Surgical treatment of brainstem tumours with special emphasis on the operative approach through the fourth ventricle floor.

Over the last 25 years there have been reports from the widely recognised neurosurgical centres on the positive clinical results of partial and even complete removal of brainstem tumours. They confirmed relatively high incidence of benign tumours like low-grade gliomas and haemangioblastomas in this region. Based on imaging studies (MRI) and surgical experiences, brainstem tumours can be divided into focal and diffuse. Focal lesions are amenable to surgery; particularly, those with a prominent exophytic portion. Open surgery remains controversial in pure intrinsic brainstem tumours as the surgical approach itself may lead to serious postoperative complications. Different approaches (including the most frequent one--through the fourth ventricle floor) are used depending on the tumour location. As minimal invasiveness is mandatory during transtegmental route safe approach zones within the rhomboid fossa were defined morphologically and morphometrically--suprafacial and infrafacial (i.e., situated above and below facial colliculus, respectively). Application of the proposed minimal invasive surgical approach through the fourth ventricle floor should reduce postoperative morbidity and mortality in patients with tumours in pons and upper medulla oblongata treated surgically.