Introduction:
Stereotactic biopsy is a relatively commonly used tool for brain tumour diagnostics. A frame-based stereotactic biopsy is the standard, but the so-called 'frameless' biopsy, which is done by using a special neuronavigation system, seems to be a safe and convenient alternative. The authors have assessed the safety and effectiveness of an MRI based 'frameless' stereotactic biopsy of brain tumours.

Material and methods:
42 cases of patients, who underwent 'frameless' brain tumour biopsies in 2011–2013, were been retrospectively analysed. The biopsies were done by using BrainLab™ neuronavigation with VarioGuide and biopsy side-cut needles. The operation plan was based on a preoperative MRI head. In every case, at least 3 specimens various trajectories were taken. Pathological analysis was performed in the same place in every case.

Results:
There were 85.7% cases with an exact histopathological result. 14.3% cases obtained a pathological result, but without exact diagnosis. One patient (2.4%) with astrocytoma WHO III died as a result of a perioperative intra-ventricular hemorrhage. Other clinically significant perioperative complications occurred in 2 cases (4.8%). The histopathological diagnostics revealed: 12 cases of GBM (28.6%), 8 cases of astrocytoma WHO III (19%), 10 cases of astrocytoma WHO II (23.8%), 1 case of metastasis (2.4%), 1 case of lymphoma (2.4%) as well as 2 other lesions (4.8%). Statistical analysis revealed no significant differences in the patients’ pre- and postoperative state.

Conclusions:
The 'frameless' biopsy is an effective and relatively safe way of diagnosing brain tumours. This type of biopsy takes less time to perform. It seems that it can be recommended as a convenient alternative to frame-based biopsy.