Medical Edge Newspaper Column

Encephalitis and Back Pain

May 14, 2007
Dear Mayo Clinic:
What is viral encephalitis, and can it cause back pain?

Answer:
Viral encephalitis is an infection of the brain caused by a virus. In some cases, it can cause back pain.

Symptoms of viral encephalitis include headache, fever, irritability, decreased level of awareness, seizures, and even focal brain dysfunction. Aseptic (and often presumed to be viral) meningitis is inflammation of the covering of the brain and spinal cord, called the meninges. Aseptic or viral meningitis commonly causes fever, headache, stiff neck and can cause backache.

Encephalitis and meningitis can occur together; it's sometimes called meningoencephalitis. When viral infection affects the spinal cord directly, it is referred to as myelitis; and back pain and spinal cord dysfunction commonly result. When encephalitis and myelitis occur together, it is referred to as encephalomyelitis.

There are many viruses that can cause meningitis, encephalitis or myelitis. Some viruses, such as West Nile, can cause two or three at the same time. Typically, a spinal tap is used to diagnose encephalitis, meningitis and myelitis. The spinal tap often is performed after imaging has ruled out abscess and tumor. Analysis of the spinal fluid obtained from the spinal tap shows inflammation that indicates -- but doesn't confirm -- viral encephalitis, meningitis or myelitis. Spinal fluid cultures only occasionally reveal the infecting virus.

More helpful are special blood and spinal fluid tests that look for antibodies to a specific virus or molecular evidence in the spinal fluid that one particular virus has infected the nervous system. About half of the patients with one of these viral infections never have the specific virus identified despite extensive microbiologic testing.

Viral encephalitis with an associated meningitis component may cause back pain by several mechanisms. As with viral meningitis, back pain can result from inflammation of the covering around the spinal cord. Back pain can also occur as a result of the spinal tap performed to obtain spinal fluid for analysis. The spinal tap -- also called a lumbar puncture -- is performed by inserting a hollow needle into the lower back. This can cause local pain for several days or longer.

Except for a few specific viruses, effective treatment is not available for viral encephalitis. Treatment of back pain symptoms is similar to that for back pain caused by other conditions. Effective therapies can include medications, physical therapy and occasional injections of a cortisone-like medicine. Back pain related to inflammation of the spinal cord and its covering generally improves over a matter of weeks after the infection. While most of the effects of viral meningitis resolve, viral encephalitis can cause permanent brain damage such as memory loss or other neurological problems. Myelitis can damage the spinal cord and leave behind limb weakness, sensory loss or impaired sphincter control.

-- Allen J. Aksamit, Jr., M.D. Neurology, Mayo Clinic, Rochester, Minn.