This prospective observational study aims to evaluate the effectiveness of Near-Infrared Spectroscopy (NIRS) and Bispectral Index (BIS) monitoring during endovascular coil embolization of cerebral aneurysms under general anesthesia. Changes in regional cerebral oxygen saturation (rSO₂) measured by NIRS will be assessed in relation to BIS values and hemodynamic parameters throughout the procedure.

The frequency, duration, and severity of cerebral desaturation episodes detected by NIRS, as well as their association with anesthetic depth and hemodynamic fluctuations, will be analyzed. The study does not involve any additional intervention beyond routine clinical monitoring.

Cerebral aneurysm coil embolization carries a potential risk of cerebral hypoperfusion and ischemia during the intraoperative period. Near-Infrared Spectroscopy (NIRS) provides continuous, non-invasive monitoring of regional cerebral oxygen saturation, while Bispectral Index (BIS) allows assessment of anesthetic depth.

In this prospective observational study, adult patients undergoing endovascular coil embolization for cerebral aneurysms under general anesthesia will be monitored using standard anesthesia monitoring, including NIRS and BIS, which are part of routine clinical practice at the study center.

Baseline NIRS and BIS values will be recorded prior to anesthetic induction, followed by continuous intraoperative monitoring at predefined time points. A decrease of ≥20% from baseline rSO₂ will be defined as clinically significant cerebral desaturation. Relationships between NIRS values, BIS measurements, and hemodynamic parameters will be evaluated.

The study aims to contribute to the understanding of multimodal neuromonitoring during neuroendovascular procedures and to support clinical decision-making regarding cerebral protection strategies.

• Age ≥18 years
• Patients scheduled for endovascular coil embolization for intracranial (cerebral) aneurysm
• American Society of Anesthesiologists (ASA) physical status I-III
• Undergoing the procedure under general anesthesia
• Ability to provide written informed consent Criteria

Exclusion Criteria:

• Refusal or inability to provide informed consent
• History of severe cerebrovascular disease other than the target aneurysm
• Severe cardiac, pulmonary, hepatic, or renal dysfunction
• Pre-existing neurological deficits interfering with NIRS or BIS interpretation
• Known scalp or skin conditions preventing proper placement of NIRS or BIS sensors
• Emergency procedures
• Pregnancy -

Adult patients diagnosed with intracranial (cerebral) aneurysm who are scheduled to undergo endovascular coil embolization under general anesthesia. Participants will be monitored intraoperatively using near-infrared spectroscopy (NIRS) and bispectral index (BIS) as part of standard anesthetic care. The study population represents a real-world cohort of patients undergoing elective neurointerventional procedures.

Individual participant data will not be made publicly available in order to protect participant confidentiality and in accordance with institutional regulations.