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Neuropathic pain

Updated: Jul 11, 2021



Central neuropathic pain

e.g. Spinal cord injury, stroke, MS, syringomyelia


Peripheral neuropathic pain

e.g. Postherpetic neuralgia, radiculopathy, phantom limb pain, polyneuropathy


Mixed neuropathic pain

e.g. Post herpetic neuralgia


Occurs in 20% of diabetics

20-50% of herpes zoster patients develop PHN

Post-surgical >10%

1/3rd of cancer patients

>50% of low back pain may have some associated neuropathic pain


Screening tools:

  • DN4

  • LANSS

  • Neuropathic pain scale questionaire

  • Pain DETECT


When working out neuropathic pain - you NEED to make sure it is neuroanatomically plausible


Mechanisms:

  • Lowered threshold of firing

  • Increased Na channel density

  • Chemical excitation of non-nociceptors

  • Recruitment of nerves just outside the injured area (Ephaptic)

  • Ectopic discharge

  • Loss of inhibitory pathways

  • Central sensitisation (maintained by peripheral stimulation)

  • Antidromic neurogenic inflammation

Problems treating neuropathic pain:

  • Higher average pain scores

  • Lower QOL

  • Higher pharmacological load

  • Less pain relief with treatment

  • Inability to tolerate treatments is common

Prevention of neuropathic pain:

Amitriptyline has been shown to reduce prevalence and severity of post-herpetic neuralgia by 50% compared to placebo

Use of antivirals has been shown to reduce the severity and duration of pain in PHN


Operative techniques for PSP and amputation pain are important. Ketamine has mixed evidence for prevention - better for Post surgical prevention now.


References / Articles / Resources

FPM Module 4

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