# Impact of Titanium Skull Plate on Transcranial Magnetic Stimulation: Analysis of Induced Electric Fields

## TL;DR

This study shows that titanium skull plates can significantly alter the electric fields during TMS, potentially affecting brain stimulation patterns.

## Contribution

The study reveals how titanium skull plates change the distribution of TMS-induced electric fields, suggesting implications for treatment adjustments.

## Key findings

- The presence of a titanium skull plate changes the distribution of the induced electric field during TMS.
- The maximum electric field occurs under one coil wing instead of the coil junction when a TSP is present.
- Deep brain regions show increased electric fields, which could lead to unintended deep brain stimulation.

## Abstract

Background: Implanted titanium skull plates (TSPs) in cranioplasty are used to replace or reconstruct areas of the skull that have been damaged or removed due to trauma, surgery, or other medical conditions. However, the presence of a TSP in the head may influence the distribution of the electric field induced during transcranial magnetic stimulation (TMS) procedures. The purpose of this study was to determine how the presence of TSP would interfere with TMS-induced cortical electric fields. Methods: The TMS with a figure-of-eight coil was applied to a realistic head model with TSPs. The distribution of the induced electric field in head tissues was calculated by employing the impedance method, and the results were compared with that of a normal head without TSP. Results: Simulation results show that the distribution of the induced electric field has changed greatly for the head model with TSP. The maximum value of the induced electric field in head tissues was present under one of the circular coil wings rather than in the tissues beneath the junction of the two wings of the Fo8 coil. Conclusions: The induced electric field in deep brain regions was increased for the head model with TSP, which could potentially lead to deep brain stimulation. Since the presence of metallic TSP can greatly influence the distribution of the induced electric field in TMS applications, it is important to adjust the treatment scheme when considering TMS for individuals with cranial titanium plates.