Delayed cerebral ischemia (DCI) and cerebral vasospasm (VS) are rare but serious post-operative complications after surgery for pituitary macroadenomas; the mechanism of which are poorly understood. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a vasoactive neuropeptide expressed in pituitary adenomas and may play a role in DCI/VS. The aim of this case-control study was to investigate the association between tumor expression of PACAP and DCI/VS following pituitary surgery. Tumor tissue from five patients with DCI/VS following pituitary surgery and nine matched controls were evaluated for PACAP expression by immunohistochemistry. Nuclear PACAP expression was significantly elevated in patients with DCI/VS following pituitary surgery compared to controls (0.396 ± 0.0.16 a.u. vs 0.093 ± 0.04 a.u, p < 0.0001). There was a positive linear relationship between nuclear PACAP expression and pre-operative tumor volume (r² = 0.41, p < 0.02) with a significant difference in slopes between the DCI/VS group compared to controls (y = x(5.0 × 10⁻³), r² = 0.76 vs y = x(7.4 × 10⁻⁴), r² = 0.07, p < 0.05). Elevated levels of tumor PACAP expression is associated with DCI/VS following pituitary surgery and may have a role in tumor growth. PACAP signaling may play a role the development of DCI, but further studies are needed.

Delayed cerebral ischemia (DCI) is a life-threatening complication of aneurysmal subarachnoid hemorrhage (aSAH). The vasoactive P450 eicosanoids 20-hydroxyeicosatretraenoate (20-HETE) and 14,15-epoxyeicosatrenoate (14,15-EET) are associated with the development of DCI and may play opposing roles in DCI risk. We hypothesized that the ratio of these opposing eicosanoids in cerebrospinal fluid (CSF) is associated with hemorrhage severity and the risk of developing DCI after aSAH. In a preclinical model, rats received intracisternal blood injections to approximate aSAH. Hemorrhage severity, cerebral blood flow (CBF), cortical spreading depolarizations were recorded, and CSF eicosanoid levels were quantified using mass spectrometry. In a parallel clinical study, CSF samples were collected and analyzed prospectively from subjects with aSAH and outcomes were tracked. Preclinically, rats with greater hemorrhage severity had impaired CBF and lower median 14,15-EET/20-HETE ratios compared to those with lesser or no hemorrhage. In aSAH patients, the CSF 14,15-EET/20-HETE ratio was negatively correlated with hemorrhage grade on imaging. Patients who developed DCI had lower median 14,15-EET/20-HETE ratios compared to those without DCI. The CSF 14,15-EET/20-HETE ratio correlates with hemorrhage severity and may reflect a mechanistic underpinning of microvascular dysfunction that contributes to DCI. These results suggest that vasoactive eicosanoids may be a therapeutic target in aSAH.