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Fatal Insomnia

By Pierluigi Gambetti, MD

Fatal insomnia is a rare prion disease that interferes with sleep and leads to deterioration of mental function and loss of coordination. Death occurs within a few months to a few years.

Fatal insomnia has two forms:

  • Familial: This form, called fatal familial insomnia, is inherited. It is due to a specific mutation in the gene for a normal protein called cellular prion protein (PrPC).

  • Sporadic: This form occurs spontaneously, without a genetic mutation.

Fatal familial insomnia and sporadic fatal insomnia differ from other prion diseases because they affect predominantly one area of the brain, the thalamus, which influences sleep.

The familial and sporadic forms typically begin between the ages of 30 and 50 years.

Symptoms

At first, people may have minor difficulties falling asleep and occasional muscle twitching, spasms, and stiffness. During sleep, they may move a lot and kick. Eventually, they cannot sleep at all. Often, the sleep problems are difficult to detect.

Later, mental function deteriorates and coordination is lost (called ataxia). The heart rate may become rapid, blood pressure may increase, and people may sweat profusely. Death usually occurs 7 to 73 months after symptoms begin.

Diagnosis

  • A doctor's evaluation

  • For the familial form, genetic testing

  • For the sporadic form, polysomnography and positron emission tomography

The diagnosis of fatal familial insomnia is suggested by typical symptoms and a family history of the disease and can be confirmed by genetic testing.

To diagnose the sporadic form, doctors use polysomnography if the person has a history of sleep problems. Positron emission tomography (PET) is also done to check for abnormalities in the thalamus.

Treatment

No treatment is available. Measures to help people sleep have been tried, but the benefits were only temporary.