400) + ESR greater than 50 + CRP greater than 10
• Temporal artery ultrasound: Halo sign (sensitivity 68%, specificity 91%) - arrange urgently if available
• Temporal artery biopsy: Gold standard (can be done up to 2 weeks after starting steroids) - arrange within 1 week

Step 3: Ophthalmology review

• Urgent if visual symptoms (within 24 hours)
• Fundoscopy: Anterior ischaemic optic neuropathy (pale, swollen disc), CRAO (pale retina, cherry-red spot)

Step 4: Discharge planning

• Steroid taper: Prednisolone 1 mg/kg daily for 4 weeks → slow taper over 12-18 months (guided by symptoms + ESR/CRP)
• PPI: Pantoprazole 40 mg daily (gastric protection)
• Bisphosphonate: Alendronate 70 mg weekly (osteoporosis prevention)
• Rheumatology follow-up: Within 1 week

Idiopathic Intracranial Hypertension (IIH)

Step 1: Diagnosis

• Modified Dandy criteria: Symptoms of raised ICP (headache, papilledema, visual obscurations) + elevated LP opening pressure (greater than 25 cm H₂O) + normal brain imaging + normal CSF composition
• CT brain: Exclude mass, hydrocephalus; may show slit-like ventricles, empty sella, optic nerve sheath distension

Step 2: Urgent ophthalmology review

• Visual fields: Formal perimetry (enlarged blind spot, inferior nasal defect)
• Fundoscopy: Papilledema grading (Frisén scale 0-5)
• Optical coherence tomography (OCT): Quantify optic nerve swelling

Step 3: Treatment

• Acetazolamide 500 mg PO BD → titrate to 1-2 g/day (carbonic anhydrase inhibitor, reduces CSF production)
• Weight loss 5-10% (single most effective intervention)
• Furosemide 40 mg PO daily (adjunct if acetazolamide insufficient)
• Repeat LP if fulminant (rapidly progressive visual loss) to acutely lower pressure

Step 4: Neurosurgery review if refractory

• Optic nerve sheath fenestration (prevents blindness)
• VP shunt (CSF diversion)
• Venous sinus stenting (if stenosis identified on MRV)

Carbon Monoxide Poisoning

Step 1: High-flow O₂ 15 L/min non-rebreather

• Half-life of COHb: Room air 4-6 hours, 100% O₂ 60-90 min, hyperbaric O₂ 20-30 min

Step 2: ABG + COHb level

• Mild: COHb 10-20% → headache, nausea
• Moderate: COHb 20-40% → confusion, syncope
• Severe: COHb greater than 40% → seizure, coma, cardiac arrest

Step 3: Hyperbaric oxygen indications

• COHb greater than 25%, pregnancy with COHb greater than 15%, neurological signs, cardiac ischaemia, loss of consciousness
• Contact: Hyperbaric unit (HBOT available in Sydney, Melbourne, Perth, Brisbane, Adelaide)

Step 4: Source identification

• Home heaters, car exhaust, industrial exposure → notify public health, ensure safety before discharge

Pregnancy-Related Headache

Key conditions to exclude:

Investigations in pregnancy:

• CT brain: Safe (fetal radiation dose below 0.01 mGy, teratogenic threshold 50-100 mGy); shield abdomen
• MRI: Safe (avoid gadolinium in first trimester)
• LP: Safe (use lowest effective insertion point - L4/5 or below)

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Disposition

Admission Criteria

Mandatory admission:

• SAH confirmed → ICU or neurosurgical HDU (aneurysm securing, nimodipine, neuro obs)
• Bacterial meningitis → ICU or medical ward (IV antibiotics 10-14 days)
• GCA with visual symptoms → medical ward (IV methylprednisolone, ophthalmology review)
• Raised ICP (mass lesion, IIH with severe papilledema) → neurosurgical ward
• CVST → stroke unit (anticoagulation, monitor for deterioration)
• CO poisoning COHb greater than 25% → medical ward (hyperbaric oxygen, extended observation)
• Pre-eclampsia/eclampsia → obstetric HDU (magnesium, BP control, delivery planning)

ICU/HDU Criteria

• GCS below 13
• SAH with Hunt-Hess grade ≥3 (somnolent, confused, or worse)
• Bacterial meningitis with shock (SBP below 90, lactate greater than 2)
• Raised ICP requiring ICP monitoring (mass lesion, hydrocephalus)
• Seizure not controlled with first-line therapy
• CO poisoning with cardiac ischaemia or arrhythmia
• Eclampsia (seizures in pregnancy)

Discharge Criteria

Safe discharge if ALL of:

• CT brain normal AND LP normal (if performed)
• No red flags present (or adequately investigated and excluded)
• GCS 15, no focal neurology
• Vital signs normal (afebrile, normotensive, HR 60-100)
• Pain controlled with oral analgesia
• Able to tolerate oral fluids
• Follow-up arranged (GP within 48 hours, specialist if indicated)

Red flags to return:

• Fever, neck stiffness, rash
• Worsening headache, confusion, weakness, seizure
• Vision changes, diplopia
• Vomiting preventing oral intake
• Any new concerning symptom

Follow-up

• SAH: Neurosurgery outpatient 2-4 weeks post-discharge (aneurysm follow-up imaging at 3-6 months)
• Temporal arteritis: Rheumatology within 1 week (temporal artery biopsy if not done, steroid taper plan)
• IIH: Ophthalmology within 1 week (visual fields, OCT repeat), neurology within 2-4 weeks
• Meningitis: Infectious diseases 4-6 weeks post-discharge (hearing test, neurological sequelae assessment)
• Primary thunderclap headache: Neurology within 2-4 weeks (CTA/MRA to exclude RCVS)
• RCVS: Neurology within 1-2 weeks, repeat CTA/MRA at 3 months to confirm resolution
• GP letter: Include diagnosis, investigations performed, medications started, follow-up plan, red flags to return

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Special Populations

Paediatric Considerations

Age-specific modifications:

• Headache red flags in children: Age below 5 years with new headache (mass lesion, hydrocephalus), vomiting on waking (raised ICP), personality change (frontal lobe tumour, encephalitis), failure to thrive (chronic illness)
• Bacterial meningitis: Bulging fontanelle (infants), irritability, high-pitched cry, refusal to feed
• CT brain: Minimize radiation (consider MRI if stable); dose reduction protocols
• LP: Paediatric dosing ceftriaxone 50 mg/kg IV, dexamethasone 0.15 mg/kg IV

Pregnancy

Pregnancy-specific headache red flags:

• Pre-eclampsia: BP ≥140/90 + proteinuria + headache (frontal, throbbing) + visual changes (scotomata) → magnesium sulfate 4 g IV loading, obstetric review
• CVST: 6× higher risk in pregnancy/postpartum (hypercoagulable state) → MRV, therapeutic anticoagulation
• PRES: Hypertension + headache + seizure + visual disturbance → BP control (labetalol, hydralazine), MRI (posterior white matter oedema)
• Pituitary apoplexy: Enlarged pituitary in pregnancy → sudden headache, vision loss, ophthalmoplegia → urgent endocrine/neurosurgery
• SAH: Unchanged risk in pregnancy; CT brain is safe (fetal radiation dose below 0.01 mGy); LP is safe

Investigations in pregnancy:

• CT brain: Safe (fetal radiation dose below 0.01 mGy, teratogenic threshold 50-100 mGy); shield abdomen
• MRI: Safe (avoid gadolinium in first trimester)
• LP: Safe (use lowest effective insertion point - L4/5 or below)

Elderly

Geriatric considerations:

• Lower threshold for CT brain: Age greater than 65 with new headache (subdural, mass lesion common)
• Subdural haematoma: High risk if anticoagulated, falls, dementia (may present with confusion, not headache)
• Temporal arteritis: Exclusively greater than 50 years (peak incidence 70-80 years)
• Meningitis: Higher mortality (30-50% in greater than 60 years vs 15% in below 60 years); less likely to have classic triad (fever, headache, neck stiffness)
• Polypharmacy: Review medications (anticoagulants, antiplatelets increase ICH risk)

Indigenous Health

Important Note: Aboriginal, Torres Strait Islander, and Māori considerations:

Health disparities:

• Bacterial meningitis: 2-3× higher incidence in Aboriginal/Torres Strait Islander Australians (overcrowding, lower vaccination rates, smoking, comorbidities) [47]
• Stroke: 2-3× higher incidence in Indigenous Australians; younger age of onset (mean 52 vs 75 years) [48]
• Rheumatic heart disease: Higher rates in Indigenous populations → increased risk infective endocarditis → brain abscess
• Diabetes: 3-4× higher prevalence → increased infection risk (meningitis, abscess)
• Smoking: Higher rates → increased stroke risk (haemorrhagic, ischaemic)
• Delayed presentation: Geographic isolation, transport barriers, cultural reluctance to seek care → more severe presentations

Cultural safety:

• Family-centred care: Involve family/community in decision-making (collectivist culture vs Western individualism)
• Interpreter services: Arrange Aboriginal Liaison Officer (ALO) or Māori health worker if language barrier
• Shame: Avoid direct questioning about sensitive topics (alcohol, substance use) - build rapport first
• Health literacy: Explain investigations in plain language (avoid medical jargon); use diagrams
• Mistrust of healthcare system: Acknowledge historical trauma (Stolen Generations); build trust through respectful communication
• Sorry Business: Be aware that patients may need to leave for cultural obligations (funerals, ceremonies)
• Men's/Women's Business: Some health issues may only be discussed with same-gender healthcare provider

Māori-specific (NZ):

• Whānau involvement: Family (whānau) integral to care - involve in all decisions
• Tikanga: Māori cultural protocols (e.g., avoid cutting hair for temporal artery biopsy without discussion)
• Kaumātua: Elders may guide healthcare decisions - involve if patient wishes
• Te Whare Tapa Whā: Māori health model incorporating physical (taha tinana), mental (taha hinengaro), spiritual (taha wairua), and family (taha whānau) dimensions

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Remote/Rural Considerations

Pre-Hospital

Challenges in remote/rural Australia:

• Delayed presentation: Median 24-48 hours from symptom onset to ED arrival (vs 2-6 hours in metro)
• Limited ambulance resources: Single ambulance for vast area (100-500 km radius); long transfer times (1-4 hours)
• Telemedicine triage: Remote Area Nurse (RAN) + Royal Flying Doctor Service (RFDS) telehealth consultation to determine retrieval urgency

Retrieval criteria for headache:

• Thunderclap headache → RFDS urgent retrieval (Code 1)
• Focal neurology → RFDS urgent retrieval
• GCS below 15 → RFDS urgent retrieval
• Suspected meningitis → Give empiric antibiotics (ceftriaxone 2 g IV) THEN retrieve
• Age greater than 50 new headache + ESR greater than 50 → Give steroids (prednisolone 50 mg PO) THEN arrange non-urgent transfer for temporal artery biopsy

Resource-Limited Setting

Modified approach when CT/LP unavailable:

No CT brain available:

1. Thunderclap headache: Telemedicine consult with neurologist → empiric nimodipine 60 mg PO Q4H + urgent RFDS retrieval for CT/CTA
2. Suspected meningitis: Empiric antibiotics (ceftriaxone 2 g IV + vancomycin 25-30 mg/kg IV + dexamethasone 10 mg IV) → RFDS retrieval for LP
3. Suspected GCA: Empiric prednisolone 1 mg/kg PO → arrange transfer for temporal artery ultrasound/biopsy

No LP kit available:

• Suspected meningitis: Give antibiotics (ceftriaxone 2 g IV) → RFDS retrieval for LP at receiving hospital (CSF culture may still be positive up to 72h post-antibiotics if pre-treated)

Cold chain for medications:

• Ceftriaxone: Stable at room temperature for 3 days (once reconstituted, refrigerate and use within 24h)
• Nimodipine: Store below 25°C (away from direct sunlight)

Retrieval

RFDS retrieval considerations:

Priority codes:

• Code 1 (emergency): Thunderclap, GCS below 13, focal neurology, seizure → aircraft dispatched immediately (ETA 1-2 hours)
• Code 2 (urgent): Suspected meningitis post-antibiotics, suspected SAH with normal GCS → aircraft dispatched within 4 hours
• Code 3 (non-urgent): GCA for temporal artery biopsy, IIH for ophthalmology review → arrange fixed-wing transfer within 24 hours

In-flight management:

• SAH: Maintain SBP below 160 mmHg (labetalol 10-20 mg IV PRN); head of bed 30° (reduce ICP); nimodipine 60 mg NG Q4H; prepare for intubation if GCS deteriorates
• Meningitis: Continue IV antibiotics during flight; 0.9% saline infusion; dexamethasone 10 mg IV Q6H
• Raised ICP: Intubate if GCS below 8; hyperventilate to PaCO₂ 30-35 mmHg (acutely reduces ICP); mannitol 0.5-1 g/kg IV or hypertonic saline 3% 2-5 mL/kg IV

Receiving hospital preparation:

• Notify neurosurgery (if SAH suspected - may need aneurysm coiling/clipping)
• Notify ICU (if GCS below 13 or ventilated)
• Book CT brain (if not done at referring hospital)

Telemedicine

Remote consultation model:

• Headache + red flags: RAN assesses patient → sends photo (rash, pupils), vital signs, brief history to RFDS duty doctor via telehealth
• RFDS doctor: Reviews case → advises empiric treatment (antibiotics for meningitis, steroids for GCA) → arranges retrieval
• Follow-up: RFDS outreach clinic visits remote communities 6-12 weekly (post-discharge follow-up for temporal arteritis, IIH)

Limitations:

• Fundoscopy: Difficult via telemedicine (RAN may not have ophthalmoscope training) - rely on clinical features (vision loss, headache)
• LP: Cannot be performed remotely - requires retrieval or GP proceduralist visit

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Pitfalls & Pearls

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Viva Practice

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OSCE Scenarios

Station 1: Focused Headache History (Thunderclap)

Format: History-taking Time: 11 minutes Setting: ED cubicle

Candidate Instructions:

You are an emergency registrar. A 48-year-old woman has presented with sudden-onset severe headache. Take a focused history to identify red flags and formulate a management plan. You do NOT need to examine the patient.

Examiner Instructions: The candidate should systematically elicit thunderclap headache features, recognize SAH as the leading differential, and outline appropriate investigations (CT brain, LP). Key discriminators: timing of onset, Valsalva triggers, associated symptoms, past headache history.

Actor/Patient Brief: You are a 48-year-old office worker. You were at work this morning when you suddenly developed the worst headache of your life while bending down to pick up a pen. It came on within 30 seconds and was so severe you thought you were going to die. You vomited once. The pain is all over your head (diffuse). You have never had a headache like this before. You are worried it is a brain tumour. You have no other medical problems and take no medications. You are a non-smoker, social drinker.

Marking Criteria:

Expected Standard:

• Pass: ≥6/11
• Key discriminators: Eliciting thunderclap onset (below 1 min to peak), recognizing need for LP after negative CT, explaining xanthochromia timing

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Station 2: Lumbar Puncture Procedure

Format: Procedural skill Time: 11 minutes Setting: ED procedure room with mannequin

Candidate Instructions:

You are an emergency registrar. A patient with thunderclap headache has had a normal CT brain. Perform a lumbar puncture on the mannequin. Explain each step to the examiner as you proceed.

Examiner Instructions: Candidate should demonstrate safe LP technique: patient positioning (lateral decubitus), aseptic technique, local anaesthetic, needle insertion (L3/4 or L4/5), measuring opening pressure before CSF withdrawal, collecting 4 tubes, and sending appropriate tests. Key errors: not measuring opening pressure, contaminating field, inserting needle without LA.

Equipment:

• LP mannequin
• LP kit (spinal needle 22G, manometer, 3-way tap, collection tubes)
• Sterile gloves, gown, drapes
• Chlorhexidine 2% skin prep
• 1% lidocaine 5 mL, 25G needle, 5 mL syringe
• Dressing

Marking Criteria:

Expected Standard:

• Pass: ≥6/11
• Key discriminators: Measuring opening pressure BEFORE CSF withdrawal (critical for raised ICP diagnosis), aseptic technique, correct spinal level identification

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Station 3: Breaking Bad News (SAH Diagnosis)

Format: Communication Time: 11 minutes Setting: ED relatives room

Candidate Instructions:

You are an emergency registrar. A 52-year-old woman presented with thunderclap headache. CT brain shows subarachnoid haemorrhage. Her husband is waiting in the relatives room. Explain the diagnosis and management plan.

Examiner Instructions: Candidate should use structured approach (SPIKES protocol): Set-up (private room, ask what patient knows), Perception (elicit understanding), Invitation (ask how much patient wants to know), Knowledge (explain SAH in plain language), Emotions (acknowledge concerns), Strategy/Summary (outline next steps). Key discriminators: avoids jargon, checks understanding, addresses emotions.

Actor/Relative Brief: You are the husband of the patient. You are worried it is a brain tumour (your mother died of brain cancer). You want to know: (1) What is wrong? (2) Will she die? (3) Will she need surgery? You are anxious but cooperative. If the doctor uses medical jargon (e.g. "subarachnoid haemorrhage"), ask "What does that mean?"

Marking Criteria:

Expected Standard:

• Pass: ≥6/11
• Key discriminators: Explains SAH in plain language (not medical jargon), addresses emotional concerns (fear of death, tumour), outlines clear next steps (neurosurgery, aneurysm treatment)

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SAQ Practice

Question 1 (8 marks)

Stem: A 55-year-old man presents to ED with sudden-onset severe headache that came on over 30 seconds while lifting a heavy box. He describes it as "the worst headache of my life." CT brain non-contrast is reported as normal. It is now 4 hours since headache onset.

Question: Outline your management from this point, including investigations and their interpretation. (8 marks)

Model Answer:

1. Lumbar puncture (LP) is mandatory after negative CT for thunderclap headache (1 mark)
   • CT sensitivity for SAH is 98-100% at 6 hours but falls to 93% at 24 hours, 50% at 1 week - negative CT does NOT exclude SAH
2. Timing of LP: Ideally wait ≥12 hours post-onset for xanthochromia to develop (1 mark)
   • Xanthochromia (bilirubin from RBC breakdown) appears 12h post-bleed, peaks 1 week, detectable up to 2 weeks
   • However, can proceed at 4 hours if using spectrophotometry (not visual inspection)
3. LP technique: Lateral decubitus position, measure opening pressure BEFORE CSF withdrawal (1 mark)
   • Collect 4 tubes (1-2 mL each), label sequentially
4. CSF tests: Cell count (RBC, WCC in tubes 1 and 4), xanthochromia (spectrophotometry), protein, glucose, Gram stain (1 mark)
5. Interpretation of results: (2 marks)
   • SAH: RBC greater than 10,000 cells/µL, equal in tubes 1 and 4, xanthochromia positive (spectrophotometry)
   • Traumatic tap: RBC decreases 50% from tube 1 to tube 4, xanthochromia negative, CSF may clot
6. If LP positive (SAH confirmed): CTA brain to identify aneurysm source (1 mark)
7. Neurosurgery consult STAT for aneurysm securing (coiling vs clipping within 24-72 hours) (1 mark)

Examiner Notes:

• Accept: LP can be performed at 4 hours with spectrophotometry (not visual inspection)
• Do not accept: "LP is not indicated if CT is normal" (incorrect - negative CT does NOT exclude SAH)
• Award partial marks for mentioning xanthochromia but not explaining timing (12h-2wks)

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Question 2 (6 marks)

Stem: A 72-year-old woman presents with 3-week history of frontal headache and jaw pain when chewing. This morning she noticed blurred vision in her left eye. On examination, the left temporal artery is tender and pulseless. ESR is 95 mm/h, CRP 42 mg/L.

Question: List the immediate management steps in the ED. (6 marks)

Model Answer:

1. Start IV steroids immediately (do NOT wait for biopsy): Methylprednisolone 1 g IV daily for 3 days (1 mark)
   • Visual symptoms present = sight-threatening emergency
2. Urgent ophthalmology review (within 4 hours): Formal visual fields, fundoscopy, OCT (1 mark)
3. Bloods: ESR, CRP, FBC (thrombocytosis - platelets greater than 400), UEC, LFTs, BSL (pre-steroid baseline) (1 mark)
4. Arrange temporal artery biopsy (within 1 week - can be done up to 2 weeks after starting steroids) (1 mark)
5. Temporal artery ultrasound (if available): Halo sign (hypoechoic wall thickening) (1 mark)
6. Admit medical ward for 3 days IV methylprednisolone, then switch to oral prednisolone 1 mg/kg + rheumatology follow-up (1 mark)

Examiner Notes:

• Accept: "High-dose steroids" (must specify IV route and dose for full marks)
• Do not accept: "Wait for biopsy before starting steroids" (incorrect - irreversible blindness risk)
• Award partial marks if mentions steroids but not IV methylprednisolone (oral prednisolone acceptable if IV unavailable, but suboptimal)

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Question 3 (8 marks)

Stem: A 28-year-old man presents with 8-hour history of headache, fever (39.4°C), and vomiting. He is drowsy (GCS 14). Neck stiffness is present. No rash. It is now 45 minutes since arrival in ED.

Question: a) List the empiric antibiotic regimen you would give (include doses). (3 marks) b) Outline the investigations required and their timing relative to antibiotics. (5 marks)

Model Answer:

a) Empiric antibiotics (3 marks):

1. Ceftriaxone 2 g IV (covers pneumococcus, meningococcus) (1 mark)
2. Dexamethasone 10 mg IV (give BEFORE or WITH first antibiotic dose - reduces mortality in pneumococcal meningitis) (1 mark)
3. Consider vancomycin 25-30 mg/kg IV if age greater than 50 or immunocompromised (covers Listeria, MRSA) (1 mark)
   • Not required in this 28-year-old patient unless immunocompromised

b) Investigations and timing (5 marks):

1. Blood cultures × 2 - draw BEFORE antibiotics if possible, but do NOT delay antibiotics greater than 5 minutes (1 mark)
2. Bloods: FBC, UEC, CRP, lactate, coagulation screen (1 mark)
3. CT brain BEFORE LP (GCS 14 is below 15 - contraindication to LP until mass lesion excluded) (1 mark)
4. LP after CT (if no mass lesion): Opening pressure, cell count, protein, glucose, Gram stain, culture, PCR (1 mark)
5. Timing: Antibiotics should be given within 60 minutes of arrival (door-to-antibiotic time below 60 min). If LP delayed (CT brain, coagulopathy), give antibiotics FIRST - CSF culture remains positive up to 72h post-antibiotics (1 mark)

Examiner Notes:

• Accept: Vancomycin optional in this age group (full marks either way)
• Do not accept: "Do LP before antibiotics" (incorrect - mortality increases 15% per hour delay)
• Award partial marks if mentions CT brain but not as contraindication to LP with GCS below 15

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Question 4 (6 marks)

Stem: You are working in a remote clinic 500 km from the nearest hospital. A 50-year-old woman presents with sudden-onset severe headache that started 2 hours ago. She is vomiting. GCS 15, BP 170/100, no focal neurology. No CT scanner available.

Question: Outline your immediate management and retrieval plan. (6 marks)

Model Answer:

1. Keep patient NBM, IV access, IV fluids 0.9% saline (1 mark)
2. Analgesia: Paracetamol 1 g IV (or PO if IV unavailable), morphine 2.5-5 mg IV titrated for pain (1 mark)
3. Blood pressure control (target SBP below 160 mmHg): Labetalol 10-20 mg IV boluses if available (1 mark)
4. Contact RFDS for urgent Code 1 retrieval (thunderclap headache = SAH until proven otherwise - time-critical) (1 mark)
5. Start nimodipine 60 mg PO/NG Q4H empirically (vasospasm prophylaxis if SAH confirmed) (1 mark)
6. During retrieval: Maintain SBP below 160 mmHg, head of bed 30°, continue IV fluids, repeat analgesia PRN. Notify receiving hospital neurosurgery and book CT brain STAT (1 mark)

Examiner Notes:

• Accept: Morphine or fentanyl for analgesia (both acceptable)
• Do not accept: "Perform LP remotely" (incorrect - risk of herniation, requires CT brain first)
• Award partial marks if mentions retrieval but not Code 1 urgency (Code 1 = emergency, dispatched immediately)

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Australian Guidelines

ARC/ANZCOR

While ANZCOR does not have specific headache guidelines, relevant ANZCOR references include:

• ANZCOR Guideline 11.10.2 - Stroke Recognition: FAST (Face-Arm-Speech-Time) assessment for stroke symptoms; headache is a red flag for haemorrhagic stroke (ICH, SAH)
• Key differences from AHA/ERC: Australian stroke guidelines emphasize telemedicine triage for remote/rural areas (RFDS consultation model); BP thresholds for thrombolysis differ (SBP below 185, DBP below 110 in Australia vs below 180/105 in USA)

Therapeutic Guidelines

Therapeutic Guidelines: Antibiotic (version 16, 2023):

Bacterial Meningitis Empiric Treatment:

• Age 3 months to 50 years: Ceftriaxone 2 g IV Q12H (or cefotaxime 2 g IV Q6H)
• Age greater than 50 years OR immunocompromised: Ceftriaxone 2 g IV Q12H + ampicillin 2 g IV Q4H (covers Listeria)
• Penicillin allergy: Vancomycin 25-30 mg/kg IV loading, then 15-20 mg/kg IV Q8-12H + moxifloxacin 400 mg IV daily
• Adjunctive dexamethasone: 10 mg IV Q6H for 4 days (give BEFORE or WITH first antibiotic dose)

Meningococcal Prophylaxis (Close Contacts):

• Rifampicin 600 mg PO BD for 2 days (adults), 10 mg/kg BD for 2 days (children)
• Ciprofloxacin 500 mg PO single dose (alternative if rifampicin contraindicated - pregnancy, drug interactions)
• Ceftriaxone 250 mg IM single dose (if oral therapy not possible)

State-Specific

NSW Health Clinical Guidelines:

• Suspected meningococcal disease: Benzylpenicillin 2.4 g IV (or 60 mg/kg in children) if below 30 min to hospital; otherwise proceed directly to hospital for ceftriaxone
• Notify public health: Meningococcal disease is notifiable within 24 hours (Public Health Unit 1300 066 055)

Victorian DHHS:

• Meningococcal prophylaxis: Public health coordinates contact tracing and chemoprophylaxis for close contacts (household, childcare, kissing contacts)

Queensland Health:

• Remote/rural meningitis: Royal Flying Doctor Service (RFDS) protocol: Give ceftriaxone 2 g IV + dexamethasone 10 mg IV BEFORE retrieval (do NOT wait for hospital transfer)

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References

Guidelines

1. Australian Resuscitation Council. ANZCOR Guideline 11.10.2: Stroke Recognition and Management. 2023. Available from: https://www.anzcor.org
2. Therapeutic Guidelines Limited. Therapeutic Guidelines: Antibiotic. Version 16. Melbourne: Therapeutic Guidelines Limited; 2023.
3. NSW Health. Infants and Children: Acute Management of Bacterial Meningitis. Sydney: NSW Health; 2022.
4. National Institute for Health and Care Excellence (NICE). Headaches in over 12 s: diagnosis and management. Clinical guideline [CG150]. London: NICE; 2021.
5. Do TP, Remmers A, Schytz HW, et al. Red and orange flags for secondary headaches in clinical practice: SNNOOP10 list. Neurology. 2019;92(3):134-144. PMID: 30567777

Key Evidence

6. Perry JJ, Stiell IG, Sivilotti ML, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013;310(12):1248-1255. PMID: 24065011
7. Edlow JA, Panagos PD, Godwin SA, et al. Clinical policy: critical issues in the evaluation and management of adult patients presenting to the emergency department with acute headache. Ann Emerg Med. 2008;52(4):407-436. PMID: 18809105
8. van de Beek D, de Gans J, Spanjaard L, et al. Clinical features and prognostic factors in adults with bacterial meningitis. N Engl J Med. 2004;351(18):1849-1859. PMID: 15509818
9. Brouwer MC, Tunkel AR, van de Beek D. Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis. Clin Microbiol Rev. 2010;23(3):467-492. PMID: 20610819
10. Hasbun R, Abrahams J, Jekel J, Quagliarello VJ. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. N Engl J Med. 2001;345(24):1727-1733. PMID: 11742046

Subarachnoid Haemorrhage

11. Perry JJ, Stiell IG, Sivilotti ML, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ. 2011;343:d4277. PMID: 21768192
12. Dupont SA, Wijdicks EF, Lanzino G, Rabinstein AA. Aneurysmal subarachnoid hemorrhage: an overview for the practicing neurologist. Semin Neurol. 2010;30(5):545-554. PMID: 21207348
13. Connolly ES Jr, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2012;43(6):1711-1737. PMID: 22556195
14. UK National External Quality Assessment Service for Immunochemistry Working Group. National guidelines for analysis of cerebrospinal fluid for bilirubin in suspected subarachnoid haemorrhage. Ann Clin Biochem. 2008;45(Pt 3):238-244. PMID: 18482910
15. Dubosh NM, Bellolio MF, Rabinstein AA, Edlow JA. Sensitivity of Early Computed Tomography for Subarachnoid Hemorrhage: A Systematic Review and Meta-analysis. Ann Emerg Med. 2016;67(6):751-760. PMID: 26830197

Thunderclap Headache and RCVS

16. Schwedt TJ, Matharu MS, Dodick DW. Thunderclap headache. Lancet Neurol. 2006;5(7):621-631. PMID: 16781992
17. Dilli E. Thunderclap headache. Curr Neurol Neurosci Rep. 2014;14(4):437. PMID: 24643327
18. Ducros A, Boukobza M, Porcher R, et al. The clinical and radiological spectrum of reversible cerebral vasoconstriction syndrome. A prospective series of 67 patients. Brain. 2007;130(Pt 12):3091-3101. PMID: 17215440
19. Miller TR, Shivashankar R, Mossa-Basha M, Gandhi D. Reversible Cerebral Vasoconstriction Syndrome. Radiographics. 2015;35(7):1873-1894. PMID: 26466175
20. Singhal AB, Hajj-Ali RA, Topcuoglu MA, et al. Reversible cerebral vasoconstriction syndromes: analysis of 139 cases. Arch Neurol. 2011;68(8):1005-1012. PMID: 21482916

Temporal Arteritis / Giant Cell Arteritis

21. Hunder GG, Bloch DA, Michel BA, et al. The American College of Rheumatology 1990 criteria for the classification of giant cell arteritis. Arthritis Rheum. 1990;33(8):1122-1128. PMID: 2285402
22. Ponte C, Grayson PC, Engel B, et al. 2022 American College of Rheumatology/EULAR classification criteria for giant cell arteritis. Arthritis Rheumatol. 2022;74(12):1881-1889. PMID: 36350072
23. Hernández P, Al Jalbout N, Matza M, et al. Temporal Artery Ultrasound for the Diagnosis of Giant Cell Arteritis in the Emergency Department. Cureus. 2023;15(7):e42350. PMID: 37621789
24. Hayreh SS. Ischemic optic neuropathy. Prog Retin Eye Res. 2009;28(1):34-62. PMID: 19063989
25. Parikh M, Miller NR, Lee AG, et al. Prevalence of a normal C-reactive protein with an elevated erythrocyte sedimentation rate in biopsy-proven giant cell arteritis. Ophthalmology. 2006;113(10):1842-1845. PMID: 16908059

Idiopathic Intracranial Hypertension

26. Mollan SP, Davies B, Silver NC, et al. Idiopathic intracranial hypertension: consensus guidelines on management. J Neurol Neurosurg Psychiatry. 2018;89(10):1088-1100. PMID: 29959146
27. Friedman DI, Liu GT, Digre KB. Revised diagnostic criteria for the pseudotumor cerebri syndrome in adults and children. Neurology. 2013;81(13):1159-1165. PMID: 23966248

Bacterial Meningitis

28. Wall EC, Chan JM, Gil E, Heyderman RS. Acute bacterial meningitis. Curr Opin Neurol. 2021;34(3):386-395. PMID: 33767093
29. Hasbun R. Progress and Challenges in Bacterial Meningitis: A Review. JAMA. 2022;328(21):2147-2154. PMID: 36472590
30. Davis LE. Acute Bacterial Meningitis. Continuum (Minneap Minn). 2018;24(5):1264-1283. PMID: 30273239
31. Heckenberg SG, Brouwer MC, van de Beek D. Bacterial meningitis. Handb Clin Neurol. 2014;121:1361-1375. PMID: 24365425
32. Roos KL, van de Beek D. Bacterial meningitis. Handb Clin Neurol. 2010;96:51-63. PMID: 20109674
33. Rajapaksa S, Starr M. Meningococcal sepsis. Aust Fam Physician. 2010;39(5):276-278. PMID: 20485712

Headache Red Flags / SNOOP

34. Do TP, Remmers A, Schytz HW, et al. Red and orange flags for secondary headaches in clinical practice: SNNOOP10 list. Neurology. 2019;92(3):134-144. PMID: 30891300
35. Chu K, Kelly AM, Kuan WS, et al. Predictive performance of the common red flags in emergency department headache patients: a HEAD and HEAD-Colombia study. Emerg Med J. 2024;41(6):368-375. PMID: 38658053
36. Grimaldi D, Nonino F, Cevoli S, et al. Risk stratification of non-traumatic headache in the emergency department. J Neurol. 2009;256(1):51-57. PMID: 19172382
37. Viera AJ, Antono B. Acute Headache in Adults: A Diagnostic Approach. Am Fam Physician. 2022;106(3):260-268. PMID: 36126007

Carbon Monoxide Poisoning

38. Rose JJ, Wang L, Xu Q, et al. Carbon Monoxide Poisoning: Pathogenesis, Management, and Future Directions of Therapy. Am J Respir Crit Care Med. 2017;195(5):596-606. PMID: 28783981
39. Weaver LK. Clinical practice. Carbon monoxide poisoning. N Engl J Med. 2009;360(12):1217-1225. PMID: 19297574
40. Hampson NB, Piantadosi CA, Thom SR, Weaver LK. Practice recommendations in the diagnosis, management, and prevention of carbon monoxide poisoning. Am J Respir Crit Care Med. 2012;186(11):1095-1101. PMID: 23087025

Pregnancy-Related Headache

41. Brewer J, Owens MY, Wallace K, et al. Posterior reversible encephalopathy syndrome in 46 of 47 patients with eclampsia. Am J Obstet Gynecol. 2013;208(6):468.e1-6. PMID: 23395926
42. Lanska DJ, Kryscio RJ. Risk factors for peripartum and postpartum stroke and intracranial venous thrombosis. Stroke. 2000;31(6):1274-1282. PMID: 10835444
43. Ducros A, Bousser MG. Reversible cerebral vasoconstriction syndrome. Pract Neurol. 2009;9(5):256-267. PMID: 19767676

CVST

44. Saposnik G, Barinagarrementeria F, Brown RD Jr, et al. Diagnosis and management of cerebral venous thrombosis: a statement for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2011;42(4):1158-1192. PMID: 21293023

Lumbar Puncture

45. Engelborghs S, Niemantsverdriet E, Struyfs H, et al. Consensus guidelines for lumbar puncture in patients with neurological diseases. Alzheimers Dement (Amst). 2017;8:111-126. PMID: 28603768
46. Seehusen DA, Reeves MM, Fomin DA. Cerebrospinal fluid analysis. Am Fam Physician. 2003;68(6):1103-1108. PMID: 14524396

Emergency Headache Management

47. Abraham MK, Chang WW. Subarachnoid Hemorrhage. Emerg Med Clin North Am. 2016;34(4):901-916. PMID: 27741994
48. Pajor MJ, Long B, Koyfman A, Liang SY. High risk and low prevalence diseases: Adult bacterial meningitis. Am J Emerg Med. 2023;65:76-83. PMID: 36592564

Australian/Indigenous Health

49. Australian Institute of Health and Welfare. Aboriginal and Torres Strait Islander health performance framework 2020 summary report. Canberra: AIHW; 2020.
50. Katzenellenbogen JM, Vos T, Somerford P, et al. Burden of stroke in Indigenous Western Australians: a study using data linkage. Stroke. 2011;42(6):1515-1521. PMID: 21493914
51. Royal Flying Doctor Service. Annual Report 2022-2023. Sydney: RFDS; 2023.
52. Azzopardi PS, Sawyer SM, Kowal E, et al. Health and wellbeing of Indigenous adolescents in Australia: a systematic synthesis of population data. Lancet. 2018;391(10122):766-782. PMID: 29477516