Abstract: @@ With the development of modern neuroimaging and the improvement of surgical instruments or devices as well as operative skills, minimally invasive neurosurgery has been progressing rapidly with great changes in surgical concepts and methods.1 Based on these changes, anatomic research has been carried out to explore new surgical approaches dealing with anticipated microtrauma. These approaches have made or been making things possible. Keyhole microsurgery has evolved into an important subject of modern minimally invasive neurosurgery.