A Commentary on Correlates Between Cerebrospinal Fluid γ-Globulins and Magnetic Resonance Imaging in Multiple Sclerosis

To the Editor.  —The results of Müller et al¹ in the April 1989 issue of the Archives, showing a significant correlation between cerebrospinal fluid γ-globulin (IgG) concentration and a nonparametric estimate of magnetic resonance imaging as well as slowed visual-evoked potentials, are in general agreement with our data despite significant differences in the methods employed.^2-4 However, their conclusion that cerebrospinal fluid IgG primarily originates from periventricular lesions implies a less statistically significant correlation between the cerebrospinal fluid IgG concentration and their global magnetic resonance imaging score (not shown by their data), since inclusion of nonperiventricular plaque area should dilute the periventricular relationship. Second, their method for quantifying IgG in the cerebrospinal fluid and serum is not specific for IgG, but includes other proteins and is no longer used by advanced cerebrospinal fluid laboratories. Our laboratory measures IgG directly,⁵ utilizing monoclonal or affinity purified antibody to IgG heavy