Serum and cerebrospinal fluid IGM in 203 neurological patients.

Simultaneous serum and CSF IgM determinations were made by electroimmunodiffusion in 5 normals and 203 patients. Absent from normal CSF, IgM was found in 56 patients (27%): (1) A blood-CSF transudation was present in 25 patients (12%). IgM seems of no diagnostic value in these cases. (2) A purely local synthesis was demonstrated in 17 patients (8%), concerning proved (bacterial, viral, parasitic) or supposed (multiple sclerosis) persistent infectious aggressions. (3) In the last 14 patients with IgM in CSF, a transudation was associated with a local synthesis of IgG (meningitis pattern). (4) A ratio IgM .10(3)/albumin above 10 seems an argument for multiple sclerosis.