Paramyxovirus-like structures in brains of multiple sclerosis patients.

Twenty-four plaques obtained at autopsy from the brains of six patients with multiple sclerosis were examined under an electron microscope. Specimens for ultrastructural study were processed from the unfixed brain tissues at the time of autopsies. Intranuclear filaments with a diameter of 150 to 260 Angstroms of possibly two different types were seen in the macrophages and in unidentified mononuclear cells that were infiltrating the perivascular regions of four plaque areas from three patients. Intracytoplasmic reticular filaments with a diameter of 100 to 130 A were seen in the astrocytes and in unidentified cell processes in five plaques from three cases. A possible link between these intranuclear filaments and paramyxovirus is suggested.