Ultrastructural microscopy of different types of nuclear and cytoplasmic inclusions in subacute sclerosing leucoencephalitis

Enzyme histochemical as well as electron microscopic studies were made in a typical case of SSLE. From the enzyme histochemical point of view the lesions were not specific, and the observed increase of oxydative enzymes is identical with that found in every reactive macro- and microgliosis. No intranuclear inclusions of microtubuli with a diameter of 170–230 A resembling certain mixoviruses could be demonstrated by electron microscopy. By light microscopy, nuclear inclusions of the Cowdry type could not be demonstrated neither; however, they are not always found in SSLE. The microtubuli inclusions, observed for the first time by one of us, seem to be the most specific element in SSLE. On the other hand, the intracytoplasmatical particles with a virus-like aspect which have been described byGonatas in SSLE and by ourselves in periaxial diffuse encephalitis of the Schilder type were also found in the present case. Our impression is that these particles are nonspecific and great caution has to take place in classifying them as viral elements. They might be secretory granules arising in the glia in certain pathological conditions, or perhaps phagocyted particles, possibly stemming from myelin.