An attempt to quantify magnetic resonance imaging in multiple sclerosis--correlation with clinical parameters

The diagnostic value of magnetic resonance imaging (MRI) in multiple sclerosis (MS) is uncontested. But only little information exists on its usefullness in monitoring disease activity. We describe a method of quantification that can be performed in longitudinal MRI-investigations. We used a standardized method of scanning and determined the area of demyelinating lesions with an interactive planimetric computer system. In order to determine the approximate lesion volumes, the computed area was multiplied by the slice thickness. In 89 patients with clinically definite MS we found an average lesion volume of 11900 mm3. The mean score in Kurtzke's expanded disability scale was 3.0. The correlation between computed lesion volume and neurological deficit was significant, but only weak (rho = 0.3). We conclude, that planimetric evaluation of MRI can be a valuable supplement to clinical rating scales in MS patients. The method described here, used in combination with high spacial resolution and better tissue specificity of latest generation MRI scanners, could be helpful in the evaluation of treatment in many other CNS diseases.