Systemic Immune-Inflammation Index Predicts Acute Symptomatic Hydrocephalus After Spontaneous Nonaneurysmal Subarachnoid Hemorrhage.

OBJECTIVE: The authors sought to investigate the association between white blood cell counts and acute hydrocephalus in spontaneous nonaneurysmal subarachnoid hemorrhage (nSAH). METHODS: We conducted a retrospective analysis of 105 consecutive patients with spontaneous nSAH. Univariate and multivariable logistic regression analyses were performed to investigate factors associated with hydrocephalus. Receiver operating characteristic curve analysis determined the optimal cutoff to differentiate between patients with and without hydrocephalus. The admission characteristics of hydrocephalic patients with aneurysmal and nSAH were compared. RESULTS: A total of 70 patients met inclusion criteria, of which 21 (30%) presented with hydrocephalus. In univariate logistic regression, leukocytes, neutrophils, lymphocytes, neutrophil-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, neutrophil-monocyte-to-lymphocyte ratio, and the systemic immune-inflammation (SII) index ([neutrophils × platelets/lymphocytes]/1000) were associated with hydrocephalus. After adjustments, the SII index independently predicted acute hydrocephalus with the highest odds among laboratory values (odds ratio 2.184, P = 0.006). Receiver operating characteristic curve analysis revealed the SII index differentiated between patients with and without hydrocephalus (area under the curve = 0.799, 95% CI: 0.688-0.909, P < 0.001) with an optimal cutoff of 1.385 103/µL. SII indices did not differ between aneurysmal and nSAH patients with hydrocephalus (3.5 vs. 3.6 103/µL, P = 0.795). CONCLUSIONS: A SII index ≥1.385 103/µL on admission predicts acute hydrocephalus in spontaneous nSAH. Hydrocephalic patients with aneurysmal and nSAH exhibit similar SII indices, and thus, an exaggerated inflammatory and thrombotic response follows spontaneous subarachnoid hemorrhage irrespective of hemorrhage etiology.