In the late 1960s, Dr. Oliver Sacks was working at the Beth Abraham Hospital in the Bronx, New York. The hospital had a group of patients who were essentially living statues. As Sacks described them:
"They would be conscious and aware – yet not fully awake; they would sit motionless and speechless all day in their chairs, totally lacking energy, impetus, initiative, motive, appetite, affect or desire; they registered what went on about them without active attention, and with profound indifference. They neither conveyed nor felt the feeling of life; they were as insubstantial as ghosts and as passive as zombies."
The patients suffered from an atypical form of encephalitis known as encephalitis lethargica (EL), or "sleeping sickness", not to be confused with the tsetse fly-transmitted sleeping sickness. The disease was characterized by the onset of flu-like symptoms, including malaise, low-grade fever, sore throat, headache, and vomiting.
EL and the Spanish Flu epidemic
The disease arrived along with the 1918 Spanish Flu epidemic, and almost five million people worldwide were affected by EL. The peak of the encephalitis lethargica outbreak occurred between October 1918 and January 1919, which is around the same time that the Spanish Flu was peaking.
Encephalitis lethargica affected those between the ages of 10 and 45 the most, with 50% of cases occurring in those between the ages of 10 and 30. There were higher incidences of EL in large cities and industrialized areas than in rural areas.
While one-third of those affected died during the acute stages of the disease, those who survived never returned to normal. Symptoms of the disease could advance rapidly. In one case, a girl walking home from a concert suddenly became paralyzed on one side of her body, within a half-hour she was asleep, and she died 12 days later.
Patients became dazed, confused, delirious, and most notably, experienced an overwhelming desire to sleep. They would sleep for abnormally long periods of time but they were aware of everything that was happening around them while they slept.
Some patients experienced involuntary movements, vocalizations, muscle twitches, and involuntary eye and jaw movements. They also experienced pain in their faces and limbs, and they had visual and tactile hallucinations.
Oddly, these patients also exhibited a sleep cycle reversal, whereby they slept all day and were awake all night.
The bodies of other patients became rigid and exhibited what's called "waxy flexibility," whereby they remained rigid but could be easily repositioned, almost like positioning a doll. While their faces were devoid of emotion, cruelly, they remained mentally intact.
The greatest medical mystery of the 20th century
To this day, EL remains "the greatest medical mystery of the 20th century." When it was discovered in the 1960s that the drug Levodopa (L-DOPA) could reverse the symptoms of Parkinson's disease, Dr. Sacks tried the drug on the encephalitis lethargica patients, some of whom had been almost comatose for 40 years.
Unfortunately, within several months, most of the patients began to experience adverse effects from the L-DOPA, such as tics, involuntary movement, and emotional instability. The drug was discontinued, and the patients returned to the states they had been in before treatment.
In 1973, Oliver Sacks published the non-fiction book Awakenings about his and the patients' experiences. A 1990 film of the same name starring Robert De Niro and Robin Williams was nominated for several Oscars.
Examining the brains of deceased EL patients, doctors concluded that influenza might predispose a person to infection with encephalitis lethargica, possibly by increasing the permeability of the nasal mucous membranes, which allowed the encephalitic virus to enter more easily.
More recent studies point to an auto-immunological trigger caused by influenza. Since 1940, there have been only around 80 published reports of encephalitis lethargica worldwide, and some scientists conclude that only 14 cases truly fit the diagnosis of EL.