Figure 1. Cerebrospinal fluid drains from the human brain in three main pathways: into the sinus arachnoid villi, down the spine into the paravertebral lymphatics, and along the cranial nerves (I, olfactory; II, optic; V, trigeminal; VIII, vestibulocochlear). The cerebrospinal fluid then flows into the facial, cervical, and thoracic lymphatics. Reprinted with permission from: Knopf PM, Cserr HF, Nolan SC, Wu TY, Harling-Berg CJ. Physiology and immunology of lymphatic drainage of interstitial and cerebrospinal fluid from the brain. Neuropathol Appl Neurobiol. 1995;21:175-180, Blackwell Publishing.