Arachnoid villi in the spinal cord of dasyurid marsupials

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Abstract
During a routine histopathological study of dasyurid marsupials a high incidence of meningo‐encephalo‐myelitis due to Toxoplasma gondii was found. Decalcified blocks of the vertebral columns contained nodules closely related to the nerve roots and projecting into the venous sinuses. At first, these nodules were considered to be granulomata, but further studies revealed a constant relationship to the anterior nerve roots, a frequency of bilateral symmetry and an organoid structure which were more in keeping with a physiological rather than a pathological structure. These structures were morphologically similar to arachnoid villi in the head of dasyurid marsupials and were confined to the lumbo‐sacral cord. It is suggested that they are spinal arachnoid villi and that their varying cellularity results from the associated Toxoplasma infection.