Cerebrospinal fluid findings in multiple sclerosis – especially biochemical findings – are quite well known. CSF cytology in multiple sclerosis was the subject of our investigation published recently in this journal. In this article we would like to show changes in cerebrospinal fluid cytology after intrathecal administration of corticoids and cytostatics, which is the method of treatment successfully used in our department. Although most samples from multiple sclerosis patients have lymphocytic cerebrospinal fluid cell reaction with activation in the lymphocyte series and frequently the presence of plasmocytic forms, after intrathecal drug administration the cerebrospinal fluid cell reaction is almost invariably monocytic, sometimes accompanied by rare neutrophils. These changes probably reflect a non-specific cellular reaction to the administration of foreign material into cerebrospinal fluid pathways. More rarely, discrete cytological signs of bleeding into the cerebrospinal fluid space can be observed. The frequent occurrence of markedly increased lipophagocytosing activity of macrophages remains a phenome- non of unexplained origin. Another phenomenon after intrathecal administration of corticosteroids and cyto- statics is the reduction of plasmocyte numbers, frequently even their complete disappearance. Aside from cytological changes, some biochemical changes are frequently observed after intrathecal drug administration. Total protein, as well as the albumin quotient, increase in some cases and decrease in others. Almost invariably, an increase in cerebrospinal fluid lactate and frequently also lactate dehydrogenase concen- trations can be seen, sometimes accompanied by a relative decrease of glucose. These changes remain unex- plained. It is necessary to know about the above mentioned changes, since they could be misinterpreted as signs of new tissue lesion, CNS hypoxia or even subarachnoid haemorrhage. However, what may seem a deterioration of the CSF finding does not correspond with clinical parameters – on the contrary, marked improvement in the patient’s clinical status is often seen after intrathecal administration of corticosteroids and cytostatics.

        Key words: multiple sclerosis, cerebrospinal fluid, CSF cytology, intrathecal administration of drugs.