The aim of the study is to compare different strategies for prevention of venous thromboembolism related to intracranial meningioma surgery. The investigators identified three hospitals where two have a very restrictive approach with respect to anticoagulant therapy while at the third hospital the use of anticoagulation the day before surgery was initiated as routine prophylaxis.

Based on this "natural experiment" it will be explored whether the use of anticoagulant prophylaxis is associated with reduced risk of venous thromboembolism and/or associated with increased risk of postoperative hemorrhage as compared to the 2 cohorts where this intervention were absent.

Inclusion Criteria:

• First included patient 1.january 2007 and latest included patient 1.july 2013 (allows for 30 day follow up with respect to morbidity)
• Histological verification of a meningioma (of any grade) from the current surgery

Exclusion Criteria:

• Intracranial surgery or venous thromboembolism the last 3 months

Patients having had surgical treatment for intracranial meningioma in Norway (St Olavs University Hospital, Trondheim, and University Hospital North Norway, Tromsø) and Sweden (Karolinska University Hospital, Stockholm).