Subarachnoid hemorrhage
Subarachnoid hemorrhage is sudden bleeding into the subarachnoid space, most often from a ruptured saccular (berry) aneurysm, presenting as the worst headache of a patient's life. Diagnosis is noncontrast head CT, then lumbar puncture if CT is negative, then catheter angiography to define the aneurysm; management is early aneurysm securement, blood pressure control, and nimodipine to reduce delayed cerebral ischemia from vasospasm.
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What this article covers
- Overview
Definition: subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space, most commonly from rupture of a saccular (berry) aneurysm at a bifurcation of the circle of Willis, most often at…
- Epidemiology
Sentinel leak history: many patients describe a milder headache consistent with a sentinel leak in the 1 to 2 weeks before presentation, an abrupt, severe, transient headache that may be focal or…
- Risk factors
Connective tissue and cystic kidney disease: autosomal dominant polycystic kidney disease and Ehlers-Danlos syndrome are both associated with saccular aneurysm formation.
- Pathophysiology
Aneurysm rupture mechanics: hemodynamic stress at arterial bifurcations, most often the anterior communicating and posterior communicating arteries, progressively weakens the vessel wall until…
- Clinical features
Thunderclap headache: severe headache reaching maximum intensity within 1 minute, classically described as the worst headache of the patient's life; this history alone should trigger urgent evaluation.
- Differential diagnosis
Intracerebral hemorrhage: presents with a focal neurologic deficit and headache but less often the abrupt, maximal-at-onset thunderclap pattern; noncontrast CT shows parenchymal rather than subarachnoid blood.
- Diagnosis
SAH is diagnosed by demonstrating blood in the subarachnoid space, either on neuroimaging or, if imaging is negative, on cerebrospinal fluid analysis; this workup is not delayed for a normal…
- Management
First, stabilize the airway and level of consciousness and admit to a specialized intensive care unit experienced in SAH management, since medical and neurologic complications are frequent and can evolve rapidly.
- Complications
Aneurysmal rebleeding: the leading cause of early morbidity and mortality within the first 48 hours before the aneurysm is secured.
- Prognosis
Overall mortality is high: approximately 50% mortality, with an additional 25% of survivors experiencing significant long-term morbidity.
- Prevention
Blood pressure control: managing chronic hypertension reduces the risk of aneurysm formation and rupture.
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Related articles
- Intracerebral hemorrhage
Spontaneous bleeding into brain parenchyma, most often from chronic hypertension affecting deep penetrating vessels or from cerebral amyloid angiopathy in lobar locations, diagnosed by noncontrast CT and managed with acute blood pressure lowering, reversal of anticoagulation, and surgical evacuation for select cerebellar or deteriorating hemorrhages.
- Acute subdural hematoma
Acute subdural hematoma is venous bleeding between the dura and arachnoid membrane from ruptured bridging veins, producing a crescent-shaped collection that crosses suture lines on CT. Older adults and patients with alcohol use disorder or on anticoagulation are most susceptible; a hematoma over 10 mm, a GCS under 9, or pupillary asymmetry mandate immediate surgical evacuation.
- Increased intracranial pressure
Sustained intracranial pressure above 20-22 mmHg from mass effect, edema, hydrocephalus, or venous outflow obstruction, diagnosed by clinical signs plus invasive monitoring and treated stepwise with head elevation, hyperosmolar therapy (mannitol or hypertonic saline), CSF diversion, and decompressive surgery when refractory.
- Carotid artery dissection
Carotid artery dissection is a tear in the wall of the internal carotid artery creating an intramural hematoma, typically presenting with unilateral head, face, or neck pain, partial Horner syndrome, and ischemic stroke or transient ischemic attack in a young or middle-aged patient. Diagnosis is by MRA or CTA of the neck, and most patients are treated with antiplatelet or anticoagulant therapy.
- Cerebral venous sinus thrombosis
Thrombosis of the dural venous sinuses or cortical veins that impairs cerebral venous drainage and CSF absorption, producing headache, papilledema, focal deficits, or seizures; MRI/MRV or CT venography establishes the diagnosis, and anticoagulation is first-line even when hemorrhagic venous infarction is present.