gms | German Medical Science

Objective: Intraoperative (iop) MRI allows an increased rate of complete removal of low grade gliomas (LGG). We examined the iopMRI findings of patients with lobar LGG in order to define if the distribution of the remnants after assumed complete removal follows some specific pattern. The knowledge and experience gained with the technique, though, could still benefit the conventional tumor surgery.

Methods: During a period of 18 months, 28 patients with lobar LGG have been operated in an OR, equipped with 1,5 Tesla MRI (Siemens Espree). The study group includes only those cases in which an unexpected remnant was seen during the intraoperative imaging. The location of the remnants was assessed on the axial, coronal and sagittal T1- and T2- weighted images. A volumetric analysis of their spatial relationship was done using the 3D-reconstruction option of Brain Lab software. The relation of the remnant to the tumor cavity was classified as: 1) subcortical, middle and deep in the vertical plane; and 2) anterior, antero-medial, antero-lateral, medial, postero-medial, posterior, posterolateral, and lateral in the horizontal plane.

Results: 13 patients with an average age of 33,8 years met the inclusion criteria: 6 with astrocytoma, 4 with oligoastrocytoma, and 3 with oligodendroglioma. 2 of the tumor were frontal, 4 were frontal precentral, 1 frontolateral, 2 parietal postcentral, 2 temporolateral and 2 temporomesial. Complete removal was planned and achieved in 7/13, while in the rest either partial or subtotal removal was intended because of tumor involvement of eloquent brain structures. The overall number of unexpected remnants was 19. In all temporomesial tumors, the remnant was posterolateral to the posterior hippocampus. In tumors located close to eloquent structures (n=6), the remnants were found in their vicinity in 73%. In case of frontal or temporolateral tumors, the distribution of remnants was more variable. However, in 34% they were subcortical, beneath the position of the retractor.

Conclusions: The location of tumor remnants after assumed complete removal follows some patterns that depend on the location of the tumor and the spatial relation to eloquent cortical areas and fiber tracts. A more targeted attention to these areas could increase the radicality of surgery, even if intraoperative imaging is not performed.