Stereotactic Brain Biopsy in Eloquent Areas Assisted by Navigated Transcranial Magnetic Stimulation: a Technical Case Report

Abstract

BACKGROUND AND IMPORTANCE Stereotactic brain biopsy (SB) is an important part of the neurosurgical armamentarium, with the possibility of achieving histopathological diagnosis in otherwise inaccessible lesions of the brain. Nevertheless, the procedure is not without the risk of morbidity, which is especially true for lesions in eloquent parts of the brain, where even a minor adverse event can result in significant deficits. Navigated transcranial magnetic stimulation (nTMS) is widely used to chart lesions in eloquent areas, successfully guiding maximal safe resection, while its potential role in aiding with the planning of a stereotactic biopsy is so far unexplored. CLINICAL PRESENTATION Magnetic resonance imaging of a 67-yr-old woman presenting with dysphasia revealed a noncontrast enhancing left-sided lesion in the frontal and parietal pars opercularis. Due to the location of the lesion, nTMS was used to chart both primary motor and language cortex, utilizing this information to plan a safe SB trajectory and sampling area according to the initial work-up recommendations from the multidisciplinary neuro-oncology board. The SB was uneventful, with histology revealing a ganglioglioma, WHO I. The patient was discharged the following day, having declined to proceed with tumor resection (awake surgery) due to the non-negligible risk of morbidity. Upon 1- and 3-mo follow-up, she showed no signs of any procedure-related deficits. CONCLUSION nTMS can be implemented to aid with the planning of a stereotactic biopsy procedure in eloquent areas of the brain, and should be considered part of the neurosurgical armamentarium.

Computed tomography-guided navigated transcranial magnetic stimulation for preoperative brain motor mapping in brain lesion resection: A case report

“…Intraoperative cortical stimulation mapping is the gold standard method, but nTMS has a very good correlation of motor points and can be performed before surgery, allowing presurgical planning. [2,12,20] nTMS has been shown to locate motor positive points within 2-4 mm of that of direct cortical stimulation (DCS) and also has been shown to have higher accuracy than noninvasive methods, for example, functional MRI and magnetoencephalography. [2,12,20] We registered MEPs using single-pulse TMS and used as a positive white marker any site that elicited a MEP amplitude higher than 50 microvolts.…”

“…[2,12,20] nTMS has been shown to locate motor positive points within 2-4 mm of that of direct cortical stimulation (DCS) and also has been shown to have higher accuracy than noninvasive methods, for example, functional MRI and magnetoencephalography. [2,12,20] We registered MEPs using single-pulse TMS and used as a positive white marker any site that elicited a MEP amplitude higher than 50 microvolts. After CT brain surface reconstruction, good presurgical planning image was achieved [Figure 1b and c].…”

Mapping of Motor Function with Neuronavigated Transcranial Magnetic Stimulation: A Review on Clinical Application in Brain Tumors and Methods for Ensuring Feasible Accuracy

“…Furthermore, integrating nTMS motor mapping in clinical workflows has provided initial evidence for the usefulness of the method for planning of a stereotactic tumor biopsy, performing endoscopic cystoventriculostomy, or facilitating a transparietal approach to the trigone of the lateral ventricle in patients with brain neoplasms [ 88 , 89 , 90 ]. In a special environment such as the intensive care unit with critically ill patients, an approach for safe and reliable use of nTMS motor mapping has been described recently, yet preliminarily in patients suffering from other diseases than brain tumors (e.g., central cord syndrome after trauma, ischemic or hemorrhagic stroke) [ 91 ].…”