Although, several studies proposed the existence of lymphatic vessels in the dura mater, the presence of the meningeal lymphatic system was accepted in 2015, when two independent studies published by Louveau et al. and Aspelund et al. provided convincing data using novel methods. Louveau et al. noticed an unusual alignment of immune cells along the dural sinus using a meningeal whole-mount technique. Using lymphatic endothelial cell-specific markers and electron microscopy, the authors found that the immune cells were not inside blood vessels, but rather were organized inside lymphatic vessels within the meninges, a system of membranes that envelop the brain and spinal cord.
