A method for treating stenosis in a spine comprises percutaneously accessing the epidural space in a stenotic region of interest, compressing the thecal sac in the region of interest to form a safety zone, inserting a tissue removal tool into tissue in the working zone, using the tool to percutaneously reduce the stenosis; and utilizing imaging to visualize the position of the tool during at least a part of the reduction step. A tissue excision system for performing percutaneous surgery, comprises a cannula comprising a tissue-penetrating member having a distal end defining an aperture on one side thereof, an occluding member slidably received on or in the cannula and closing the aperture when the occluding member is adjacent the cannula distal end, means for engaging adjacent tissue via the aperture, and cutting means for resecting a section of the engaged tissue.