BackgroundThe primary aim was to determine the diagnostic yield of vascular work-up, the clinical course during neurointensive care (NIC), and rate of functional recovery for patients with computed tomography (CT)-negative, lumbar puncture (LP)-verified SAH.MethodsIn this retrospective study, 1280 patients with spontaneous SAH, treated at our NIC unit, Uppsala University Hospital, Sweden, between 2008 and 2018, were included. Demography, admission status, radiological examinations (CT angiography (CTA) and digital subtraction angiography (DSA)), treatments, and functional outcome (GOS-E) at 12 months were evaluated.ResultsEighty (6%) out of 1280 SAH patients were computed tomography (CT)-negative, LP-verified cases. Time between ictus and diagnosis was longer for the LP-verified SAH cohort in comparison to the CT-positive patients (median 3 vs 0 days,p< 0.001). One fifth of the LP-verified SAH patients exhibited an underlying vascular pathology (aneurysm/AVM), which was significantly less common than for the CT-verified SAH cohort (19% vs. 76%,p< 0.001). The CTA- and DSA-findings were consistent in all of the LP-verified cases. The LP-verified SAH patients exhibited a lower rate of delayed ischemic neurological deficits, but no difference in rebleeding rate, compared to the CT-verified cohort. At 1-year post-ictus, 89% of the LP-verified SAH patients had recovered favorably, but 45% of the cases did not reach good recovery. Having an underlying vascular pathology and an external ventricular drainage were associated with worse functional recovery (p= 0.02) in this cohort.ConclusionsLP-verified SAH constituted a small proportion of the entire SAH population. Having an underlying vascular pathology was less frequent in this cohort, but still occurred in one out of five patients. Despite the small initial bleeding in the LP-verified cohort, many of these patients did not reach good recovery at 1 year, this calls for more attentive follow-up and rehabilitation in this cohort.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00701-023-05640-4.