What causes neuropathic pain in patients with cancer?
Neuropathic pain represents a derangement of central and peripheral nervous system pain signaling, which is a consequence of nerve injury/destruction, disease (acquired, viral, or congenital), or toxins (drugs, ingested/inhaled substances). Malignancies may cause neuropathic pain due to tumor infiltration that invades and destroys neural tissue or through tumor spread that impinges on nerve structures. Neuropathic pain caused by tumor invasion usually presents as a plexopathy (injury to nerve fibers in a specific distribution)—typically brachial, thoracic, or lumbosacral. Neuropathic pain may also arise from treatment side effects such as surgery, radiation-induced injury to peripheral nerves or spinal cord, drug-induced neuropathy, or chemotherapy. Several commonly used chemotherapeutic agents (cisplatin, vincristine, procarbazine) can cause painful peripheral neuropathy, typically in a stocking-glove distribution. Motor neuropathies may also occur, such as the peroneal palsy (foot-drop) that results from chemotherapeutic agents.