The pathology of the spinal cord in progressive supranuclear palsy

We describe the results of a study of the spinal cord of 5 patients with progressive supranuclear palsy (PSP). Examination of the 6^th cervical, 7^th thoracic, and 5^th lumbar segments revealed variable degree of gliosis and density of neuropil threads (NTs), nerve cell loss, and tau-positive cytoplasmic staining of neurons, some of which was reminiscent of neurofibrillary tangles (NFT). Tau-positive neurons were seen at each spinal level and in the 3 zones in which each level was subdivided. Cells with the appearance of NFT predominated in the intermediate zone. Morphometric study revealed 47%, 52%, and 32% decrease in cell numbers in the motor area (lamina IX) at the 3 spinal levels, respectively, and 39% in the intermedio-lateral column. This is the first report describing severe neuronal loss throughout the whole spinal cord in patients with PSP and its results are in keeping with a previous study of the nucleus of Onufrowicz. The reasons why cell loss fails to produce clinical symptoms are analyzed and the clinico-pathological correlations between anatomical changes and dystonia are considered. On the basis of existing data, we conclude that previous suggestions implicating spinal interneurons in the pathogenesis of neck dystonia should not be supported.