Neuropathic pain is primarily a result of a damage or dysfunction of the peripheral or central nervous system, rather than stimulation of the pain receptors.
Neuropathic pain is characterized by the pain which intensity is not proportional to tissue damage, the occurrence of dysesthesia (eg, burning, tingling) and signs of the nerve damage found during neurological physical examination. Although neuropathic pain responds to opioids, it is mostly treated by adjuvant medicines (anticonvulsants, antidepressants, baclofen, local medicines).
The pain can occur after an injury of any part of the nervous system, either the peripheral or central, and can affect the sympathetic nervous system (sympathetically mediated pain). Specific syndromes include postherpetic neuralgia, avulsion (tearing) of the roots, painful traumatic mononeuropathy, painful polyneuropathy (within diabetes), central pain syndrome, post-operative pain syndrome (eg. Postmastectomy, postthoracotomy, phantom pain) and complex regional pain syndrome (reflex sympathetic dystrophy and causalgia).
Symptoms and diagnosis
Dysaesthesias (spontaneous or induced burning pain, often with sharp, cutting component) are typical for neuropathic pain, although pain may be deep, stabbing. Other sensory phenomena - such as hyperesthesia, hyperalgesia, allodynia (pain caused by the simple touch), hyperpathia (particularly unpleasant, heightened pain response) - can occur with neuropathic pain. Symptoms are long lasting, and generally occur after the removal of the pain cause, because of the sensitization and remodeling of CNS.
Typical symptoms of neuropathic pain occur after the proven or unproven nerve damage (eg, amputation, diabetes). Pain that stops after the blockade of sympathetic nerves is the pain that is supported by sympathetic nervous system (SNS).
Several types of drugs proved effective in the treatment of neuropathic pain, although a complete recovery is rarely achieved. Antidepressants and antiepileptics are most frequently used. Best results are achieved by tricyclic antidepressants (Elavil, Amyzol), and when it comes to antiepileptic drugs, the drug of choice are gabapentin (Neurontin, Nirvax) and carbamazepine (Karbamazepin, Karbapin, Tegretol).
Opioid medicines can cause temporary pain relief, but their efficacy in neuropathic pain is much weaker than in nociceptive pain. Adequate analgesia usually cannot be achieved because of the side effects.
Effective analgesia is achieved with lidocaine patches and local medicines.
From the beginning of the treatment it is necessary to pay special attention to the psychological condition and, if necessary, to establish an adequate therapy. Also, it is necessary to start treating anxiety and depression as soon as possible.