Pain

Pain resulting from injury to the nervous system (neuropathic) may not indicate tissue damage and thus may not be a useful sensory phenomenon: rather it may constitute a pathologic process itself.
Malignant pain :
The goal is to reduce suffering during a terminal illness. opioids can be used in high doses unless excessive adverse effects occur. Tricyclic antidepressants, anticonvulsants, and nsaid may provide additional relief. Other drug: bupivacaine and clonidine may relieve pain related to nerve invasion. When medical management fails, the surgical treatment is indicated such as 1. Epidural administered morphine, 2. Ablation to interrupt pain transmission.
Cancer pain that is unilateral and focal may be treated with cordotomy, creating a lesion in the spinothalamic tract designed to interrupt pain transmission. Percutaneous cordotomy using a radiofrequency needle is done at the C1-2 level. This is less traumatic for the patient and may produce analgesia in both the arm and the leg. Other, Ablative are used rarely. These include midline myelotomies, rhizotomies, and neurectomies.