Fig. 9. Schematic model of the brain lymphatic system and its drainage pathways.

The overall system is divided into dorsal and ventral systems. The dorsal system includes ISF-lymphatic fluid present along dural venous sinuses that drains along the jugular veins and foramen magnum. The thickest of these fluid spaces occurs at the midsagittal level. Decreased caliber of this space present at the level of the posterior sagittal sinus is most likely due to effects of gravity while in the supine position during scanning. The ventral system includes ISF-lymphatic fluid along the olfactory nerves in the anterior cranial fossa, optic groove, dura at the orifice of the Meckel’s caves, dura at the orifice of the internal auditory canals, and dura at the level of the orifices of jugular foramen. The green signal at the orifices of neural foramina represents lymphatic fluid. These pathways channel ISF-lymphatic fluid outside of the intracranial along the space epidural surfaces of the cranial nerves. ISF-Lymphatic signals along the cranial nerves, jugular veins and petrous and cervical ICAs in the neck show connections between each other and cervical lymph nodes. The schematic depicts direct connections between meningeal ISF-Lymphatic fluid to deep neck nodes via multiple neural foramina and along the skull base structures in humans.