- Last Update On : 2013-01-26
Since cerebrospinal fluid (CSF) is an ultrafiltrate of plasma, it has much lower concentrations of the highest molecular weight proteins such as IgG, IgA and IgM. Elevated CSF IgG levels can either be the result of diffusion of plasma IgG across an altered blood brain barrier or intrathecal synthesis. Patients with multiple sclerosis and other demyelinating disorders often have elevated CSF IgG concentrations due to intrathecal synthesis. Analysis of cerebrospinal (CSF) IgG is helpful in diagnosing multiple sclerosis and other demyelinating diseases.
About 50% of multiple sclerosis patients have elevated CSF protein levels and about 75% have increased gamma globulins. Several tests have been devised to determine if the elevated gamma globulin is the result of intrathecal IgG synthesis. The percent of IgG present is more useful than the absolute concentration, because it compensates for increased blood brain permeability. The first ratio devised was the CSF IgG to CSF total p