• Neuropathic pain overview
    • Initiated or caused by a primary lesion or dysfunction of the nervous system
    • Can be classified as 'central' or 'peripheral'
    • IASP definition
      • An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in such terms
    • Symptoms
      • Positive
        • Hyperalgesia
          • Increased response to normally painful stimulus
        • Allodynia
          • Pain in response to non-painful stimulus
        • Hyperaesthesia
          • Increased sensitivity to stimulation (includes allodynia and hyperalgesia)
        • Dysaesthesia
          • Unpleasant abnormal sensations, not necessarily painful (includes allodynia and hyperalgesia)
        • Paraesthesia
          • Abnormal sensation but not unpleasant or painful
        • Hyperpathia
          • Abnormal pain response to stimuli (often repetitive) applied to an area of decreased sensitivity.
      • Negative
        • Hypoaesthesia
          • Decreased sensitivity to stimulation
        • Hypoalgesia
          • Decreased sensitivity to painful stimuli
    • Signs
      • Trophic
        • Hair loss, skin thickening, calluses, ulcers
      • Vasomotor
        • Temp/colour differences, oedema
      • Sudomotor
        • Hyperhidrosis, dryness
      • Musculoskeletal
        • Muscle wasting
        • Deformity
        • Osteopenia
    • Investigations
      • Quantitative sensory testing (QST)
    • Potential treatments
      • Ion channel blockers - inhibit the tetrodotoxin resistant Na⁺ channels
      • NGF has been tried
      • NMDA receptor antagonists such as ketamine
      • GABA or glycine agonists may be helpful
      • Gene therapy
    • Treatments
      • Pharmacological
        Link:ceaccp.oxfordjournals.org/content/5/4/134.full.pdf?sid=c868e507-1583-4a6a-a4c6-03b7178e0072
        • TCAs
        • Anticonvulsants
        • Opioids
        • Cannabinoids
        • Topical capsaicin
        • Lidocaine
      • Psychological
        • Relaxation/diversion
        • Counselling
        • CBT
        • Stress management
        • PMP
      • Physical
        • Simple
          • Physio
          • TENS
          • Accupuncture
        • Complex
          • SCS
          • Intrathecal drug delivery
          • Nerve blocks
    • Mechanisms of pain
      • Nociceptive terminal may become abnormally responsive and can express different receptors
      • Neuroma formation may produce ectopic firing and exhibit lower thresholds to stimulation
      • Axons change their expression of voltage-gated Na⁺ channels and alter their excitability
      • DRG changes occur and they sprout sympathetic terminals which may contact sensory neurones resulting in Nociceptive/sympathetic cross talk
      • Dorsal horn is extremely complex with complex connections and descending pathways all of which show considerable plasticity. In particular, there are reductions in GABA and glycine inhibition, and increases in NMDA receptors
      • Nerve injury causes rewriting of the dorsal horn due to the loss of NGF
    • CEACCP
      Link:ceaccp.oxfordjournals.org/content/2/3/65.full.pdf?sid=facc3f99-e994-4074-9270-a2763dca9bb9