Post-polio syndrome spinal cord pathology. Case report with immunopathology

Post-polio syndrome (PPS) describes the clinical onset of progressive muscular weakness many years after survival of acute paralytic poliomyelitis, often in muscle groups clinically unaffected by the original disease process. Prior pathologic descriptions of this often disabling, but not usually fatal, syndrome have been scanty. These have emphasized the presence of persistent or new inflammation in the meninges, spinal cord, and muscles of affected patients. The inflammation suggests several pathogenetic hypotheses, including persistent active poliovirus infection, autoimmune attack on central and peripheral nervous system elements, or increased vulnerability of poliovirus-damaged tissue to new infections. We have recently examined the central nervous system from a PPS patient. The cord showed focal perivascular intraparenchymal chronic inflammatory infiltrates. Immunoperoxidase staining demonstrated that the infiltrates were virtually pure populations of B lymphocytes (immunopositive with antibody L26, and immunonegative with the T cell marker UCHL1 as well as the macrophage marker HAM56). There were rare macrophages (HAM56 immunopositive) and no T cells. The character of the infiltrates suggests that PPS could be an autoimmune disorder mediated by antibodies produced in situ, and not by a cell-mediated process. Additional important pathological features were the presence in the anterior horns of axonal spheroids and of moderate Wallerian degeneration in the lateral columns. The brain was entirely unremarkable, with no detectable cell loss of gliosis in the internal capsules or precentral gyri.