In the group with MTHFR gene polymorphism we also included patients with factor V G1691A- Leiden mutation (18 cases, 15.78%), prothrombin G20210A gene mutation (3 cases, 2.63%), PAI-1 675 4G/5G gene mutation (49 cases, 42.98%) as well as hyperhomocysteinemia (40 cases, 35.08%) without infectious causes of CVST. The gene discussed is F2; the disease is hyperhomocysteinemia.