CSF DRAINS DIRECTLY FROM THE SUBARACHNOID SPACE INTO NASAL LYMPHATICSIN THE RAT - ANATOMY, HISTOLOGY AND IMMUNOLOGICAL SIGNIFICANCE

Cerebrospinal fluid (CSF) drainage pathways from the rat brain were in vestigated by the injection of 50 mu l Indian ink into the cisterna ma gna. The distribution of the ink, as it escaped from the cranial CSF s pace, was documented in 2 mm thick slices of brain and skull cleared i n cedar wood oil and in decalcified paraffin sections. Following injec tion of the ink, deep cervical lymph nodes were selectively blackened within 30 min and lumbar para-aortic nodes within 6 h. Within the cran ial cavity, carbon particles accumulated in the basal cisterns but wer e also distributed in the paravascular spaces around the middle cerebr al arteries and the nasal-olfactory artery. Carbon particles in the su barachnoid space beneath the olfactory bulbs drained directly into dis crete channels which passed through the cribriform plate and into lymp hatics in the nasal submucosa. Although ink was distributed along the subarachnoid space of the optic nerves and entered the cochlea, the na sal route was the only direct connection between cranial CSF and lymph atics. Arachnoid villi associated with superior and inferior sagittal sinuses were identified and a minor amount of drainage of ink into dur al lymphatics was also observed. This study demonstrates the direct dr ainage of cerebrospinal fluid through the cribriform plate in anatomic ally defined channels which connect with the nasal lymphatics. Such a pathway is compatible with the observed rapidity of the bulk flow drai nage of CSF in the rat, accords with the known specificity of immunolo gical reactions to antigens injected into brain tissue, and may also s erve as a route for drainage for lymphocytes and macrophages from the brain to the regional cervical lymph nodes.