Several scientists have published the results of important DM research. Dr. Katharine Hagerman, PhD, Research Assistant at Stanford University, has provided MDF with lay summaries of some of this research. See below for the summaries and for links to the research studies and abstracts.
1. Evaluation of CNS involvement in myotonic dystrophy type 1 and type 2 by transcranial sonography
Many cognitive symptoms have been described in individuals with myotonic dystrophy (DM), including altered executive functioning (multitasking and planning), sleepiness, and depression. Researchers in Germany, led by Dr. Schneider-Gold, sought to identify structural changes in the brain that might correlate with cognitive symptoms in people with DM. Similar to previous studies, they found that many people with DM1 and DM2 had excessive daytime sleepiness (71% and 50%, respectively).
Using ultrasound technology, the researchers detected a region of the brain, called the brainstem raphe, that was significantly different in many adults with DM1 as compared to unaffected individuals. The brainstem raphe is known to be responsible for alertness and sleep cycles, so not surprisingly the researchers discovered through the ultrasounds that those people with excessive daytime sleepiness most often had a structurally altered brainstem raphe. These structural changes may be responsible for the symptoms of sleepiness in people with DM.
2. Muscle force, balance and falls in muscularly impaired individuals with myotonic dystrophy type 1: a five year prospective cohort study
Progressive muscle weakness can be seen in many individuals with myotonic dystrophy. This weakness can affect balance, and result in stumbling and falling. Researchers from Sweden, led by Dr. Lindberg, performed a five-year observational study of adults with type 1 myotonic dystrophy (DM1) which measured the changes in strength, balance and falls. They selected participants who already reported muscle weakness, and followed their symptoms for five years. The researchers found that many different muscles weakened over the period. The largest loss of strength occurred in the ankle dorsiflexor muscles - the muscles responsible for lifting the foot up. Overall there was a strength decrease of 12% after five years, and it was more pronounced in men than in women. Walking speed slowed, with participants taking on average two seconds longer to walk 30 feet. They also found that all of the men in the study had at least one fall in the past year, whereas only 60% of the women had fallen during the final year of the study.
This study highlights the need for physiotherapy evaluations in individuals with DM1 and symptoms of weakness, and suggests that future studies should focus on how effective rehabilitation interventions can be for reducing falls.
3. Resveratrol enhances splicing of insulin receptor exon 11 in myotonic dystrophy type 1 fibroblasts
One common symptom seen in individuals with myotonic dystrophy type 1 and type 2 (DM1 and DM2) is insulin resistance. Previous studies have shown that this is caused by an improper form of the insulin receptor being made, which makes it less sensitive to insulin, and creates glucose intolerance. Researchers in Japan, led by Dr. Matsuo, searched for a chemical that might help make the correct form of the insulin receptor. They identified a chemical called resveratrol, which when applied to cells from people with DM1 switched the cells back to making the healthy form of the insulin receptor. Resveratrol also brought the receptor up to a level even higher than healthy cells derived from people not affected by myotonic dystrophy. While resveratrol is a chemical that naturally occurs in many plants, how it works in human cells is not well understood. The authors believe that with further testing, resveratrol might be used to improve glucose tolerance in people with DM.