4/1/2010

What’s the difference between encephalitis and meningitis? As most of you know, attaching -itis to a word indicates inflammation. The word encepha – refers to the brain itself. So encephalitis is a condition in which brain tissue is inflamed. The causes of inflammation may be numerous and include bacterial or viral infections. The meninges are three separate layers of tissue that surround the brain and spinal cord (the dura, the arachnoid, the pia). So the term meningitis refers to inflammation of the meninges, also without indicating the cause, which can include bacterial or viral infections.

Many cases of meningitis are transmitted from the environment (from another individual) into the person through the air. The nerves for smell (olfactory nerve), located in the roof of the nose, provides a common direct route for bacteria to reach the brain and meninges. Often, the cause of the infection is unknown.

Meningitis and encephalitis are potentially life threatening diseases that require prompt diagnosis and treatment. Signs of meningitis include sleepiness, nausea, vomiting, headache, fever, and a stiff neck. Because the brain is bathed in spinal fluid (CSF), obtaining a sample of fluid through a “spinal tap” is the most accurate method of diagnosis. Normally CSF has no cells in it and contains protein and sugar. If the meninges are infected the CSF shows white cells, bacteria, and abnormal amounts of protein and glucose. Cases of encephalitis may show only an increase in cells. MRI and/or CT scans are usually also required as part of the evaluation.