Reading about BSE and prions and came across this incredibly alarming condition:
Fatal Familial Insomnia

"Fatal familial insomnia is a genetic disease, due to a specific mutation in the PrPc gene. However, the disease can occur spontaneously, without a mutation. This form is called sporadic fatal insomnia. 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 disease usually begins between the ages of 40 and 60 but may begin in a person's late 30s. Most often, it runs in families. At first, people may have minor difficulties falling asleep and occasional problems with muscle movements. Eventually, they lose the ability to sleep. Other changes include muscle twitching, rapid heart rate, and dementia. Death usually occurs after about 7 to 36 months of illness. No treatment is available."

-The Merck Manual, Second Home Edition