gms | German Medical Science

Objective: Defining margins of cerebral tumours often proves the most challenging part in brain surgery. Achieving an appropriate extent of resection can further determine the therapeutic success. After establishing diagnostic criteria for confocal laser endomicroscopy, we compared instantaneous sections from the Institute of Pathology to the results gathered with the endomicroscope in a blinded trial.

Method: We used the confocal laser endomicroscope (EndoMAG 1, KARL Storz GmbH) to investigate tumour specimens provided during the resection. The tissue samples were examined in their native state, as well as after staining with methylene blue. Simultaneously, instantaneous sections were examined by the Neuropathologist and would later serve as the reference.

Results: We investigated 12 high-grade gliomas, 7 low-grade gliomas, 9 meningeomas, 5 metastasis and 4 schwannomas. Since the images acquired with the confocal laser endomicroscope are not entirely comparable to histology slices, we observed different structural patterns and structures that were previously established. In all cases of high-grade gliomas as well as schwannomas, instantaneous sections as well as endomicroscope findings were identical. Low-grade gliomas were correctly identified in 86%, Meningeomas in 78%. Of the latter, one was diagnosed as high-grade glioma, which ultimately proved to be a recurring meningeoma WHO grade II, and one as low-grade glioma. Metastasis on the other side proved to be more difficult to detect. Only 20% of these were correctly diagnosed, three of them being classified as high-grade gliomas and one as a meningeoma.

Conclusions: We proved that confocal laser endomicroscopy can serve as a complimentary tool to instantaneous sections and that further development of the technology could ultimately be used to screen resection margins in order to determine pathological tissue.