RESUMO
Background: Ventriculostomy is a common neuroendoscopic operation but one with disastrous complications in rare cases. Aims: The aim of this study was to perform an intravital analysis of the configuration at the floor of the third ventricle as a possible basis for selection of the ventriculostomy site. Materials and Methods: The study population consisted of 32 patients who underwent ventriculostomy for the treatment of hydrocephalus. Perforation of the floor of the third ventricle was carried out on an individual basis following evaluation of the anatomic situation. Video material and magnetic resonance images (MRI) were analyzed. Results: A classification system including three major groups was developed using the inner distance of the mamillary bodies as the key criterion. It was defined as narrow for values between 0 and 1 mm (observed range: 0-0.5 mm), medium for values between 1.1 and 3.4 mm (range 1.1-3.4 mm) and large for values greater than 3.4 mm (range: 3.8-6.9 mm). Statistical analysis of MR and video measurements revealed a good correlation. The ventriculostomy site was rostral of the mamillary bodies in 23 of the patients (n=27) and sligthly occipital in four. The ventriculostomy site was located more to the left in 22 patients and more to the right in five. Conclusion: As a conclusion the ventriculostomy site has to be chosen in each case following a careful review of all available information. A classification system for the anatomical variations as well as the exact size and site of ventriculostomy should be introduced.