CSF Per2 expression levels cannot predict occurrence of vasospasm but may be associated with incidence of DCI. (a) CSF Per2 expression levels on days 1 and 7 after SAH did not differ between patient subgroups with or without sonographic vasospasm (day 1: p = 0.119, n = 40, day 7: p = 0.572, n = 35). (b) Occurrence of delayed cerebral ischemia was associated with lower CSF Per2 mRNA expression levels on day 7, but not days 1 and 14 after SAH (day 7: p = 0.012, n = 35, day 1: p = 0.791, n = 39, day 14: p = 0.92, n = 11). CSF: cerebrospinal fluid, DCI: delayed cerebral ischemia, Per2: Period-2, SAH: subarachnoid hemorrhage, VSP: vasospasm. Data presented as mean + SEM, * p < 0.05.