Recommendations for Cerebrospinal Fluid Cytology. A Review Article

Abstract

The description of cytological findings in cerebrospinal fluid (CSF) is very inconsistent in the literature since no generally recognized uniform classification of these findings has been proposed to date. The need for developing such a classification system becomes quite obvious against the background of renaissance CSF cytology is currently experiencing in our country. A precondition sine qua non for developing a uniform classification system is its general applicability and recognition as well as a capacity to establish, using precisely formulated conclusions, the aetiological diagnosis, something quite impossible with today's terminology. Our draft classification is that used by a team of physicians working previously in the CSF Laboratory of the Department of Neurology of Charles University School of Medicine I in Prague. The classification employed there is based on monitoring pathology in the cytological picture both according to the presence of the prevailing cellular population in CSF and to the presence of activation in elements of lymphocyte and monocyte lines. We were able to combine both criteria into a single viable system expressing the current status of cellular response in CSF. The presence of a pathological cytological finding provides the basis for defining individual cytological CSF syndromes closely related to the etiological diagnosis of the patient, which in the great majority of cases make it possible to formulate the diagnostic conclusion. The classification employed allows to establish the diagnosis in diseases manifesting themselves by at least a mild alteration of the cytological picture. In general, it is useful for classifying inflammatory, neoplastic diseases, inter-meningeal haemorrhage and morphological manifestations of CNS tissue destruction. A distinct advantage is the plausible classification of cytological findings in oligo-cellular CSF specimens which to date has been difficult to make due to the low numbers of cellular elements detected in samples. In cytological examination of CSF, the parameters evaluated include, in addition to the number of elements, qualitative representation of individual cellular lines. (1-Monografie). When evaluating the monocyte-macrophage system and/or the reticuloendothelial system, attention is focused on the proportions of activated monocytes and, particularly, on the presence of macrophages showing a specific substrate of phagocytosis. It is according to this substrate that macrophages are further divided into erythron-phages, sidero-phages, lipo-phages, lympho-phages, leuko-phages or myco-phages, etc. To visualize a substrate, it is often necessary to use additional staining e.g., staining by Oil Red for lipids, Berlin Blue for iron, etc. If inter-meningeal haemorrhage is suspected, monitoring of the phagocytosis of red blood cells and haematogenic pigments allows us to determine the approximate age and course of the bleeding. Monitoring of lipo-phagocytosis visualizing the scavenging response on CNS parenchymal damage also has a number of potential applications. As the number of CSF examinations increases, proportionately increasing numbers of cells are being detected. This is true especially of diseases involving the presence of primary or secondary neoplastic processes right in the CNS or in the vicinity of CSF pathways. The currently employed cytological methods of CSF examination, whenever malignant elements were detected, have made it possible to establish the presence of a tumor disease in general only. For instance, monitoring of the functional status of nucleoli, PAS positivity, or the presence of adipose droplets in the cytoplasm suggest only indirectly an increased metabolic activity of the cells monitored. Other morphological markers of atypical cells (polymorphism of cells, nuclei, polynuclear elements, cytoplasm basophilia, atypical mitoses, etc.,) may only raise suspicion of the presence of a tumorous process, but not identify the cellular system the belong to. Another problem which by no means is negligible is the low number of cells detected. As a result, we started to study the mode of reaction of atypical elements with certain monoclonal antibody binding to individual antigens, tumor markers specific for the respective cellular populations. Moreover, the method can be used to determine the degree of their maturity, presence of individual receptors, state of activation in the course of their cellular cycle.