yulius hermanto
Neuropathic Pain, a Problematic Disease
Link: neurology.org
IntroductionTalking about pain, what is pain by definition? Pain is an unpleasant sensory and emotional experience arising from actual or potential tissue damage or described in terms of such damage.
There are several types of pain such as nociceptive pain, inflammatory pain and neuropathic pain, but here i gonna discuss about neuropathic pain.
Neuropathic pain, is caused by various central and peripheral nerve disorders, and commonly becomes problematic because of its severity, chronicity and resistance to simple analgesics.Neuropathic pain also special because it is often experienced in parts of the body that otherwise appear normal, and it is further aggravated by allodynia (touch-evoked pain).
About 2-3% of the population have neuropathic pain, and personally devastating to the people who experience it. The personal impact of neuropathic pain is most vividly appreciated by people who experience this devastating condition. Those affected have described their pain using the McGill Pain Questionnaire with descriptors such as "punishing–cruel" and "tiring–exhausting." Ample evidence indicates that neuropathic pain impairs patients' mood, quality of life, activities of daily living and performance at work.
Clinical Presentation
Neuropathic pain has been defined by the International Association for the Study of Pain as pain "initiated or caused by a primary lesion or dysfunction in the nervous system," But it may have several underlying causes include infections, trauma, metabolic abnormalities, chemotherapy, surgery, irradiation, neurotoxins, inherited neurodegeneration, nerve compression, inflammation, and tumor infiltration.
In diagnosis or recognition of neuropathic pain, the complete assessment of pain and other symptoms is important. Besides the assessment of sensory complaint, a further examination of motoric component also needed because muscle weakness or motoric symptoms can be found in neuropathic patient.
A distinction should be made between stimulus-evoked pain and spontaneous (stimulus-independent) pain, which may have different underlying mechanisms. Spontaneous pain can be either constant or intermittent (even paroxysmal), and most patients describe having both (eg, constant "burning" pain plus intermittent pain that is "shooting" or "electric shock–like"). In addition, spontaneous paresthesias and dysesthesias manifest as abnormal sensations, including crawling, numbness, itching, and tingling. When obtaining the patient's history, it is important to assess the location, radiation intensity, quality, and duration of spontaneous pain and abnormal sensations.
Pain may be evoked by everyday environmental stimuli such as the gentle touch and pressure of clothing, wind, riding in a car, and hot and cold temperatures.
Chronic pain has a significant negative effect on quality of life, and various measures of physical and emotional function. Neuropathic pain also has some psychological comorbidity (eg, depression or anxiety), sleep disturbance, work-related issues, treatment expectations, rehabilitative needs, and the availability of social support from family and friends that should not be overlooked.
Mechanism of Neuropathic Pain
Our understanding about neuropathic pain is still developed, since its complexity and problematic. Many factors are involved in development of neuropathic pain. But all experts have one consensus that neuropathic pain is caused by abnormal stimuli in nerve system, not from the tissue that being innervated by the nerve.
A simple focal peripheral nerve injury promotes a range of peripheral and central nervous system processes that can all contribute to persistent pain and abnormal sensation. Inflammation and repair mechanisms of neural tissues in response to injury, and the reaction of adjacent tissues to injury lead to a state of hyperexcitability in primary afferent nociceptors, a phenomenon termed peripheral sensitization. In turn, central neurons innervated by such nociceptors undergo dramatic functional changes including a state of hyperexcitability termed central sensitization.
Injury or permanent loss of primary afferent fibers (deafferentation)
differentiates peripheral neuropathic pain from other types of pain. Positive sensory phenomena (spontaneous pain, allodynia, and hyperalgesia) that are characteristic of patients with neuropathic pain are likely to have many underlying mechanisms, including ectopic generation of impulses as well as the de novo expression of neurotransmitters and their receptors and ion channels. Direct injury to central structures may permanently alter sensory processing, and in some patients it causes central neuropathic pain and dysesthesias.
Management of Neuropathic Pain
Neuropathic pain management is complex, since
Nonpharmacologic management
Although many patients with neuropathic pain pursue complementary and alternative treatments, rigorous evidence supporting efficacy of nondrug therapy is limited.
For me, patient with chronic pain is very debilitating, causing psychological stress. Thus stress relieve is needed and done simultantly with pharmacological therapy. Besides that stress relieve can give effect to perception of pain, thus may help in pain relieve by drugs.
Pharmacologic
Antidepressants
Tricyclic antidepressants have repeatedly been shown to reduce neuropathic pain. Analgesic actions may be attributable to noradrenaline and serotonin reuptake blockade (presumably enhancing descending inhibition). TCA (amytriptyline) is effective in neuropathic pain, since its give effect to central nervous system in modulation of pain, thus give the pain relieve effect.
Anticonvulsants
Carbamazepine and phenytoin have shown efficacy in treatment for diabetic peripheral neuropathy. But, both have significant adverse effects, making them generally poor candidates for first-line therapy. Carbamazepine, however, is still considered first-line therapy for trigeminal neuralgia, a unique neuropathic pain condition.
Gabapentin, an -2-delta subunit voltage-gated calcium-channel antagonist, has repeatedly demonstrated analgesic efficacy and improvements in mood and sleep in several studies.
Opioid analgesics
The role of opioid analgesics in neuropathic pain has been controversial. However, a recent meta-analysis provides convincing evidence of benefit. But, beneficial effects on mood, quality of life and disability are not consistent. There were no reports of addiction or abuse in the trials, although the risk is likely to be low given the common exclusion criterion of substance abuse history.
Topical agents
Locally acting analgesics are attractive because they may cause minimal systemic side effects. The lidocaine patch 5% has been shown to relieve localized pain in postherpetic neuralgia with no increase in side effects. Capsaicin, an ingredient of hot peppers, has shown mixed results in trials and some patients with post-herpetic neuralgia have reported pain exacerbation.
There are others modalities in treatment of neuropathic pain, the decision of modalities in each patient depends on several factors such degree of pain severity, cost, activity, etc.
The discussion between patient and doctor is needed to achieve mutual understanding about disease progression.
