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:
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.
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.
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.