The drainage of cerebrospinal fluid into the lymphatic system of the neck in humans.

A histo- and immunohistochemical examination of the superior deep cervical lymph nodes was performed in a group of 19 patients who died from intracerebral haemorrhage. For comparison two control groups without cerebral lesions were studied (n = 17, n = 13). Free iron deposits as shown within the lymph nodes by Prussian blue reaction were seen significantly more often following intracerebral haemorrhage than without bleeding. The expression of CD 68 (a marker for macrophages) or CR 3/43 (microglia) gave a strong reaction, but there are no significant differences between the three groups. Glial fibrillary acidic protein was rarely seen in the three groups. Raising the CSF pressure results in increased CSF drainage into the cervical lymph nodes. The clinical importance of this lymphatic drainage suggests a communication between the brain and the immune system of the head and neck, with a possible selective up- and down-regulation.