In vitro NMR micro imaging of the spinal cord of chronic relapsing EAE rats.

Chronic relapsing experimental allergic encephalomyelitis (Cr-EAE) was induced in Lewis rats with an emulsion of guinea pig spinal cord tissue in complete Freund's adjuvant enriched with Mycobacterium tuberculosis H37 RA. The sensitized rats developed Cr-EAE showing two to three relapses during the first 40 days. In vitro transverse T2-weighted spin echo images of the spinal cord of Cr-EAE rats, sacrificed at the clinical height (hind leg paralysis and urinary incontinence) of the third bout and their controls, were compared with the corresponding histopathology. Lesions extended over the entire spinal cord, however, the larger lesions were predominantly present in the cervical and upper thoracic regions. In the white matter only areas of demyelination and large perivascular demyelination were discernable on the MR images. Size and shape of these lesions correlated well with the morphological characteristics revealed by histopathology. Plaques in the ventrolateral funiculus were generally located peripherally, while plaques in the dorsal funiculus were mainly present in the medial part. The NMR images, however, could not distinguish between demyelination, remyelination, inflammation, and oedema. Also lesions in the gray matter could not be distinguished with MR imaging techniques. However, if lesions were localized at the interface of the gray and white matter the boundary between the gray and white matter was less well defined.