Unlike the pain that one feels as a result of trauma or infection (also known as nociceptive pain), neuropathic pain is more complex in its origin and treatment. Neuropathic pain results from injury or dysfunction of nerves.
The injury occurs usually as a result of:
- direct injury to the nerve such as a trauma as a result of a penetrating object
- an illness such as diabetes or infection such as shingles that ultimately leads to nerve dysfunction
Neuropathic pain can occur as a result or injury or dysfunction in the peripheral nerves in the body or the central nerves in the spinal cord or brain. Neuropathic pain may not behave like nociceptive pain and go away after a period of time. It usually persists long after the injury and may be difficult to treat. Neuropathic pain is often described as burning or searing but also has been described as electric shock-like or buzzing and sometimes as plain aching and throbbing.
Examples of neuropathic pain include painful diabetic neuropathy, post-herpetic neuralgia or pain after a thalamic stroke (also known as Dejerine-Roussy syndrome). Another condition that manifests primarily as neuropathic pain is known as Complex Regional Pain Syndrome (CRPS) (also referred to as Causalgia and Reflex Sympathetic Dystrophy (RSD)). Though originally described by Mitchell during the civil war, the triggers for CRPS are yet not totally understood but the treatments of this difficult entity have come a long way.
Other causes of neuropathic pain include trauma, plexopathy (damage to nerves as they come out of the spine) from tumor or radiation, some connective tissue diseases, trench foot, alcoholic neuropathy, Beriberi, Guillain-Barre syndrome (Acute inflammatory polyneuropathy), HIV and idiopathic peripheral neuropathy.
Some causes of neuropathic pain that involve the spinal cord or the brain include herniated intervertebral disc, spondylolisthesis, spondylosis, trigeminal neuralgia, post-herpetic neuralgia, tumor, arachnoiditis, trauma and multiple sclerosis.
Features of neuropathic pain on physical examination may include an exaggerated painful response to a stimulus that would normally be perceived as mild discomfort (hyperalgesia). Pain may also be experienced even in response to a harmless stimulus such as light touch (allodynia).
Given its unique nature, the management of neuropathic pain involves the use of unconventional medications and interventions in its management. The medications used may include some anti-seizure medication and some antidepressant medication, likely because these drugs work on the nervous system. Sometimes narcotic medications or local anesthetics are used.
If pain is relentless, invasive procedures may be used which may include nerve blocks, spinal infusion of medication through an implanted pump, or neurostimulation of the spinal cord (spinal cord stimulation) or the peripheral nerves (peripheral nerve stimulation). Physical therapy is directed at improving function after improving pain control. Alternative medicine in the form of acupuncture or other therapies is at times also attempted.