Aneurysmal subarachnoid hemorrhage: update for emergency physicians.

Aneurysmal subarachnoid hemorrhage (SAH) is a serious cause of stroke that affects 30,000 patients in North America annually. Due to a wide spectrum of presentations, misdiagnosis of SAH has been reported to occur in a significant proportion of cases. Headache, the most common chief complaint, may be an isolated finding; the neurological examination may be normal and neck stiffness absent. Emergency physicians must decide which patients to evaluate beyond history and physical examination. This evaluation--computed tomography (CT) scanning and lumbar puncture (LP)--is straightforward, but each test has important limitations. CT sensitivity falls with time from onset of symptoms and is lower in mildly affected patients. Traumatic LP must be distinguished from true SAH. Cerebrospinal fluid analysis centers on measuring xanthochromia. Debate exists about the best method to measure it--visual inspection or spectrophotometry. An LP-first strategy is also discussed. If SAH is diagnosed, the priority shifts to specialist consultation and cerebrovascular imaging to define the offending vascular lesion. The sensitivity of CT and magnetic resonance angiography are approaching that of conventional catheter angiography. Emergency physicians must also address various management issues to treat or prevent early complications. Endovascular therapy is being increasingly used, and disposition to neurovascular centers that offer the full range of treatments leads to better patient outcomes. Emergency physicians must be expert in the diagnosis and initial stabilization of patients with SAH. Treatment in a hospital with both neurosurgical and endovascular capability is becoming the norm.