My REM sleep behavior disorder

About six weeks ago, I was awakened from sleep by a fall to the floor. I remember my dream vividly.  I was being chased by someone trying to kill me. I stumbled on a path and then rolled to my right into a ditch to avoid the attack. I awoke in confusion on the floor, 32 inches from the top of the mattress.  I was sore for several days, but fortunately I had no significant injuries. Once before, sometime in the last year, I fell out of bed, but I don’t recall now if I had been dreaming at that time. Physically acting out dreams is not normal.

Recall that REM (rapid eye movement) sleep is the phase of sleep during which we do most of our dreaming. A fascinating but normal characteristic of REM sleep is that it is associated with atonia; we are essentially paralyzed during REM sleep.  That is why we don’t normally act out our dreams. Rapid eye movements are generated in the dorsal pons, the midsection of the brainstem, by neuronal circuits that function like a flip-flop switch, alternately stimulating and inhibiting a projection of neurons from the pons to the forebrain. This is thought  to regulate the EEG components of REM sleep.  A second projection of neurons extends from the pons to the lower brainstem (medulla) and spinal cord and regulates atonia during REM sleep. These findings demonstrating independent pathways mediating atonia and the EEG components of REM sleep provide a basis for their occasional dissociation in pathological states such as REM sleep behavior disorder. For more detail about these neuronal circuits important in REM, see P.M. Fuller et al. The pontine REM switch: past and present. The Journal of Physiology 2007; 584: 735-741 (free access).

The most common adverse outcome of a REM sleep behavior disorder attack is injury from unprotected falls. However, REM sleep behavior disorder can be frightening and perhaps even lethal.  Striking a bedmate is not uncommon. Killing a bedmate is very rare, but defense attorneys have had a  handful of successes in exonerating  defendants with documented REM sleep movement disorder and no other motive for murder. 

REM sleep behavior disorder can be seen in response to a variety of injuries to the pons.  Rare cases have been seen in strokes and vasculitis, but the most common association is with Parkinson’s disease and related disorders such as Lewy body dementia. In these latter examples, neurodegenerative changes in the pons and symptoms of REM sleep behavior disorder typically begin many years before the onset of motor, gate, and cognitive signs.

There is much less information available about REM sleep behavior disorder in people with carefully documented Alzheimer’s disease.  It clearly is less common in Alzheimer’s than in Parkinson’s and related dementias.  When it has been found in Alzheimer’s, it has sometimes been explained by possible misdiagnosis or mixed dementia. About 50% of autopsied brains show signs of two or more types of dementia. Could I have Lewy body dementia or Parkinson’s disease in addition to Alzheimer’s disease? 

So what is going on in my pons to give me REM sleep behavior disorder? I went back to look carefully at the series of tau PET scans done in 2015, 2018, and 2022 at UCSF as part of a longitudinal study. 

In 2015, there was just a hint of abnormal tau appearing in the temporal lobes, and none in the pons. By 2018, there was a lot more tau in both temporal lobes, and there clearly was some tau in the pons. In 2022 there are now at least two accumulations of tau in the pons and increases elsewhere in the brain. I think this is really interesting.  I have a very specific biomarker for Alzheimer’s disease in my pons, exactly where a stroke or other abnormality could cause REM sleep behavior disorder. I think this suggests that Alzheimer’s pathology by itself can injure the pons in a way to produce this disorder of sleep.

So what did I do?  I immediately contacted my neurologist. He agreed with my diagnosis and suggested that I try taking melatonin. Melatonin and clonazepam have both been shown to be effective at improving REM sleep behavior disorder, but melatonin generally has fewer side effects. I’m sleeping very well on the melatonin. I still dream, but the dreams tend to be pleasant dreams, no nightmares. I haven’t had any more episodes of acting out my dreams. I’m very encouraged, but I’m not ready yet to take the safety rails off my bed.