uords: Cercbrospinal fluid: CSF flow: Blood CSF barricr: Sclcctivity: Permeability: Protein diffusion: ('SF ~ scrtun quotients: Albumin: IgG: lgA: lgM: Ncurological diseases: Pathophysiology

Many neurological diseases are accompanied by increased protein concentrations in the ccrcbrospinal fluid (('SF). dcscribcd as a blood-('SF barrier dysfunction. Thc earlier interprctation as a "'leakage" of the blood-CSF barricr for serum proteins could be revised by introduction of a "population variation coefficient" of thc CSF/scrum quoticnts for Ig(}, lgA and IgM (..IQ 'Q) which is evaluatcd as a function of increasing albumin quotients (OAll~). The data prcscnted hcrc arc based t)ll specimens lrom 4380 neurological patients. These population variation coefficients were found to bc constanl ovcr two orders of magnitudc of normal and pathological CSF prolcin concentrations (OAIb = 1.6' 10 3--15(1' 10 ~). This constanc_~ indicatcs that there was no changc in blood-CSF barrier rclated structures with respect to diffusion controlled prolcin transfer from blood into ( 'SF and hcnce no change in molecular sizc dependcnt selectivity. The pathological increase of plasma protein concenirations in ('SF in neurological diseases could also bc explaincd quantitatively by a decrease of CSF llox~ ratc due to its bifuuctional infhicnce on CSF protein concentration: reduccd wHume cxchange, and as newly stated, increased nlolecular net Ilux into ('SF v~ithoul changc of permeability coefficients. Again, on the basis of a changing CSF flow rate, the hyperbolic functions, which describe cmpiricalb the changing quotient ratios between proteins of different size (e.g. O i+<+ : O.,\tb) with increasing ('SF prolchl content (O<l,) can likcwise be derivcd from the laws of diffusion as the physiologically rclcvant description. The hyperbolic discrinfina tion line hctwccn brain-derived and blood-derived protein fractions in CSF in the quotient diagrams for ( 'SF diagnosis can be lurthcr improved on the basis of thc large number of cases investigated. Other physiological anti pathological aspects, such as high CSF prolcin vahics in the normal ncwborrL, in spinal blockadc, in mcningcal inflammatory processes, ('NS lcukcmia or polyradiculitis as ,acll as animal species dependent variations can each be interpreted as duc to a difference or change in the ('SF flow rate.