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

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.