The Lymphatic System and CSF Drainage

An Alternate Route to IH Etiology?

Miles Johnston, Ph.D., Professor of Laboratory Medicine and Pathobiology at the University of Toronto in Toronto, Canada, offered a different perspective on CSF drainage and the lymphatic system. The commonly-held belief maintains that CSF drains through the tiny channels or villi of the arachnoid granulations into the venous blood system.

But a link between CSF and the lymphatic system has been known for over a century. Dr. Johnston suggested that the lymphatic system may act as a drainage conduit for CSF, based on animal models and anatomical evidence. He discovered that in many diff erent animals, increasing intracranial pressure
elevates lymphatic fl ow in the neck. Whether the same is true in humans is unknown.

Additionally, in animals, if CSF access to paranasal lymphatics is blocked, cranial CSF absorption is reduced. In a sheep model, some CSF drainage may
have occurred directly into the cranial venous system (blood circulation), though Dr. Johnston found that there was little evidence that this absorption took place through the arachnoid granulations. According to the study, the lymphatic anomalies may be associated with disorders of the
CSF system. Hydrocephalus animal models have revealed physical abnormalities in the lymphatic system.

Dr. Johnston suggested that lymph may be a main or secondary pathway for draining CSF. He also theorized that elevated intracranial pressure may be the result of an impaired lymphatic system that cannot drain CSF properly, which would mean that improving lymphatic drainage would lower intracranial pressure.