Abstract
The purpose of this investigation was to enhance our understanding of cerebrospinal fluid (CSF) absorption pathways. To achieve this, Microfil (a coloured silastic material) was infused into the subarachnoid space (cisterna magna) of sheep post mortem, and the relevant tissues examined macroscopically and microscopically. The Microfil was taken up by an extensive network of extracranial lymphatic vessels in the olfactory turbinates. In addition however, Microfil also passed consistently through the dura at the base of the brain. Microfil was noted in the spaces surrounding the venous network that comprises the cavernous sinus, in the adventitia of the internal carotid arteries and adjacent to the pituitary gland. Additionally, Microfil was observed within the endoneurial spaces of the trigeminal nerve and in lymphatic vessels emerging from the epineurium of the nerve. These results suggest several unconventional pathways by which CSF may be removed from the subarachnoid space. The movement of CSF to locations external to the cranium via these routes may lead to its absorption into veins and lymphatics outside of the skull. The physiological importance of these pathways requires further investigation.
Highlights
Microfil is a coloured, liquid silicone rubber compound
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 cerebrospinal fluid (CSF) absorption [2,3,4,5,6]
We present these findings and speculate on whether these unconventional anatomical locations have a role in cranial CSF absorption
Summary
Liquid silicone rubber compound. This agent facilitates the generation of three-dimensional images of the spaces into which it has been injected. 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 [2,3,4,5,6]. We present these findings and speculate on whether these unconventional anatomical locations have a role in cranial CSF absorption
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