Spinal cerebrospinal fluid pathways and their significance for the compensation of kaolin-hydrocephalus

To study the mechanisms of CSF-outflow in hydrocephalus we used radiological and histological methods to examine pathways of CSF absorption. Two, four and six weeks after occlusion of the cisterna magna by kaolin solution, CSF-dynamics were determined. Direct magnification radiography was used to visualize the outflow of X-ray contrast. Ten rats in each group were sacrificed for histological analysis following ventricular perfusion with marker proteins. ICP was increased to 15 +/- 1 mmHg (mean +/- SD) compared to control animals (7 +/- 2 mmHg) in the four week group. Six weeks following kaolin injection no increase in ICP (6 +/- 1 mmHg) could be demonstrated. Outflow resistance was markedly raised in all animals (1074 +/- 315 mmHg min-1 ml-1) displaying highest values (2160 +/- 960) in the four week group as compared to control animals (504 +/- 71). Cisternography demonstrated blocked cranial absorption and CSF-outflow along lumbosacral nerve roots. Histological examination showed syrinx formation in the cervical and thoracic spinal cord. Marker proteins left the subarachnoid space along thoracic and lumbo-sacral spinal rootlets. The radiological and histological findings and the normalisation of ICP after six weeks at doubled CSF-outflow resistance indicated a recruitment of spinal perineural CSF outflow pathways for the compensation of the disturbed cranial CSF-absorption.