Herpes Zoster

Introduction

• Herpes zoster is categorized as a viral infection caused by varicella zoster virus. It is commonly known by the names shingles, zona or zoster. 
• Clinically, it can be grouped under 3 phases namely prodrome, acute and chronic. During initial viral replication active ganglionitis develops with resultant neuronal necrosis and severe neuralgia.
•  It is characterized by the occurrence of a painful skin rash(maculopapular lesions) in a stripe or belt-like dermatomal pattern which is limited to one side of the body and does not cross the midline. These rashes convert into vesicles with erythematous base. The vesicles finally turn into scabs and heal in 2-3 weeks.
• Ophthalmic division of trigeminal nerve is most commonly involved.

Pathophysiology

 This particular virus is responsible for the acute onset of chicken pox, usually occurs in children and young adults. Herpes zoster is a continuation of this infection as the virus is not eliminated from the body but becomes latent in the cranial nerves, dorsal roots, nerve cell bodies or autonomic ganglion.The virus may travel from one ganglion to another thereby infecting other dermatomes. 

Herpes zoster mainly occurs in older individuals (50 yrs of age) with imuunocompromise status due to age, psychological stress, cancer therapies,underlying malignancy, mechanical trauma, hereditary or exposure to immunotoxins etc. recurrence is rare; in HIV patients the recurrence rate is quite high.

Clinical features

• Symptoms of herpes zoster include headache, fever, and malaise. These are potentiated by paresthesia –pricking pain, tingling, numbness; burning pain, itching and oversensitivity of the tissues. 
• These skin rashes over a period of time convert into opaque vesicles (1-4 mm) and blisters filled with serous exudates. This exudate is replaced by blood and the vesicles are crusted giving the skin a darkened hue. Finally the crust falls off and the skin heals. This phenomenon takes place within a period of 7-10 days. Scarring remains after the disease subsides.
• Maxilla is frequently involved associated with devitalisation of teeth. Significant bone necrosis with loss of teeth is also present in some cases. 
• Tongue, lips and hard palate are other common sites.
• Pulpal necrosis and internal root resorption.These lesions are often misdiagnosed and endodontic treatment and extractions may be carried out by the dental surgeon .
• Facial paralysis may be observed.
• In the pregnancy period, this infection (chicken pox) may lead to complications in the foetus and newborn.

Complications

Post herpetic neuralgia- When the pain persists in the lesional area after the healing of mucocutaneous lesions that lasts more than 3 months after the initiation of acute rash, it is termed as post herpetic neuralgia. It is a burning, throbbing, stabbing kind of pain which is flared by light, contact with clothes or any other trigger factors. This may take 2 months to 1 year time to resolve completely. Prognosis is bad in such cases. High risk in old age due to decline in cell mediated immunity.

Zoster sine herpete/Zoster sine eruptione – Such patient has all the symptoms of herpes zoster except the characteristic rash.

Herpes zoster opthalmicus - It involves eyes and occurs in approximately 10–25% of cases. It is caused by the virus invading and reactivating the ophthalmic division of trigeminal nerve. It may lead to conjunctivitis, keratitis and optic nerve nerve palsies.

Herpes zoster oticus/ Ramsay Hunt Syndrome II - Involves the ear. Nerves like facial and vestibulocochlear are affected resulting in hearing defects and vertigo/rotational dizziness.

Diagnosis:

Polymerase chain reaction and Dot blot technique-detection of VZV DNA in lymph of blisters.

Specific IgM antibody test of blood/fluorescein conjugated monoclonal antibodies.

Electron microscope examination – For virus particles.

Tsanck smear helps to diagnose acute infection with a herpes virus, but does not distinguish between HSV and VZV.

Differential diagnosis:

Herpes Simplex virus

Treatment:

Aimed to shorten the course of disease, prevent post herpetic neuralgia and dissemination.

Preventive vaccine: Zostavax

              Analgesics

§        Mild to moderate NSAIDs

§        Severe pain-opioid analgesics like morphine

§        Topical calamine lotion

§        Capsaicin cream (Zostrix)

§        Topical lidocaine nerve blocks

§        Gabapentine with antivirals- post herpetic neuralgia

    Antiviral drugs

§        Acyclovir

§        Famciclovir

§        Valacyclovir

These drugs are most beneficial if taken within 72 hours of development of the    first vesicle. People who are at a high risk for repeated attacks of infection, five daily oral doses of acyclovir are usually effective.

Steroid therapy

Controversial results have been mentioned in various studies due to their high risk of inducing post herpetic neuralgia. But, in immunocompromised elderly patients corticosteroids along with antiviral drugs have proved to be useful in healing and crusting of lesions.

Percutaneous nerve stimulation

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