Current status and potential application of navigated transcranial magnetic stimulation in neurosurgery: a literature review

Abstract

Transcranial magnetic stimulation (TMS) is a noninvasive neurophysiologic technique that can stimulate the human brain. Positioning of the coil was often performed based merely on external landmarks on the head, meaning that the anatomical target in the cortex remains inaccurate. Navigated transcranial magnetic stimulation (nTMS) combines a frameless stereotactic navigational system and TMS coil and can provide a highly accurate delivery of TMS pulses with the guidance of imaging. Therefore, many novel utilities for TMS could be explored due to the ability of precise localization. Many studies have been published, which indicate nTMS enables presurgical functional mapping. This review aimed to provide a comprehensive literature review on nTMS, especially the principles and clinical applications of nTMS. All articles in PubMed with keywords of "motor mapping," "presurgical mapping," "navigated transcranial magnetic stimulation," and "language mapping" published from 2000 to 2018 were included in the study. Frequently cited publications before 2000 were also included. The most valuable published original and review articles related to our objective were selected. Motor mapping of nTMS is validated to be a trustful tool to recognize functional areas belonging to both normal and lesioned primary motor cortex. It can offer reliable mapping of speech and motor regions at cortex prior to operation and has comparable accuracy as direct electrical cortical stimulation. nTMS is a powerful tool for mapping of motor and linguistic function prior to operation, has high application value in neurosurgery and the treatment of neurological and psychiatric diseases, and has gained increasing acceptance in neurosurgical centers across the world.

Keywords: Motor mapping; Neurosurgery; Speech mapping; Transcranial magnetic stimulation.

Fig. 1

The procedure of nTMS motor mapping and image of nTMS-based DTI tracts. (A) Upload T1-weighted image. (B) Overlay of the 3D head model derived from MRI imaging and the actual patient head by means of surface registration to enable real-time neuronavigation. (C) Motor mapping stimulation. (D) Mark the nTMS positive spots on the cortex. (E) Left, nTMS-based DTI tracts: cortical nTMS positive spots (yellow) and nTMS-based DTI tracts (blue); Right, image fused with MRI: tumor (red), cortical nTMS positive spots (yellow), and nTMS-based DTI tracts (blue). DTI diffusion tensor imaging, MR magnetic resonance, nTMS navigated transcranial magnetic stimulation