The majority of patiens with Chiari ´s malformation I and partly also type II without myelodysplasia, i.e.without an inborn efect of the hinbrain is significantly influenced by the presence of another spinal patology –syrinx.Syringomyelia devastating the spinal parenchyma dominates the clinical picture, has an adverse impact on the results of surgery and prognosis of the congenital developmental defect. Based on the results of surgical treatment of 40 patients with diagnoses of malformation of the hinbrain (Chiari type)the authors recommend,consistent with the literature,a different approach to and classification of patiens based on the presence of syringomyelia (A/B classification:A:syringomyelia present on MR,B:not present.For the patological development of syrinx an impediment of the natural liquor circulation in the subarachnoid space of the craniocervical transit is responsible (Williams dissociation theory).The authors are convincend that by common (statical)grafic methods (CT,MR)it is not possible to prove the presence nor behaviour of the liquor block and thus it is not possible to select reliably the optimal type of treatment.The method which can be used to assess acurately the presence and behaviour of a blocked liquor circulation and which moreover provides dynamic infor- mation on the block during the daily rhytm in the course of several days are direct measurements (and monitoring)of the of liquor pressure in different compartments of liquor pathways (intracranial/in- traspinal compartment,i.e.before and after the assumed block).The authors prezent the results of a prospective study of measurments in 25 patients with the diagnosis of malformation of the hinbrain. They describe the metod of paralell monitoring of both liquor compartments adjusted according to Williams method and two different types of dissociation tests which can prove the presence of liquor block.The authors also give an account of short-term (3-year)results of surgical treatment of patiens with malformation of the hinbrain where two different therapeutic approaches were indicated based on results of dissociation tests.The authors discuss the advantages and disadvantages of direct measurements and parallel monitoring of liquor pressure as compared with radiological methods and emphasize the essential radicalism when restoring the liquor paths in patients with confirmed liquor block.

        Key words: malformation on hinbrain,liquor pressure,assessment and monitoring