Introduction

Encephalitis is a rare disease that occurs in approximately 0.5 per 100,000 individuals — most commonly in children, the elderly, and people with weakened immune systems (i.e., those with HIV/AIDS or cancer). Encephalitis literally means an inflammation of the brain, but it usually refers to brain inflammation caused by a virus.

Symptoms

Symptoms in milder cases of encephalitis usually include:

• fever
• headache
• poor appetite
• loss of energy
• a general sick feeling

In more severe cases of encephalitis, a person is more likely to experience high fever and any of a number of symptoms that relate to the central nervous system, including:

• severe headache
• nausea and vomiting
• stiff neck
• confusion
• disorientation
• personality changes
• convulsions (seizures)
• problems with speech or hearing
• hallucinations
• memory loss
• drowsiness
• coma

Causes

The cause of encephalitis is most often a viral infection. Some examples include herpes viruses; arboviruses transmitted by mosquitoes, ticks and other insects; and rabies transmitted through animal bites.Encephalitis takes two forms, categorized by the two ways that viruses can infect your brain:

• Primary encephalitis. This occurs when a virus directly invades your brain and spinal cord. It can happen to people at any time of the year (sporadic encephalitis), or it can be part of an outbreak (epidemic encephalitis).
• Secondary (post-infectious) encephalitis. This form occurs when a virus first infects another part of your body and secondarily enters your brain.

Also, bacterial infections, such as Lyme disease, can sometimes lead to encephalitis, as can parasitic infections, such as toxoplasmosis (in people with weakened immune systems).

Treatment

Treatment for mild cases mainly consists of rest and a healthy diet, including plenty of liquids, to let your immune system fight the virus. Using acetaminophen (Tylenol, others) can relieve headaches and fever. Anti-inflammatory drugs can help reduce swelling and pressure within your skull. If you’re having seizures, your doctor may prescribe an anticonvulsant medication. In some cases, you may also need physical and speech therapy.

Encephalitis can be difficult to treat because the viruses that cause the disease generally don’t respond to medications. However, some viruses, particularly the herpes simplex virus and varicella-zoster virus, respond to antiviral drugs such as acyclovir (Zovirax). If you have one of these kinds of virus-induced encephalitis, your doctor will likely start treatment with acyclovir immediately. Another antiviral that’s sometimes used is ganciclovir (Cytovene).