Possible role of the cavernous sinus veins in cerebrospinal fluid absorption

Microfil is a coloured, liquid silicone rubber compound. This agent facilitates the generation of three-dimensional images of the spaces into which it has been injected. In previous reports, we infused Microfil into the subarachnoid compartment of a variety of species including mice, rats, rabbits, pigs, sheep, monkeys and humans. We noted that this contrast agent was carried through the cribriform plate into an extensive network of lymphatic vessels in the nasal submucosa of these species [1]. These data supported in vivo physiological studies that demonstrated an important role for extracranial lymphatic vessels in CSF absorption [2-6]. Additionally, we also noted the presence of Microfil at locations not associated commonly with CSF transport pathways. In this paper, we present these findings and speculate on whether these unconventional anatomical locations have a role in cranial CSF absorption.Details of the methods can be found in our earlier publications [1,7]. Briefly, randomly bred sheep (n = 29; 2.6–35 kg) including newborns (2–7 days old) and adult animals (6–8 months old) were used for this investigation. The newborns were anaesthetized initially by mask administration of incremental concentrations of halothane from 0.5 to 3%. The adult sheep were anesthetized initially by intravenous infusion of 2.5% sodium Pentothal solution. Subsequently, 1–3% halothane was delivered through an endotracheal tube via an A.D.S.1000 or Narkomed 2 respirator for surgical maintenance. A laminectomy was performed on the upper regions of the spinal cord (generally between C1–C2) and the cisterna magna was cannulated with an angiocatheter or a silastic tube of appropriate size. A ligature was placed around the spinal cord and tightened to compress the spinal cord and meninges. This ligature prevented Microfil from passing into the spinal subarachnoid compartment during injection. Following sacrifice of the animals with an intravenous overdose of pentobarbital (euthanyl, Bimed