Herpes zoster (shingles) is the reactivation of latent VZV infection. There is a lifetime incidence of almost 20 percent, with the majority of cases being among the elderly. It occurs only in people who have had chicken pox. After a single occurrence in an immunocompetent host, there is a 4 percent likelihood of a second occurrence.
The lesions of shingles are identical to those of chickenpox, but are limited to a single dermatome in distribution. Thoracic and lumbar dermatomes are most common. The cranial nerves may be affected as well, with the potential complications of herpes zoster ophthalmicus (HZO) and Ramsay Hunt syndrome. What triggers the reactivation is unknown. The disease begins with a prodrome of pain in the affected area for 1 to 3 days, followed by the outbreak of a maculopapular rash that quickly progresses to a vesicular rash. The course of the disease is usually around 2 weeks, but may persist for a full month.
HZO is due to involvement of the ophthalmic branch of CN V and is a vision-threatening condition. The Hutchinson sign (lesions on the tip of the nose) may be seen before ocular involvement is recognized, but its absence does not rule out HZO. 20 Ocular involvement can be seen in the presence of only a slight rash on the forehead. HZO induces a keratitis and may be followed by involvement of deeper structures. There is usually facial pain, regional adenopathy, and occasionally a red eye preceding the appearance of the rash. A dendriform corneal ulcer can often be identified with fluorescein staining. The presence of a skin rash helps differentiate HZO from ocular HSV. HZO or suspected HZO mandates an ophthalmologic consultation due to the threat to vision.
CN VII can also be affected. Involvement of the maxillary or mandibular branches can result in intraoral lesions. Involvement of the geniculate ganglion of CN VII results in Ramsay Hunt syndrome, which clinically presents as a facial palsy resembling Bell palsy with a unilateral motor weakness, loss of taste on the anterior two-thirds of the tongue, and vesicles in the ear canal or on the tympanic membrane (the only sites of CN VII cutaneous innervation). Ramsay Hunt syndrome has also been described as an infrequent cause of altered mental status in the elderly. 21 This is treated in the same fashion as Bell palsy. Immunocompromised patients should be admitted for IV acyclovir.
The most common complication of shingles is postherpetic neuralgia (PHN). This is uncommon in younger patients, but increases in frequency with age. The pain at times may be so severe as to be debilitating. Occasionally, the anterior horn cells become involved, causing a transient local weakness or paralysis, with these patients being particularly prone to severe pain. PHN occurs in 10 to 20 percent of all patients after an episode of acute zoster, but in up to 70 percent of patients aged 70 years or older. It generally resolves in 1 to 2 months, but may last greater than a year in some patients.
The treatment of zoster in the normal host is aimed at decreasing the risk of PHN, as the antivirals have a clinically small, but statistically significant, effect on the duration of the acute disease. Treatment should begin as soon as possible, and within 72 h of onset of disease for maximal benefit. The present literature shows that all three currently available antiherpes agents are more effective than placebo at reducing the duration of PHN, but not at reducing its incidence. 22,23 and 24 There is a suggestion that both famciclovir and valacyclovir may be more effective than acyclovir, but this has not been shown to be clinically significant. 25 Corticosteroids have not been shown to be effective, but have been shown to improve quality-of-life indices in affected elderly, and a 21-day taper beginning at 60 mg PO qd should be considered in patients older than age 50 if no contraindications exist. 2 27
Initial treatment of patients with PHN is typically systemic analgesia, often narcotics. Patients should be referred back to their primary care provider, because first-line agents often fail, and a trial of amitriptyline or carbamazepine may be tried as second-line therapy.
Immunocompromised patients have an increased risk of disseminated disease. This can be recognized clinically by evidence of the rash involving more than a single dermatome or crossing the midline. Disseminated disease may occur in patients with skin lesions limited to a single dermatome. Patients with disseminated disease may develop pneumonitis, hepatitis, meningoencephalitis, or other organ system involvement and should be admitted for IV acyclovir. Immunocompromised patients with shingles without evidence of dissemination can be treated as outpatients with oral acyclovir at the standard dosing, with instructions to return if the rash spreads or if they develop respiratory symptoms, headaches, or other signs of organ system disease. Close follow-up with their primary care provider is recommended.
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