Patterns of disease activity in multiple sclerosis: clinical and magnetic resonance imaging study.

Objective: To compare the abnormalities shown by magnetic resonance imaging of the brain in three clinically distinct groups of patients with multiple sclerosis, and to correlate the extent of abnormality with the degree of clinical disability in the three groups.

Design: All patients underwent magnetic resonance imaging and full neurological examination, and their disability was scored according to the expanded Kurtzke disability state scale.

Setting: National Hospital for Nervous Diseases (Multiple Sclerosis NMR Research Group).

Patients: Three groups of patients with confirmed multiple sclerosis were studied: 12 patients with minimal disability despite a long (greater than 10 years) duration of illness (benign multiple sclerosis), 16 who had developed progressive disability after a relapsing and remitting course (secondary progressive multiple sclerosis), and 13 who had had progressive disability from the onset of the disease (primary progressive multiple sclerosis).

Main Outcome Measures: Number and size of lesions in 17 anatomically defined sites; total lesion load, estimated with an arbitrary scoring system weighted for the size of lesions; and disability score.

Results: Magnetic resonance imaging showed that all 41 patients had abnormalities. These were extensive in the groups with secondary progressive and benign disease compared with the group with primary progressive disease. The lesions in the patients with secondary progressive disease were larger and more confluent than those in the two other groups (p = 0.007). Most lesions (85%) in the patients with primary progressive disease were under 5 mm in diameter; this percentage was higher than that in the two other groups (p = 0.032). Consequently the patients with primary progressive disease had the lowest mean lesion load (36.7); that in the patients with benign disease was 52.7 and that in the patients with secondary progressive disease 64.6 (p = 0.05). No correlation existed between disability and total lesion load. The distribution of brain lesions and of detectable lesions of the spinal cord, and the frequency of cortical atrophy, were similar in all groups.

Conclusions: No relation was found between the degree of clinical disability and the extent of abnormality shown by magnetic resonance imaging: patients with clinically benign disease often had extensive abnormalities and those with primary progressive disease had surprisingly few lesions. Though magnetic resonance imaging increases knowledge of the disease process in multiple sclerosis and is invaluable in diagnosis, it is not helpful in predicting disability in individual patients.