Encephalitis

Inflammation of the brain (encephalitis) should always be considered as a diagnosis for anyone with an altered mental status. 

Causes
Encephalitis is usually caused by a virus. There are many types of viruses that can cause encephalitis, such as the herpes simplex virus, Japanese encephalitis virus (which is spread through the bite of a mosquito), and the rabies virus (spread through the saliva of an infected animal). Encephalitis can also develop after having a viral illness such as measles, mumps or chicken pox.

Signs and Symptoms
Encephalitis results in alterations in mental status, such as lethargy, confusion or unconsciousness. Fever, headache, and seizures are also common. There may also be other symptoms such as weakness or altered sensation in areas of the body.

Encephalitis can cause long term neurological dysfunction and even death.

Investigations
Encephalitis is usually diagnosed according to the patient’s history and physical examination. However, other investigations (such as lumbar puncture and CT scan of the head) are often performed to exclude other neurological diseases. 

Routine bloods should be taken. A blood glucose must be checked on anyone with altered mental status. Blood culture is used to determine whether there is infection in the blood stream.

Treatment
If the patient is unconscious then an open airway must be maintained, and oxygen administered as required. Any seizures must be treated as required.

Antiviral medications may be required, depending on the virus suspected.