Chicken arachnoid granulations: a new model for cerebrospinal fluid absorption in man

Cerebrospinal fluid (CSF) absorption was investigated in chicken and rat us ing infusion tests into the cisterna magna. Data were analysed according to a mathematical model by Johnson et al. Results in rat predicted a predomin ant lymphatic mechanism, which was confirmed by rapid outflow of X-ray cont rast media into the olfactoric mucosa. In contrast, dynamics measurements s uggested CSF drainage via arachnoid granulations in chicken. CSF spaces alo ng the optic nerve were contrasted radiographically resulting in venous dra inage. Electron microscopically, villus-like structures were found at the d istal optic nerve connecting the subarachnoid space with accompanying veins , resembling human arachnoid granulations. We hypothesize that CSF absorpti on through arachnoid villi in microsmatic chicken reflects the situation in man very well. NeuroReport 12:553-557 (C) 2001 Lippincott Williams & Wilki ns.