ABSTRACT NUMBER: ESOC2026A739 DIAGNOSTIC EVALUATION OF ANGIOGRAPHY-NEGATIVE SUBARACHNOID HEMORRHAGE: A NATIONWIDE STUDY

Abstract Background and aims Diagnostic evaluation of angiography-negative non-perimesencephalic subarachnoid hemorrhage (SAH) remains controversial. Although guidelines recommend repeated imaging, there is no consensus on timing, imaging modality, and frequency. Digital subtraction angiography (DSA) is considered the gold standard, but is an invasive procedure with risk of complications. Meanwhile, quality of non-invasive imaging is improving. This study aims to explore the variation in diagnostic work-up in patients with angiography-negative non-perimesencephalic SAH in the Netherlands. Methods An online survey was distributed among Dutch vascular neurologists, neurosurgeons, and (interventional) neuroradiologists involved in SAH care. The survey included questions on diagnosing non-perimesencephalic SAH, preferences regarding repeated imaging, acceptable missing rates of repeated imaging, and willingness to implement non-invasive imaging. Clinical and radiological characteristics influencing the diagnostic work-up were assessed by presenting five cases. Results Thirty-one of the sixty-seven invited physicians (46%) completed the survey, of which thirteen vascular neurologists (42%), ten (interventional) neuroradiologists (32%), and eight vascular neurosurgeons (26%). Most respondents (61%) preferred DSA as repeated imaging modality. CTA (84%) was favored over MRA (16%) as non-invasive alternative. The most common cited indication of non-invasive imaging was an increased catheterization risk based on the initially performed DSA (61%). The median acceptable missing rate was 2% (IQR 1-3). A vast majority of 84% respondents were willing to adopt non-invasive repeated imaging as standard care if proven cost-effective. Conclusions This study showed large variability in diagnostic evaluation of angiography-negative non-perimesencephalic SAH. Further research is needed to compare different strategies in the diagnostic work-up to standardize care in patients with this type of SAH. Conflict of interest O.P.B. Wenzler: nothing to disclose; M.H. den Hertog: nothing to disclose; D. Verbaan: nothing to disclose; J.M.C. van Dijk: nothing to disclose; H.D. Boogaarts: nothing to disclose