Brain proton magnetic resonance spectroscopy and brain atrophy in myotonic dystrophy.

OBJECTIVES To evaluate by magnetic resonance spectroscopy the age-related cerebral alterations present in myotonic dystrophy (MD) and to compare these results with those obtained by magnetic resonance imaging. DESIGN Twenty-one patients (aged 16-63 years) with MD were compared with 16 age-matched healthy control subjects. RESULTS In magnetic resonance spectroscopy, the mean (+/- SD) ratio of N-acetylaspartate to creatine and phosphocreatine in the patients with MD (1.09 +/- 0.32) was significantly lower than that in the control subjects (1.93 +/- 0.43) (P<.001). The mean ratio of N-acetylaspartate to choline-containing compounds in the patients with MD (1.70 +/- 0.44) was also significantly lower than that in the control subjects (2.75 +/- 0.53) (P<.001). These changes could be observed already in the younger patients. In magnetic resonance imaging, the mean brain area was significantly decreased and the mean ventricular space was significantly increased in patients with MD compared with the control subjects. Although we have confirmed brain atrophy in patients with MD in previous reports, a regression analysis indicated that the brain shrinks progressively with age in patients with this disorder and in control subjects, resulting in overlapping values for younger subjects. CONCLUSION Magnetic resonance spectroscopy indicates that the cerebral abnormalities in patients with MD may be present at an early stage, when the results of magnetic resonance imaging studies are still equivocal.