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DR. AYESHA ASLAM

POST-HERPETIC NEURALGIAAND ITSMANAGEMENT

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Post herpetic Neuralgia is defined as painalong cutaneous nerves persisting formore than 30 days after the onset of

Herpes Zoster rash.

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INCIDENCE

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incidence of post herpetic neuralgiaincreases with age

uncommon in patients younger than 60years

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0

1

2

3

4

5

6

7

8

9

10

01 MONTH 03 MONTHS 01 YEAR

8.8

2.0

PATIENTS < 60 YRS

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0

5

10

15

20

25

30

35

4045

01 MONTH 03 MONTHS 01 YEAR

INCIDENCE

40.8

13.0

7.8

PATIENTS > 60 YRS

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PATHOPHYSIOLOGY OF PHN

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Varicella-Zoster Virus

Reactivation- HZ

Replication of virus inGanglionic nerve cells

Migration along Peripheral

Afferent Sensory Pathways

Demyelinatin of Afferent fibres& Dorsal horn neuronal

plasticity

Loss of inhibition andincreased activity withinsensory afferent fibres

Post-Herpetic Neuralgia

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neurochemical, physiologicaland anatomical modifications

to afferent and central neurons

afferent terminal sprouting andinhibitory interneuron loss

Na channel accumulation

Hyperexcitability

increased NMDA glutamatereceptor-dependent excitabilityof spinal dorsal horn neurons

neuropathic pain state of PHN

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FREQUENCY

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In US each year approximately 1,000,000individuals develop herpes zoster.

Of those individuals approximately 20%,or 200,000 individuals, developpostherpetic neuralgia.

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PRE-DISPOSING FACTORS

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Susceptibility to HZ - > in caucasians

Old & Debilitated

Immuno-compromised patients

Acute neuritis in the early phase ofdisease

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CLINICAL PRESENTATION

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SYMPTOMS: Pain

- ranges from mild discomfort to severeburning, aching or gnawing

- constant

Allodynia

Headaches Fatigue

Sleep disturbances

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PAIN INTENSITY IN PHN

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SIGNS: Cutaneous scarringof HZ lesions in the

affected areas

Altered sensationsover the affecteddermatome

- Lowered threshold for cold, warmth &vibration-Poor two-point discrimination

Muscle weakness, tremor or paralysis -ifthe nerves involved also control muscle

movement

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SCARRING AND PIGMENTARY CHANGES INTHE AFFECTED DERMATOME

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DIAGNOSIS

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History

Examination - dermatomal pattern ofdistribution and the appearance of the herpeszoster rash

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In cases where the diagnosis is in doubt: PCR Techniques - detect the varicella DNA in

fluid taken from the vesicles

Direct Immunofluorescent Antigen StainingTest

VZ specific IgM

Virus cultures

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PREVENTION

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No treatment has been shown to preventpostherpetic neuralgia completely.

However, some treatments may shortenthe duration or lessen the severity ofsymptoms.

Prevention could be:

Primary

Secondary

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PRIMARY PREVENTION

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The only really effective way of preventingpost herpetic neuralgia from developing isto protect yourself from shingles and/or

chicken pox with the

chickenpox (varicella) vaccinethe shingles (varicella-zoster) vaccine

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CHICKENPOX VACCINE Varivax vaccine routinely given to children aged 12 -18

months to prevent chickenpox also recommended for adults and older

children who have never had chickenpox

does not provide 100% immunity butreduces the risk of complications andseverity of the disease.

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VACCINE FOR CHICKENPOX

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SHINGLES VACCINE Zostavax vaccine

helps protect adults over 60 who have had

chickenpox. Recommended that people over 60 have this

vaccine, regardless of whether or not they

have had shingles before. The vaccine is preventative, and is notused to treat people who are infected.

http://www.medicalnewstoday.com/articles/107639.phphttp://www.medicalnewstoday.com/articles/107639.phphttp://www.medicalnewstoday.com/articles/107639.phphttp://www.medicalnewstoday.com/articles/107639.phphttp://www.medicalnewstoday.com/articles/107639.phphttp://www.medicalnewstoday.com/articles/107639.php

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VACCINE FOR SHINGLES

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SECONDARY PREVENTION

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Aggressively treating shingles with

antiviral agents such as Acyclovir within 02days of the rash can reduce both the risk

of developing subsequent neuralgia or the

length and severity if it does.

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TREATMENT OF PHN

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DIRECT PAIN INHIBITION

ANALGESICSo Topicalo Systemic

PAIN MODIFICATION THERAPY

ANTI-DEPRESSANTS

ANTI-CONVULSANTSSTEROIDS

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OTHERS

TENS PERIPHERAL NERVE STIMULATION SPINAL CORD STIMULATION SURGICAL INTERVENTION

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1. ANALGESICS

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TOPICAL AGENTS Lidocaine Skin Patches

small, bandage-like patches that containlidocaine

must be applied directly to painful skin todeliver relief for 04-12 hours.

avoid contact with mucus membranese.g. eyes, nose and mouth.

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TOPICAL CAPSAICIN an extract of hot chilli peppers

depletes substance P from nerveterminals & desensitizes them

0.025 % cream (Zostrix) applied four times

daily

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EMLA A eutectic mixture of lidocaine and

prilocaine

Reported to be beneficial in pain relief

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Aspirinmixed into an appropriate solvent such asdiethyl ether may reduce pain

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SYSTEMIC AGENTS OPIOIDS

- Oxycodone (Oxycontin) 10 mg twicedaily

- a small risk of dependency exists

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PAIN MODIFICATION THERAPY

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1. TRICYCLICANTI- DEPRESSANTS Affect key brain chemicals, such as

serotonin and norepinephrine

Influence how the body interprets pain

Dosages tend to be lower

Examples include

Amitriptyline 10-75mg /d

Desipramine (Norpramin) 25mg/dNortriptyline (Pamelor) 10-25mg/d

Duloxetine (Cymbalta)

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AMITRIPTYLINE Single most effective drug

Anticholinergic and cardiovascular side-effects must be considered

Given at bedtime to improve tolerance

and prevent daytime somnolence

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2. ANTI-CONVULSANTS effective in calming down nerve impulses

stabilize abnormal electrical activity in thenervous system caused by injured nerves

Effective in patients who experiencestabbing pain in addition to the burningsensation

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Examples include

Gabapentin(Neurontin) 100-300mg/d

Pregabalin(Lyrica) 50-75mg/d

Lamotrigine (Lamictal)Carbamazepine (Tegratol)

Phenytoin (Dilantin)

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3. STEROIDS METHYLPREDNISOLONE is injected into

the area around the spinal cord i.eintrathecally

Effective for patients with chronic pain

Administered only after the shinglespustular skin rash has completely

disappeared

Patients unresponsive to oral/topicaltherapy should be considered

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TRANSCUTANEOUS ELECTRIC NERVESTIMULATION

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Electrodes are placed over the areaswhere pain occurs

Small electrical impulses are emitted and

provide pain relief

The patient turns the TENS device on andoff as required

TENS stimulates ENDORPHIN release-the body's natural painkillers

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PERIPHERAL NERVE STIMULATION

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The devices are surgically implantedunder the skin, along the course ofperipheral nerves.

As soon as the electrodes are in place,they are switched on to administer a weakelectrical current to the nerve.

The patient will have a tingling sensationin the area.

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SPINAL CORD STIMULATION

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The spinal cord stimulatoris insertedthrough the skin into the epidural spaceover the spinal cord

Works in the same way as peripheralnerve stimulator

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SURGICAL TREATMENT

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For patients who do not respond tomedical therapy

Outcome of surgical procedures in case of

PHN is far from certain in regard to painmanagement

Blockade of affected nerves

Neurectomy Surgery at the level of dorsal root ganglion

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PROGNOSIS

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The natural history of PHN involves slowresolution of the pain syndrome

In those patients who develop PHN, most

will respond to agents such as the TricyclicAntidepressants

A subgroup of patients may develop

severe, long-lasting pain that does notrespond to medical therapy

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