48. Herpes zoster and Postherpetic neuralgia

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48. Herpes zoster and Postherpetic neuralgia
R2 ? ? ?
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Object of this chapter

• Epidemiology
• Natural History
• Pathophysiology
• Treatment
• Prevention of Herpes zoster and Post herpetic
  neuralgia

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Epidemiology of Herpes Zoster (1)

• Virus ? reactivation
• VZV infection (primary chicken pox infection) ?
  sensory ganglia ? ??
• Single dorsal root ? cranial nerve ganglion
• Corresponding dermatome, neural tissue ??? spread
• Annually in approximately 500,000 in USA
• Lifetime incidence
• 20-30 of population
• 85 ? ?? ?? ? ? 50 ? ?? ???

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Epidemiology of Herpes Zoster (2)

• ?? ??
• Aging
• Cell-mediated immunity ? ??? ??
• HIV infection, ??? ?? ??, ?, ?? ??
• BMT, immunosuppressive treatment
• VZV transmission
• Primary chicken pox infection
• Latent and reactivated VZV infection in
  population
• Seronegative individual ? vesicular phase of rash
• Seropositive individual ? subclinical reinfection
  

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Natural History (1)
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Natural History (2)

• Zoster sine herpete
• Dermatomal pain without rash
• VZV DNA in CSF
• Neurological disorder
• Motor neuropathy, cranial polyneuropathy,
  transverse myelitis, cerebral angitis, stroke
  after ophthalmic zoster
• Ophthalmologic Cx
• 26 incidence
• Keratitis, uveitis, iridocyclitis,
  panophthalmitis, glaucoma

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Treatment (1)

• Antiviral agent
• Acyclovir, famciclovir, valacyclovir
• Viral replication ??
• Viral shedding ?? ??
• Rash healing ??, acute pain ??, severity ??
• Most important complication of herpes zoster
  infection
• Chronic pain (refractory in 1st line treatment
  but also to all other therapies)
• Prevention of Postherpetic neuralgia
• Viral replication ? ???, neural damage ?? ? PHN
  ? ???? ????

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Treatment (2)

• Antiviral Treatment in HZV
• Prolonged pain ? risk ? ?? ????, ?? ?????, PHN ?
  ?? ??? ??

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Treatment (3)

• Supplement treatment
• Corticosteroids
• Tricyclic antidepressants
• Nerve block with local anesthetics and
  corticosteroids
• Peripheral ,sympathetic and epidural block
• Role in preventing PHN ?
• Antiviral treatment effective pain relief
• Further lessen the risk of PHN
• If no benefit ?

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Prevention

• Live attenuate varicella vaccine
• Effective in protecting against varicella and its
  complication
• Administration of a varicella-zoster vaccine to
  older adult
• Mean anti-VZV antibody level, VZV-specific
  cell-mediated immunity level ? ??

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POSTHERPETIC NEURALGIA
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Epidemiology and Natural History (1)

• Definition
• Rash healing ?? ?? ??, rash onset ? 6 ?? ?? ?? ??
  pain

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Epidemiology and Natural History (2)

• ? ?? ?? ??
• Reduction in quality of life
• Depression, psychological, distress, physical,
  occupational, and social disability
• Pain ??
• Herpes zoster sharp, stabbing pain
• PHN burning pain
• Risk factor of PHN
• Old age
• Pts with mire severe acute pain
• Painful prodrome
• HZ rash ?? ? ??

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Epidemiology and Natural History (3)

• Other putative risk
• ?? ? dermatome ? ?? sensory abnormality
• Subclinical sensory deficits
• DM
• Cell-mediated and humoral immunity
• MRI brain stem, cervical cord abnormality
• EMG motor abnormality
• Psychological distress
• Fever

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Pathophysiology

• Neural damage ? ??
• Development of PHN ? ??
• Post-mortem study
• In pts with PHN
• Dorsal horn atrophy
• Pathological change
• Not on the unaffected site
• Herpes zoster Hx ? ???, pain ? ?? ?? ?? ??
• ???, ?? ?? pathological change ? ??? ??

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Treatment

• 1st line treatment
• Gabapentin
• Lidocaine patch 5
• Tramadol
• 2nd line treatment
• Tricyclic antidepressants
• Opioid

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Gabapentin

• 2nd generation anti-epileptic drug
• Reduction in daily pain ratings
• ??? ??, mood, ?? ?? ??
• Side effect
• ??, dizziness, mild peripheral edema
• Gait balance problem
• Cognitive impairment in elderly
• ???? ??? ??, ??? ???? ?? ??? ?? low dose ? start

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Tramadol

• Norepinephrine serotonin reuptake inhibitor
• Major metabolite ? mu-opioid agonist
• Maximum dose 1?? 400 mg
• Increased risk of seizure in pts with tramadol
• Serotonin syndrome
• SSRI, MAOI ? ? ?? ???
• ???? ??? ??, low dose ? start
• 50 mg qd or bid

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TCAs

• Reduce pain in diabetic neuropathy and
  postherpetic neuralgia
• Amitriptyline
• Most widely used TCAs
• Elderly pts
• Cardiac toxicity and side effect ? ??
• Side effects
• Dry mouth, constipation, sweating, dizziness,
  disturbed vision, drowsiness

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Lidocaine patch 5

• Excellent safety and tolerability
• Mild side effect
• Mild skin reaction

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Opioids

• Iv morphine
• P.O oxycodone
• Maximum dosage of 60 mg daily
• Significant benefit on pain, disability and
  allodynia
• Side effects
• Constipation
• Sedation
• Nausea
• Cognitive dysfunction

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Beyond 1st and 2nd line treatment

• Sympathetic nerve block
• ????, ?? ??
• Longer-lasting benefit ? ???? ??
• ?? ??? ?? ??? ???
• Intrathecal methylprednisolone
• Dramatic benefit in PHN pain
• Not approved by the FDA
• Spinal cord stimulation
• Pain relief daily function ? ??
• ??? ??? ??? PHN ? ??? ?? ? ?? ??
• Comprehensive approach ? ??

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49. PHANTOM PAIN
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Phantom sensation (1)

• ?? ?, ??? ??? ?? ???? nonpainful sensation
• ?? ? 6?? ???, ? 90 ??? ????? ??
• ?? ?? ???, tongue, bladder, rectum, breast,
  genitalia ???? ??? ??? ??

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Phantom sensation (2)

• Kinetic sensation
• ??, ??? ?? ???? ???? ??
• ?) ??? ???? flexion extension
• Kinesthetic perception
• ??? ???, ???, position ? distorted representation
• ?) ??? ?? ??
• Extroceptive perception
• Paresthesia, tingling, touch, pressure, heat,
  cold, wetness
• Distal portion of limb ?? ??
• Hand, feet
• Rich innervations of these regions, large
  cortical representation

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Telescoping

• Phantom body part ? ???? shortening ? ?? ??? ???
  ?
• Distal part of limb ? more proximal ?? ??? ??
• ?) ???? forearm ? ???, stump ??? ??? ??
• ?? ?? ??? 2/3 ?? ??

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Phantom pain

• Missing or deafferented body part ?? ????,
  painful, unpleasant sensation
• Post-amputation ??? 2/3 ?? ??, ?? ?, 6?? ?? ??
• Extereoceptive like pain (Knifelike or sticking)
• ? proprioceptive like pain (Squeezing burning)
• ?? 6?? ??, severity, duration, frequency ? ?? ?
• ?? pain ? 6 ?? ?? ???? ??, ??? ???

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Stump pain

• Pain localized to residual body part
• ? 20 ??, 2 ? ?? ??
• Secondary to local pathologic process
• Infection, local ischemia
• Lesion of skin, soft tissue, or bone
• Bony spur, ill-fitting prosthesis ?? ??

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Theoretical Mechanisms
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Treatment

• Not only the physical functioning of the
  individual but may also have significant
  psychological, social consequences
• Controlled trials of preoperative and early
  postoperative interventions
• Epidural anesthesia, regional nerve block, iv
  calcitonin, transcutaneous electrical nerve
  stimulations
• Controlled trials of late postoperative
  interventions
• TENS, ketamine infusion, vibratory stimulation

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Treatment (Stump pain)

• 1st step
• Identify specific etiology for pain
• Examined for localized tender spot
• Bony abnormality, evidence of ischemia
• TENS
• Beneficial in 25- 50 of case
• NSAIDS, COX-2 inhibitor, opioids
• Pain ? somatic, mechanism ? ??
• TCAs, anticonvulsants (gabapentin)
• Neuropathic mechanism
• Surgical therapies

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Treatment (Phantom pain)

• Amputation? ??, ????, ??? ?? ?? ?? ? ??? ??? ???
  ?
• Preemptive epidural or peripheral nerve block
• ?? ? 72 ?? ?? ??
• Medical treatment
• Opioid
• Calcitonin
• Ketamine
• Physical therapy
• Psychological intervention
• Neurostimulation
• Ablative procedure