Each year, the International Association for the Study of Pain (IASP) designates a focus topic in order to raise awareness and promote research into an area of pain. The focus for 2014-2015 is Neuropathic Pain.
Neuropathic pain is defined as pain arising from a lesion (a disease or injury) that affects the somatosensory nervous system. Central
neuropathic pain arises from lesions to the central nervous system (CNS -
brain or spinal cord), with two of the most common causes being spinal
cord injury and stroke. Peripheral neuropathic pain arises from lesions
to the peripheral nervous system (PNS - nerves outside of the CNS).
Neuropathic pain can also be caused by cancer and diabetes.
Put simply, neuropathic pain is the result of sensory nerve cells becoming ‘maladaptive’ – unable to respond correctly to stimuli, although the precise underlying mechanisms are complex, variable and not fully understood.
The pain is commonly described as burning, cold, sharp or like electric shocks, and can accompanied by numbness, tingling, ‘pins and needles’, itching and weakness. Certain neuropathic painful conditions may also be accompanied by sweating, changes in skin colour, swelling and abnormal hair and nail growth. People with neuropathic pain may also experience hypersensitivity to light touch, painful stimuli (such as a pinprick) and changes in temperature.
Neuropathic pain conditions include Complex Regional Pain Syndrome (CRPS), diabetic neuropathy, neuropathic cancer pain, postherpetic neuralgia (pain that lasts more than 3 months after a herpes zoster / ‘shingles’ outbreak), failed back surgery syndrome (chronic back pain following spinal surgery) and other chronic pain originating from the spine, such as sciatica.
Treatment of neuropathic pain is usually multimodal and highly individualised. Medications include opioids (i.e. morphine, oxycodone, buprenorphine), anticonvulsants (i.e. gabapentin, pregabalin), antidepressants (tricyclic and serotonergic; i.e. amitriptyline, duloxetine, venlafaxine), and topical analgesics (patches and creams).
Procedures that aim to disrupt the transmission of pain signals may be performed and include nerve blocks (direct injection of anaesthetic) and radiofrequency neurotomy (delivery of electrical current via probe).
Advanced pain management may be required if conventional treatment is ineffective and includes neurostimulation (i.e. peripheral nerve or spinal cord stimulation) and implanted drug delivery (i.e. intrathecal pump). Treatment of neuropathic pain is most effective if diagnosed early.