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Initial Evaluation of Suspected Subarachnoid Hemorrhage (October 1996)

Subarachnoid hemorrhage (SAH) is an acute life-threatening medical emergency associated with high mortality and morbidity. Outcome can be significantly improved with rapid diagnosis and triage to neurosurgical treatment. The clinical management goals of these guidelines are to:

  • Identify patients with clinical suspicion of subarachnoid hemorrhage;
  • Proceed promptly with the appropriate evaluation of these patients;
  • Arrange for speedy triage and referral of patients with SAH to a neurosurgical center.

Initial Presentation:
The sudden onset of the "worst-ever" headache with transient impairment ofconsciousness followed by nausea, vomiting, nuchal rigidity, and focal neurological signsis the classic presentation of SAH. The headache can vary in character, being eithergradual or step-wise in evolution and localized or holocranial in location. Disturbancesin consciousness as a result of the hemorrhage, secondary seizures, or hydrocephalus maybe manifested by confusion and transient of prolonged coma. Autonomic symptoms such aslow-grade fever, diaphoresis, shivering, hypertension, and cardiac arrhythmia are alsocommon. Sighs and symptoms of meningeal irritation, as manifested by neck of back pain andstiffness, are occasionally more prominent that the headache itself. Neuroophthalmologicmanifestations such as photophobia, blurred vision, eye pain, and limitations ofextraocular movement may be present. Focal neurological symptoms can result from the masseffect of the aneurysm or hematomas and cerebral ischemia. Since the overall presentationis often not classic, a delay in diagnosis and referral for neurosurgical care oftenoccurs. Even in large medical centers, misdiagnosis has occurred in up to 50% ofpatients. (8-11)

A substantial proportion of patients with ruptured cerebral aneurysms have warningsymptoms. The interval from the initial warning to a major aneurysm rupture is typicallyfrom six to 20 days. Although patients with a warning sign, e.g. a "sentinelleak," appear less ill than patients with a larger subarachnoid hemorrhage, theirprognosis with treatment is better, making the need fro correct diagnosis more urgent. (15)

Thunderclap headache is a paroxysmal, excruciating hheadachewwhichclinically resemblesSAH. However, no evidence of subarachnoid hemorrhage is found on CT scan or lumbarpuncture. The prognosis for these patients is extremely good and cerebral angiography isnot indicated. (16)

Diagnostic Tests:
The sudden onset of the "worst-ever" headache with transient impairment ofconsciousness followed by nausea, vomiting, nuchal rigidity, and focal neurological signsis the classic presentation of SAH.

A CT scan of the brain without contrast is the diagnostic procedure of choice for suspected SAH and should be obtained urgently.

When the CT scan is negative, lumbar puncture (LP) must be done in cases of suspected SAH.


  1. A CT scan should be done urgently in all patients with suspected SAH. The scanshould be interpreted immediately by an experienced physician. (Expert Opinion: Strong Consensus)

  1. When the CT scan is negative, a lumbar puncture must be done by an experienced physician. (Expert Opinion: Strong Consensus)
  1. The results of CT and/or LP must be obtained and interpreted as soon as possible,and a clinical diagnosis determined. If the diagnosis of SAH is made, the patient shouldbe referred immediately to the regional neurosurgical center. (Expert Opinion: Strong Consensus)
American Academy of Neurology American Association of Neurological Surgeons
American Association of Neuroscience Nurses American College of Emergency Physicians
American Society of Neuroradiology American Stroke Association, a Division of American Heart Association
Centers for Disease Control and Prevention Congress of Neurological Surgeons
National Association of Chronic Disease Directors National Association of EMS Physicians
National Association of State EMS Officials
National Institute of Neurological Disorders and Stroke National Stroke Association
Neurocritical Care Society Society of NeuroInterventional Surgery
Stroke Belt Consortium Veterans Administration