 Cingulotomy involves cutting the fibers that carry signals directly from the cingulate gyrus to the entorhinal cortex in the brain.It reduces the unpleasantness of pain (without affecting its intensity), but may have cognitive side effects.Delivery of an opioid such as morphine, hydromorphone, fentanyl, sufentanyl or meperidine directly into the subarachnoid cavity (the space between the spinal cord's inner, waterproof sheath and its outer protective sheaths) provides enhanced analgesia with reduced systemic side effects, and has reduced the level of pain in otherwise intractable cases.