The Basics - Shingles

The shingles rash may resemble contact dermatitis or impetigo, explains Dr Judy Duckworth.

Ophthalmic shingles may be confused with other causes of red eye (Photograph: SPL)
Ophthalmic shingles may be confused with other causes of red eye (Photograph: SPL)

Shingles, or herpes zoster, is a commonly encountered condition characterised by a painful, itchy, vesicular rash. Following chickenpox infection, varicella zoster virus lies dormant in the ganglia of cranial and spinal nerves, but may reactivate and attack segmental nerves, with clinical features manifesting in the affected dermatome.

Shingles occurs at any age, but most commonly affects elderly people. A GP with a list size of 2,000 will see four to six cases per year. Incidence in the over-80s is 11 per 1,000 patients per year. As the population ages, the incidence of shingles rises due to the decline in cell-mediated immunity that occurs with age.

It is impossible to catch shingles; however chickenpox infection may be transmitted to non-immune or immunocompromised people through direct contact with vesicular fluid.

1. Signs and symptoms
Malaise, headache and myalgia, with pain or itching of the affected dermatome, precede erythema and appearance of vesicles and pustules. Localised muscle weakness and allodynia may develop. The rash resolves in two to three weeks with scarring and altered pigmentation.

The rash may resemble contact dermatitis or impetigo. Ophthalmic shingles may be confused with other causes of an acute red eye. Herpes simplex virus usually affects younger patients than herpes zoster. Attacks often recur with vesicle groups spread bilaterally, whereas shingles is usually unilateral, affecting one or adjacent dermatomes. It rarely recurs unless the patient is immunocompromised.

Shingles most commonly affects elderly people, especially over-80s

2. Complications
The ophthalmic division of the trigeminal nerve is involved in 10-15 per cent of cases of shingles and visual impairment may be permanent. The presence of vesicles on the nose should arouse suspicion.

Post-herpetic neuralgia is defined as persistent pain at the site of the rash 16 weeks after onset. Risk factors include a painful prodrome, severe pain, severe rash and female gender. It occurs commonly in elderly people. Without antivirals, 75 per cent of patients in the over-70 age group will have chronic pain.

Motor nerve damage may lead to paralysis of skeletal muscle. Shingles affecting cervical, lumbar and sacral nerves may adversely affect bladder and diaphragm function, with serious consequences. Secondary bacterial infection can cause septicaemia in immunocompromised patients.

Rarer complications, including meningitis, encephalitis, myelitis, and visceral and vascular involvement should be considered when atypical symptoms or signs develop following recent shingles. If clinical diagnosis is uncertain, PCR analysis of vesicular fluid is diagnostic.

3. Management
Oral antiviral therapy shortens the duration of symptoms during attacks of shingles. It reduces the incidence and severity of post-herpetic neuralgia, lowering pain scores by 50 per cent at six months. Aciclovir is highly cost-effective, but famciclovir or valaciclovir three times a day may improve compliance. Treatment lasts seven days and is generally well-tolerated.

Simple analgesics (paracetamol, codeine) should be tried before stronger opioids (tramadol, oxycodone and morphine). There is little evidence for the effectiveness of lidocaine patches, capsaicin cream, acupuncture and transcutaneous electrical nerve stimulation.

Epidural injections and oral steroids administered by specialists reduce acute pain in severe attacks but do not prevent chronic pain. Oral steroids are controversial and may cause disseminated herpes zoster infection and septicaemia in immunocompromised patients.1

Post-herpetic neuralgia is associated with high morbidity in elderly people, and chronic pain is a major cause of depression. Symptoms respond poorly to treatment, and routine vaccination may be cost-effective in the over-60s. US vaccination programmes have reduced herpes zoster cases by more than 50 per cent, leading to a fall of 66.5 per cent in the incidence of post-herpetic neuralgia.2

Tricyclic antidepressants provide low cost, effective pain control. Amitriptyline or nortriptyline may be started as 25mg at night (10mg for frail elderly patients, with weekly increments to a maximum of 75mg. Side-effects (drowsiness, unsteadiness) may reduce compliance. Cardiotoxicity and glaucoma are of particular concern in elderly patients.

Gabapentin is more expensive than amitriptyline, but has similar efficacy and lower incidence of serious adverse effects. Begin at 300mg once daily, titrating to 300mg three times a day over several days, up to a maximum of 3,600mg daily.3

4. Referral
Suspicion of meningitis, encephalitis, or acute myelitis all warrant admission or immediate specialist review.

Ophthalmic herpes zoster should be reviewed by a specialist within 24 hours.

In pregnancy, pre-existing maternal antibodies confer protection to the fetus.

Routine referral is indicated for refractory pain, recurrence in a patient not known to be immunocompromised, and where new vesicles develop despite a seven-day course of antivirals.

Criteria for Antivirals4
  • All patients >50 years of age within 72 hours from onset of rash.

Patients (any age) with:

  • Herpes zoster ophthalmicus.
  • Immunocompromised status.
  • Rash located on the neck, limbs or perineum.
  • Moderate or severe rash or pain.

Late presentation up to seven days from onset of rash:

  • Treat patients at high risk of complications, that is older patients, herpes zoster ophthalmicus, severe pain or ongoing new vesicle formation.

References
1. He L, Zhang D, Zhou M et al. Corticosteroids for preventing postherpetic neuralgia. Cochrane Database Syst Rev 2008, Issue 1. Art No: CD005582. DOI: 10.1002/14651858.CD005582.pub2.

2. Oxman MN, Levin MJ, Johnson GR et al. A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults. N Engl J Med 2005; 352: 2271-84.

3. BNF 59. London, BMJ/RPS, 2010.

4. International Herpes Management Forum. Improving the management of varicella, herpes zoster and zoster associated pain. Worthing, IHMF, 2002.

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