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Fatal Insomnia

by Pierluigi Gambetti, MD

Fatal insomnia is a rare hereditary or sporadic prion disorder causing difficulty sleeping, motor dysfunction, and death.

Fatal insomnia (FI) usually results from an autosomal dominant mutation, but several sporadic cases have been identified. Average age at onset is 40 yr (ranging from the late 20s to the early 60s). Life expectancy is 7 to 73 mo.

Early symptoms include difficulty falling asleep, as well as cognitive decline, ataxia, inability to stay asleep, and psychiatric symptoms. Sympathetic hyperactivity (eg, hypertension, tachycardia, hyperthermia, sweating) may occur later.

FI should be considered when patients have rapidly progressive cognitive impairment accompanied by behavioral or mood changes, ataxia, and sleep disturbances. Suspicion of sporadic FI should prompt a sleep study by polysomnography. Genetic testing can confirm the diagnosis of the familial form. MRI and measurement of 14-3-3 protein and tau in CSF are not useful, but polysomnography and PET can confirm the diagnosis.

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