Relationship between intracranial pressure and cervical lymphatic pressureand flow rates in sheep

Previous reports from our group demonstrated that about one-half of the tot al volume of cerebrospinal fluid (CSF) removed from the cranial vault in sh eep is transported into extracranial lymphatics, especially cervical lympha tic vessels in the neck. In this study, we tested the hypothesis that an el evation of intracranial pressure (ICP) would increase cervical lymphatic pr essure and lymph flow rates in anesthetized sheep. Catheters were inserted into both lateral ventricles, the cisterna magna, cervical lymphatics, and the jugular vein. A ventriculo-cisternal perfusion system was employed to r egulate ICP. Mean (P = 0.008), peak (P = 0.007), and baseline (P = 0.013) c ervical lymphatic pressures increased as ICP was elevated from 10 to 70 cmH (2)O in 20-cmH(2)O increments. Similarly, cervical lymph flow rates increas ed (P < 0.001), with flows at 70 cmH(2)O ICP observed to be approximately f ourfold higher than those at 10 cmH(2)O TCP. No changes were observed in me senteric lymph flow rates (vessels not expected to drain CSF). We conclude that cervical lymphatic vessels play an important role in the transport of CSF from the cranial vault when ICP is elevated.