Visual evoked potentials in patients with neuropathy and macroglobulinemia.

Visual evoked potentials were studied in 11 patients with neuropathy and macroglobulinemia. The P100 latency was increased bilaterally in 5 of the 6 patients whose IgM M-proteins reacted with myelin-associated glycoprotein (MAG) and in 1 of the other patients. In patients whose M-protein bound to MAG, abnormal visual evoked potentials correlated with the presence of the M-protein in the cerebrospinal fluid. Subclinical involvement of the central nervous system is frequent in patients with neuropathy and anti-MAG M-proteins and may be due to the binding of M-proteins to central nervous system myelin.