Although it is rare, a condition known as fatal familial insomnia is a serious sleep disorder that rapidly progresses to death within two years. It's caused by a genetic mutation.
Difficulty Initiating Sleep is Early Sign
Fatal familial insomnia usually begins when someone has problems falling asleep, a common symptom among all the various types of insomnia. Within several months, though, this condition causes a severe, intractable inability to sleep. It most commonly strikes adults in their late 40s, but onset can range from 25 to 61 years.
Other Symptoms Set This Disorder Apart
In addition to the unrelenting insomnia that develops over several months, there are other symptoms that set fatal familial insomnia apart from typical insomnia. These symptoms are collectively called dysautonomia, which refers to abnormal functioning of the autonomic nervous system, the part of the nervous system responsible for automatic body functions, such as maintaining blood pressure, heart rate and temperature.
Therefore, fatal familial insomnia also causes high blood pressure, a rapid heart rate, and excessive sweating. Other signs include difficulty walking, muscle twitches called myoclonus, and tremor.
The disease lasts from six months to 3 years with a rapid progression to coma and death.
Exploring the Cause of Fatal Familial Insomnia
The cause of fatal familial insomnia is genetic. In more complex term, it's likely due to an autosomal dominant pattern of inheritance. A gene mutation results in the substitution of one amino acid for another. Amino acids are the building blocks of proteins, and this substitution leads to protein misfolding and dysfunction. Ultimately, the protein problems lead to severe loss of neurons and scarring changes called gliosis in part of the brain known as the thalamus.
What Do Tests Show?
Typically the sleep study, or polysomnogram, for fatal familial insomnia will demonstrate an absence of slow-wave sleep. In addition, there will be decreased amounts of stage 2 NREM sleep. Finally, there is dissociated REM sleep without loss of muscle tone.
A routine EEG will show something known as "diffuse slowing" while routine imaging of the head such as CT or MRI will reveal normal brain structure. A PET scan shows decreased glucose metabolism in areas of the brain called the thalamus and putamen. Cognitive testing may show poor attention, disorientation, confusion, or hallucinations. These findings tend to become apparent late in the disease.
Treatment of Fatal Familial Insomnia
Unfortunately, there are few treatment options available for fatal familial insomnia. Medications such as barbiturates and benzodiazepines may be used to induce sleep patterns on EEG. However, the course in fatal familial insomnia is relentless and, as the name implies, ultimately fatal.
Source:
Mowzoon, N. and Flemming, K. “Fatal Familial Insomnia.” Neurology Board Review: An Illustrated Study Guide. 2007; pp. 319, 732.
