Choroid plexus and ependymal cells in CSF cytology.

Choroid plexus and ependymal cells were only demonstrated in 10 of a series of 2620 CSF cytograms. Choroid plexus cells sometimes stained positive for acid phosphatase while in ependymal cells this enzyme activity was not observed. Choroid plexus and ependymal cells in CSF were found to be associated with various neurological disorders involving mainly the brain stem and spinal cord. This is probably due to the higher chance of sedimentation of viable cells in the lumbar sac in these conditions. Loss of these cells might explain the incidental observation of granular ependymitis in post-mortem brains.