Heterotopic regeneration of peripheral nerve fibres into the subarachnoid space.

Within the spinal cord meninges of SJL/J mice afflicted with chronic relapsing experimental allergic encephalomyelitis for up to seven months postinoculation, networks of aberrant regenerated nerve fibres myelinated by Schwann cells have been observed. These P.N.S. elements are believed to have been derived from incoming sensory fibres from the spinal nerve roots which had been interrupted during acute stages of the disease. This phenomenon might also have been related to the occurrence of marked nerve fibre loss and gliosis within superficial tracts in the spinal cord. P.N.S. elements within the subarachnoid space were first apparent six weeks postinoculation, and were distributed around the entire spinal cord and tended to be more concentrated around meningeal blood vessels. Schwann cells associated with these fibres frequently contained centrioles and cilia and daughter Schwann cells apparently arose from parent cells already committed to axons.