Neuronavigation-guided Repetitive Transcranial Magnetic Stimulation for Aphasia

Summary

This study is designed to test the hypothesis that neuronavigational system-guided transcranial magnetic stimulation has higher accuracy for targeting the intended target as demonstrated by eliciting a greater degree of virtual aphasia in healthy subjects, measured by delay in reaction time to picture naming.

Abstract

Repetitive transcranial magnetic stimulation (rTMS) is widely used for several neurological conditions, as it has gained acknowledgement for its potential therapeutic effects. Brain excitability is non-invasively modulated by rTMS, and rTMS to the language areas has proved its potential effects on treatment of aphasia. In our protocol, we aim to artificially induce virtual aphasia in healthy subjects by inhibiting Brodmann area 44 and 45 using neuronavigational TMS (nTMS), and F3 of the International 10-20 EEG system for conventional TMS (cTMS). To measure the degree of aphasia, changes in reaction time to a picture naming task pre- and post-stimulation are measured and compare the delay in reaction time between nTMS and cTMS. Accuracy of the two TMS stimulation methods is compared by averaging the Talairach coordinates of the target and the actual stimulation. Consistency of stimulation is demonstrated by the error range from the target. The purpose of this study is to demonstrate use of nTMS and to describe the benefits and limitations of the nTMS compared to those of cTMS.

Introduction

Repetitive transcranial magnetic stimulation (rTMS) non-invasively activates neuronal circuits in the central and peripheral nervous systems.¹ rTMS modulates brain excitability² and has potential therapeutic effects in several psychiatric and neurological conditions, such as motor weakness, aphasia, neglect, and pain.³ The target sites for rTMS other than the motor cortex are conventionally identified using the International 10-20 EEG system or by measuring distances from certain external landmarks.

However, inter-individual differences in size, anatomy, and morphology of the brain cortex are not taken into ....

Protocol

Ethics statement: This study was approved by the institutional review board of a blinded hospital.

1. Preparing Materials (Table 1)

1. Use TMS equipment with maximum output of 3.0 Tesla and a power supply of 200-240 Vac 50/60 Hz 5A at a pulse width of 350 µsec.
2. Acquire resting motor threshold (RMT) in each subject by electromyography (EMG) to determine the motor evoked potential (MEP) using the TMS system and the active electrode (see step 3.1 for details). Set the RMT as individual intensity for the actual TMS study protocol (Figure 1).
   Note: The neuronavigational system includes a computer s....

Results

Kim et al. demonstrated a more superior effect of TMS with neuronavigational system guidance compared to the non-navigated conventional method by less dispersion of stimulus and more focal stimulation to the right M1 area,⁸ as shown in Figure 9. Further evidence to support incorporating the neuronavigational system with TMS is demonstrated by a randomized crossover experiment to induce virtual aphasia in healthy subjects by targeting Brodmann area 44 a.......

Discussion

TMS is widely used both in clinical practice and basic research.¹⁰ Valuable therapeutic effects are offered by the physiologic influence of rTMS, including an inhibitory neuromodulatory effect on cortical excitability with low frequency rTMS for treatment of aphasia.¹¹ Transient disruption of neural processing or virtual lesioning induced by rTMS can change behavioral performance.¹² However, the desired effect of rTMS may be diluted or even not occur with the coil misplaced on the target........

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Medtronic MagPro X100	MagVenture	9016E0711
MCF-B65 Butterfly coil	MagVenture	9016E042
Brainsight TMS Navigation	Rogue Research	KITBSF1003