Sporadic fatal insomnia (sFI) is a rare progressive neurodegenerative disease with no cure.

Sporadic fatal insomnia (sFI) causes cognitive issues and sleep disturbances (insomnia) that rapidly worsen over a few months or years, leading to coma and death.

It’s a rare subtype of Creutzfeldt‐Jakob disease resulting from misfolding a protein found in the brain called a prion. The misfolding of this prion leads to the buildup of toxic substances that destroy brain tissue and function.

The disease is similar to a related condition called familial fatal insomnia. But unlike familial fatal insomnia, which is inherited, sFI occurs spontaneously. Researchers aren’t sure how or why the prion misfolding occurs.

How rare is sporadic fatal insomnia?

SFI is extremely rare. As of July 2023, there have only been 39 cases in the United States.

Symptoms of sFI vary from person to person and often mimic other brain disorders.

In the early part of the disease, you may experience trouble sleeping (insomnia), but not everyone with sFI reports insomnia. Sleep studies often show disorganized and interrupted sleep patterns.

Other early symptoms of sFI may include:

As the disease progresses, you may experience:

While familial fatal insomnia is known to occur in a series of four stages, sFI doesn’t have a clearly defined disease course. The disease is so rare that researchers don’t know much about its progression. Symptoms may vary from person to person, and not everyone experiences insomnia in the early stages of the disease.

Once symptoms start, they tend to rapidly progress to loss of consciousness and death.

SFI is due to a misfolded protein in the brain, but the reason why the protein misfolds isn’t understood. It occurs in people without any known risk factors or gene mutations.

The disease is considered a rare subtype of Creutzfeldt‐Jakob disease, which typically affects people in their 60s. However, the median age of onset in a study of 44 people with sFI was only 49 years of age.

Both sFI and Creutzfeldt‐Jakob disease are among a group of neurodegenerative disorders known as prion diseases. These diseases affect about 1–2 million people around the world each year, according to a 2016 study.

SFI affects a part of the brain called the thalamus. The thalamus acts as a relay station where information must first pass through before being directed to the brain’s cerebral cortex for interpretation.

Among other things, the thalamus is responsible for movement, learning, memory, consciousness, sensory processes, and sleep.

Damage to this part of the brain from sFI interferes with many bodily processes, including sleep, movement, and memory. It quickly progresses to dementia, loss of consciousness, and death.

Fatal insomnia is difficult to diagnose because the disease appears spontaneously, and its symptoms often mimic other neurodegenerative disorders like Parkinson’s disease.

Once your doctor rules out other similar conditions, they may be able to confirm a diagnosis with a sleep study or polysomnography and a positron emission tomography (PET) scan of the brain.

For many people, a diagnosis isn’t confirmed until an autopsy is performed after death.

At the moment, there’s no cure for sFI. Research into treatments is ongoing, but since the disease is rare and difficult to diagnose, little progress has been made so far.

A few new drugs have been identified to treat prion diseases. The most advanced is PRN100, a monoclonal antibody, which has been shown to extend survival in mice infected with a prion disease. The drug is currently undergoing early-stage human clinical trials.

Treatment for sFI is supportive. It’s aimed to make you feel more comfortable as the disease progresses and to potentially slow down the progression of the disease.

A team of doctors will try to manage your symptoms with medications like anti-seizure drugs, sedatives, and other medications typically used for movement disorders.

Treatment with vitamins B6, B12, iron, and folic acid has also been shown to improve the well-being of people with sFI. Medications that typically treat insomnia don’t work for sFI.

There’s no way to prevent sFI. The disease isn’t contagious, and you can’t get it from contact with someone else.

Contact your doctor if you’re experiencing any rapidly progressing:

  • cognitive issues
  • behavioral or mood changes
  • loss of coordination
  • vision problems
  • sudden and progressive problems with sleep

These symptoms are much more likely to be caused by something other than sFI, but sFI should be considered as a rare possible cause.

There is no cure for sFI, and the disease is known to progress rapidly and be fatal in all cases.

In a study of 13 people with sFI in Europe over the past 20 years, the average duration of the disease was 30 months, with a range of 7–96 months. In another study of 44 people with a diagnosis of sFI, the median disease duration was 24 months, also with a range of 7–96 months.

SFI is extremely rare. Though there is no cure, researchers are examining and characterizing the prions associated with sFI and other prion diseases and searching for new therapeutic targets to treat them.

If you or a loved one has sFI, you may wish to consider participating in a clinical trial so scientists can learn more about the disease and one day find a cure.