الفهرس 
Anatomy of PainOnly 14 pages are availabe for public view
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Abstract
Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage”. Types of pain can be described as nociceptive, psychogenic and neurogenic pain. Neurogenic pain is caused by functional abnormalities of structural lesions in the peripheral or central nervous system, and occurs without peripheral nociceptor stimulation. It is especially problematic because of its severity, chronicity and resistance to simple analgesics. The diagnosis of neurogenic pain is based primarily on history (e.g., underlying disorder and distinct pain qualities) and the findings on physical examination (e.g., pattern of sensory disturbance); however, several tests may sometimes be helpful. Obtain a detailed history, including an assessment of the pain characteristics, impact of the pain on multiple domains (physical, psychosocial, role functioning, work, etc.), related concerns and comorbidities (other symptoms, psychiatric disorders including substance use disorder, etc.), prior work-up and working diagnosis, and prior therapies. Conduct a physical examination, emphasizing the neurological and musculoskeletal examination obtain and review past medical records and diagnostic studies, develop a formulation including 1) working diagnoses for the pain etiology, pain syndrome and inferred pathophysiology, and 2) plan of care including need for additional diagnostic studies and initial treatments for the pain and related concerns. Clinical features of neurogenic pain described by the patient as a burning sensation, a sharp, stabbing or shooting pain, or ’like an electric shock’. Other features may include:
o Allodynia: seemingly harmless stimuli, such as light touch, provoking pain.
o Hyperpathia: a short episode of discomfort causing prolonged severe pain.
o Hyperalgesia: discomfort, which would otherwise be mild, being felt as severe pain. The IASP states that hyperalgesia is a psychophysical term; it is has been suggested as the umbrella term for all conditions of increased pain sensitivity. Its definition parallels that of the physiological term ’sensitization’ .
Many common diseases, such as post herpetic neuralgia, trigeminal neuralgia, diabetic neuropathy, complex regional pain syndrome, spinal cord injury, cancer, stroke, and degenerative neurological diseases may produce neurogenic pain. Recently, theories have been proposed that state there are specific cellular and molecular changes that affect membrane excitability and induce new gene expression after nerve injury, thereby allowing for enhanced responses to future stimulation. In addition, the ectopic impulses of neuroma, changes of sodium and calcium channels in injured nerves, sympathetic activation, and deficient central sympathetic activation, and inhibitory pathway contribute to the mechanisms of neurogenic pain.
Currently, treatment of neurogenic pain is still a challenge. Pharmacotherapies (antidepressants, antiepileptics) remain the basis of neurogenic pain management. However, patient satisfaction in the results of the treatment of neurogenic pain is still disappointing. Since it has been established that intense noxious stimulation produces a sensitization of central nervous neurons, it may be possible to direct treatments not only at the site of peripheral nerve injury, but also at the target of central changes. In order to provide better pain control, the mechanism based approach in treating neuropathic pain should be familiar to physicians.
Treatments are generally palliative and include conservative non pharmacologic therapies, drugs and more invasive interventions (e.g., spinal cord stimulation). Individualizing treatment requires consideration of the functional impact of the neurogenic pain (e.g., depression, disability) as well as ongoing evaluation, patient education, reassurance and specialty referral. We propose a primary care algorithm for treatments with the most favourable risk-benefit profile, including topical lidocaine, gabapentin, pregabalin, tricyclic antidepressants, mixed serotonin-norepinephrine reuptake inhibitors, and opioids. The best evidence for date is amitriptyline, Carbamazepine is a reasonable first choice in second line drug if treatment fails with antidepressants.
Non-pharmacological measures includes:
• Steroid injection, which includes Dorsal root ganglion injection and epidural steroid injection.
• Electrical stimulation: interpretation of systematic trials is difficult due to differing methodologies. It includes spinal cord stimulators, peripheral nerve stimulators and electrical spinal cord stimulation, deep brain stimulation. However, transcutaneous electrical nerve stimulation (TENS) performs consistently well compared with placebo. National Institute for Health and Clinical Excellence (NICE) recommends the use of spinal cord stimulation in patients who have had chronic pain for six months despite conventional medical management (providing a prior trial of stimulation has proved to be effective)..
• Blockade of the sympathetic nervous system include nerve block, sympathetic block of stellate ganglion and lumbar sympathetic block.
• Surgery in the form of decompression, transposition or neurotomy.
• Psychological techniques : The evidence base suggests that psychological treatment is beneficial in helping patients cope with the emotional consequences of pain but has only a weak effect on the intensity of pain itself. Studies of chronic pain management suggest that a combination of psychological, pharmacological and physical therapies, tailored to the needs of the individual patient, may be the best approach.
• Physical therapy: Which is important for neurogenic pain management because active people heal and adapt faster. Because muscle spasms can add significantly to a patient’s pain, it is vital that muscles be kept active and loose.
In patients with refractory neurogenic pain, administration of combination therapy of two or more agents with synergistic mechanisms, or implantation of neuromodulator devices, such as spinal cord stimulators, or intrathecal drug delivery pumps, can be acquired .
In the future, it is hoped that a combination of new pharmacotherapeutic developments, careful clinical trials, and an increased understanding of the contribution and mechanisms of neuroplasticity will lead to an improvement in the results of clinical treatments and prevention of neuropathic pain.