[Involvement of apparently normal white brain substance in the disease process of multiple sclerosis]

In a group of patients with a clinically definite diagnosis of multiple sclerosis (MS) the cerebral white matter was investigated by means of quantitative nuclear magnetic resonance imaging (MRI). Measurements were taken from plaque-free regions and compared to a control group of healthy volunteers. A significant prolongation of T1 and T2 values was seen for all regions investigated (frontobasal, temporal, temporoparietal, and upper parietal white matter). In a comparison of MS patients with a short duration of the disease (mean: 1.7 years) with MS patients with a long-standing course of the disease (mean: 15.2 years) a significant prolongation of T2 relaxation times was found in the upper frontal and upper parietal white matter only for the latter group. In keeping with neuropathological findings the noted prolongation of T2 values might most probably be due to an increase of extracellular water secondary to astroglial proliferation. The increase of relaxation times could either be due to degeneration of commissural fibers or be the result of an exhausted capacity for remyelination. Both events are known to occur predominantly in the later stage of the disease. It is concluded that MS represents a disease which is not restricted to limited areas of demyelination but rather involves the entire cerebral white matter. These findings imply possibilities for the assessment of disease progression as well as for therapy.