Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 24-08: Stroke + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Sudden ("thunderclap") severe headache Signs of meningeal irritation usually present Obtundation is common Focal deficits frequently absent +++ General Considerations ++ 5–10% of strokes are due to subarachnoid hemorrhage Trauma is the most common cause Frequently results from the rupture of an arterial saccular ("berry") aneurysm or from an arteriovenous malformation Factors associated with a higher risk of subarachnoid hemorrhage Older age Female sex "Non-white" ethnicity Hypertension Tobacco smoking High alcohol consumption (exceeding 150 g per week) Previous symptoms Posterior circulation aneurysms Larger aneurysms See also Aneurysm, Intracranial See Table 24–3 + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs ++ Sudden onset of headache with severity never experienced previously by the patient May be followed by nausea and vomiting and loss or impairment of consciousness (transient, or progressing to coma and death) Patient is often confused and irritable and may show other symptoms of an altered mental status Nuchal rigidity and other signs of meningeal irritation are seen, except in deeply comatose patients Focal neurologic deficits may be present and may suggest the site of the underlying lesion See also Aneurysm, Intracranial +++ Differential Diagnosis ++ Meningitis Migraine Intracerebral hemorrhage Ischemic stroke + Diagnosis Download Section PDF Listen +++ +++ Laboratory Findings ++ Cerebrospinal fluid demonstrates an elevated red blood cell count Peripheral leukocytosis Transient glycosuria +++ Imaging Studies ++ CT scan (preferably with CT angiography) should be performed immediately to confirm that hemorrhage has occurred and to search for its source CT is faster and more sensitive in detecting hemorrhage in the first 24 hours than MRI Rarely, CT is normal in patients with suspected hemorrhage If CT is normal in such patients, examine cerebrospinal fluid for blood or xanthochromia before the possibility of subarachnoid hemorrhage is discounted +++ Diagnostic Procedures ++ Electrocardiographic evidence of arrhythmias or myocardial ischemia has been well described and probably relates to excessive sympathetic activity Cerebral arteriography helps determine the source of bleeding Bilateral carotid and vertebral arteriography are necessary because aneurysms are often multiple, while arteriovenous malformations may be supplied from several sources CT angiography or MR angiography may also be revealing but is less sensitive than conventional arteriography + Treatment Download Section PDF Listen +++ +++ Medications ++ Phenytoin to prevent seizures; however, evidence of benefit is conflicting +++ Surgery ++ Surgical clipping of aneurysm base or endovascular treatment by coil embolization is definitive treatment, ideally performed within 2 days of the hemorrhage +++ Therapeutic Procedures ++ Major aim is to prevent further hemorrhage Conscious patients Confine to bed Advise against exertion or straining Treat symptomatically for headache and anxiety Give laxatives or stool softeners Systolic blood pressure should be lowered to 140 mm Hg until the aneurysm is definitively treated + Outcome Download Section PDF Listen +++ +++ Complications ++ Hydrocephalus Cerebral vasospasm Renal salt-wasting May develop abruptly during first several days of hospitalization The resulting hyponatremia and cerebral edema may exacerbate intracranial hypertension and may require carefully titrated treatment with oral sodium chloride or intravenous hyperosmotic sodium solution Hypopituitarism may occur as a late complication +++ Prevention ++ See Aneurysm, Intracranial +++ Prognosis ++ Approximately 20% of patients with aneurysms have further bleeding within 2 weeks and 40% within 6 months The greatest risk of further aneurysmal hemorrhage is within a few days of the initial bleed, thus early obliteration (within 2 days) is preferred When an arteriovenous malformation is responsible, treatment may be delayed until the patient's state is optimal +++ When to Refer ++ All patients +++ When to Admit ++ All patients + References Download Section PDF Listen +++ + +Lawton MT et al. Subarachnoid hemorrhage. N Engl J Med. 2017 Jul 20;377(3):257–66. [PubMed: 28723321] + +Lindgren A et al. Endovascular coiling versus neurosurgical clipping for people with aneurysmal subarachnoid hemorrhage. Cochrane Database Syst Rev. 2018 Aug 15;8:CD003085. [PubMed: 30110521] + +Perry JJ et al. Validation of the Ottowa subarachnoid hemorrhage rule in patients with acute headache. CMAJ. 2017 Nov 13;189(45):E1379–85. [PubMed: 29133539]