[Diagnosis of brain gliomas in stereotactic biopsy assisted by optical neuro-navigation system]

Recently, stereotactic procedures of brain tumours have been enriched by an optical neuronavigation system, enabling us to assess the tumour location and size by means of three-dimensional magnetic resonance imaging (MRI). The aim of the study was to check which areas of brain gliomas would be most useful in neuropathological diagnosis of the material taken during stereotactic biopsy. We also analysed whether the MRI processed in the computerised neuronavigation system would be reliable in determination of a safety margin of glioma resection.

Material from the stereotactic biopsy has been examined neuropathologically by means of the Stealth Station navigation system. Tissue specimens were taken from the centre of neoplasm, its intermediate area, edge of the tumour and the nearest vicinity of neoplasm. 2-3 specimens in each area of the tumour were taken. The material was fixed in buffered formalin and embedded in paraffin and then stained with hematoxylin and immunostained for GFAP, cytokeratin and vimentin.

Astrocytomas II were diagnosed in 17 cases, including fibrillary astrocytoma in 13 cases and gemistocytic astrocytoma in 2 cases. In other cases protoplasmatic astrocytomas were suspected. In 6 cases anaplastic astrocytoma and in 16 cases glioblastoma multiforme were diagnosed. In 3 cases the degree of malignancy was not possible to be defined. In 2 cases the neoplasm was not found. "Sensitivity" of the method was 91.1% and its "specificity" was 82.2%. The best results were achieved analysing the material from the intermediate area of neoplasm. There was the lowest number of "false negative" diagnostic results in this area. A few positive results were found in the central area and a high number of results (almost 50%) could be defined as "negative", assuming the specimens with no neoplastic cells. In more than 40% of biopsies from the edge of the tumour, neoplasm was not found, while in more than 20% of biopsies from the nearest vicinity of the tumour, neoplastic cells were present.

Intermediate zone of brain gliomas located between its central parts and the tumour edge appears to be the most appropriate neoplastic area for diagnostic stereotactic biopsy assisted by the optical neuronavigation system. Because of infiltrative character of brain gliomas as well as their real dislocation during surgical procedure compared to the position based on the earlier neuroimaging, the territories considered in the optical neuronavigation system as the vicinity or neoplastic edge, run a risk of neuropathological misdiagnosis in this biopsy.