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| ==Background==
| | ''Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space. Clinical approach differs by etiology — see the appropriate page below:'' |
| *Bleeding into the subarachnoid space (between arachnoid and pia mater)
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| *Ruptured cerebral aneurysm accounts for ~85% of nontraumatic SAH
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| **Most common locations: anterior communicating artery (30%), posterior communicating artery (25%), MCA bifurcation (20%)
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| *Other causes: arteriovenous malformation, perimesencephalic (benign, ~10%), vasculitis, coagulopathy, drug use
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| *Mortality: ~50% overall (25% die before reaching hospital, 25% die within 30 days)
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| *Risk factors:
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| **[[Hypertension]] (most important modifiable risk factor)
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| **Smoking, heavy alcohol use
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| **Family history of SAH or aneurysm (first-degree relative)
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| **Polycystic kidney disease, Ehlers-Danlos, connective tissue disorders
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| **Prior SAH (risk of rebleeding)
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| **Sympathomimetic drug use ([[cocaine]], [[amphetamines]])
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| *Peak incidence: age 40-60; female predominance (1.6:1)
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| ==Clinical Features==
| | *[[Aneurysmal subarachnoid hemorrhage]] — spontaneous/non-traumatic SAH (most commonly ruptured cerebral aneurysm) |
| *"Worst headache of my life" — sudden onset, maximal at onset (thunderclap headache)
| | *[[Traumatic subarachnoid hemorrhage]] — SAH due to blunt or penetrating head trauma |
| *'''Sentinel headache''': warning leak days-weeks before major rupture (present in ~30-50%)
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| *Meningismus (neck stiffness, photophobia) — may take 6-12 hours to develop
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| *Loss of consciousness at onset (~50%)
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| *Nausea, vomiting (common)
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| *Focal neurologic deficits (CN III palsy → posterior communicating artery aneurysm)
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| *Seizures (~10% at onset)
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| *Terson syndrome: intraocular hemorrhage (subhyaloid/vitreous) associated with severe SAH
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| *'''May present as syncope, cardiac arrest, or altered mental status without headache'''
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| ===Hunt-Hess Grading===
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| *Grade I: asymptomatic or mild headache
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| *Grade II: moderate-severe headache, nuchal rigidity, CN palsy
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| *Grade III: drowsiness, confusion, mild focal deficit
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| *Grade IV: stupor, moderate-severe hemiparesis
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| *Grade V: coma, decerebrate posturing
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| ==Differential Diagnosis==
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| *Primary [[headache]] (migraine, tension, cluster) | |
| *[[Meningitis]] / [[encephalitis]]
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| *[[Intracerebral hemorrhage]]
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| *[[Cerebral venous sinus thrombosis]]
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| *[[Hypertensive emergency]]
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| *Reversible cerebral vasoconstriction syndrome (RCVS)
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| *[[Cervical artery dissection]]
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| *[[Pituitary apoplexy]]
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| {{Headache DDX}}
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| ==Evaluation==
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| ===Non-Contrast CT Head===
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| *First-line test
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| *Sensitivity ~98% within 6 hours of onset, ~93% at 12 hours, decreasing to ~50% by day 5-7<ref>Perry JJ, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage. ''BMJ''. 2011;343:d4277. PMID 21768192</ref>
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| *Fisher grade: amount of blood predicts vasospasm risk
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| *Modern thin-cut CT with experienced radiologist within 6 hours may approach 100% sensitivity
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| ===Lumbar Puncture===
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| *Required if CT negative and clinical suspicion remains
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| *Classic finding: xanthochromia (yellow discoloration from bilirubin in CSF)
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| **Takes 6-12 hours to develop — LP performed <6 hours after onset may miss xanthochromia
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| *'''Elevated RBCs that do NOT clear''' across sequential tubes (vs traumatic tap which clears)
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| *Elevated opening pressure
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| *Traumatic tap vs SAH: controversial; visual xanthochromia and clinical context are most important
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| ===Ottawa SAH Rule===
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| *For alert patients >15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour
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| *100% sensitivity (validation study) — if none present, SAH effectively ruled out<ref>Perry JJ, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. ''JAMA''. 2013;310(12):1248-1255. PMID 24065011</ref>:
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| **Age ≥40
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| **Neck pain or stiffness
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| **Witnessed loss of consciousness
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| **Onset during exertion
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| **Thunderclap headache (instant peak)
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| **Limited neck flexion on exam
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| ===CT Angiography (CTA)===
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| *Obtain with initial CT if SAH confirmed or high suspicion
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| *Identifies aneurysm location and morphology for surgical/endovascular planning
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| *Sensitivity >95% for aneurysms >3 mm
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| ===Labs===
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| *CBC, BMP, coagulation studies (PT/INR, PTT)
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| *Type and screen
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| *Troponin (neurogenic myocardial stunning)
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| *Finger stick glucose
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| ==Management==
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| ===ED Management===
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| *ABCs, IV access, continuous monitoring
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| *Blood pressure control:
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| **Target SBP <160 mmHg until aneurysm secured (reduce rebleeding risk)
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| **Nicardipine infusion (5-15 mg/hr, titrate q5min) — preferred
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| **Labetalol 10-20 mg IV q10-20min
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| **Avoid nitroprusside (increases ICP)
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| *Seizure management: benzodiazepines acutely; prophylactic AEDs controversial
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| *Treat headache: acetaminophen; short-acting opioids cautiously
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| **Avoid ketorolac (platelet inhibition)
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| *Aminocaproic acid (tranexamic acid): may reduce rebleeding risk before aneurysm secured — 4g IV loading dose (discuss with neurosurgery)
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| *Reverse anticoagulation if applicable
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| ===Definitive Treatment===
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| *Neurosurgery/neurointerventional consultation emergently
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| *Aneurysm securing (within 24 hours ideally):
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| **Endovascular coiling (preferred for most aneurysms) OR
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| **Surgical clipping
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| *ICU admission
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| ===Complications (Post-Hemorrhage)===
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| *'''Rebleeding''': highest risk in first 24 hours (~4%); '''most devastating complication'''
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| *Vasospasm: occurs days 3-14 (peak day 7); monitor with daily TCDs
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| **Treat with nimodipine 60 mg PO/NG q4h x 21 days (improves outcomes; does not prevent vasospasm)
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| **Triple-H therapy (hypertension, hypervolemia, hemodilution) — only after aneurysm secured
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| *Hydrocephalus: acute (requires EVD) or chronic (VP shunt)
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| *Hyponatremia: cerebral salt wasting vs SIADH
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| *Neurogenic cardiac dysfunction: Takotsubo-like, neurogenic pulmonary edema
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| ==Disposition==
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| *All confirmed SAH: emergent neurosurgical consultation and ICU admission
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| *Transfer to neurosurgical center if local capabilities unavailable
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| *SAH ruled out (negative CT + negative LP): may discharge with headache precautions and PCP follow-up
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| == Calculators ==
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| {{Ottawa SAH Calculator}}
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| {{Fisher Scale Calculator}}
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| ==See Also==
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| *[[Intracerebral hemorrhage]] | |
| *[[Subdural hemorrhage]]
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| *[[Epidural hemorrhage]]
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| *[[Headache]]
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| *[[Thunderclap headache]]
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| *[[Lumbar puncture]]
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| *[[Modified brain injury guideline (mBIG)]] — ''applies only to '''traumatic''' SAH/intracranial hemorrhage; '''not''' for spontaneous/aneurysmal SAH''
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| ==References==
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| <references/>
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| *Connolly ES Jr, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline from the AHA/ASA. ''Stroke''. 2012;43(6):1711-1737. PMID 22556195
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| *Edlow JA, et al. Diagnosis of subarachnoid hemorrhage. ''Stroke''. 2023;54(4):1058-1072. PMID 36848423
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| *van Gijn J, et al. Subarachnoid haemorrhage. ''Lancet''. 2007;369(9558):306-318. PMID 17258671
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| [[Category:Neurology]] | | [[Category:Neurology]] |
| [[Category:Critical Care]] | | [[Category:Critical Care]] |
| [[Category:Neurosurgery]]
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