Neuropathology of Demyelinating Diseases in Japan

We reviewed and compared the neuropathology of multiple sclerosis (MS), neuromyelitis optica (NMO), neuromyelitis optica spectrum disorders (NMOSD) and acute disseminated encephalomyelitis (ADEM) in Japan. Demyelinating lesions of MS are well circumscribed as compared with the lesions of NMO and NMOSD, which reveal variable, irregularly shaped and ill-defined borders that extend longitudinally along vessels, causing destructive changes with poor gliosis. Although the optic nerves and chiasm, spinal cord, cerebral white matter, brainstem, and cerebellum are involved in both MS and NMO/NMOSDs, the formation patterns of demyelinating lesions appear to differ between MS and NMO/NMOSD. NMO/NMOSD preferentially exhibit central lesions of the spinal cord with strongly softening features. Furthermore, the expression of myelin basic protein (MBP) is strongly diminished in the demyelinating lesions of MS, without loss of aquaporin-4 (AQP4) or GFAP expression. However, AQP4 and GFAP expression is decreased in the demyelinating lesions of NMO/NMOSD. Therefore, AQP4 and MBP immunoreactivity may distinguish NMO/NMOSD from MS neuropathologically. Serial sections of the spinal cord demonstrate longitudinally extensive lesions in NMO/NMOSD, although some cases with MS also reveal similar longitudinally extensive lesions of the spinal cord. In ADEM, demyelinating lesions form primarily in small perivenous foci that differ from the lesions of MS and NMO/NMOSD. Therefore, the shape and formation patterns of demyelinating lesions appear to be disease specific, and it might be possible to distinguish among MS, NMO and ADEM; the immunoreactivity patterns of MBP, AQP4, and GFAP may also aid diagnosis.