Motor neuron disease and amyotrophic lateral sclerosis: relation of high CSF protein content to paraproteinemia and clinical syndromes.

From 1984 to 1988, 11 of 120 patients (9%) with motor neuron disease (MND) had paraproteins detected by serum immunofixation electrophoresis (IFE), compared with 4 (3%) by cellulose acetate gels: 1 patient had progressive spinal muscular atrophy, 5 patients had amyotrophic lateral sclerosis (ALS), and 5 patients had ALS with probable upper motor neuron signs. Four of 5 patients (80%) with cerebrospinal fluid (CSF) protein content above 75 mg/dl had paraproteins, as did 6 of 30 with values above 50 mg/dl. Four of 14 patients with cerebrospinal oligoclonal bands (OCB) also had paraproteins. Two patients with ALS, CSF protein content above 75 mg/dl, and paraproteinemia had lymphoma. We conclude the following about patients with MND: high CSF protein content (especially above 75 mg/dl) or CSF OCB makes paraproteinemia more likely; some of these patients may have lymphoma; there is an inordinately high occurrence of paraproteinemia in MND; and IFE on agarose is more sensitive than electrophoresis on cellulose acetate in detecting paraproteins. Syndromes of paraproteinemia and high CSF protein are not restricted to the lower motor neuron but qualify as "ALS" with coexisting upper motor neuron signs.