brain, spinal cord, and nerve disorders
Encephalitis
Diagnosis of Encephalitis
Magnetic resonance imaging A spinal tap Doctors suspect encephalitis based on symptoms, especially if an epidemic is in progress. Magnetic resonance imaging (MRI) and a spinal tap are usually done. MRI can sometimes detect abnormalities in certain areas of the brain. These abnormalities may help confirm the diagnosis of encephalitis and/or suggest which virus is causing encephalitis. If MRI is not available, computed tomography (CT) may be done. MRI and CT can help doctors exclude disorders that can cause similar symptoms (such as Ischemic Stroke and a A Spinal Tap (lumbar puncture) is done to obtain a sample of cerebrospinal fluid, which flows through the tissues (meninges) that cover the brain and spinal cord. Normally, the spinal fluid contains very few white blood cells. But when the brain and meninges are inflamed, the number of white cells in cerebrospinal fluid increases. To identify the virus causing encephalitis, doctors take samples of blood and cerebrospinal fluid and test them for antibodies to the virus when the person is sick and later when the person is recovering. Sometimes techniques are used to grow (culture) viruses in the cerebrospinal fluid so that they can be identified more easily. Some Overview of Enterovirus Infections (such as those that can cause polio-like illnesses) can be cultured, but most other viruses cannot. The polymerase chain reaction (PCR) technique is used to identify many of the viruses that can cause encephalitis. PCR, which produces many copies of a gene, is used to detect the genetic material of these viruses in a sample of cerebrospinal fluid. Prompt identification of the herpes simplex virus by PCR is difficult, so treatment is usually started immediately if the herpes simplex virus is thought to be the cause. Prompt treatment is essential because the encephalitis it causes is destructive and, if untreated, is often fatal. Immediate treatment can help lessen the severity of symptoms and prevent death. Rarely, a sample of brain tissue is removed and examined under a microscope (biopsy) to determine whether herpes simplex virus or another organism is the cause. Sometimes, even after extensive testing, no virus, bacteria, or other cause of infection is identified. In such cases, the cause may be autoimmune or cancer-related (paraneoplastic) encephalitis because tests cannot always confirm those disorders. 