Serial Changes in Inflammatory Biomarkers Preceding Intracranial Aneurysm Rupture

Small aneurysms classified as low risk by the PHASES score may become unstable during surveillance. We evaluated within-patient changes in the neutrophil-to-lymphocyte ratio (NLR) and systemic immune-inflammation index (SII) during the late clinical phase preceding aneurysm rupture.

This retrospective study centered on a primary longitudinal cohort of 43 patients with an aneurysm documented as unruptured at baseline: 27 remained rupture-free for at least 5 years (Group 1) and 16 subsequently ruptured during follow-up (Group 2). An additional 32 patients presenting with acute aneurysmal subarachnoid hemorrhage (aSAH; Group 3) were included as a secondary post-rupture comparator. NLR, SII, and aneurysm morphology were assessed longitudinally in the primary cohort.

Baseline NLR and SII were similar in Groups 1 and 2. During the final 30 days before rupture, NLR increased from 1.7 ± 0.2 to 3.4 ± 0.5 and SII from 418 ± 43 to 862 ± 109 (both p < 0.001). Thirteen of 16 patients were symptomatic during this period. At rupture-time imaging, 13 of 16 aneurysms (81%)were irregular, whereas all were regular at baseline; the timing of this change could not be established. In a 1-year landmark analysis, baseline and first-year values did not discriminate subsequent rupture.

Rising NLR and SII characterized a late, frequently symptomatic pre-rupture inflammatory phase in this selected cohort rather than providing prospective rupture prediction. Rupture-time morphological irregularity was complementary but not synchronized with biomarker sampling. The prognostic value of serial biomarker changes remains unestablished and requires evaluation in prospective studies with standardized sampling.