OBJECTIVEThe authors sought to identify mRNA biomarkers of cerebral vasospasm in whole blood of patients suffering from aneurysmal subarachnoid hemorrhage (aSAH).METHODSA prospective transcriptomic study for vasospasm was conducted in whole blood samples of 44 aSAH patients who developed (VSP⁺ group, n = 22) or did not develop (VSP⁻ group, n = 22) vasospasm. Samples from all patients were profiled for 21,460 mRNA probes using the Illumina Human HT12v4.0 array. Differential statistical analysis was performed using a linear mixed model.RESULTSLevels of sphingosine-1-phosphate receptor 4 (S1PR4) mRNA were significantly higher (p = 8.03 × 10⁻⁶) at presentation in patients who developed vasospasm after aSAH than in patients who did not.CONCLUSIONSThe results, which are consistent with findings of previous experimental investigations conducted in animal models, support the role of S1PR4 and its ligand, sphingosine-1-phosphate (S1P), in arterial-associated vasoconstriction, which suggests that S1PR4 could be used as a biomarker for cerebral vasospasm in aSAH patients.