New Discovery Makes Researchers Rethink CSF Absorption

The discovery of lymphatic vessels in the brain overturns decades of scientific dogma and provides a new target for scientific investigation. For hydrocephalus researchers, this discovery is extremely exciting because the lymphatic system represents an alternative route for cerebrospinal fluid (CSF) absorption.

The lymphatic system is a network of vessels, tissues, and organs that serves two key roles in the body. The lymphatic system plays a major role in fighting disease, producing white blood cells to fight inflammation or to fight a toxic or foreign substance. Has a doctor ever told you your lymph nodes are swollen? They are reacting to an infection or illness, trapping and destroying bacteria, viruses, and other harmful substances.

The lymphatic system is also responsible for maintaining fluid balance by draining excess fluid, called lymph, into the bloodstream. In doing so, the lymphatic system helps maintain appropriate fluid volumes and clears waste products from tissue.

Previously, it was believed that the lymphatic system did not exist in the brain. One of the few known connections was through the cribriform plate. The cribriform plate is located at the junction of the nose and forehead. It is perforated, allowing direct connections between CSF and the lymphatic system. Past Hydrocephalus Association grantee, Miles Johnston, PhD, tested drugs administered via a nasal mist to modulate the absorption of CSF through this pathway. In his proof of concept paper, the nasal mist increased CSF absorption at elevated intracranial pressures.

Two new studies from Aspelund and colleagues, and Louveau and colleagues show that lymphatic vessels are in fact present in the brain. In addition, both studies show that these vessels are actively involved in CSF clearance. What we do not yet know is if these lymphatic vessels are a major player in CSF absorption, are involved in the development of hydrocephalus, or if they can be modulated to help improve CSF absorption and decrease intracranial pressure. The potential to increase fluid uptake into these vessels provides a new target for hydrocephalus researchers searching for non-invasive ways to increase CSF absorption.