Herpes Zoster
Key Facts
Primary infection with VZV causes chickenpox, following which the virus remains latent in sensory ganglia
Development of shingles may indicate a decline in cell-mediated immunity such as that due to age or malignancy
Caused by reactivation of varicella zoster virus, usually within the dorsal root ganglia
Epidemiology
Can effect all ages but seen as a disease of the elderly
Incidence and severity increase with age
90% of children have been exposed to chicken pox before they are aged 16
Shingles CANNOT be caught from contact with a person with chickenpox
Aetiology
Varicella zoster virus
Risk Factors
Immunocompromised
HIV, Hodgkin's lymphoma and bone marrow transplants
Increasing age
Pathophysiology
Resulting in perineurial and intramural inflammation
In immunocompromised patients, the most frequent site of reactivation is the thoracic nerves followed by the ophthalmic division of the trigeminal nerve
When latent virus is reactivated in the dorsal root ganglia it travels down the affected nerve via the sensory root in DERMATOMAL DISTRIBUTION over a period of 3-4 days
Can also affect the cervical, lumbar and sacral nerve roots
Viral infection affecting peripheral nerves
Person with weeping shingles rash can cause chickenpox in non-immune person after close contact
Clinical Presentation
Malaise, myalgia, headache and fever can be present
Can be over a week before eruption appears
Pain and paraesthesia in dermatomal distribution priced rash for days
Rash - consists of papule and vesicles RESTRICTED to SAME DERMATOME - neuritic pain, crust formation & drying occurs over the next week with resolution in 2-3 weeks, patients are infectious until lesions are dried, RASH DOESN'T EXTEND OUTSIDE DERMATOME
Differential Diagnosis
Cluster headaches or migraine
Atopic eczema, contact dermatitis, herpes simplex or impetigo
Before rash appears the pain may come from chest or there may be abdominal pain - may think cholecystitis or renal stones
Treatment
Diagnosis
Clinical diagnosis
Eruption of rash is virtually DIAGNOSTIC
Complications
Topical antibiotic treatment for secondary bacterial infection
Analgesia for pain
Oral antiviral therapy begun WITHIN 72hrs of rash onset - oral aciclovir
Ophthalmic branch of trigeminal nerve - if damaged will affect sight
Post herpetic neuralgia - pain lasting for more than 4 months after developing shingles. Treat with tricyclic antidepressant, anti-epileptic, anti-convulsant