The main objectives of this study are comparison of the incidence of intraoperative air embolism and the extent of blood loss in patients undergoing posterior cranial fossa (PCF) and pineal region (PR) surgeries in sitting and horizontal position. Additionally, the overall treatment outcome, neurological functional outcome, degree of tumor removal, clinical course in the postoperative period, and the patient satisfaction will be compared between the groups.

This was a prospective observational study to assess the effects of patient positioning during craniotomies on surgical outcomes. Patients were distributed into 2 major groups based on the surgical position: sitting and horizontal. Each group was further divided into subgroups based on the type and location of the lesion. To achieve the study goals, comparison of the 2 approaches in equivalent patient groups was performed, including comparable demographics, diagnoses, topographic location of the lesions, anesthetic approaches, and surgical experience.

The operating surgeons decided patient positioning based on clinical judgment. Type of anesthesia was defined by the anesthesiologist in charge of the patient however, it was maximally standardized for both sites. All the surgeries were performed by neurosurgeons with sufficient experience of sitting craniotomies.

Inclusion Criteria:

• Patients 18 - 75 years old undergoing open posterior cranial fossa and pineal region surgery and diagnosed with space-occupying or vascular lesions willing consent to participate in the study.

Exclusion Criteria:

• Significant cardio-vascular comorbid conditions (cardiac insufficiency, recent infarction, advanced arterial hypertension)
• Advanced chronic respiratory comorbid conditions
• Uncorrected hypovolemia, anemia, hypoalbuminemia
• De-compensated acid base and electrolyte disorders
• Anticoagulated patients and patients with coagulation disorders, deep venous thrombosis (history of deep vein thrombosis or clinically established)
• Preoperative evidence of spinal or peripheral nerve dysfunction that may interfere with patient positioning.
• Cervical myelopathy
• Cervical spine disorders (atlanto-occipital arthritis, previous fractures etc.)

Patients undergoing elective craniotomies on posterior cranial fossa or pineal region were identified on each site before surgery. Patients were asked to be part of the study explaining that no intervention was necessary besides a phone call performed by the research team 3 months after their surgery.

All individual participant data that underlie results in a publication