Immunoglobulin and Albumin quotient diagrams (Reibergrams) of the normal controls (filled squares) and patients with blood-CSF barrier dysfunctions without an intrathecal immune response (open circles). Oligoclonal IgG was absent in all patients, also in the one patient with a borderline IgM quotient. The age-related reference range for normal QAlb values (normal blood-CSF barrier function) was calculated according to the formula QAlb < (4+ age (years)/15) × 10-3. An intrathecal synthesis of IgG, IgA and IgM is indicated by quotient values above the hyperbolic upper limit curve, Qlim (bold line). The reference range for the blood–derived fractions in CSF is derived from data of 4300 patients (mean ± 3SD , corresponding to 99% probability of intrathecal synthesis if QIg > Qlim). The dashed lines above Qlim indicate the extent of the intrathecally synthesized fractions in% with reference to Qlim as 0% . These diagrams are developed for maximal specificity for intrathecal synthesis with the Qmean + 3SD. For statistical comparison of mean values of groups the calculation refers to Qmean and for counting the frequencies of intrathecal fractions of the group we refer to Qmean + 2 SD (CSF Statistics Tool , with which also the diagram was created).