Diagnosis

There's no specific test for Reye's syndrome. Instead, screening for Reye's syndrome usually begins with blood and urine tests as well as testing for fatty acid oxidation disorders and other metabolic disorders.

Sometimes more-invasive diagnostic tests are needed to evaluate other possible causes of liver problems and investigate any neurological abnormalities. For example:

• Spinal tap (lumbar puncture). A spinal tap can help the doctor identify or rule out other diseases with similar signs and symptoms, such as infection of the lining that surrounds the brain and spinal cord (meningitis) or inflammation or infection of the brain (encephalitis).

  During a spinal tap, a needle is inserted through the lower back into a space below the end of the spinal cord. A small sample of cerebrospinal fluid is removed and sent to a lab for analysis.

• Liver biopsy. A liver biopsy can help the doctor identify or rule out other conditions that may be affecting the liver.

  During a liver biopsy, a needle is inserted through the skin on the upper right side of the abdomen and into the liver. A small sample of liver tissue is removed and sent to a lab for analysis.

• Computerized tomography (CT) scan or magnetic resonance imaging (MRI). A head CT or MRI scan can help the doctor identify or rule out other causes of behavior changes or decreased alertness.

  A CT scan uses a sophisticated imaging machine linked to a computer to produce detailed images of the brain. An MRI scan uses a strong magnetic field and radio waves rather than X-rays to generate images of the brain.

• Skin biopsy. Testing for fatty acid oxidation disorders or metabolic disorders may require a skin biopsy, although direct gene sequencing together with blood and urine tests are often sufficient to make such a diagnosis.

  During a skin biopsy, a doctor takes a small skin sample for analysis in a lab. A biopsy can usually be done in a doctor's office using a local anesthetic.