Mapping and Preserving the Visuospatial Network by repetitive nTMS and DTI Tractography in Patients With Right Parietal Lobe Tumors

Giovanni Raffa; Maria Catena Quattropani; Giuseppina Marzano; Antonello Curcio; Vincenzo Rizzo; Gabriella Sebestyén; Viktória Tamás; András Büki; Antonino Germanò

doi:10.3389/fonc.2021.677172

Mapping and Preserving the Visuospatial Network by repetitive nTMS and DTI Tractography in Patients With Right Parietal Lobe Tumors

Front Oncol. 2021 Jun 25:11:677172. doi: 10.3389/fonc.2021.677172. eCollection 2021.

Authors

Giovanni Raffa¹, Maria Catena Quattropani², Giuseppina Marzano², Antonello Curcio¹, Vincenzo Rizzo³, Gabriella Sebestyén⁴, Viktória Tamás⁴, András Büki⁴, Antonino Germanò¹

Affiliations

¹ Division of Neurosurgery, BIOMORF Department, University of Messina, Messina, Italy.
² Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy.
³ Division of Neurology, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy.
⁴ Department of Neurosurgery, Medical School, University of Pécs, Pécs, Hungary.

Abstract

Introduction: The goal of brain tumor surgery is the maximal resection of neoplastic tissue, while preserving the adjacent functional brain tissues. The identification of functional networks involved in complex brain functions, including visuospatial abilities (VSAs), is usually difficult. We report our preliminary experience using a preoperative planning based on the combination of navigated transcranial magnetic stimulation (nTMS) and DTI tractography to provide the preoperative 3D reconstruction of the visuospatial (VS) cortico-subcortical network in patients with right parietal lobe tumors.

Material and methods: Patients affected by right parietal lobe tumors underwent mapping of both hemispheres using an nTMS-implemented version of the Hooper Visual Organization Test (HVOT) to identify cortical areas involved in the VS network. DTI tractography was used to compute the subcortical component of the network, consisting of the three branches of the superior longitudinal fasciculus (SLF). The 3D reconstruction of the VS network was used to plan and guide the safest surgical approach to resect the tumor and avoid damage to the network. We retrospectively analyzed the cortical distribution of nTMS-induced errors, and assessed the impact of the planning on surgery by analyzing the extent of tumor resection (EOR) and the occurrence of postoperative VSAs deficits in comparison with a matched historical control group of patients operated without using the nTMS-based preoperative reconstruction of the VS network.

Results: Twenty patients were enrolled in the study (Group A). The error rate (ER) induced by nTMS was higher in the right vs. the left hemisphere (p=0.02). In the right hemisphere, the ER was higher in the anterior supramarginal gyrus (aSMG) (1.7%), angular gyrus (1.4%) superior parietal lobule (SPL) (1.3%), and dorsal lateral occipital gyrus (dLoG) (1.2%). The reconstruction of the cortico-subcortical VS network was successfully used to plan and guide tumor resection. A gross total resection (GTR) was achieved in 85% of cases. After surgery no new VSAs deficits were observed and a slightly significant improvement of the HVOT score (p=0.02) was documented. The historical control group (Group B) included 20 patients matched for main clinical characteristics with patients in Group A, operated without the support of the nTMS-based planning. A GTR was achieved in 90% of cases, but the postoperative HVOT score resulted to be worsened as compared to the preoperative period (p=0.03). The comparison between groups showed a significantly improved postoperative HVOT score in Group A vs. Group B (p=0.03).

Conclusions: The nTMS-implemented HVOT is a feasible approach to map cortical areas involved in VSAs. It can be combined with DTI tractography, thus providing a reconstruction of the VS network that could guide neurosurgeons to preserve the VS network during tumor resection, thus reducing the occurrence of postoperative VSAs deficits as compared to standard asleep surgery.

Keywords: Hooper visual organization test; brain tumors; diffusion tensor imaging tractography; navigated transcranial magnetic stimulation (nTMS); parietal lobe; superior longitudinal fasciculus (SLF); visuospatial abilities; visuospatial network.