Objective: In neonatal lambs, the quantitative evidence suggests that a significant volume of cranial CSF drainage is associated with transport along olfactory nerves with absorption primarily into extracranial lymphatics in the paranasal region. Arachnoid granulations appear to be poorly developed at this level of development and their function is unknown. In this report, we tested whether a CSF protein tracer ((131)I-human serum albumin) could transport directly into the superior sagittal sinus of newborn lambs.
Methods and results: The concentration of the tracer administered into the CSF compartment was measured in the confluence of the intracranial venous sinuses (torcula) and in the peripheral blood (inferior vena cava). Enrichment of the CSF tracer in the cranial venous system was most evident when the CSF-venous sinus pressure gradients approached 20-30 cm H(2)O.
Conclusion: The data suggests that neonatal CSF can be absorbed directly into the cranial venous system. However, contrary to the classical view, this route may represent an auxiliary system that is recruited to compliment lymphatic transport when intracranial pressures are very high.