Encephalitis lethargica Dr Trisha Macnair This mysterious illness, also known as sleeping sickness, can lead to a prolonged state of unconsciousness.

In this article

What is it? What causes it?

What are the symptoms? What's the treatment?

Between 1917 and 1928 a puzzling illness swept around the world. Young people, especially women, seemed to be the most vulnerable, although it affected thousands of people of all ages.

Doctors named it encephalitis lethargica, which simply means 'inflammation of the brain that makes you tired'.

Although an epidemic of encephalitis lethargica hasn't recurred, occasional cases are still seen. Some experts suggest it may be more common than we realise, but that many minor cases go undiagnosed.

Many other names have been given to the condition or to diseases that appear to cause the same symptoms. These include von Economo's disease, Cruchet's disease, Akureyri disease, benign myalgic encephalomyelitis and sleeping disease.

Many people believe a virus or other type of infection may be to blame for encephalitis lethargica, but there's currently no good evidence to suggest any particular organism.

Some researchers have suggested it might be an autoimmune disease, where the body's immune system is triggered by a throat infection (perhaps with a Streptococcus-like bacteria) to attack the nervous system.

Research shows that areas of the brain called the mid-brain and basal ganglia become inflamed during the illness. But while antibrain antibodies can be detected, no viruses have been found. This suggests the syndrome isn't caused by a virus directly entering and attacking the brain, but it could be that the body's immune cells are attacking the nerve cells there.

The illness usually starts with a high fever, headache and sore throat

The symptoms of encephalitis lethargica can be variable, but the illness usually starts with a high fever, headache and sore throat. Double vision, disturbance of eye movements, weakness of the upper body, tremors and strange movements, neck stiffness, intense muscle pains, a slowing of physical and mental response, drowsiness and lethargy soon follow.

Unusual brain and nerve symptoms may occur and the person's behaviour and personality may change. Occasionally, the person may become psychotic, with extremely disturbed thinking.

Sometimes the illness is mistaken for epilepsy, hysteria, or even drug or alcohol abuse.

As the body shuts down, patients become increasingly sleepy and some may lose consciousness, slipping into a coma that can last months or even years.

Many people died during the original epidemic, but modern medicine can help to keep people alive.

Most people recovering from encephalitis lethargica develop a form of Parkinson's disease, with typical symptoms of slowness, tremor and abnormal muscle movements called dystonia.

As with Parkinson's there may be little facial movement, so although the person can hear, understand and is mentally fine, they don't appear to respond much to the world around them.

These problems may develop as long as a year after recovery. There may also be problems with swallowing or vision, as well as long-term behavioural disorders. However, some people do make a full recovery.

There's no cure for encephalitis lethargica, but treatment is targeted at supporting the person through their illness and dealing with the symptoms as they occur.

Treatment in an intensive care unit may be necessary

In the early stages, treatment in an intensive care unit may be necessary to keep the person breathing, fed and protected from other infections, especially if they're in a coma. Steroid drugs may help to reduce inflammation in the brain.

As the person recovers, physiotherapy, nutritional support and speech therapy may help to speed them on the path back to normality. They may also need psychological support to deal with emotional and behavioural problems.

This article was last medically reviewed by Dr Rob Hicks in February 2008