Neuropathic Pain Flashcards
Neuropathic
Pain caused by a lesion or a disease of the somatosensory
system
● Peripheral - e.g., painful diabetic neuropathy, post-herpetic
neuralgia, carpal tunnel syndrome, trigeminal neuralgia
● Central - e.g., post-stroke, multiple sclerosis, spinal cord
injury
● Mixed - e.g., amyloidosis, vitamin deficiencies, chemical toxins
Pain may be a manifestation of nerve injury, but there are
few predictors to indicate which patients will develop this
complication
neuropathy may not always be painful
Neuropathic Pain
describe
Pain may be spontaneous or stimulus evoked
Often described as burning, tingling, sharp, or stabbing
Paresthesia/dysesthesia, allodynia, hyperalgesia are
common
No single sign or physical finding is diagnostic
● ~ 50% of patients with musculoskeletal pain use words that
are commonly associated with neuropathic pain to describe
Non-pharmacologic Treatment
● Psychological (e.g., CBT)
● Physiotherapy
● Exercise
● Stress management
● Education
Chronic Neuropathic Pain
Management
gabapentinoids / TCA/SNRI
then tramadol / opioids
cannabinoids
4th line agents (topical lidcoane, methadone, lamotrigine)
No NSAIDS, acetaminphen
Dont typically respond
Unless for mixed pain
Painful Diabetic Neuropathy
Damage of the nerves and blood vessels in arms or legs
Often present with gradual onset of paresthesias and
pain in legs and feet
Allodynia and burning pain are common and often worse
at night
Examination will often show graded distal sensory loss
Good glycemic control can prevent appearance and
worsening
1st Line
→ Gabapentinoids, SNRIs, TCAs
● Are one of these options preferred?
Evidence
Duloxetine and pregabalin appear similarly effective for
diabetic peripheral NeP for ≥ 50% pain reduction (open label RCT)
with similar rates of patients experiencing any AE
Pregabalin and amitriptyline appear similarly effective for
≥ 50% pain reduction in patients with diabetic NeP, but
pregabalin associated with fewer AE (crossover RCT without ITT)
● NNH 3 for amitriptyline
Duloxetine and amitriptyline appear similarly effective for
≥ 50% pain reduction in patients with diabetic NeP, but
duloxetine appears better tolerated
What about combinations of 1st line therapy?
Combination of TCA or SNRI with gabapentinoid might
reduce diabetic NeP more than either alone in patients
who respond to monotherapy, but might not in patients
who do not respond to monotherapy
Amitriptyline most common AE drowsiness
Switch to duloxetine if no effect of pregab
If partial effect from pregab add on duloxetine
2nd Line
tramadol, other opioids (most studied: morphine, oxycodone)
May consider during acute exacerbations or when other
options ineffective
Shown to have a modest effect in peripheral NeP
less beneficial the more cnetral the pain is
Challenges with long-term use (AEs, misuse, etc)
if opioids do show benefit, it is a 30% improvement, not 50%
some list it as 3rd or 4th line
trials with combination thearpy
Started on either ami, pregab or dulox
1st 6 wks, if pain score 3 or less
If not there, would add 2nd agent
No diff in intiial agent used
2nd agent led to further decrease in pain
Not much diff between the combinations either
All similar in reducing pain
3rd Line
→ Cannabinoids
Chronic neuropathic pain conditions are where
cannabinoids have shown the most promise
Evidence to suggest a modest effect on neuropathic pain
dosing trial is similar to chronic pain
pdt with THC and CBC may be more beneficial than nabilone
4th Line Agents
SSRIs (citalopram, paroxetine, escitalopram)
● Show limited effect on NeP
Topicals (lidocaine, capsaicin) → will come back to these
Methadone
● May be useful
● Challenges with use
Postherpetic Neuralgia
Long lasting complication of reactivation of Varicella
Zoster Virus
● Postherpetic neuralgia = pain persisting > 3
months beyond rash duration
● Occurs in 10-50% of patients who experience this
Pain may rarely occur months to years after
resolution of acute herpes zoster episode and can be
associated with a precipitating factor (e.g., surgery)
Herpes Zoster (Shingles
● Risk factors for activation:
○ Age > 50 years (risk ↑ with age due to ↓ immune control of VZV)
○ Decreased immunologic competence
● Presents as severe or stabbing pain and dysesthesia
followed by a blistering skin eruption
○ Rash typically resolves in 2-4 weeks
● Pain can persist > 4 weeks after healing
● Main pain-related goals of treatment of herpes zoster:
○ Relieve acute pain
○ Prevent postherpetic neuralgia
● Treatment involves a 7 day course of antivirals and
24 analgesics for management of acute pain
Herpes Zoster (Shingles)
Acute pain treatment
● Mild
○ APAP
○ NSAIDs
● Moderate - Severe
○ Tramadol
○ Strong opioids
○ Topical lidocaine (NOT topical capsaicin here)
Capsaicin causes buring and acute pain can feel like brunign too
○ Consider adjuvant with gabapentinoid or TCA
Cannot just start out w gabapentinoid or TCA
- Taks a while for it to start working
This is acute pain
○ Prednisone (if severe)
25 ■ (60 mg/d x 7, then 30 mg/d x 7, then 15 mg x 7)
May improve qol, does not speed up recovery or decrease incidence of postherpetic neuralgia
Risk factors for postherpetic neuralgia:
● Increasing age
● More severe acute pain
● Larger rash surface area
● Ophthalmic involvement
● Severe prodromal pain
Symptoms typically have unilateral and dermatomal
distribution and may be intermittent or constant
● Pain may be described as aching, burning, itchy, sharp
● Allodynia, hyperalgesia may be present
Pain can last for years and cause substantial suffering
and reduction in QOL
● For patients with severe pain 3 months after rash
onset, average duration of PHN is ~ 12 months
Pain can be discontinuous, with pain-free intervals of
varying durations
