1-3 Little is known about the underlying mechanisms and individual disease characteristics that affect the rate at which brain parenchyma decreases. To assess the impact of ongoing disease activity on atrophy development, we correlated the increase of ventricular volume and diameter with the cumulative number of contrast-enhancing lesions and their characteristics on serial monthly MRI scans. In contrast to the spinal cord, most supratentorial lesions do not affect primary efferent pathways. Their effects on neurologic function may be, therefore, less readily assessable. Disability as a function of ventricular enlargement or cumulative lesion count was, therefore, not a primary objective of this study.
Contrast enhancement is a transient feature of some acute lesions.
In general, lesions do not remain enhancing for more than 2 to 4 weeks and the volume of enhancement varies with time after the onset of blood-brain barrier breakdown. Since MRI scans were performed monthly, we elected to account for the number and the characteristics of the lesions rather than the volume of enhancement. Five individuals did not have clinically significant exacerbations during the study period. Measurement of third ventricular width and the diameter of the lateral ventricles was performed on all scans. A graded caliper with a 0.1-mm scale was used for linear measurements on film copies.