gms | German Medical Science

Objective: 5-ALA fluorescence-guided resection has been proven to increase the rate of complete resection of malignant gliomas. Since the visualisation of 5-ALA induced fluorescence is dependent on a sufficient exposure to fluorescent light, residual tumor tissue in deep-seated resection cavities might not be detected. In addition, subcortical parts of a large spherical tumor might not be visualized, due to a tangential position at the periphery of the microscopic field. With the availability of a specially designed endoscope, capable to induce and visualize 5-ALA fluorescence, we were interested in the impact of this new technique on the visualisation of residual glioma tissue in deep-seated and spherically configurated resection cavities.

Methods: 9 patients with deep-seated brain tumors received a standard dose of 5-ALA 20 mg/kg 3 h prior to surgery. A standard surgical exposure was performed using a Zeiss neurosurgical microscope (OPMI Pentero, Zeiss, Oberkochen, Germany). Surgery was supplemented by the use of a specially designed endoscope (Karl Storz Hopkins II telescope with 4 mm diameter, viewing angle 0° and 45°, respectively) with an option of 5-ALA fluorescence guidance (KARL STORZ, Tuttlingen, Germany). After microscopic visualisation of the surgical cavity with both white light and blue light (wavelength: 400 nm), endoscopic visualisation was employed. If additional fluorescence tissue was detected, microscopic visualisation was performed and detected remnants of the tumor removed.

Results: In all cases, Fluorescence guided endoscopic surgery identified residual ALA positive tumor tissue not sufficiently exposed by conventional microscopic visualisation.

Conclusions: As additional instrument fluorescence guided endoscopic surgery might help to overcome technical limitations of the conventional microscopic exposure of 5-ALA positive glioma tissue.