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NEUROPATHIC PAIN
Neuropathic pain is the sensation of pain due to abnormal discharges of impaired or injured neural structures in the peripheral &/or central nervous system.
It is characterized by hyperesthesia, hyperalgesia and allodynia.
Common neuropathic pain syndromes are central neuropathic pain, painful diabetic peripheral neuropathy, postherpetic neuralgia, trigeminal neuralgia, postsurgical neuropathic pain, HIV-related neuropathy, lumbosacral radiculopathy and complex regional pain syndrome.

Introduction

 Neuropathic pain

  • Pain arising as a consequence of a lesion or disease of the peripheral and/or central nervous system affecting the somatosensory system
  • Nerve conduction blockage causes nerve dysfunction, leading to numbness, weakness and loss of deep tendon reflexes in the area of involved nerve
  • Neuropathic conditions (eg brain infarction, spinal cord trauma, ischemic neuropathies) also cause aberrant symptoms of spontaneous and provoked pain

Pathophysiology

  •  Mechanisms involved in the pathophysiology of neuropathic pain:
    • At the neuroma site and along the length of the nerve after nerve injury there is proliferation of sodium channels that results to foci of ectopic activity that leads to spontaneous pain observed in patients with neuropathic pain
    • Sympathetic axons sprout around the dorsal root ganglion where the neuropathic pain is sympathetically mediated
    • Nerve injury diminishes the inhibitory control over dorsal horn neurons through various mechanisms
    • Central sensitization of the dorsal horn neurons manifested as a heightened response to noxious stimuli as well as pain associated with stimuli in the non-noxious range

Epidemiology

  • Prevalence of neuropathic pain varies due to its multiple etiologies and presentations
  • In Malaysia, the prevalence of neuropathic pain is estimated to range from 1.5% of the general population
    In Europe, it is estimated to afflict 7-8% of the general population
  • In studies using population-based questionnaires in Canada, it shows the prevalence as 4-8%
  • Diabetic polyneuropathy has been estimated to occur in 10-100% of diabetic patients in the Western world

Signs and Symptoms

  • Characterized by burning, stabbing and electrical pain which may be constant, aching or paroxysmal, pins and needles
  • Nerve conduction blockage causes nerve dysfunction, leading to numbness, weakness and loss of deep tendon reflexes in the area of involved nerve
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