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December 18, 2007
Brain Effects Appear Less Serious in MMD2
A recent review of several studies of cognitive and behavioral aspects of type 1 myotonic dystrophy (MMD1) and type 2 myotonic dystrophy (MMD2) shows that, in general, these aspects of the disease are present in MMD2 but to a lesser extent than they are in MMD1.
MMD1 is a disease of varying severity caused by an expanded section of DNA on chromosome 19, and MMD2 is a more recently identified and usually less severe disease resulting from an expanded DNA section on chromosome 3.
In the September issue of Muscle & Nerve, Giovanni Meola and Valeria Sansone at the University of Milan (Italy) and San Donato Hospital in Milan review their and others’ studies of cognitive and behavioral aspects of MMD1 and MMD2.
Deficits in visual-spatial skills (as shown by putting together puzzles, reading maps, etc.) and deficits in attention were noted in both diseases, but they were less severe in MMD2 than in MMD1.
Excessive daytime sleepiness is a prominent feature in MMD1, but it’s less frequently found in MMD2.
However, difficulty with planning and executing tasks has been noted in both MMD1 and MMD2, and both groups of patients have been described as having “avoidant” personalities.
Recent studies have shown that some atrophy (shrinkage) of the brain’s cerebral cortex occurs in both diseases, but to a lesser degree in MMD2 than in MMD1. Some impairment of blood flow to parts of the brain appears to be similar in MMD1 and MMD2. However, studies using magnetic resonance spectroscopy have suggested that brain metabolic activities are different in the two diseases.
Meola said that taking into account the possibility of cerebral involvement in the myotonic dystrophies could help patients manage their daily lives better.
In their paper, the investigators also note that “it may help physicians, family members, and employers to understand why, despite mild muscle disability, patients with DM [MMD] may not function as well as expected by their muscle strength and status.” |
