Role of Cytology in the Intraoperative Diagnosis of Central Demyelinating Disease

OBJECTIVE: To determine the usefulness of cytology in the intraoperative diagnosis of central demyelinating disorders. STUDY DESIGN: Smears of three multiple sclerosis (MS) plaques and two progressive multifocal leukoencephalopathy (PML) lesions prepared intraoperatively were examined and compared. The cytologic features were contrasted with those of infiltrating astrocytomas. RESULTS: The preparations of demyelinating lesions revealed normal or reactive astrocytes and large numbers of foamy macrophages, the key diagnostic finding. The preparations of the lesions of PML contained virally infected oligodendrocytes. The specific cell types were identified easily because cytoplasmic margins could be distinguished. CONCLUSION: Cytologic preparations of lesions of PML and MS permitted rapid identification of the diagnostic features and distinguished them from infiltrating astrocytomas, the most important lesion in the differential diagnosis. The findings demonstrated the utility of cytology in the diagnosis of central demyelinating diseases.