Contrast-enhanced magnetic resonance activity in relapsing remitting multiple sclerosis patients: a short term natural history study.

Magnetic resonance imaging (MRI) has been used to study the history of multiple sclerosis (MS). We analyze the relationship between MRI activity in the first scan compared to the subsequent five scans, and we evaluate whether a shorter observation period of 3 months may predict the subsequent 3 months. Monthly enhanced MRI was performed in 103 relapsing remitting (RR) MS patients for 6 months. Thirty-five per cent of patients had an inactive scan on the initial examination. More than 80% of them developed MRI activity during the following 5 months. Eighteen per cent of patients had three consecutive inactive scans; 65% of them had at least one active scan on the subsequent 3 monthly MRI's. The relationship between the first scan and all subsequent scans demonstrates a clear weakening over time. Eighty-two per cent of patients had at least one active scan during the initial 3 consecutive months, the chance of becoming inactive decreased from 23% to 0% over the subsequent 3 months, according with the mean number of enhancing lesions during the first 3 months. These results suggest that neither a single scan nor a short baseline of 3 months may adequately describe the natural history of disease in an individual RRMS patient.