Abstract
The outflow of the cerebrospinal fluid (CSF) in animals was over the years the subject of detailed analysis. For a long time it was stated that arachnoid granulations of the venous sinuses play a key role in CSF circulation. However, recent studies on this subject have shown that a considerable part of the CSF is drained to the lymphatic vessels. Moreover, disorders in the CSF passage may result in severe central nervous system diseases such as e.g. hydrocephalus. In this paper, we summarize the current knowledge concerning the lymphatic drainage of the CSF in mammals. We present in detail comparative anatomy of different species taking into account cranial and spinal compartment. In addition, we clarified role of the lymphatic vessels in the CSF outflow and the relationship between impairment in this transport and central nervous system diseases. In the author’s opinion knowledge on CSF circulation is still poorly examined and therefore required comment.
Highlights
Arachnoid granulations protruding into dural venous sinuses were seen as the main outflow tract of cerebrospinal fluid (CSF) from the subarachnoid space (SAS)
In conditions of low intracranial pressure, almost 100% of CSF drained from the cranial cavity to the lymphatic vessels through the cribriform plate in the vicinity of the olfactory nerve
The information presented in this article clearly prove that in mammals, lymphatic vessels, and mainly lymphatic vessels of the nasal cavity, play a very important role in CSF absorption from the area of SAS
Summary
Arachnoid granulations protruding into dural venous sinuses were seen as the main outflow tract of cerebrospinal fluid (CSF) from the subarachnoid space (SAS). Studies on rat confirmed that the lymphatic system plays the main role in CSF outflow from the cranial cavity In this species, [14C] sucrose administered intraventriculary did not reach the SAS located over the cerebral cortex, it did not reach arachnoid granulations protruding into the sagittal dorsal sinus (GhersiEgea et al 1996). The contrast agent reached the area of the cribriform plate after 21 min in older animals and in 23.8 min in younger individuals (the presented values are the median, and the flow time was significantly different between individuals) In this case, no transportation to the venous sinuses was noted, and a substantial amount of the contrast agent got into the SAS of the spinal cord. Similar conclusions might be drawn from other studies on rat, in which kaolin was deposited in basal cisterns In those animals, a significant impairment of CSF outflow through the cribriform plate into the nasal cavity was obtained. It closed the connection between the cranial compartment and the spinal compartment, and cut off some compensatory mechanisms that might remove CSF excess
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