Subarachnoid Hemorrhage

II. Background

See Traumatic Intracranial Subarachnoid Hemorrhage
This page refers primarily to Nontraumatic Subarachnoid Hemorrhage (Aneurysmal Subarachnoid Hemorrhage)

III. Epidemiology

Of the 10% of all CVAs that are hemorrhagic, 3% are Aneurysmal SAH
1. Incidence: 14.5 in 100,000
Represents 1-3% of Headache presentations to U.S. emergency departments (20,000 cases/year)
1. Subarachnoid Hemorrhage diagnosis is missed in up to 30% of cases on initial evaluation

IV. Causes

Cerebral Aneurysm (e.g. Berry Aneurysm) rupture
1. Incidence: 50 per 100,000 patients over age 30 years old
2. Age: Rupture peaks at 40-60 years old (mean age 53 years old)
3. Higher Incidence in African American
4. Gender: Women represent 70% of ruptured SAH
  1. Post-Menopause, female gender Relative Risk doubles to 2
Congenital Arteriovenous Malformation (AVM)
1. Most common cause of Subarachnoid Hemorrhage in children (rare event)
Trauma (most common cause of Subarachnoid Hemorrhage)
1. See Traumatic Intracranial Subarachnoid Hemorrhage
2. See Head Injury
3. Fall with Head Injury in the elderly
4. Motor Vehicle Accident in younger patients

V. Risk factors

See Cerebral Aneurysm
Most significant risk factors
1. Hypertension (especially >160/100)
2. Tobacco Abuse
Other predisposing factors
1. Bleeding Diathesis or Anticoagulation
2. Autosomal Dominant Polycystic Kidney Disease
3. Hyperlipidemia
4. Diabetes Mellitus
5. Substance Abuse
  1. Heavy Alcohol use (>2 drinks/day)
  2. Cocaine
  3. Methamphetamine
6. Connective Tissue Disease
  1. See Cerebral Aneurysm
Other possible risk factors
1. Obstructive Sleep Apnea

VI. Symptoms

Classic presentation (highly suggestive of Subarachnoid Hemorrhage)
Headache Characteristics: Severe, sudden, atypical and unrelenting
1. Sudden onset Thunderclap Headache
2. "Worst Headache of my life" (+LR 1.20, less predictive than other red flags as below)
3. Headache reaches maximum intensity in minutes (<10 to 60 minutes)
4. Thunderclap Headache is absent in up to 25% of Aneurysmal SAH
5. Continued unrelenting Headache
6. Headache different in characteric than prior Headaches (or no Headache History previously)
  1. Different location is less predictive of SAH
  2. Inadequate pain response to typical Headache Management is less predictive of SAH
  3. Adequate Headache response to analgesia does not exclude Subarachnoid Hemorrhage
Headache regions most common
1. Orbital Headache
2. Occipital Headache with neck stiffness
Associated symptoms
1. Onset during exertion
2. Nausea and Vomiting (75% of cases)
3. Dizziness
4. Loss of consciousness (may be fleetingly brief) at Headache onset
5. Altered Level of Consciousness
6. Transient motor deficits (e.g. sudden buckling of legs)
7. Vision change
8. Incoordination
9. Seizure (at Headache onset)
Initial herald bleed (sentinel Hemorrhage)
1. Warning leak of small volume
2. May precede full Cerebral Aneurysm rupture in >30-50% of cases
3. Present as atypical, new or different Headaches with rapid onset
  1. May last days at a time
  2. May occur weaks before a major SAH

VII. Signs

Neurologically intact in 40% of SAH patients on presentation
Identify subtle focal neurologic changes
Meningismus (e.g. Nuchal Rigidity)
Ocular Motor Nerve palsy (especially third Cranial Nerve palsy)
Ataxia
Fundoscopic exam
1. Papilledema
2. Subhyaloid Hemorrhage (red blood layering behind the eye)
3. Intraocular Hemorrhage (Terson Syndrome)
  1. Found in 1 in 7 patients (up to 46% in some studies) with Subarachnoid Hemorrhage
  2. Associated with poor prognosis and increased mortality

VIII. Labs

Complete Blood Count
Serum chemistry
ProTime (PT, INR)
Partial Thromboplastin Time (PTT)

IX. Grading

Hunt and Hess Classification
1. Grade 1: Minimal Headache, slightly stiff neck (may represent sentinel bleed)
2. Grade 2: Moderate to severe Headache, stiff neck, Cranial Nerve palsy
3. Grade 3: Drowsy
4. Grade 4: Stuporous. Moderate to severe Hemiparesis
5. Grade 5: Deep coma. Decerebrate rigidity
6. Hunt (1968) J Neurosurg 28(1): 14-20 [PubMed]
Modified Fisher Scale
1. Based on imaging findings of Subarachnoid Hemorrhage (SAH) and intraventricular Hemorrhage (IVH)
2. May predict SAH associated cerebral vasospasm risk (Ischemic CVA risk)
3. Grade 0: No SAH and No IVH
4. Grade 1: Thin SAH (<1 mm) and No IVH
5. Grade 2: Thin SAH (<1 mm) and IVH
6. Grade 3: Thick SAH (>1 mm) and No IVH
7. Grade 4: Thick SAH (>1 mm) and IVH
8. Frontera (2006) Neurosurgery 59(1): 21-7 [PubMed]
World Federation of Neurological Surgeons Scale
1. Based on Glasgow Coma Scale (GCS) and Motor Exam
2. Grade 1: GCS 15 and NO motor deficit
3. Grade 2: GCS 13 to 14 and NO motor deficit
4. Grade 3: GCS 13 to 14 and FOCAL motor deficit
5. Grade 4: GCS 7 to 12 with or without motor deficit
6. Grade 5: GCS <7 with or without motor deficit

X. Precautions: Red Flags suggestive of further evaluation for SAH

Ottawa Subarachnoid Hemorrhage Rule for age >15 years (all absent excludes nearly 100% of SAH cases)
1. Age over 40 years old
2. Witnessed loss of consciousness (+LR: 3.77)
3. Neck Pain or stiffness (more suggestive of severe SAH, +LR 2.29)
4. Limited neck flexion on exam
5. Thunderclap headadache (severity peaks rapidly, within 15-60 minutes)
6. Onset during exertion (Exertional Headache, +LR 2.16)
Other red flag findings (outside Ottawa Rules)
1. Arrival to Emergency Department via Ambulance
2. Hypertension (>160/100)
References

XI. Differential Diagnosis

See Headache Red Flag (includes Thunderclap Headache)
See Headache Causes
See Hemorrhagic CVA
Tension Headaches may present in similar fashion to a herald bleed
1. Do not miss herald bleed phase of Subarachnoid Hemorrhage

XII. Diagnosis

CT Head without contrast
1. Findings
  1. Aneurysmal SAH demonstrates hyperdense blood in Subarachnoid Cisterns
  2. Traumatic SAH demonstrates blood along brain convexity
2. Overall misses 5% of Subarachnoid Hemorrhage (may be 2% with new 5th generation CT scans)
  1. False Negative Rate increases if Hemoglobin <10 g/dl (results in isodense SAH appearance)
  2. False Negative Rate also increased with delay of CT from time from onset of Headache (see below)
  3. Despite this, ED physicians performed CT without LP in 50% of "worst Headache of life" patients
    1. Morgenstern (1998) Ann Emerg Med 32(3 Pt 1): 297-304 [PubMed]
3. Third generation CT scans read by a qualified radiologist are very accurate when performed early after Headache
  1. CT Head within 6 hours of acute onset severe Headache in neurologically intact patient
  2. Caveats
    1. Lumbar Puncture should still be performed after negative CT Head in high suspicion cases
    2. Studies excluded high risk patients
      1. Neurologic deficits
      2. Prior Subarachnoid Hemorrhage
      3. Papilledema
      4. Ventricular Shunt
      5. Brain Neoplasms
    3. Backes paper was in Netherlands at referral center
      1. High SAH Incidence, with imaging read by neuroradiology
    4. Reviews of the Perry paper suggest flaws (inconsistent follow-up and LP protocol)
      1. Newman (2012) EM:RAP 12(3): 6-7
    5. Later study showed 5% miss rate with early CT Head
      1. Perry (2020) Stroke 51(2):424-30 PMID:31805846 [PubMed]
  3. Indications for Head CT without LP (expert opinion)
    1. Head CT within 6 hours of Thunderclap Headache onset AND
    2. Normal Neurologic Exam AND
    3. CT read by radiologist AND
    4. No Neck Pain (Head CT may miss spinal AVM) AND
    5. Informed Consent with reliable patient
      1. Risk of missed SAH on CT Head alone is at least 1 in 700 within first 6 hours
    6. Edlow (2012) Stroke 43(8): 2031-2 [PubMed]
4. Head CT Test Sensitivity for SAH decreases within days of event (most sensitive closest to Headache onset)
  1. CT sensitivity decreases after first 6-12 hours
  2. Day 3: 95% Test Sensitivity
  3. Day 5: 85% Test Sensitivity
  4. Day 7: 50% Test Sensitivity
  5. Day 14: 30% Test Sensitivity
Lumbar Puncture
1. Indicated for high clinical suspicion for SAH but negative CT Head (esp. >6 hours from Headache onset)
2. Most useful in Hunt and Hess Scale 1 and 2 (more severe events are typically seen on CT)
3. Findings consistent with Subarachnoid Hemorrhage
  1. CSF RBCs: >2000 in Tube 4 within 2-12 hours after Headache
  2. CSF Leukocytes and Protein may also be increased
  3. Increased opening pressure
  4. Xanthochromia in centrifuged Cerebrospinal fluid (may be absent in first 12 hours)
    1. Most sensitive CSF finding for SAH
4. Efficacy for diagnosis of SAH
  1. Perry study used<2000 CSF RBCs in last tube AND no Xanthochromia
    1. Negative Predictive Value: 100%
    2. Test Sensitivity: 100%
    3. Test Specificity: 91.2%
    4. Perry (2015) BMJ 350:h568 +PMID:25694274 [PubMed]
  2. Dupont study used <100 CSF RBCs in last tube AND no Xanthochromia
5. SAH diagnosis made by LP when CT Head was negative
  1. True positive Lumbar Puncture for SAH: 0.4% (PPV 9.8%)
  2. False positive Lumbar Puncture: 4.2%
  3. Sayer (2015) Acad Emerg Med 22(11): 1267-73 +PMID:26480290 [PubMed]
Cerebral CT Angiogram (CTA)
1. Indications
  1. Positive imaging or Lumbar Puncture for SAH (to identify bleeding source)
  2. Equivocal Lumbar Puncture (differentiate from bloody tap)
2. Avoid using CTA instead of Lumbar Puncture (unless Non-contrast CT positive)
  1. CT increases risk to 1% for False Positives (small insignificant aneurysms)
  2. Incidental, unrelated aneurysms are identified in 2.3% of patients
  3. CT Angiogram is poorly sensitive for blood
  4. Unnecessary radiation exposure
  5. LP remains the standard of care for ruling out Subarachnoid Hemorrhage
    1. Indicated when clinical suspicion is high, but noncontrast CT Head is normal
  6. Bederson (2009) Stroke 40(3): 994-1025 [PubMed]
  7. Worrall in Majoewsky (2012) EM:Rap 12(12): 3 [PubMed]
3. Efficacy: Aneurysms 4 mm or larger
  1. Test Specificity: 100%
  2. Tests Sensitivity: 96-99.7%
Catheter angiography
1. Indicated by neurosurgery to identify source of bleeding if not identified on CTA
2. Increased risk of neurologic complications and rebleeding than CTA
3. Source may not be identified in up to 20-25% of cases with first catheter angiography
  1. Continue to monitor patient closely in hospital
  2. Repeat catheter angiography in 7 days if initial angiography negative for SAH aneurysmal source
Magnetic Resonance Imaging
1. May be an alternative to non-contrast Head CT in a stable patient
2. Consider in delayed presentation due to its sustained abnormal patterns after SAH (see efficacy below)
  1. MRI Test Sensitivity for SAH increases with time (while CT Head sensitivity decreases after 6 hours)
  2. T2 weighted images cannot distinguish Hemorrhage from CSF
  3. FLAIR and echo T2 images, in contrast, have good Test Sensitivity for Hemorrhage at 12 to 48 hours
    1. Hemorrhage appears bright white on Fluid Attenuated Inversion Recovery (FLAIR) images
    2. Hemorrhage appears black on echo T2 ("T2-star") images
3. Disadvantages compared with Head CT
  1. Much longer acquisition times are not viable for an Unstable Patient
  2. CT Head is better at imaging acute Intracerebral Hemorrhage
4. Efficacy
  1. Test Sensitivity is reduced in the anterior Midbrain (perimesencephalic region)
    1. Region may account for up to 38% of nontraumatic SAH
  2. Flair Sequences
    1. Day 0 to 5 of Headache: 100% Test Sensitivity for SAH
    2. Best Test Sensitivity for frontoparietal, tempero-occipital and Sylvan cistern bleeding events
  3. Susceptibility Weighted Images (SWI)
    1. Best Test Sensitivity for interhemispheric and intraventricular Hemorrhage
  4. T2-Weighted gradient echo
    1. Days 6 to 30 of Headache: 100% Test Sensitivity for SAH
  5. References
    1. Sohn (2005) AJNR Am J Neuroradiol 26(3):662-5 +PMID: 15760884 [PubMed]
    2. Yuan (2005) J Chin Med Assoc 68(3): 131-7 [PubMed]
Magnetic Resonance Angiography
1. Not routinely recommended as an alternative to CT angiogram in identifying SAH source
2. Indicated for stable patients in whom iodinated contrast for CTA is contraindicated
3. Efficacy
  1. Aneurysm 5 mm or larger: 85-100% Test Sensitivity
  2. Aneurysm less than 5mm: 56%

XIII. Management: General

Neurosurgery Consultation (emergent)
1. Aneurysmal repair within first 24 hours has best outcomes
2. Even severe SAH (Hunt and Hess 4-5) has a favorable outcome in 40% of patients who undergo repair
3. Endovascular coiling has initial benefits over surgical clipping
  1. Higher one year survival: 23.7% versus 30.6%
  2. Shorter delay to procedure: 1.1 versus 1.7 days
  3. (2002) Lancet 360:1267-74 [PubMed]
4. Surgical clipping has a lower rate of recurrence than endovascular coiling (0.6% vs 2% at 30 days)
  1. Surgical clipping may be preferred in younger patients
Head of Bed at 30 degrees
1. Indicated in most cases of Intracranial Hemorrhage
2. Avoid if hypotensive
3. See Increased Intracranial Pressure below
Consider RSI and intubation
Blood Pressure management
1. See Hypertension Management for Specific Emergencies
2. Overall goals (balance two juxtaposed criteria)
  1. Cerebral Perfusion Pressure >60 mmHg
  2. Avoid worsening bleeding into Hemorrhagic CVA
  3. Avoid recurrent Hemorrhage if bleeding has stopped
3. Normal Intracranial Pressure
  1. Target Systolic Blood Pressure <160 mmHg (some guidelines suggest <140 mmHg)
  2. Contrast with Spontaneous Intracerebral Hemorrhage, where target is <180 mmHg
    1. Qureshi (2016) N Engl J Med 375(11):1033-43 [PubMed]
4. Increased Intracranial Pressure (suspected or confirmed)
  1. Systolic Blood Pressure >180 mmHg (or MAP >130 mmHg)
    1. Continuous Antihypertensive infusion (e.g. Nicardipine) is preferred
    2. Intermittent Intravenous Antihypertensives (e.g. Labetalol) is an alternative
  2. Systolic Blood Pressure >200 mmHg (MAP<150 mmHg)
    1. Continuous Antihypertensive infusion (e.g. Nicardipine)
Seizure Management
1. Seizures occur in 15% of patients after Aneurysmal SAH (more common with SAH clipping than with coiling)
2. Treat Seizures as they occur and continue anticonvulsants for 7 days after Seizure
3. Electroencephalogram (EEG) monitoring if Decreased Level of Consciousness
4. Prophylaxis Indications (no longer recommended routinely without Seizures)
  1. High grade Aneurysmal SAH
  2. Hydrocephalus
  3. Cortical infarct
  4. Intracranial Hemorrhage
  5. Middle Cerebral Artery aneurysm
Metabolic disorders (risk of delayed cerebral ischemia)
1. Hyponatremia
  1. Consider Fludrocortisone (avoid Hydrocortisone)
2. Hypovolemia
  1. Maintain euvolemia with Intravenous Fluids, but avoid hypervolemia
  2. Prevent vasospasm with good hydration
3. Hyperglycemia
  1. Glycemic control (but avoiding intensive Glucose management)
Other measures
1. Minimize cough with Cough Suppressants
2. Minimize Pain (Dilaudid, Morphine sulphate)
3. Minimize Constipation
4. Encourage early mobilization after SAH
  1. Decreases aneurysmal vasospasm and improves function
5. VTE Prophylaxis after SAH management
  1. Venous Thromboembolism occurs in 4 to 24% with acute SAH

XIV. Management: Intracranial Pressure

Signs of Increased Intracranial Pressure
1. Papilledema
2. Hypertension with Bradycardia (Cushing Reflex)
3. Contralateral paralysis with dilated pupil (Uncal Herniation)
4. Head CT with signs of Hemorrhage
Indications for monitoring Intracranial Pressure (pressure catheter)
1. Glasgow Coma Scale <8
2. Transtentorial Herniation signs
3. Significant intraventricular Hemorrhage
4. Hydrocephalus
Management
1. Elevate head of bed to 30 degrees (see above)
2. Target Cerebral Perfusion Pressure 50-70 mmHg
3. Mannitol
  1. Start at 1 gram/kg and titrate
  2. Check Serum Osmolality (keep 305-315)
  3. Check Serum Sodium every 6 hours (keep >140)
4. Hypertonic Saline
  1. Previously considered alternative to Mannitol in Increased Intracranial Pressure
  2. Does not improve Intracranial Pressure or benefit mortality in Severe Closed Head Injury
    1. Berger-Pelleiter (2016) CJEM 18(2): 112-20 +PMID:26988719 [PubMed]

XV. Management: Anticoagulant Reversal

See Anticoagulant Reversal
General agents
1. Tranexamic Acid (not FDA approved)
Warfarin
1. Prothrombin Complex Concentrate 4 (PCC4) or if not available, Fresh Frozen Plasma (FFP) AND
2. Vitamin K 10 mg IV
Heparin or Low Molecular Weight Heparin (e.g. Enoxaparin or Lovenox)
1. Protamine
Factor Xa Inhibitors (e.g. Rivoroxaban or Xarelto, Apixaban or Eliquis) or Direct Thrombin Inhibitors (e.g. Dabigatran)
1. Factor VII Inhibitor Bypass Activity (FEIBA)
2. Recombinant activated Clotting Factor VII (rFVIIa or NovoSeven)
3. Prothrombin Complex Concentrate 4 (PCC4, Kcentra or outside U.S. Octaplex, Beriplex)
Aspirin only
1. Historical: Transfuse 1 unit (equivalent to 6 pack) of Platelets
  1. Platelet Transfusion associated with worse outcomes (death and worse neurologic function)
  2. Baharoglu (2016) Lancet 387(10038):2605-13 +PMID: 27178479 [PubMed]
ADP Inhibitors (e.g. Clopidogrel)
1. Historical: Transfuse 2 units (equivalent to 12 pack) of Platelets
  1. Repeat every 12-24 hours for a large Hemorrhage
  2. Platelet Transfusion associated with worse outcomes (see above, under Aspirin)
2. Desmopressin (DDAVP) 0.3 mcg/kg

XVI. Management: Small Traumatic Subarachnoid Hemorrhage

Background
1. Small Traumatic Subarachnoid Hemorrhage (SAH) is a common finding on CT Head after Closed Head Injury
2. Unlike Aneurysmal SAH, small Traumatic SAH is much less likely to have neurologic decompensation
  1. Cerebral Vasoconstriction is much less likely in Traumatic SAH (contrast with Aneurysmal SAH)
Monitoring
1. Serial Neurologic Exams
2. Repeat CT Head in 6 hours after first imaging CT Head
  1. Indicated for early discharge or as needed for Neurologic Exam changes on exam
Indications to consider early discharge after repeat Head CT (at 6 hours)
1. Glasgow Coma Scale (GCS) 15
2. No Anticoagulation or antiplatelet agents
3. Safe home social situation (e.g. not homeless, available for close interval follow-up)
4. Small peripheral Subarachnoid Hemorrhage consistent with Traumatic SAH
  1. Central SAH is much more suggestive of Aneurysmal SAH
References
1. Marcolini and Swaminathan in Swadron (2023) EM:Rap 23(5): 13-4

XVII. Prognosis

Aneurysmal Subarachnoid Hemorrhage diagnosed at initial medical contact
1. Good or excellent outcome: 91% (contrast with 53% for incorrect initial diagnosis)
2. Mayer (1996) Stroke 27(9): 1558-63 [PubMed]
Missed Aneurysmal Subarachnoid Hemorrhage
1. Mortality risk at 2 hours: 20%
2. Mortality risk at 7 days: 40%
3. Rebleeding risk: 20% in first 2 weeks (esp. in first 72 hours, 1.5% risk per day)
4. Prehospital mortality: 10 to 15%
Outcomes of those surviving initial Aneurysmal Subarachnoid Hemorrhage
1. Poor neurologic recovery and mortality in 30 days is 30 to 60%
2. Those surviving beyond first 30 days, have residual significant neurologic morbidity in 30 to 50%
3. Rebleeding within 6 months in untreated aneurysm: 30%

XVIII. Complications

Very high Neurologic Morbidity and Mortality (see prognosis above)
Aneurysmal Rebleeding
Acute Respiratory Distress Syndrome (ARDS, occurs in up to 4% of SAH cases)
Obstructive Hydrocephalus
1. Complicates SAH in 20% of cases within 2 weeks of Hemorrhage onset
2. Lumbar Puncture of CSF reduces risk of secondary delayed cerebral ischemia
Vasospasm and cerebral Ischemia (Ischemic CVA risk)
1. Delayed cerebral ischemia occurs in up to 30% of patients
2. Secondary vasospastic ischemia typically occurs at 3 to 14 days after SAH
3. Associated with GCS decrease of 2 points within 1 hour
4. Predicted by CT perfusion study at 3 days after Aneurysmal SAH
5. Consider CTA Brain or transcranial Doppler Ultrasound of Middle Cerebral Artery for vasospasm
6. Consider Nimodipine for prevention of delayed ischemia
7. Consider intraarterial vasodilator administration for treatment (avoiding Hypotension)
Unconscious Patients
1. Consider neurostimulants (e.g. Modafinil, Amantadine) to improve consciousness and function
Cognitive deficits
1. Present in 50% of patients overall (and 25% of patients with good outcomes)
2. See Montreal Cognitive Assessment
3. Consider Cognitive Rehabilitation
4. Longterm increased risk for Dementia (RR 3)
5. Risk Factors for cognitive deficits
  1. Hydrocephalus
  2. Seizures
  3. Fever
  4. Prolonged Intensive Care
  5. Delayed cerebral ischemia
Mental health conditions

XIX. References

Swaminathan and Marcolini in Herbert (2017) EM:Rap 17(6):17-18
Burgess and Stowens (2014) Crit Dec Emerg Med 28(5): 2-13
Levy (2015) Crit Dec Emerg Med 29(4): 10-4
Arnold (2024) Am Fam Physician 110(2): 204-6 [PubMed]
Bederson (2009) Stroke 40(3): 994-1025 [PubMed]
Cohen-Gadol (2013) Am Fam Physician 88(7): 451-6 [PubMed]
Hoh (2023) Stroke 54(7): 314-70 [PubMed]
Kane (2023) Am Fam Physician 108(4): 386-95 [PubMed]
van Gijn (2007) Lancet 369(9558): 306-18 [PubMed]

II. Background

III. Epidemiology

IV. Causes

V. Risk factors

VI. Symptoms

VII. Signs

VIII. Labs

IX. Grading

X. Precautions: Red Flags suggestive of further evaluation for SAH

XI. Differential Diagnosis

XII. Diagnosis

XIII. Management: General

XIV. Management: Intracranial Pressure

XV. Management: Anticoagulant Reversal

XVI. Management: Small Traumatic Subarachnoid Hemorrhage

XVII. Prognosis

XVIII. Complications

XIX. References

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