The most common neurological manifestation of Lyme disease is lymphocytic meningoradiculitis (Banwarth's syndrome, stage II). In rare cases, chronic progressive encephalomyelitis (stage III) with symptoms similar to multiple sclerosis is observed. Antibodies against Borrelia burgdorferi are detectable in 70-90% of stage II cases, with IgM-antibodies predominating in the first two weeks, and IgG-antibodies thereafter. Detection of specific intrathecal antibodies is the best serodiagnostic parameter for diagnosing neuroborreliosis. With the aid of a CSF/serum index determination (on the basis of a comparison of IgG-antibody ELISA titers in CSF and serum with identical IgG concentrations) involvement of the nervous system was shown in 64% and 77%, respectively, of 76 stage II cases (diagnostic significance 98% and 100%, respectively). In particular when tertiary forms of the disease are suspected immunoblot techniques (Western blot, IEF-affinity blot) are recommended confirmatory tests.