Optic neuritis and chronic relapsing experimental allergic encephalomyelitis: relationship to clinical course and comparison with multiple sclerosis.

Optic nerve tissue from strain 13 guinea pigs sensitized for chronic (relapsing) experimental allergic encephalomyelitis has been examined up to 3 years postinoculation. The changes were compared with the clinical history in each case, with lesions occurring elsewhere in the central nervous system and with optic nerve tissue from a single case of chronic multiple sclerosis. In chronic experimental allergic encephalomyelitis was found that optic neuritis was a consistent finding. Active lesions in the optic nerve were a feature of animals sampled up to 4 months postinoculation. Unlike lesions in the spinal cord, changes occurring in long term animals did not parallel clinical signs. The absence of active lesions in long term animals was apparently not due to a resistance to recurrent disease on the part of the tissue since a second challenge with central nervour system tissue was capable of producing active inflammation in the optic nerve. It appears, therefore, that in its unmanipulated state, chronic experimental allergic encephalomyelitis is more a disease of the spinal cord. Optic nerve changes in the case of multiple sclerosis did not compare well with the guinea pit lesions--discrepancies which we speculate as being related to differences in anatomy, age, species, and longevity of the disease process (among others), rather than a difference in pathogenesis.