48. Herpes zoster and postherpetic neuralgia 49. Phantom pain

1. 48. Herpes zoster and postherpetic neuralgia49. Phantom pain 마취통증의학과 R2 민진기

2. Herpes zoster and postherpetic neuralgia Objective of this chapter overview of epidermiology, natural Hx, pathophysology, treatment, and prevention of herpes zoster and postherpetic neuralgia Herpes zoster- viral inf. that is accompanied by acute pain in majority of pts. PHN- diagnosed when HZ pain persists

3. Herpes zosterepidermiology Reactivation of virus and its spread from single dorsal root or cranial nerve ganglion to corresponding dermatome and neural tissue of same segment Annually in approximately 500,000 in USA During lifetime of as much as 20~30%of population

4. epidermiology As many as 50% of those living until 85 years of age Marked increase in incidence with aging Also significantly increased in pts. with supressed cell-mediated immunity Can be transmitted during vesicular phase of rash  primary inf. in seronegative individual

5. Natural history Prodrome bregins several days before rash onset Thoracic dermatome- 50~70% of all case cranial, cervical, and lumbar- each 10~20% Rash vesicle  crust healed: 2~4 weeks

6. Natural history Acute pain gradually resolves before or shortly after rash healing in most case Dermatomal pain without rash zoster sine herpete: finding of VZV DNA in CSF Neurological disorder- motor neropathy, cranial polyneritis, transverse myelitis, cerebral angiitis, storoke after ophalmic zoster Ophthalmological Cx- 2~6%: keratitis, uveitis, iridocyclitis, panophthalmitis and glaucoma

7. Treatment Acyclovir, famciclovir, and valacyclovir- inhibit viral replication, reduce duration of viral shedding, hasten rash healing, decrease severity and duration of acute pain Most important Cx- chronic pain( can be refractory) :prevention of PHN important clinical goal Inhibit viral replication limit degree of neural damage PNH 가능성 줄어듬

8. treatment Antiviral Tx in HZ significantly reduce risk of prolonged pain but not prevent PHN in all pts.

9. treatment Supplemently Corticosteroid Tricyclic antidepressant Nerve block Combinig antiviral therapy with effective relief of acute pain in pts. with HZ will further lessen the risk of PHN

10. prevention A live, attenuate varicella vaccine- effective in protecting against varicella and its complications Incidence of varicella- substantially reduced in regions where vaccine is accepted

11. Post herpetic neuralgiaepidemiology and natural history Definition- variable: from any pain persisting after rash healing to pain that has persisted at least 6 months after rash onset

12. Epidemiology and natural history Herpes zoster- sharp, stabbing pain PHN- burning pain Risk factor of PHN old age(well estabilished) pts. with more severe acute pain pts. with painful prodrome greater severity and duration of HZ rash

13. Epidemiology and natural history Other putative risk factor of PHN greater sensory abn. in affected dermatome generalized subclinical sensory deficits diabetes more pronounced cell-mediated and humoral immune response MRI brain stem and cervical cord abn. EMG motor abn., psychological distress, fever

14. pathophysiology Greater neural damage more development of PHN Post-mortem study, dorsal horn atropy and pathological change on affected side, not on un affected side,also not in pts. with history of HZ whose pain did not persist

15. treatment 1) Tricyclic antidepressants 2) Gabapentin 3) Lidocaine patch 5% 4) Tramadol 5) Opioid analgesics 2), 3), 4)- first line treatments 1), 5)- second line treatments: greater caution in often elderly with PHN

16. gabapentin Second-generation antiepileptic drug Side effect- somnolence, dizziness and mild peripheral edema gait and balance problem, cognitive impairment in elderly To reduce side effect and increase pts. compliance, should be initiated low dosage

17. tramadol Norepinephrine and serotonin reuptake inhibitor with major metabolites that is mu-opioid agonist Increased risk of seizure in pts. treated with tramadol Serotinin syndrome may occur with SSRIs and MAO inhibitors To decreased likelihood of side effect, should be initiated at low dosage

18. TCAs Reduce pain in diabetic neuropathy and postherpetic neuralgia Amitriptyline- clinically most widely used TCAs Despite efficacy of TCAs in treatment of PHN, cardiac toxicity and side effect profile reguire caution in elderly Side effect- dry mouth(m/c), constipation, sweating, diziness, disturbed vision, and drowsiness

19. Beyond first and second-line treatment Sympathetic nerve block- temporary pain relief but typically do not provide longer-lasting benefits Intrathecal administration of methylprednisolone Spinal cord stimulation demonstrated long-term benefits in 82% Conclusion: comprehensive treatment approach

20. Key points • HZ (shingles)- reactivation of VZV which establishes latency in sensory ganglia after primary infection (chicken pox) • Vesicular rash heals within 2~4 weeks and is accompanied by pain in majority in pts. • Older age- increased risk due to age associated decline in VZV specific cell mediated imminity • Antiviral Tx inhibit viral replication, reduce duration of viral shedding, hasten rash healing, decrease duration of pain

21. Key points • Peripheral, sympathetic, and epidural nerve block appear to relieve acute pain in HZ, but their role in PHN is uncertain • PHN- pain that continues after healing of rash. can last for years • Risk factor of PHN- older age, more intense acute pain, more severe rash, prodrome before rash • Qualitatively different type of pain that characterize PHN have different underlying mechanism

22. Phantom pain Amputation of limb painful and nonpainful sequelae such as phantom sensation, telescoping, stump pain and phantom pain Postamputation pain delay rehabilitation, limit use of prosthetic devices, and profound influence on quality of life of amputee

23. Phantom sensation Nonpainful sensation perceived as emanating from missing body part Common after surgery with 90% during first 6 months after surgery Excision of other body part( tongue, bladder, rectum, breast, and genitalia) may also present with phantom sensation

24. Phantom sensation Kinetic sensation- perception of movements in amputated body region (flexion and extension of toes) Kinesthetic perception- distorted representation in size or position of missing part (perception that hand of foot is twisted) Extroceptive perception- paresthesia, tingling, touch, pressure, itching, heat, cold, wetness

25. Phantom sensation Complete paraplegic and quadriplegic pts. also have phantom sensation Commonly experienced in distal portion of limb (hand and feet)- possibly due to rich innervation of these region and large cortical representation of these region

26. telescoping Perception of progressive shortening of phantom body part resulting in sensation that distal part of limb is becoming more proximal Feel a hand close to stump, but not forearm of distal arm Occur in two-thirds of limb amputees

27. Phantom pain Perception of painful, unpleasant sensation in distribution of missing or deafferented body part Occur in two-thirds of post amputation pts. in first 6 months after surgery Extereoceptive like pain (knifelike or sticking) proprioceptive type of pain (squeezing and burning)

28. Phantom pain Frequecy, duration, and severity decrease during first 6 months and did not change significantly One factor that increase incidence of phantom pain- pain in limb before amputation

29. Stump pain Pain localized to residual body part Incidence of stump pain more than 2 years after amputation- about 20% Usually secondary to local pathologic process such as inf., lesion of skin, soft tissue, or, bone, or local ischmia

30. Theoletical mechanism

31. Treatmentstump pain First step- to identify specific etiology for pain Examined for localized tender spot (neuroma), ulcer, bony abn.,evidence of ischemia, recurrence in case of malignancy TENS- beneficial in 25~50% of pts.

32. stump pain Pain by somatic mechanism: NSAIDs, COX-2 antgonist, and/or opioids Pain by neuropathic mechanism: TCAs, anticonvulsants Specific rectifiable pathology-protruding bone, bony exostosis, wound inf., poorly healed wounds surgical treatment

33. Phantom pain treatment Education, and counseling of pts. on consequences of amputation, rehabilitation process, prosthetic option Preemptive epidural or peripheral nerve block Wide variety of medication- opioid, calcitonin, ketamine Physical therapy Psychological intervention Neurostimulation Ablative procedure

34. Flow rates are for gravity flow of one unit of packed cells diluted with 250 mL normal saline passing through catheters of equal length. Hagen-Poisseuille equation에 따르면 flow rate는 압력의 변화와 r의 4제곱에 비례하며 점성이나 line의 길이에는 반비례한다.