Central nervous system complications

CENTRAL NERVOUS SYSTEM

Central nervous system complications also are seen in varicella. Cerebellar ataxia is the most common, with an incidence of approximately 1 per 4,000 cases in children younger than 15 years of age. It has an excellent prognosis. Varicella encephalitis usually develops 7 to 10 days into the disease, but it has been recorded as early as 1 day prior to or as late as 20 days after development of the rash. Encephalitis early in the disease process may represent replication of the virus in brain tissue, but post-infectious hypersensitivity phenomena also may produce clinical encephalitis. There are two clinical syndromes of varicella encephalitis. The first, which is more common, is characterized by a gradual onset of lethargy, ataxia, and encephalop-athy. The second presentation is heralded by sudden high fever, with convulsions and paralysis. Mild cerebrospinal fluid lympho-cytosis is seen in nearly 50% of the patients presenting with either form of encephalitis. Acute varicella encephalitis has a mortality rate of 5% to 20%, and neurologic sequelae are seen in 15% of survivors. The incidence of encephalitis is 1.7 per 100,000 cases. Other neurologic syn- dromes, including aseptic meningitis, transverse myelitis, and Guillain-Barre syndrome, have been reported, but are less common.

PNEUMONIA

Varicella pneumonia is the third most common complication and occurs much more frequently in previously healthy adults or in immunocompromised children, although it has been reported in otherwise well children. Chest radiography usually reveals bilateral patchy infiltrates.

MISCELLANEOUS

Hemorrhagic varicella is seen occasionally, and there are several forms. Hemorrhage at sites of pox lesions does not always herald a more severe course, although some patients develop malignant chickenpox with purpura, which is associated with a 70% mortality. In any hemorrhagic form of varicella, thrombocytopenia is common, and there may be a slightly increased bleeding time, although clotting times are normal. A syndrome of late, postinfectious purpura also can occur, which is characterized by a much longer duration of bleeding and thrombocytopenia (sometimes as long as 5 weeks).

Reye syndrome, which presents with persistent vomiting and decreasing mental status, has been associated with varicella more frequently than with other viral infections. The reported incidence has been decreasing steadily over the past 15 years, and the reasons for the decline are not entirely clear. It is reassuring to ascribe the changing incidence to the decreased use of aspirin in childhood, but the decline seems to be more striking than the curtailed use of aspirin products. Nevertheless, aspirin or salicylate-containing products (including, for example, bismuth subsalicylate) should not be given to any child who has varicella.

Mono or polyarticular arthritis has been reported with VZV infection, and the virus has been grown from joint fluid. However, acute bacterial septic arthritis is more common. Myocarditis and glomerulonephritis also have been reported

Zoster or shingles is a disease that increases in frequency with advancing age, but it can be seen at any age, including in neonates. It is three times more common among adolescents than it is among preschoolers. Children who contract varicella in the first year of life have a 3- to 20-fold increased risk of developing zoster. Nearly 50% of all zoster cases in children involve the thoracic area. Severe pain and postherpetic neuralgia are uncommon. Lesions may persist for 3 to 4 weeks. Despite the frequent development of zoster in patients who have leukemia, herpes zoster in children does not imply occult malignancy. Infants who have zoster have had VZV infection in the womb, and signs of congenital varicella should be sought, especially chorioretinitis.

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