March 3, 2008

MMD1 Sleepiness Differs From Narcolepsy

An abnormally low level of a protein called hypocretin 1, which is associated with a sleep disorder known as narcolepsy, doesn’t play a role in the excessive daytime sleepiness reported by many people with type 1 myotonic muscular dystrophy (MMD1), says a study in the Jan. 15 issue of Neurology. Narcolepsy is a neurological disorder characterized by frequent, uncontrollable bouts of falling asleep during normal activities.

MDA grantee Emma Ciafaloni at the University of Rochester (N.Y.) Medical Center coordinated the research team, which also included Charles Thornton, co-director of the MDA clinic at that institution. Study participants came from URMC and from the University of Milan (Italy).

When the investigators compared levels of hypocretin 1 in the spinal fluid of 38 people with MMD1, 17 of whom reported excessive daytime sleepiness, to hypocretin 1 levels in 33 people without MMD1 or excessive sleepiness, they got identical results.
 
The researchers say these findings support the idea that excessive sleepiness in MMD1 results from a central nervous system defect different from that found in narcolepsy.

Since earlier studies have shown that several proteins produced in MMD1 patients are the fetal or newborn form instead of the mature form, the investigators on this new study suggest that MMD1-affected cells may make fetal or newborn forms of proteins affecting sleep regulation.

The speculation is bolstered by overnight sleep study results in seven MMD1-affected participants with excessive sleepiness that showed a sleep pattern typical of newborns.