When patients present to the emergency department (ED) with acute headache concerning for subarachnoid hemorrhage (SAH) and a lumbar puncture (LP) shows blood in the CSF, it is difficult to distinguish the results of a traumatic LP from those of SAH. CT angiography (CTA) is often performed, but the long-term outcome for patients with a positive LP and normal neurovascular imaging remains uncertain. The primary objective of this study was to determine whether patients who presented to the ED with acute headache and had red blood cells (RBCs) in their CSF on LP but negative cerebrovascular imaging suffered subsequent SAH.
A case series study of consecutive adult ED patients who incurred charges for LP between 2001 and 2009 was performed from 2010 through 2011. Inclusion criteria were: headache, > 5 RBCs/mm3 in CSF, noncontrast head CT with no evidence of hemorrhage, and cerebrovascular CTA or MRA without aneurysm or vascular lesion within 2 weeks of the ED visit. Patients with less than 6 months of available follow-up were excluded. The primary outcomes were 1) subsequent nontraumatic SAH and 2) new vascular lesion. Secondary outcomes were complications related to SAH, or LP or angiography.
Of 4641 ED patients billed for an LP, 181 patients (mean age 42 years) were included in this study. Over a median follow-up of 53 months, 0 (0%) of 181 patients (95% CI 0%–2.0%) had a subsequent SAH or new vascular lesion identified. Although not the primary outcome, there was 1 patient who was ultimately diagnosed with vasculitis. Eighteen (9.9%) of 181 patients (95% CI 6.0%–15.3%) had an LP-related complication and 0 (0%) of 181 patients (95% CI 0%–2.0%) had an angiography-related complication.
Patients who present to the ED with acute headache concerning for SAH and have a finding of bloody CSF on LP but negative findings on cerebrovascular imaging are at low risk for subsequent SAH and thus are likely to be safe for discharge. Replacement of the CT/LP with a CT/CTA diagnostic algorithm merits further investigation.