The goal of this observational study is to learn about the role of biomarkers in spontaneous subarachnoid hemorrhage (sSAH) as predictors of severity of clinical outcome. The test of biomarkers is based on regular blood and urinary samples. Blood levels of highly specific cardiac troponin (cTNI), natriuretic peptides (NT-ProBNP), S100 beta protein, neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase (UCH-L1), soluble Tumor Necrosis Factor Receptor-2 (sST2), and soluble urokinase plasminogen activator receptor (suPAR), as well as urinary levels of epinephrine and norepinephrine are the biomarkers explored. All adult participants with spontaneous subarachnoid hemorrhage are involved in the study.

The main questions aim to answer are:

• which of these molecules can be prognostic for patients' outcome
• which are the prognostic levels of these biomarkers to predict patients' outcome.

Participants will undergo blood and urinary samples during hospitalization at 24 hours, 72 hours and after 7 days.

Spontaneous subarachnoid hemorrhage (sSAH) is one of the most severe neurological conditions. The hemodynamic instability due to endogenous catecholamine response and inflammatory patterns influences the risk of an unfavorable outcome and the development of clinical implications such as neurological and non-neurological issues. Serum levels of highly specific cardiac troponin (cTNI), natriuretic peptides (NT-ProBNP), S100 beta protein, neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase (UCH-L1), soluble Tumor Necrosis Factor Receptor-2 (sST2), and soluble urokinase plasminogen activator receptor (suPAR), as well as urinary levels of epinephrine and norepinephrine, can be measured as biomarkers in sSAH to explore the systemic response to the stress of bleeding. However, not all sSAH cases equally develop this endogenous cascade responsible for neurological and systemic events. There is no clear validation of threshold levels of endogenous factors applicable in clinical practice to define hemodynamic instability that has only a neurological or multi-organ impact post-SAH.

Inclusion Criteria:

• Patients with spontaneous subarachnoid hemorrhage, including those with perimesencephalic subarachnoid hemorrhage and aneurysmal subarachnoid hemorrhage.
• Adult patients.
• Confirmed presence of spontaneous subarachnoid hemorrhage through neuroimaging.
• Obtained informed consent for specific study biomarkers

Exclusion Criteria:

• Age <18 years.
• Post-traumatic subarachnoid hemorrhage.

All adult patients (>18 years) diagnosed with spontaneous subarachnoid hemorrhage admitted at the Fondazione Policlinico Universitario Agostino Gemelli will be enrolled in the study. Bleeding will be defined as hemorrhage measured on CT using a volumetry program conducted by the Department of Radiology. For all patients, angioCT and angiography (performed if necessary for diagnosis) data will be collected from the initial diagnosis. Radiological images obtained at the time of diagnosis will be collected and anonymized