Multiple system atrophy (MSA) is a rare and fatal degenerative neurological disease that is almost always accompanied by severe sleep disorders. There is clinical evidence that some of the sleep problems associated with this condition can be relieved by medications that replace depleted dopamine.
To investigate this clinical finding, researchers from the University of Michigan studied the brain chemistry of 13 patients with MSA and 27 healthy control subjects.
Radioactive tracers that attach specifically to proteins in dopamine and acetylcholine producing cells were administered to the participants. The brains were then scanned using positron emission tomography (PET) and single-photon emission computed tomography (SPECT).
The scans were performed during two successive nights of polysomnography, which involves continuous recording of specific physiologic variables during sleep. The results from PET and SPECT scans were correlated with the polysomnography recordings.
The results revealed that MSA patients have a lower density of dopamine and acetylcholine-producing neurons than normal control subjects. The lower the density of these neurotransmitter-producing cells, the worse the subjects’ sleep problems.
Depleted dopamine producing neurons in the striatum of the brain were associated with symptoms of thrashing, talking and violent flailing while asleep. In contrast, patients with the lowest levels of acetylcholine-producing neurons in the brainstem had more interruptions in breathing during sleep.
The researchers also observed that brain areas that control the muscles of the upper airway and tongue were associated with the largest deficits in acetylcholine neurons.
The authors conclude that chemical imbalances in the brain may be partly responsible for sleep disorders, but that further research is required to confirm these findings in otherwise healthy individuals and other neurological disorders.