Violent sleep disorder linked to dementia

Mayo Clinic scientists and a group of international collaborators have discovered a connection between an extreme form of sleep disorder and eventual onset of parkinsonism or dementia. The findings appear in the current issue of the journal Brain
Clinical observations and pathology studies, as well as research in animal models, led to the findings that patients with the violent rapid eye movement sleep (REM) behavior disorder (RBD) have a high probability of later developing Lewy body dementia, Parkinsons disease or multiple system atrophy (a Parkinsons-like disorder), because all of these conditions appear to stem from a similar neurodegenerative origin.

"Our data suggest that a number of patients with idiopathic (not linked to any other neurologic symptoms) RBD may be exhibiting early signs of an evolving neurodegenerative disease, which in most cases appear to be caused by some mishap of the synuclein protein," says Bradley Boeve, M.D., Mayo Clinic neurologist and lead author of the study. Synuclein proteins are linked to synapses in the brain, and clumps of abnormal alpha-synuclein protein are present in some forms of dementia. "The problem does not seem to be present in the synuclein gene itself, but its something that happens to the protein following gene expression. Just what happens to it to cause the conditions isnt clear".

The result, however, is quite clear. The patients -- commonly older males -- strike out violently, often yelling, when they enter REM sleep. Mayo scientists following these individuals over a number of years saw a number of of them develop symptoms of dementia. Postmortems showed they all had developed Lewy bodies but not the pathology of Alzheimers disease. Earlier studies by two of the co-authors on this paper (from the University of Minnesota) had described this sleep disorder and associated it with eventual onset of Parkinsons disease or Parkinsons disease-like disorder in some patients. This Mayo study builds on that work and makes the connection to onset of a non-Alzheimers dementia.

Dr. Boeve says a number of cases may go unreported because the individual sleeps alone, the activity is tolerated or the condition is misdiagnosed. Violent movements during sleep do not always mean someone has this condition. Sometimes the behavior is due to untreated sleep apnea and the condition resolves with regular sleep apnea therapy -- use of a CPAP breathing machine. In those cases, the cause is sleep apnea. Its the idiopathic RBD findings on sleep studies that may precede dementia or parkinsonism by years or decades -- underscoring the need for patients with suspected RBD to undergo a sleep study.

"This association may provide one of the earliest indicators thus far of eventual dementia or parkinsonism," says Dr. Boeve. "While some patients dont exhibit symptoms of dementia, all patients we have seen with RBD do develop the pathology." This is both good news and bad news. While Lewy body dementia and Parkinsons disease have no cure, they can be treated. Unlike Alzheimers disease, medications can restore cognitive function for a number of with Lewy body dementia. The quandary facing physicians is whether to inform patients that they have an increased risk of developing dementia or parkinsonism, when symptoms may not appear for years or may never appear at all.

"Its an ethical dilemma," says Dr. Boeve. "We know that a number of patients with RBD will develop dementia or parkinsonism, but we cant positively predict what will happen in each individual case. Some physicians choose to tell very little of this to their patients. I try to explain this, but also emphasize the positive -- that some people never show any symptoms and live a normal life. There are documented cases of patients who have had RBD for decades and die from heart disease, stroke or cancer, and never show any signs of dementia or parkinsonism".


Posted by: Daniel    Source