Subarachnoid Haemorrhage (Adult)

1. Overview

Subarachnoid Haemorrhage (SAH) is a catastrophic neurological emergency defined by the presence of blood within the subarachnoid space—the CSF-filled compartment between the arachnoid mater and pia mater surrounding the brain. [1]

The Clinical Imperative

SAH represents approximately 5% of all strokes but carries disproportionate mortality and morbidity. The condition is characterized by:

• Pre-hospital mortality: 15% die before reaching medical care
• 30-day mortality: 40-50% overall
• Functional dependency: 30% of survivors have significant disability
• Median age: 50-55 years (younger than ischaemic stroke)
• Life-years lost: Highest among stroke subtypes due to younger age of onset [2]

Pathological Classification

The Diagnostic Hallmark: Thunderclap Headache

The thunderclap headache is pathognomonic:

• Sudden onset reaching maximal intensity within less than 60 seconds
• Severity: "Worst headache of my life" or "being struck by lightning"
• Associated features: Nausea, vomiting, photophobia, neck stiffness
• Loss of consciousness at onset in 50% of cases [3]

Modern Management Paradigm (2023 AHA/ASA Guidelines)

The contemporary approach emphasizes:

1. Ultra-early diagnosis: 6-hour CT rule
2. Immediate neuroprotection: Nimodipine within 4 hours
3. Early aneurysm securing: Within 24 hours to prevent re-bleeding
4. Coiling-first approach: Endovascular treatment preferred (ISAT evidence)
5. Complication surveillance: Daily TCD for vasospasm; serial neurological assessment [1,4]

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2. Epidemiology

Global Incidence Patterns

Overall Incidence: 6-9 per 100,000 person-years in Western populations

Geographic Variation:

• Japan: 20-23 per 100,000 (highest globally)
• Finland: 18-20 per 100,000
• South America: 4-5 per 100,000
• China: 2-3 per 100,000 (increasing with urbanization)

The geographic variation reflects both genetic predisposition and environmental risk factors (hypertension prevalence, smoking rates). [5]

Demographic Risk Factors

Modifiable Risk Factors

Hypertension (RR 2.8):

• Present in 50-70% of SAH cases
• Chronic hypertension weakens arterial walls
• Risk increases linearly with BP > 140/90 mmHg [6]

Smoking (RR 3.5):

• Dose-dependent: > 20 pack-years has RR 4.7
• Mechanism: Endothelial dysfunction, increased proteolytic activity
• Risk persists 5-10 years after cessation [7]

Alcohol excess (RR 2.1):

• Binge drinking (> 5 units in one session)
• Acute BP elevation and impaired coagulation
• Chronic alcoholism: nutritional deficiencies affecting vessel wall integrity

Cocaine use (RR 7.0):

• Acute sympathomimetic surge
• Particularly dangerous in undiagnosed aneurysm carriers
• Peak risk within 24 hours of use [8]

Genetic Syndromes and Familial Risk

Familial Intracranial Aneurysm (FIA): 7-10% of patients with SAH have a first-degree relative with aneurysm or SAH. Screening with MRA is recommended when ≥2 first-degree relatives are affected. [9]

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3. Aetiology & Pathophysiology

Aneurysm Formation: The Hemodynamic Stress Hypothesis

Step 1: Endothelial Injury Chronic turbulent flow at arterial bifurcations (particularly the Circle of Willis) causes repetitive mechanical trauma to the endothelium. This leads to:

• Loss of endothelial NO production
• Upregulation of inflammatory mediators (IL-1β, TNF-α)
• Recruitment of macrophages and smooth muscle cells

Step 2: Matrix Degradation Inflammatory cells secrete matrix metalloproteinases (MMP-2, MMP-9) that degrade:

• Type IV collagen in the basement membrane
• Elastin in the internal elastic lamina
• Fibrillar collagen in the tunica media [10]

Step 3: Aneurysm Growth Progressive thinning of the arterial wall allows focal dilatation under systolic pressure. The aneurysm wall consists of:

• Endothelium (often disrupted)
• Thickened intima with foam cells
• Absent internal elastic lamina (pathognomonic finding)
• Thin layer of collagenous tissue (no smooth muscle)

Step 4: Rupture Wall stress (σ) increases with radius (LaPlace's Law: σ = Pr/2h). When wall stress exceeds tensile strength, rupture occurs. Peak rupture risk with aneurysms > 7mm diameter. [11]

Anatomical Distribution of Aneurysms

The Molecular Cascade of Injury

Phase 1: Early Brain Injury (First 72 Hours)

Immediate Events (Seconds to Minutes):

1. ICP Spike: At the moment of rupture, ICP transiently equals mean arterial pressure (MAP), causing:

   • Global cerebral ischaemia
   • Loss of consciousness (50% of patients)
   • Activation of Cushing reflex (hypertension + bradycardia)

2. Acute Hydrocephalus: Blood obstructs CSF flow through:

   • Arachnoid granulations (impaired CSF reabsorption)
   • Fourth ventricle outlets (obstructive hydrocephalus)
   • Sylvian aqueduct (communicating hydrocephalus) [12]

Subacute Events (Hours to Days):

3. Excitotoxicity: Haemoglobin breakdown releases:

   • Iron (Fe²⁺): Generates hydroxyl radicals via Fenton reaction
   • Haem: Activates Toll-like receptor 4 (TLR-4) → microglial activation
   • Glutamate: Massive release causes NMDA receptor overstimulation
   • Potassium (K⁺): Extracellular accumulation to 12-15 mM (normal 3-5 mM) [13]

4. Spreading Depolarizations (SDs):

   • Waves of near-complete neuronal depolarization
   • Propagate at 2-5 mm/min across cortex
   • Detected in 60-70% of SAH patients with invasive monitoring
   • Each SD increases metabolic demand in already ischaemic tissue
   • Frequency correlates with poor outcome [14]

5. Neuroinflammation:

   • Microglial activation within 6 hours
   • Cytokine storm: IL-6, IL-1β, TNF-α
   • Blood-brain barrier breakdown
   • Leucocyte infiltration into brain parenchyma

Phase 2: Delayed Cerebral Ischaemia (Days 3-14)

The Vasospasm Paradigm:

Delayed cerebral ischaemia (DCI) occurs in 30% of SAH patients, peaking on days 5-9. The pathophysiology is multifactorial:

Mechanism 1: Nitric Oxide (NO) Scavenging

• Oxyhaemoglobin (OxyHb) in CSF binds NO with extremely high affinity
• Loss of endothelial NO → Loss of vasodilation
• Smooth muscle cells shift to contractile phenotype
• Molecular basis for nimodipine efficacy [15]

Mechanism 2: Endothelin-1 (ET-1) Release

• Haemoglobin breakdown stimulates endothelial ET-1 production
• ET-1 is the most potent endogenous vasoconstrictor
• Binds ET-A receptors on smooth muscle → sustained contraction
• Elevated ET-1 levels predict vasospasm severity [16]

Mechanism 3: Cortical Spreading Ischaemia

• Distinct from vasospasm; occurs even without angiographic narrowing
• Microthrombosis in cortical arterioles
• Endothelial dysfunction and inflammation
• Explains why 30% of DCI occurs without angiographic vasospasm [17]

Clinical Consequences:

• Gradual onset of confusion, drowsiness, or focal deficit
• May mimic aneurysm re-rupture
• Requires urgent imaging (CT perfusion, CTA) and potential intervention
• Transcranial Doppler (TCD): MCA velocity > 120 cm/s suggests vasospasm

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4. Clinical Presentation

The Sentinel (Warning) Headache

Epidemiology: 30-50% of patients report a distinct headache in the days to weeks before major SAH

Pathophysiology: Minor leak ("warning leak") from aneurysm without full rupture

Clinical Features:

• Sudden but less severe than thunderclap
• May be attributed to "migraine" or "tension headache"
• Resolves spontaneously within hours
• Critical missed opportunity: Only 25% correctly diagnosed

Clinical Implication: Any patient with sudden-onset severe headache should trigger SAH investigation, even if symptoms improve. [18]

The Thunderclap Event

Timing: Sudden onset reaching peak intensity in less than 60 seconds (diagnostic criterion)

Character:

• "Worst headache of my life"
• "Being hit with a baseball bat from behind"
• "Explosion inside my head"

Associated Features:

• Loss of consciousness at onset: 50%
• Nausea and vomiting: 75%
• Seizure at onset: 10-25% (more common with MCA aneurysm)
• Neck stiffness: Develops over 6-12 hours as meningeal irritation evolves

Activity at Onset:

• Occurs during physical exertion in 35% (Valsalva, sexual activity, weightlifting)
• Occurs during rest or sleep in 40%
• Non-specific triggers in 25%

Physical Examination Findings

General Examination

Vital Signs:

• Hypertension: Present in 70-80% (may be pre-existing or reactive)
• Tachycardia or bradycardia: Cushing reflex if raised ICP
• Fever: May develop due to chemical meningitis

Conscious Level:

• Alert (GCS 15): 50%
• Drowsy but rousable (GCS 13-14): 30%
• Stuporose (GCS 9-12): 15%
• Comatose (GCS 3-8): 5%

Neurological Examination

Meningism:

• Neck stiffness: Positive in 75% by 6 hours
• Kernig's sign: Resistance to passive knee extension with hip flexed
• Brudzinski's sign: Hip flexion when neck is flexed
• Develops as blood breakdown products irritate meninges

Focal Signs (Present in 30%):

Cranial Nerve III (Oculomotor) Palsy (Pathognomonic for PComm Aneurysm):

• Eye position: "Down and out" (unopposed action of lateral rectus and superior oblique)
• Pupil: Dilated and unreactive (parasympathetic fibres run on surface of nerve)
• Ptosis: Complete (levator palpebrae paralysis)
• Pain: Distinguished from medical causes (diabetes, vasculitis) which are painless
• Surgical urgency: High risk of aneurysm rupture; requires immediate securing [19]

Fundoscopy

Terson Syndrome (10-20% of SAH):

• Vitreous or subhyaloid haemorrhage
• Mechanism: Sudden rise in ICP causes retinal vein rupture
• Appearance: Boat-shaped haemorrhage anterior to retina
• Prognostic significance: Marker of severe SAH; associated with worse outcome [20]

Papilloedema:

• Rare in acute SAH (takes days to develop)
• Suggests sustained raised ICP or hydrocephalus

Clinical Grading Systems

World Federation of Neurosurgical Societies (WFNS) Scale

Most widely used in clinical practice and research. [21]

Hunt and Hess Scale (Historical)

Still referenced in neurosurgical literature but largely superseded by WFNS.

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5. Investigations

Immediate Diagnostic Pathway

Non-Contrast CT Head: The 6-Hour Rule

NICE 2022 Guidance: A high-quality non-contrast CT performed within 6 hours of headache onset and reported by a trained specialist has > 99% sensitivity for SAH. If negative, SAH is effectively excluded without need for lumbar puncture. [22]

Imaging Findings:

Sensitivity by Timing:

• 0-6 hours: 98-100%
• 6-12 hours: 93-95%
• 12-24 hours: 85-90%

• 24 hours: 50-60%

• After 1 week: less than 30% (Blood becomes isodense with brain)

Reasons for False Negatives:

• Small-volume bleed
• Severe anaemia (Hb less than 70 g/L)
• Poor-quality scan (motion artefact)
• Inexperienced interpreter
• Delayed presentation (> 24 hours) [23]

Lumbar Puncture: The 12-Hour Xanthochromia Rule

Indication: CT negative and onset > 6 hours ago

Critical Timing: Must wait 12 hours from headache onset for xanthochromia (bilirubin) to develop. Performing LP earlier may yield false negative.

Procedure:

• Opening pressure: Often elevated (> 20 cmH₂O)
• Collect 4 sequential tubes
• Send immediately for cell count and spectrophotometry
• Protect from light: Bilirubin is photodegraded

Interpretation:

Spectrophotometry is the gold standard for detecting xanthochromia. Visual inspection alone misses 20-30% of cases. [24]

Aneurysm Localization

CT Angiography (CTA)

First-line investigation after SAH confirmed:

Advantages:

• Rapid (5-10 minutes)
• Widely available
• Sensitivity 95-98% for aneurysms > 3mm
• Identifies aneurysm location, size, and neck characteristics
• Reveals anatomical variants (fenestrations, hypoplastic segments)

Limitations:

• Ionizing radiation
• Iodinated contrast (contraindicated in renal impairment, allergy)
• Misses aneurysms less than 3mm
• Artefact from bone or clips

Technique: Thin-slice (0.5-1mm) acquisition during arterial phase; 3D reconstruction for surgical planning. [25]

Digital Subtraction Angiography (DSA)

Gold Standard for aneurysm characterization:

Indications:

• CTA negative or equivocal
• Pre-treatment planning (especially for complex aneurysms)
• Catheter-based treatment (diagnostic + therapeutic in one session)

Advantages:

• Highest spatial resolution
• Dynamic flow information
• Ability to assess collateral circulation
• Allows coiling in same session

Risks:

• Invasive: 0.5-1% risk of stroke or arterial injury
• Requires arterial puncture and catheterization
• Iodinated contrast load

Perimesencephalic SAH: If initial DSA is negative and blood distribution is limited to cisterns anterior to brainstem, diagnosis is non-aneurysmal perimesencephalic SAH. Excellent prognosis; no need for repeat angiography. [26]

MR Angiography (MRA)

Role: Screening of unruptured aneurysms in high-risk populations (family history, genetic syndromes)

Not routinely used in acute SAH:

• Takes too long in emergency setting
• Less sensitive than CTA/DSA
• Contraindicated if patient unstable

Assessment of Complications

Fisher Scale (CT Grading for Vasospasm Risk)

Modified Fisher Scale (more predictive):

• Grade 0: No SAH or IVH
• Grade 1: Thin SAH, no IVH
• Grade 2: Thin SAH, with IVH
• Grade 3: Thick SAH, no IVH
• Grade 4: Thick SAH, with IVH

Grades 3 and 4 have highest DCI risk. [27]

Transcranial Doppler (TCD)

Purpose: Non-invasive monitoring for vasospasm

Technique: Daily measurements of flow velocity in MCA, ACA, ICA

Interpretation:

• Normal: MCA velocity less than 120 cm/s
• Mild vasospasm: 120-150 cm/s
• Moderate vasospasm: 150-200 cm/s
• Severe vasospasm: > 200 cm/s

Lindegaard Ratio (MCA velocity / ICA velocity):

• less than 3: No vasospasm (hyperdynamic flow alone)
• 3-6: Moderate vasospasm

• 6: Severe vasospasm

Sensitivity 60-70%; specificity 80-85%. Cannot replace clinical assessment. [28]

CT Perfusion

Advanced imaging for DCI detection:

• Measures cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT)
• Identifies regions at risk before infarction
• Guides decision for rescue therapy
• MTT prolongation > 6 seconds predicts infarction

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6. Management

Pre-Hospital and Emergency Department

Initial Stabilization (First 60 Minutes)

Airway, Breathing, Circulation:

• GCS ≤8: Intubation for airway protection
• Target SpO₂ > 94%
• Avoid hyperventilation (causes cerebral vasoconstriction)
• Secure IV access (2x large-bore cannulae)

Immediate Interventions:

1. Blood Pressure Control:

   • Target SBP less than 160 mmHg before aneurysm secured
   • Avoid aggressive lowering (may worsen cerebral perfusion)
   • First-line agents: Labetalol IV 10-20mg boluses or nicardipine infusion
   • Once aneurysm secured, permissive hypertension allowed [1]

2. Analgesia:

   • Morphine 2.5-5mg IV (caution: may depress respiration)
   • Paracetamol 1g IV
   • Avoid NSAIDs (theoretical bleeding risk)

3. Anti-Emetics:

   • Ondansetron 4-8mg IV
   • Prevents Valsalva during vomiting (re-bleeding risk)

4. Avoid Straining:

   • Bed rest with head elevated 30°
   • Laxatives (lactulose, docusate)
   • Avoid Valsalva manoeuvres

Investigations to Order:

• Non-contrast CT head (STAT)
• Full blood count, coagulation screen
• Urea and electrolytes (SIADH common post-SAH)
• Troponin (10-15% have ECG changes mimicking MI)
• ECG (QT prolongation, deep T-wave inversions)

Neuroprotection: The Nimodipine Mandate

Evidence Base: British Aneurysm Nimodipine Trial (1989) demonstrated 40% reduction in poor outcome with nimodipine. Cochrane review confirms benefit. [29]

Mechanism:

• L-type calcium channel blocker
• Neuroprotective (blocks calcium-mediated neuronal injury)
• Not primarily a vasodilator in brain at therapeutic doses
• Reduces incidence and severity of delayed cerebral ischaemia

Dosing Protocol:

• 60mg orally every 4 hours (6 doses per day)
• Start within 4 hours of admission
• Continue for 21 days (entire period of DCI risk)
• If unable to take orally: 1mg/h IV via central line (risk of hypotension with peripheral administration)

Monitoring:

• Blood pressure: May cause systemic hypotension
• If SBP falls less than 100 mmHg: Reduce dose to 30mg q4h or increase IV fluids
• Do NOT discontinue unless absolutely necessary

Class I Recommendation: AHA/ASA and European guidelines. One of the few interventions with proven mortality benefit in SAH. [1,4]

Aneurysm Securing: Timing and Technique

The Case for Ultra-Early Treatment

Re-bleeding Risk:

• First 24 hours: 4-5% risk
• First week: 10-15% cumulative risk
• Mortality with re-bleeding: 70-80%

Guideline Recommendation: Secure aneurysm within 24 hours of presentation. Earlier treatment (within 12 hours) preferred for good-grade patients. [1]

Endovascular Coiling

Technique:

• Catheter advanced via femoral artery to aneurysm
• Platinum coils deployed into aneurysm sac
• Coils promote thrombosis and seal aneurysm from circulation

Advantages:

• Less invasive than clipping
• Lower 30-day morbidity and mortality
• Preferred for posterior circulation aneurysms
• Can be performed under local anaesthesia in poor-grade patients

Disadvantages:

• Higher long-term re-bleeding rate (2-3% over 10 years)
• Requires lifelong imaging surveillance
• Not suitable for wide-neck aneurysms (dome-to-neck ratio less than 2)

ISAT Trial (2002, 2005): Landmark RCT comparing coiling vs. clipping in 2143 patients. Results:

• 30-day mortality: Coiling 8.1% vs. Clipping 10.1%
• 1-year independence: Coiling 78% vs. Clipping 69% (ARR 9%, NNT 11)
• 10-year re-bleeding: Coiling 2.3% vs. Clipping 1.1%
• Conclusion: Coiling superior for suitable aneurysms [30,31]

Cochrane Review (2018): Confirms coiling reduces poor outcome by 24% (RR 0.76, 95% CI 0.67-0.87). [32]

Neurosurgical Clipping

Technique:

• Craniotomy to expose aneurysm
• Titanium clip applied across aneurysm neck
• Permanent exclusion from circulation

Indications:

• Wide-neck aneurysms unsuitable for coiling
• Middle cerebral artery aneurysms (better long-term occlusion)
• Intracerebral haematoma requiring evacuation
• Young patients (less than 40 years) where long-term durability important

Advantages:

• Definitive treatment (re-bleeding rate less than 1%)
• Allows haematoma evacuation if needed
• No need for lifelong surveillance

Disadvantages:

• Invasive craniotomy
• Higher 30-day morbidity (especially posterior circulation)
• Requires general anaesthesia

Decision-Making: Multidisciplinary discussion between interventional neuroradiologist and neurosurgeon. Patient age, aneurysm characteristics, and institutional expertise all factor into decision.

Management of Complications

Acute Hydrocephalus (20-30% of Patients)

Pathophysiology:

• Blood obstructs CSF flow/reabsorption
• Occurs within first 48 hours

Clinical Features:

• Deteriorating GCS
• Cushing's triad: Hypertension, bradycardia, irregular breathing
• Dilated pupils

Management:

• External Ventricular Drain (EVD): Gold standard
• Catheter inserted into lateral ventricle (usually right frontal)
• Allows CSF drainage and ICP monitoring
• Set to drain if ICP > 15-20 mmHg
• Risk: 5% infection rate (ventriculitis); prophylactic antibiotics not recommended

Timing of EVD Removal:

• Once ICP normalizes and CSF clears
• Trial of clamping to assess need for permanent shunt
• 15-20% require ventriculoperitoneal shunt long-term [33]

Delayed Cerebral Ischaemia (DCI) (25-30% of Patients)

Clinical Features:

• Days 3-14 post-SAH (peak day 5-9)
• Gradual onset confusion, drowsiness
• New focal neurological deficit
• Distinguished from re-bleeding by gradual onset

Diagnosis:

• Clinical suspicion (declining neurological exam)
• CT perfusion: MTT prolongation, CBF reduction
• CTA: Vessel narrowing (but DCI can occur without angiographic vasospasm)
• TCD: Elevated velocities (> 120 cm/s in MCA)

Management:

First-Line: Hypertension ("H"):

• Induced hypertension to overcome vasospasm
• Target SBP 160-200 mmHg
• Achieved with noradrenaline infusion
• Only after aneurysm secured
• Evidence: Observational data; no RCT support for "Triple-H" therapy
• Modern approach: Euvolaemia + induced hypertension (avoid hypervolaemia and haemodilution) [34]

Second-Line: Intra-Arterial Therapy:

• Intra-arterial vasodilators: Verapamil, nimodipine, milrinone
• Angioplasty: Mechanical dilatation of proximal vessels
• Reserved for cases refractory to medical management
• Complications: Vessel rupture, thrombosis

Emerging Therapies (not yet standard of care):

• Clazosentan (endothelin receptor antagonist): Reduces angiographic vasospasm but no outcome benefit in trials
• Lumbar CSF drainage: May reduce DCI burden [7,35]

Seizures (10-25% at Onset; 5-10% Delayed)

Management:

• Do NOT give prophylactic anti-epileptics (no evidence of benefit; potential harm from sedation)
• Treat seizures if they occur: Levetiracetam 500mg BD (preferred; less sedating)
• Phenytoin avoided (drug interactions, side effects)
• Duration: 3-6 months post-SAH, then wean if no further seizures [36]

Systemic Complications

Cardiac (20-30%):

• Neurogenic stress cardiomyopathy (Takotsubo pattern)
• ECG changes: Deep T inversions, QT prolongation, ST elevation
• Troponin elevation (non-ischaemic)
• Management: Supportive; usually resolves within weeks

Metabolic:

• SIADH (30-40%): Hyponatraemia from hypothalamic injury; treat with fluid restriction
• Cerebral Salt Wasting (10-20%): Hyponatraemia with hypovolaemia; treat with IV saline
• Hyperglycaemia: Stress response; associated with worse outcome; target glucose 6-10 mmol/L

Pulmonary:

• Neurogenic pulmonary oedema (5-10%): Acute onset after SAH; treat with diuresis and ventilatory support
• Aspiration pneumonia: Common in decreased GCS

Thromboembolic (2-5%):

• DVT/PE risk high due to immobility
• Prophylaxis: Intermittent pneumatic compression stockings (avoid pharmacological prophylaxis until aneurysm secured)
• Once secured: Low-molecular-weight heparin

Neurocritical Care Monitoring

Invasive ICP Monitoring:

• Indicated in WFNS grade IV-V
• Target ICP less than 20 mmHg
• Cerebral perfusion pressure (CPP) = MAP - ICP; target CPP 60-70 mmHg

Multimodal Monitoring (specialist centres):

• Brain tissue oxygen (PbtO₂): Target > 20 mmHg
• Microdialysis: Detects metabolic crisis (lactate/pyruvate ratio)
• Continuous EEG: Detects non-convulsive seizures and spreading depolarizations

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7. Prognosis and Long-Term Outcomes

Mortality

30-Day Mortality: 40-50% overall

• WFNS Grade I-II: 5-15%
• WFNS Grade III: 20-35%
• WFNS Grade IV-V: 70-90%

1-Year Mortality: 50-55%

Predictors of Mortality:

• Age > 70 years
• Poor clinical grade (WFNS IV-V)
• Large intraventricular haemorrhage
• Posterior circulation aneurysm
• Delayed cerebral ischaemia
• Re-bleeding before securing

Functional Outcome

Modified Rankin Scale at 1 Year:

• mRS 0-2 (independent): 50-60%
• mRS 3-4 (dependent): 15-20%
• mRS 5 (severely disabled): 5-10%
• mRS 6 (death): 25-30%

Cognitive Impairment: 40-60% of survivors have persistent cognitive deficits:

• Executive dysfunction
• Memory impairment
• Reduced processing speed
• Depression and anxiety (30-50%)

Return to Work: Only 50% return to pre-SAH employment level. [37]

Aneurysm Recurrence and Re-Bleeding

After Coiling:

• Recurrence rate: 20-30% on follow-up imaging
• Need for re-treatment: 10-15%
• Long-term re-bleeding: 2-3% over 10 years
• Surveillance: MRA at 6 months, 2 years, 5 years, then 5-yearly

After Clipping:

• Recurrence rate: less than 5%
• Long-term re-bleeding: less than 1%
• Surveillance: Single angiogram at 6-12 months; no further imaging if complete occlusion

Unruptured Aneurysm Follow-Up

Screening of Additional Aneurysms:

• 15-30% of SAH patients have additional unruptured aneurysms
• Treatment threshold: > 5-7mm depending on location
• Annual growth rate: 1-2% for aneurysms less than 7mm

PHASES Score: Risk prediction tool for rupture of unruptured aneurysms based on:

• Population (geographic)
• Hypertension
• Age
• Size
• Earlier SAH
• Site

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8. Differential Diagnosis

Thunderclap Headache Differentials

Key Principle: Thunderclap headache is SAH until proven otherwise. Requires imaging + LP if CT negative.

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9. Prevention and Screening

Primary Prevention

Modifiable Risk Factors:

• Smoking cessation: Reduces risk by 50% after 5 years
• BP control: Target less than 140/90 mmHg
• Moderate alcohol consumption: less than 14 units/week
• Avoid cocaine and amphetamines

Screening for Unruptured Aneurysms

Indications for Screening:

• ≥2 first-degree relatives with SAH or unruptured aneurysm
• ADPKD + 1 affected relative
• Ehlers-Danlos Type IV
• Coarctation of aorta

Screening Modality: MRA (non-invasive, no radiation)

Screening Schedule:

• Baseline at age 20-30
• If negative: Repeat at 40, then 5-yearly until age 70
• If aneurysm detected: Annual imaging; treat if > 5-7mm

Treatment of Unruptured Aneurysms:

• ISUIA Study: Rupture risk for aneurysms less than 7mm is 0.1% per year
• Treatment recommended if:
  • Size > 7mm (anterior circulation) or > 5mm (posterior circulation)
  • Symptomatic (mass effect, TIA)
  • Rapid growth (> 1mm/year)
  • Family history of SAH

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10. Examination Scenarios

MRCP PACES Station 3: Cardiovascular and Neurology

Stem: "This 58-year-old woman was admitted 2 weeks ago with sudden-onset headache. Please examine her cranial nerves and discuss your findings."

Examination Findings:

• Right eye: "Down and out" position, ptosis, dilated pupil (6mm vs. 3mm on left)
• Neck stiffness (meningism)
• Subhyaloid haemorrhage on fundoscopy

Presentation: "This patient has a right partial third nerve palsy with pupillary involvement, consistent with a compressive lesion. In the context of sudden-onset headache, this suggests a ruptured posterior communicating artery aneurysm causing subarachnoid haemorrhage. The presence of subhyaloid haemorrhage (Terson syndrome) and ongoing neck stiffness supports the diagnosis."

Examiner Questions:

1. "What is the significance of pupillary involvement in third nerve palsy?"

   • Parasympathetic fibres travel on the surface of the third nerve and are preferentially affected by external compression (e.g., aneurysm, uncal herniation). Medical causes (diabetes, vasculitis) affect the nerve core and typically spare the pupil.

2. "How would you investigate suspected SAH?"

   • Immediate non-contrast CT head. If performed within 6 hours of onset and negative, SAH is excluded. If CT negative and onset > 6 hours ago, proceed to lumbar puncture at 12 hours post-onset for xanthochromia.

3. "What is nimodipine and why is it given?"

   • Nimodipine is an L-type calcium channel blocker that reduces delayed cerebral ischaemia. It is neuroprotective, reducing poor outcome by 40%. Dosed at 60mg every 4 hours for 21 days. Class I recommendation.

MRCP SCE Viva

Scenario: "A 52-year-old presents with thunderclap headache. CT head at 4 hours is reported as normal. What is your next step?"

Model Answer: "Given the CT was performed within 6 hours of onset and reported as normal, SAH is effectively excluded per the NICE 2022 guidance, assuming the scan was high-quality and interpreted by a specialist. I would discharge the patient with safety-netting advice to return if symptoms recur. If there was any doubt about scan quality or interpretation, or if the patient presented after 6 hours, I would proceed to lumbar puncture at 12 hours post-onset to assess for xanthochromia by spectrophotometry."

Examiner Follow-Up: "The patient re-presents 1 week later with worsening headache and confusion. Repeat CT shows diffuse SAH. What went wrong?"

Model Answer: "This suggests the initial CT may have been a false negative, possibly due to a small-volume bleed, poor scan quality, or misinterpretation. Alternatively, this could represent a new bleeding event from a previously unruptured aneurysm. I would now proceed urgently with CT angiography to identify the aneurysm, involve neurosurgery immediately, commence nimodipine 60mg every 4 hours, control blood pressure to SBP less than 160mmHg, and arrange for endovascular coiling or surgical clipping within 24 hours to prevent re-bleeding."

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11. Clinical Cases for Revision

Case 1: The Missed Sentinel Headache

Presentation: A 45-year-old woman presents to her GP with sudden-onset headache 5 days ago. She describes it as "the worst headache I've ever had" but it resolved after 6 hours. She is now asymptomatic. GP diagnoses migraine and prescribes sumatriptan.

Outcome: She presents to A&E 1 week later with catastrophic headache, collapse, and GCS 3. CT shows massive SAH with intraventricular extension. She dies despite maximal intervention.

Learning Points:

• 30-50% of SAH patients have a sentinel headache
• Any sudden-onset severe headache warrants investigation, even if resolved
• Sentinel headaches are a critical missed opportunity for prevention

Case 2: The Traumatic Tap Dilemma

Presentation: A 60-year-old man presents with thunderclap headache. CT at 8 hours is negative. LP performed at 14 hours shows:

• Tube 1: RBC 5000/mm³
• Tube 4: RBC 4800/mm³
• Xanthochromia: Positive by spectrophotometry

Question: Is this SAH or traumatic tap?

Answer: SAH. The RBC count is persistently elevated (no significant drop from tube 1 to 4) and xanthochromia is present. In a traumatic tap, RBCs would decrease significantly across tubes and the supernatant would be clear after centrifugation.

Case 3: The Role of Nimodipine

Presentation: A 55-year-old woman with WFNS Grade II SAH post-coiling develops declining GCS on day 6. BP is 180/95 mmHg. Nimodipine was stopped on day 3 due to hypotension.

Question: What is the likely diagnosis and management?

Answer: Delayed cerebral ischaemia (vasospasm). This occurs in 30% of patients, peaking days 5-9. The premature discontinuation of nimodipine removed her neuroprotection. Management includes:

1. Urgent CT perfusion to identify ischaemic regions
2. Restart nimodipine immediately (dose-adjust if needed)
3. Induced hypertension (target SBP 160-200 mmHg with noradrenaline)
4. Consider intra-arterial vasodilators if refractory

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12. Key Guidelines and Evidence

AHA/ASA Guideline for SAH (2023)

Class I Recommendations (should be done):

• CT head within 6 hours for suspected SAH (Level A)
• LP if CT negative and onset > 6 hours (Level B)
• Nimodipine 60mg q4h for 21 days (Level A)
• Aneurysm securing within 24 hours (Level B)
• Endovascular coiling preferred over clipping for suitable aneurysms (Level A)

Class III Recommendations (should NOT be done):

• Prophylactic anti-epileptic drugs (Level A)
• Triple-H therapy (hypervolaemia, haemodilution, hypertension) – only induced hypertension recommended (Level B)

NICE NG228 (2022)

Key Changes from Previous Guidance:

• 6-hour CT rule obviates need for LP if negative
• Emphasizes spectrophotometry over visual xanthochromia
• Recommends coiling over clipping as first-line for most aneurysms
• Stresses importance of specialist neuroscience centres for management

European Stroke Organisation (ESO) Guidelines (2013)

Recommendations:

• Diagnosis: CT + CTA in one session
• Treatment: Early aneurysm securing (less than 72h)
• Nimodipine: Mandatory
• Monitoring: Daily TCD for vasospasm screening

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13. Single Best Answer (SBA) Questions

Question 1

A 55-year-old male presents with sudden-onset severe headache 4 hours ago. GCS is 15. A non-contrast CT head is performed and reported as normal by a specialist neuroradiologist. What is the most appropriate next step?

• A) Perform a lumbar puncture immediately
• B) Perform a lumbar puncture in 8 hours
• C) Perform a CT angiogram
• D) Discharge with safety-netting advice
• E) Admit for 24 hours of observation

Answer: D. Per the 2022 NICE guidelines, a high-quality CT reported as negative within 6 hours of onset is sufficient to exclude SAH with sensitivity > 99%. No LP is required. The patient can be safely discharged with advice to return if symptoms recur.

Question 2

A 45-year-old female is diagnosed with ruptured posterior communicating artery aneurysm. On examination, her right pupil is dilated and fixed, and the eye is deviated inferiorly and laterally. What is the mechanism of nimodipine's benefit in SAH?

• A) Prevents aneurysm re-rupture by lowering blood pressure
• B) Directly dilates cerebral vessels to prevent vasospasm
• C) Blocks neuronal calcium entry to reduce delayed cerebral ischaemia
• D) Reduces CSF production to prevent hydrocephalus
• E) Increases blood resorption from subarachnoid space

Answer: C. Nimodipine is neuroprotective, blocking L-type calcium channels on neurons to prevent calcium-mediated excitotoxicity. This reduces the incidence and severity of delayed cerebral ischaemia by approximately 40%, independent of any effect on vasospasm.

Question 3

A 62-year-old woman undergoes endovascular coiling for a ruptured anterior communicating artery aneurysm. On day 7 post-procedure, she becomes increasingly confused and drowsy. BP is 165/90, HR 72, GCS drops from 15 to 12. What is the most likely diagnosis?

• A) Aneurysm re-bleeding
• B) Hydrocephalus
• C) Delayed cerebral ischaemia
• D) Seizure activity
• E) Infection (meningitis)

Answer: C. Delayed cerebral ischaemia peaks between days 5-9 post-SAH. The gradual onset of deterioration (as opposed to sudden collapse with re-bleeding) and timing are characteristic. Urgent CT perfusion and TCD are indicated, followed by induced hypertension and potentially intra-arterial therapy.

Question 4

Which of the following findings on lumbar puncture most reliably distinguishes subarachnoid haemorrhage from a traumatic tap?

• A) RBC count > 10,000/mm³ in tube 1
• B) Presence of xanthochromia on spectrophotometry
• C) Opening pressure > 25 cmH₂O
• D) RBC count that does not decrease from tube 1 to tube 4
• E) Presence of oxyhaemoglobin

Answer: B. Xanthochromia (yellow discoloration due to bilirubin) detected by spectrophotometry is the gold standard for distinguishing SAH from traumatic tap. Bilirubin forms in vivo over 12 hours from RBC breakdown and cannot be produced by a traumatic tap. Visual inspection alone misses 20-30% of cases.

Question 5

A 48-year-old man with ADPKD and a family history of SAH (father died age 52) asks about screening for intracranial aneurysms. What is the most appropriate management?

• A) No screening required (ADPKD alone is insufficient indication)
• B) MR angiography now, repeat in 5 years if negative
• C) CT angiography annually
• D) Digital subtraction angiography (gold standard)
• E) Reassure; screen only if he develops headaches

Answer: B. Patients with ADPKD and a first-degree relative with SAH or unruptured aneurysm should undergo screening with MRA. If negative, repeat at 5-year intervals. MRA is preferred over CTA (no radiation) and DSA (non-invasive). The prevalence of intracranial aneurysms in ADPKD is 10-15%, rising to 20% with positive family history.

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14. Viva Scenarios

Scenario 1: The Painful Third Nerve Palsy

Examiner: "A 52-year-old woman presents with sudden-onset right-sided headache and diplopia. On examination, her right eye is deviated down and out, she has complete ptosis, and the right pupil is 7mm compared to 3mm on the left. What is your diagnosis and immediate management?"

Model Answer: "This is a compressive right third nerve palsy, evidenced by pupillary involvement. The acute presentation with severe headache strongly suggests a ruptured posterior communicating artery aneurysm causing subarachnoid haemorrhage with direct compression of the third nerve.

My immediate management would be:

1. ABCDE assessment and stabilization
2. Immediate non-contrast CT head to confirm SAH
3. Urgent neurosurgical referral – this is a surgical emergency given the risk of further bleeding
4. Blood pressure control to SBP less than 160 mmHg before the aneurysm is secured
5. Commence nimodipine 60mg every 4 hours
6. CT angiography to localize the aneurysm
7. Arrange definitive treatment (endovascular coiling or surgical clipping) within 24 hours

The painful, pupil-involved third nerve palsy is the key to diagnosis and distinguishes this from medical causes such as diabetic third nerve palsy, which is typically painless and pupil-sparing."

Scenario 2: The Negative CT Dilemma

Examiner: "A 45-year-old presents 18 hours after thunderclap headache onset. CT head is reported as normal. What do you do next?"

Model Answer: "Given the CT was performed more than 6 hours after onset, a negative scan does not exclude SAH (sensitivity falls to ~85% at 12-24 hours). I would proceed with lumbar puncture, ensuring at least 12 hours have elapsed since headache onset to allow xanthochromia to develop.

On LP, I would:

1. Measure opening pressure (often elevated in SAH)
2. Collect 4 sequential tubes to assess for RBC decline
3. Request cell count and spectrophotometry (gold standard for xanthochromia)
4. Protect samples from light (bilirubin is photodegraded)

Interpretation:

• SAH: Persistently elevated RBCs across all tubes + xanthochromia on spectrophotometry
• Traumatic tap: Declining RBC count from tube 1→4 + clear supernatant + no xanthochromia

If xanthochromia is positive, I would proceed with CT angiography to identify an aneurysm and involve neurosurgery urgently."

Scenario 3: Day 7 Deterioration

Examiner: "A patient had endovascular coiling for SAH 7 days ago. She was WFNS Grade II and recovering well. Today she becomes drowsy and confused. What are your differential diagnoses and how would you investigate?"

Model Answer: "The differential for neurological deterioration at day 7 post-SAH includes:

1. Delayed cerebral ischaemia (most likely) – peaks days 5-9
2. Aneurysm re-bleeding – sudden rather than gradual onset
3. Hydrocephalus – can be acute or delayed
4. Seizure activity – non-convulsive status epilepticus
5. Metabolic disturbance – hyponatraemia (SIADH/cerebral salt wasting)
6. Infection – meningitis, ventriculitis (especially if EVD in situ)

Investigation approach:

1. Clinical assessment: GCS, focal signs, meningism
2. Urgent non-contrast CT head: To exclude re-bleeding, hydrocephalus, new infarction
3. CT perfusion: To identify ischaemic territories (MTT prolongation, CBF reduction)
4. Transcranial Doppler: Assess for vasospasm (MCA velocity > 120 cm/s)
5. Bloods: U&Es (sodium), glucose, FBC, CRP
6. CT angiography: If CT perfusion suggests DCI

If delayed cerebral ischaemia is confirmed:

• Ensure nimodipine continued at full dose
• Induced hypertension (target SBP 160-200 mmHg with noradrenaline)
• Maintain euvolaemia
• Consider intra-arterial vasodilators or angioplasty if refractory"

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15. Patient and Family Education

Explaining SAH to a Patient

"You've had what we call a subarachnoid haemorrhage, which is a serious type of bleeding in the brain. There's a blood vessel with a weak spot—like a bulge in a tire—that has burst. This released blood into the space around your brain, which caused the sudden, severe headache you experienced.

The good news is we've now sealed the weak spot using a minimally invasive procedure where we inserted tiny coils through a blood vessel in your leg. This stops any further bleeding.

For the next 3 weeks, you'll take a medication called nimodipine every 4 hours. This is very important because it protects your brain from a complication called vasospasm, where the blood vessels can go into spasm and reduce blood flow.

You'll be monitored closely in our neuroscience unit. We'll do daily ultrasound checks of your brain blood vessels and watch for any signs of complications. Most patients spend 2-3 weeks in hospital.

Recovery takes time—typically 3-6 months before you feel back to normal. Some people experience fatigue, headaches, and difficulty concentrating for many months. We'll arrange follow-up with physiotherapy, occupational therapy, and cognitive rehabilitation as needed."

Long-Term Follow-Up Information

Imaging Surveillance:

• MRA at 6 months to check the coiled aneurysm
• Repeat MRA at 2 years, 5 years, then 5-yearly lifelong
• If additional aneurysms found, these are monitored separately

Lifestyle Modifications:

• Stop smoking (critical)
• Blood pressure control (target less than 140/90)
• Moderate alcohol (less than 14 units/week)
• Avoid cocaine and amphetamines
• Manage cardiovascular risk factors

When to Seek Urgent Help:

• Sudden severe headache (could be re-bleeding)
• New weakness or speech difficulty
• Seizures
• Severe confusion or drowsiness

Support Resources:

• Brain and Spine Foundation (UK)
• Headway (brain injury charity)
• Stroke Association

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Last Updated: 2026-01-06 | MedVellum Editorial Team
Citation Count: 28
Evidence Level: High
Target Examination: MRCP, MRCS, FRCS (Neurosurgery), FRACP