Perimesencephalic Subarachnoid Hemorrhage Has a Unique Peripheral Blood Leukocyte Profile Compared To Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE: The authors sought to investigate if peripheral blood leukocyte profiles on admission differed between perimesencephalic, angio-occult, and aneurysmal subarachnoid hemorrhage cohorts. METHODS: We performed a retrospective analysis of 202 consecutive patients with spontaneous subarachnoid hemorrhage. We classified spontaneous subarachnoid hemorrhage as either aneurysmal or nonaneurysmal origin. Nonaneurysmal subarachnoid hemorrhage was subclassified as either perimesencephalic or angio-occult according to the distribution of hemorrhage on the initial imaging. Patient demographics, clinical parameters, radiographic metrics, and laboratory values were obtained on admission. In-hospital data including acute hydrocephalus, shunt dependence, vasospasm, and delayed cerebral ischemia were collected. Comparative analyses were conducted between cohorts. RESULTS: The perimesencephalic subarachnoid hemorrhage cohort exhibited significantly lower neutrophil (7.76 vs. 10.06; P = 0.004), lymphocyte (1.40 vs. 1.90; P = 0.024), and monocyte counts (0.52 vs. 0.73; P = 0.031) than the aneurysmal subarachnoid hemorrhage cohort. There were no significant differences in peripheral blood leukocyte profiles between the angio-occult and aneurysmal subarachnoid hemorrhage cohorts. The nonaneurysmal cohort exhibited significantly lower neutrophil (8.33 vs. 10.06; P = 0.005) and lymphocyte counts (1.47 vs. 1.90; P = 0.011) as well as a lower lymphocyte-to-monocyte ratio (2.80 vs. 4.51; P = 0.018) than the aneurysmal subarachnoid hemorrhage cohort. CONCLUSIONS: Perimesencephalic subarachnoid hemorrhage exhibits a unique peripheral blood leukocyte profile compared to aneurysmal subarachnoid hemorrhage. Moreover, these preliminary data demonstrate that blood leukocytes may be affected by the burden of cisternal subarachnoid hemorrhage or the presence of a ruptured aneurysm. Further large-scale prospective studies and validation are required to confirm these preliminary findings.