Open pathways for cerebrospinal fluid outflow at the cribriform plate

Irene  Spera1,  Nikola  Cousin2,  Miriam  Ries2,  Anna  Kedracka2,  Alina  Castillo1,  Simone Aleandri3,  Mykhailo  Vladymyrov1,  Josephine  A.  Mapunda1,  Britta  Engelhardt1,  Paola Luciani3, Michael Detmar2 and Steven T. Proulx1 
1 Theodor Kocher Institute, University of Bern, Bern, Switzerland,
2 Institute of Pharmaceutical Sciences, ETH Zürich, Zürich, Switzerland, and
3 Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland 

Correspondence: Steven T. Proulx. Email:  This email address is being protected from spambots. You need JavaScript enabled to view it.   

Routes  along  the  olfactory  nerves  crossing  the  cribriform  plate  to  lymphatic  vessels  in  the  nasal submucosa are critical cerebrospinal fluid (CSF) outflow pathways. However, it remains unclear how fluid pathways along the nerves connect to the lymphatic vessels and where the arachnoid barrier is breached. Here, we anatomically defined the connections between the subarachnoid space (SAS) of the central nervous system and the lymphatic system.  

PEGylated fluorescent microbeads were infused into the CSF space of Prox1-GFP reporter mice to identify the CSF outflow pathways. A labeled anti-CD31 vascular antibody was infused into the cisterna magna to study the connections to the lymphatic vessels in the olfactory region. In some samples, we did immunofluorescence staining on decalcified sections to detect the arachnoid barrier.

PEG microbeads were within lymphatic vessels in the nasal submucosa and the lumen of lymphatic vessels that crossed the cribriform plate alongside the olfactory nerves. The labeled antibody revealed a continuous functional network of lymphatic vessels draining CSF from the SAS through the nasal submucosa. In addition, we observed discontinuity of the arachnoid barrier at the olfactory region.  

Micron-sized PEG beads are suitable for studying CSF bulk flow and clearance pathways. We observed direct and open connections from the CSF space to the lymphatic vessels crossing the cribriform plate and in the nasal submucosa. Finally, the discontinuous distribution of the arachnoid barrier in this area could explain how CSF within the SAS accesses the lymphatic system.