We know that total resection of the tumor can have a good prognosis and can prolong life and time to recurrence. But the tumor is located in the lateral fissure and deep temporal lobe, and if the surgery damages the brain tissue, there is no language effect in the non-dominant hemisphere. But in the dominant hemisphere may affect language and memory. If the patient has speech disorder before surgery, we can determine that the tumor is in the dominant hemisphere, but the patient does not have speech and memory deficits before surgery, and it is impossible to be sure if it is in the dominant hemisphere or not. This makes the question of how much to remove intraoperatively problematic. Previously, it was believed that 95% of right-handed patients had their dominant hemisphere in the left hemisphere and 50% of left-handed patients had their dominant hemisphere in the left hemisphere. However, recent studies have shown that only 3% of left hands are in the right hemisphere and 97% in the left hemisphere. So when the lesion is in the left hemisphere, the chances of impaired function are high. The oldest and most reliable way to determine the dominant hemisphere is the Wada test.