The aim of the work was to study the laboratory indexes of the autoimmune affections of the nervous system during mild cranial traumas (CT) of patients with rheumatoid arthritis (RA). Under the examination there were 16 patients with neurological signs of RA got the mild CT. The group of compare consisted of 30 patients with RA and the nervous system lesions without traumas of it in the life histories. The control group consisted of 30 healthy people. The autoimmune affection of the nervous system was diagnosed by definition of the antibody-synthetic activity of the B-cells over the cerebrolysin. The work confirms presence of the autoimmune component of the CT pathogenesis and gives prove of need of rheumatologist or immunologist participation in the treatment of patients with RA with CT. Described laboratory method of the B-cells activity definition can be recommended as a complementary diagnostic method of the nervous system affections during RA, presence and activity of the autoimmune component of the CT pathogenesis in such patients.