Postherpetic Neuralgia

1. See Also
   1. Herpes Zoster
   2. Zoster Ophthalmicus
2. Epidemiology
   1. Incidence following Herpes Zoster
      1. Age over 80 years: 30%
      2. Age 60-65 years: 20%
      3. Age <50 years: Uncommon (only <20% of neuralgia cases are under age 50 years)
3. Pathophysiology
   1. Most common complication following Herpes Zoster infection
   2. Virus replication destroys Basal Ganglia
4. Risk Factors
   1. Advanced age
   2. Female gender
   3. Severe prodrome or severe rash
   4. Severe acute pain with the acute zoster outbreak
   5. Prodromal pain prior to acute rash development
   6. Zoster Ophthalmicus
   7. Immunosuppression
   8. Diabetes Mellitus
   9. Systemic Lupus Erythematosus (SLE)
5. Symptoms
   1. Pain in dermatomal distribution persists >90 days after Herpes Zoster rash resolves
   2. Burning or electric-shock pain
   3. Hyperalgesia
   4. Allodynia
6. Management: Topical
   1. Lidocaine 5% patch (Xylocaine, or OTC 4% patch at $2/patch)
      1. Apply (up to 3 patches/day) to affected area for 12 hours of every 24 hours (must have 12 hours free)
      2. Expensive alternatives (e.g. ZTlido 1.8% at $9/patch), but unlikely to result in better efficacy
         1. (2018) presc lett 25(11): 66
      3. Evidence of benefit is marginal
         1. Derry (2014) Cochrane Database Syst Rev (7): CD010958 [PubMed]
   2. Capsaicin cream (Zostrix) 0.075% cream
      1. Apply to affected area three to four times daily
      2. Also marginal evidence for use
         1. Derry (2012) Cochrane Database Syst Rev (9): CD010111 [PubMed]
7. Management: Neuro-Psychiatric medications
   1. General
      1. Amitriptyline more effective than Gabapentin, but adverse effects limits tricyclic use
      2. Gnann (2002) N Engl J Med 347:340 [PubMed]
   2. Tricyclic Antidepressants
      1. Agents
         1. Amitriptyline (Elavil)
         2. Nortriptyline (Pamelor)
         3. Imipramine (Tofranil)
         4. Desipramine (Norpramin)
      2. Efficacy
         1. As effective and better tolerated than Opioids
         2. Raja (2002) Neurology 59:1015-21 [PubMed]
   3. Serotonin-Norepinephrine Reuptake Inhibitors (SNRI)
      1. Cymbalta
      2. Venlafaxine
   4. Anticonvulsants
      1. Gabapentin (Neurontin) titrate up to 600-1200 mg three times daily
      2. Pregabalin (Lyrica) titrate up to 200 mg three times daily
8. Management: Refractory Postherpetic Neuralgia
   1. See also Chronic Pain Management
   2. Transcutaneous Electric Nerve Stimulation (TENS)
   3. Biofeedback
   4. Nerve Block
   5. Opioid Analgesics
   6. Intrathecal Methylprednisolone 60 mg at L2-L3
      1. Good to excellent pain relief in refractory cases
      2. Relief persists longer than 2 years
      3. References
         1. Kotani (2000) N Engl J Med 343:1514-9 [PubMed]
9. Course
   1. Typical duration: 30 days to 6 months
   2. Some cases may persist years
10. Prevention
    1. See Herpes Zoster
    2. Herpes Zoster Vaccine (Zostavax)
11. References
    1. Fashner (2011) Am Fam Physician 83(12): 1432-7 [PubMed]
    2. Kost (1996) N Engl J Med 335:32-42 [PubMed]
    3. Rowbotham (1998) JAMA 28:1837-42 [PubMed]
    4. Saguil (2017) Am Fam Physician 96(10): 656-63 [PubMed]
    5. Stankus (2000) Am Fam Physician 61(8):2437-44 [PubMed]