SUBARACHNOID HAEMORRHAGE

✓ Medically ReviewedDISEASEID: MDBT0125🚨 TRIAGE: EMERGENCYICD-10: I60

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Definition

CLINICAL DEFINITION

Subarachnoid haemorrhage is bleeding into the subarachnoid space (fluid-filled area around brain and cord). Blood spreads in cerebrospinal fluid (clear fluid cushioning brain). It raises intracranial pressure (pressure inside skull). Most spontaneous cases follow rupture of a saccular aneurysm (small artery bulge). Trauma can tear surface vessels with the same spread.

IN PLAIN ENGLISH

Bleeding spreads over the brain surface. It starts with a sudden very severe headache. People call it thunderclap headache. It needs emergency hospital care.

COMMON MISCONCEPTION / WHAT IT DOES NOT MEAN

Subarachnoid haemorrhage is not bleeding inside brain tissue itself. It is not subdural clot (blood between outer and middle covers). It is not extradural clot (blood outside outer cover, often with skull fracture). Headache alone without blood in fluid spaces is not this diagnosis.

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Word Breakdown

sub-

=below or beneath

arachn-

=spider web, referring to arachnoid (middle brain cover)

-haemorrhage

=bursting forth of blood

Literal Meaning: bleeding below the spider-web membrane

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Abbreviations

SAH=Subarachnoid haemorrhage - bleeding into fluid space around the brain

aSAH=Aneurysmal bleed - rupture of artery wall bulge

nSAH=Non-aneurysmal bleed - no bulge seen on vessel imaging (artery pictures)

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Synonyms & Variants

Subarachnoid Hemorrhage›Subarachnoid Bleeding›Aneurysmal Subarachnoid Haemorrhage›

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Category-Specific Context

Subarachnoid haemorrhage is a Disease because it is a vessel-rupture process with course and rescue. It is not a Symptom (patient complaint) such as headache alone. It is not a Sign (exam finding) such as stiff neck alone. It spans aneurysmal and non-aneurysmal origins (bulge and no-bulge levels). Care targets vessel repair with spasm and fluid control rather than pain relief alone.

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Clinical Context & Usage

CLINICAL SETTINGS

Emergency DepartmentNeurosurgical CentreIntensive Care UnitStroke UnitPrimary Care for Sentinel Headache Follow-up

USAGE & DOCUMENTATION NOTES

Use subarachnoid haemorrhage after imaging confirms blood in fluid spaces. State traumatic versus spontaneous when known. Specify aneurysmal versus non-aneurysmal after vessel imaging. Do not use it for unconfirmed thunderclap headache (sudden severe pain) alone.

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Primary Causes & Pathophysiology

PATHOPHYSIOLOGY

Rupture jets arterial blood into clear brain fluid at high pressure. Blood irritates meninges (brain covers) causing stiffness and vomiting. High pressure lowers perfusion (blood flow to brain) and drops consciousness. Breakdown products trigger vasospasm (delayed vessel narrowing) after days. Spasm can cause delayed ischaemia (late stroke from low flow). Blood can block fluid uptake causing hydrocephalus (fluid buildup with swelling).

PRIMARY CAUSES

Ruptured saccular aneurysm of branch arteries

Weak dome tears at branch points and jets blood into fluid space

Cranial trauma with vessel tear

Impact shears surface vessels and bruised brain bleeds outward into fluid

Ruptured arteriovenous malformation (tangled abnormal vessels)

Thin nidus (central tangle) bursts under pressure into fluid and nearby tissue

Perimesencephalic venous leak around midbrain

Low-pressure leak pools in midbrain fluid pockets without artery rupture

Reversible vasoconstriction syndrome (transient vessel tightening)

Severe tightening injures small walls and allows leak, often after birth or vasoactive drugs

Mycotic aneurysm with vasculitis or fistula (infected bulge, vessel inflammation, abnormal connection)

Wall injury from infection or inflammation weakens vessels while fistula raises vein pressure

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Drug-Induced Causes

💊 Cocaine and amphetamines ↗

Mechanism: Cause abrupt pressure spikes with spasm that can rupture a bulge

→ Stop stimulant at once, control pressure with short-acting agents and secure vessel urgently

💊 Anticoagulants including warfarin, apixaban and rivaroxaban ↗

Mechanism: Impair clot forming and enlarge bleeding after rupture

→ Hold drug and reverse urgently with vitamin K plus concentrate for warfarin and specialist input for others

💊 Antiplatelets including aspirin and clopidogrel with thrombolytics including alteplase ↗

Mechanism: Block platelet plug (clot seal) or dissolve clot and prevent sealing

→ Hold agents and give platelets if urgent surgery is needed per local protocol

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Epidemiology

Prevalence:Spontaneous bleeding affects about 6 to 9 people per 100000 each year. It forms about 5 percent of strokes (sudden brain events). Risk rises with age and high pressure. Rates vary with smoking levels and case capture.

Age Group:Peak occurs in adults aged 40 to 65 years with mean near 55 years in many cohorts (study groups). Traumatic cases occur at any age after injury. Midbrain-limited bleeds also cluster in middle adulthood.

Geographic Distribution:Subarachnoid haemorrhage occurs worldwide in all populations. Higher recorded rates occur in Japan and Finland. Differences reflect genes, smoking and detection. Detection tracks access to CT with vessel imaging.

Red Flags & Triage ★

TRIAGE LEVEL

🚨 EMERGENCY

DO NOT MISS — LIFE-THREATENING PRESENTATIONS

Sentinel headache as warning leak days before major bleed
Meningitis with fever
Rebleeding with sudden decline
Acute fluid buildup with drowsiness
Seizure with aspiration risk

URGENT EVALUATION TRIGGERS

Thunderclap headache peaking in seconds
Collapse or reduced consciousness after headache
Stiff neck with vomiting or light sensitivity
Focal deficit or seizure after headache
Severe hypertension with slow pulse suggesting raised pressure

Contraindications & Precautions

CONTRAINDICATIONS

Do not give blood thinners before the bulge is secured
Do not use prolonged antiplatelets without neurosurgical input
Do not allow low pressure or low volume that cuts brain flow
Do not delay vessel imaging while awaiting full workup

SPECIAL PRECAUTIONS

Watch neurology with pressure and fluid balance closely
Use nimodipine (vessel-relaxing drug) when prescribed and watch pressure
Screen for spasm, fluid buildup and salt shifts
Counsel smoking stop with pressure control after recovery

Complications

DOWNSTREAM CLINICAL COMPLICATIONS

Aneurysm rebleeding with sudden decline
Delayed ischaemia from vasospasm (vessel narrowing causing late stroke)
Acute and chronic hydrocephalus (fluid buildup)
Seizures with aspiration risk
Heart and lung injury from brain surge with salt loss
Fatigue with thinking, anxiety and mood change

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Confused With (LASA & DDx) ★

LEXICAL (LASA) — SIMILAR NAMES

Subdural Haemorrhage

Shares meningeal bleeding wording but means blood between outer and middle covers, often from bridging veins after trauma

Epidural Haemorrhage

Confused by haemorrhage wording but means blood outside outer cover, often lens-shaped clot with fracture

Subarachnoid Block

Shares subarachnoid wording but means spinal numbing injection into fluid space, not bleeding

CLINICAL DIFFERENTIAL DIAGNOSES (DDx)

Migraine with aura

Key Distinguishing Feature: Recurrent stereotyped attacks with visual aura and relief, no blood on CT

Bacterial meningitis

Key Distinguishing Feature: Fever with stiff neck and raised markers, fluid shows infection not blood

Intracerebral haemorrhage

Key Distinguishing Feature: Focal deficit with blood inside tissue and less diffuse fluid-space blood

Ischaemic stroke

Key Distinguishing Feature: Sudden focal deficit without thunderclap pain, CT shows no fluid-space blood

Cerebral venous thrombosis

Key Distinguishing Feature: Progressive headache with seizures or disc swelling, vein clot on venography (vein imaging)

Reversible vasoconstriction syndrome

Key Distinguishing Feature: Recurrent thunderclap headaches with reversible narrowing and no bulge found

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Clinical Pearls

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Treat thunderclap headache as bleed until proven otherwise even if pain eases. Sentinel leaks (warning bleeds) often precede major rupture by days.

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Arrange plain CT promptly because sensitivity falls after hours. With high suspicion and negative scan, arrange spinal fluid test or vessel imaging.

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Watch days 4 to 14 for vasospasm (vessel narrowing) with new drowsiness or deficit. New change in this window suggests delayed stroke, not simple recovery.

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Do not label exertional or sex-related thunderclap as migraine without excluding bleed. Vomiting with stiff neck needs emergency workup.

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Nurse flat only if advised with pressure, fluid and salt checks. Give nimodipine (spasm-reducing drug) when prescribed and monitor pressure closely.

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Example Usage & SOAP

CLINICAL SENTENCE

""Sudden thunderclap headache with stiff neck suggests subarachnoid haemorrhage for urgent scan.""

IN A SOAP NOTE

S: 54-year-old woman with sudden worst headache peaking in seconds, vomiting and neck pain. O: Temp 37.2C, BP 178/96, HR 92, RR 20, SpO2 97 percent on air, drowsy but obeying with stiff neck and light sensitivity. A: Suspected subarachnoid haemorrhage with raised pressure. P: Urgent plain CT with vessel imaging, neurosurgical referral, close neuro watch and intensive care planning.

DIFFERENTIAL DIAGNOSIS CONTEXT

Thunderclap onset favours bleed over migraine when pain peaks in seconds with vomiting. Fever with infection markers favours meningitis. Recurrent aura with relief favours migraine. Confirm bleed with CT and vessel imaging (artery pictures) plus spinal fluid test when scan is negative.

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Classifications & Scoring

GRADING SYSTEM

Hunt and Hess Grade

Clinical grade from 1 to 5 using headache, stiffness and consciousness to predict outcome.

GRADING SYSTEM

World Federation of Neurosurgical Societies Grade

Grade using coma score with focal deficit to guide surgery timing.

STAGING SCALE

Fisher Scale

CT scale of blood amount and pattern to predict vessel-narrowing risk.

STAGING SCALE

Modified Fisher Scale

Revised CT scale adding thick blood with ventricle blood to refine spasm prediction.

SCORING TOOL

VASOGRADE

Combined grade with imaging score using grade and modified Fisher to stratify late stroke risk.

SCORING TOOL

Subarachnoid Early Brain Oedema Score

CT swelling score tracking early swelling burden to predict outcome and late events.

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Prognosis

SHORT-TERM OUTCOME

Early death is common with about one third dying within weeks. Rebleeding with early brain injury (initial pressure damage) drives death. Poor grade on arrival predicts worse outcome. Securing the bulge with intensive care improves survival.

LONG-TERM PROGNOSIS

Many survivors keep fatigue and thinking effects for months. Return to work often needs rehab (recovery therapy). Rebleed risk falls sharply after secure repair. Midbrain-limited bleeds have much better recovery than aneurysmal bleeds.

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References & Coding

ICD-10 DIAGNOSTIC CODE

I60

LITERATURE CITATIONS & GUIDELINES

[1]WHO ICD-10 I60 Subarachnoid haemorrhage

[2]American Heart Association guidance for aneurysmal subarachnoid haemorrhage

[3]NICE guidance on subarachnoid haemorrhage from head injury

[4]Harrison's Principles of Internal Medicine cerebrovascular disorders

MEDICAL DISCLAIMER — This content is intended for educational purposes and qualified healthcare professionals only. Always refer to current clinical diagnostic criteria, institutional protocols, and official guidelines. Medobo is not responsible for clinical decisions made based on this content.