Reye syndrome is sudden (acute) brain damage (encephalopathy) and liver function problems of unknown cause. The syndrome has been associated with the use of aspirin to treat chickenpox or the flu in children.

Reye syndrome is most often seen in children from 4 to 12 years old. Most cases associated with chicken pox have been shown to occur in children age 5 to 9, while those associated with the flu (influenzae type B) have occurred in children aged 10 to 14.

Children with Reye syndrome get sick very suddenly. Typically, Reye syndrome follows an upper respiratory infection (URI) or chickenpox by about 1 week. It frequently begins with vomiting, which is persistent over many hours.

The vomiting is rapidly followed by irritable and combative behavior. As the condition gets worse, the child may have problems with their alert (conscious) level). Untreated, seizures and coma may develop, which can quickly lead to death.

Symptoms of Reye syndrome include:

• Recent upper respiratory infection or chickenpox
• Nausea and vomiting
• Mental status changes
• Lethargy
• Confusion
• Combative behavior
• Loss of consciousness or coma may develop
• Seizures
• Unusual placement of arms and legs (decerebrate posture) -- the arms are extended straight and turned toward the body, the legs are held straight, and the toes are pointed downward)

• Weakness in arms or legs
• Muscle function loss or paralysis of the arms or legs
• Double vision
• Speech difficulties
• Hearing loss

The following tests may be used to diagnose Reye syndrome:

• Blood chemistry tests show low blood sugar (glucose) levels
• Liver function tests show higher than normal levels of liver enzymes
• Serum ammonia test may be higher than normal
• Liver biopsy
• Spinal tap
• Head CT or head MRI scan help rule out other causes of mental status changes