(See also Overview of Prion Diseases Overview of Prion Diseases Prion diseases are rare progressive, fatal, and currently untreatable degenerative disorders of the brain (and rarely of other organs) that result when a protein changes into an abnormal form... read more .)
Fatal insomnia has two forms:
Fatal familial insomnia and sporadic fatal insomnia differ from other prion diseases Overview of Prion Diseases Prion diseases are rare progressive, fatal, and currently untreatable degenerative disorders of the brain (and rarely of other organs) that result when a protein changes into an abnormal form... read more because they affect predominantly one area of the brain, the thalamus, which influences sleep.
In fatal familial insomnia, symptoms may begin in a person's late 20s to the early 70s (average is 40 years). Death usually occurs 7 to 73 months after symptoms begin. The sporadic form begins slightly later, and life expectancy is slightly longer.
In the familial form, early symptoms include minor difficulties falling and staying asleep and occasional muscle twitching, spasms, and stiffness. During sleep, people may move a lot and kick. Eventually, they cannot sleep at all. Later, mental function deteriorates and coordination is lost (called ataxia Coordination Disorders Coordination disorders often result from malfunction of the cerebellum, the part of the brain that coordinates voluntary movements and controls balance. The cerebellum malfunctions, causing... read more ). The heart rate may become rapid, blood pressure may increase, and people may sweat profusely.
In the sporadic form, early symptoms include a rapid decline in mental function and loss of coordination. People with this form may not report sleep problems, but sleep studies can detect abnormalities.
Doctors consider fatal insomnia as a rare possible diagnosis when people have typical symptoms, such as rapidly deteriorating mental function, loss of coordination, and/or sleep problems. The following are done to confirm the diagnosis:
Positron emission tomography Positron Emission Tomography (PET) Positron emission tomography (PET) is a type of radionuclide scanning. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing... read more (PET), which can detect certain abnormalities in the thalamus
The diagnosis of fatal familial insomnia is confirmed by genetic testing.