Doctors left baffled over mysterious illness that makes patients gouge their own eyes out

A terrifying condition that left doctors puzzled in the early 1900s sounds like something out of a horror movie, with patients growing increasingly feral and going as far as gouging their own eyes out.

The illness, known as encephalitis lethargica or 'sleepy sickness', sees patients experiencing some flu-like symptoms, followed by a state of comatose sleeping.

Those who manage to survive this agonising phase would either emerge on the other side completely fine, or would go on to exhibit concerning personality changes, resulting in self-harm and violent behaviour.

If this all sounds like the plot of 28 Days Later, we're sorry to say it is actually very real, or at least it was at the height of the Spanish Flu epidemic in the 1918-20, with sporadic cases ever since.

Here's an in-depth look at what encephalitis lethargica actually is, its strange history, symptoms and possible causes.

There have only been 80 registered cases of encephalitis lethargica in the last 85 years. (Franz Deuticke, ss. 1-79. Leipzig-Wien 1918/Public Domain/Wikimedia commons)

What is encephalitis lethargica?

Encephalitis lethargica is an atypical form of encephalitis.

First described in 1917 by neurologist Constantin von Economo and pathologist Jean-René Cruchet, this is a rare neurological disease characterised by inflammation of the brain and causing neurological and psychiatric symptoms.

It was first observed in a pandemic between 1916 and 1930, with sporadic cases (80 in the last 85 years) still occurring today.

The disease is marked by a range of neurological and psychiatric symptoms, including excessive sleepiness, psychiatric changes, and eye movement problems.

The bizarre history of encephalitis lethargica

Encephalitis lethargica puzzled doctors around the globe in the early 20th century, but there had been cases registered long before that, with the first dating back to the late 16th century.

The illness reached its peak before, during and after the First World War, spreading through Europe to other territories.

The exact number of people affected during the epidemic is unknown, but it's estimated to be over a million worldwide.

Even more puzzling is that, as soon as it manifested in numerous cases in the 1910-20s, the illness appeared to vanish just as suddenly in subsequent decades.

There are currently no known causes or cures for the condition. (Getty Stock Photos)

What are the symptoms of encephalitis lethargica?

Encephalitis lethargic starts out with flu-like symptoms, including a sore throat, cough, fever, headaches and muscle soreness.

Patients may experience hypersomnolence (excessive sleepiness), having fatigue and falling asleep or freezing during normal activities.

As the illness progresses, patients start to experience psychiatric changes, including irritability, mood changes, confusion and lack of interest for everyday activities.

The condition also affects the eyes, leading to ophthalmoplegia, a paralysis of the muscles that control eye movement, causing difficulties in focusing and other visual issues.

Finally, movement is also impacted, with EL patients having symptoms resembling those of Parkinson's disease such as tremors, stiffness and slow movements.

Sufferers would go through a period of comatose sleeping, seeing them in an apparent sleep-like phase while being completely awake but unable to respond to external stimuli or communicate.

After this sleep stage, patients would either recover well or die due to respiratory complications. But a portion of patients surviving the sleep stage went on to display alarming changes to their personality and behaviour.

They would show little to no interest in the external world, going on to exhibit restless and erratic behaviour, resulting in lying, a violent attitude and self-harm.

In one registered case, someone went as far as removing their own eyes.

It can trigger symptoms similar to Parkinson's (Kinga Krzeminska/Getty stock photo)

What causes encephalitis lethargica?

Doctors still don't know what could cause encephalitis lethargica.

As most cases initially saw patients have symptoms similar to those of flu, some think there was a connection to the Spanish Flu pandemic, though no direct link to a virus has been established.

Another cause could be a potential connection to the streptococcal bacteria, which could trigger an autoimmune response leading to brain inflammation.

Finally, some modern cases of EL are suspected to be forms of autoimmune encephalitis, such as NMDA-receptor encephalitis, which has similar symptoms.

How is encephalitis lethargica treated?

There is currently no cure for encephalitis lethargica, with treatment focusing on managing symptoms.