Date of Award

2009

Embargo Period

8-1-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

College of Graduate Studies

First Advisor

Gail W. Stuart

Second Advisor

Jan Grossman

Third Advisor

John Welton

Fourth Advisor

Mark S. George

Abstract

Clinicians are using transcranial magnetic stimulation (TMS) as a noninvasive tool to treat depression; however, standards for determining the motor threshold (MT), which often determines the final location of the TMS coil and the intensity of simulation for the depression treatment, are not clear. This study compared the observation of movement (OM) method and electromyography (EMG) method of determining motor threshold in a group of experienced TMS administrators and nurses with no previous MT knowledge. We hypothesized that between methods and groups the MT estimates would vary by ≤ 5% of stimulator output and the ideal motor scalp location between methods would vary by ≤ 1 cm. TMS administrators determined the MT twice with each MT method on one subject in a randomly assigned order. The subject and administrators were blind to TMS machine output. After determining the ideal motor scalp location, each TMS administrator then used the 5 cm rule to locate the optimal prefrontal treatment site. The scalp position over the anatomical hand knob and the EEG F3 position were located for comparison. There was no significant difference in the motor threshold estimates between the OM and EMG MT methods (t(14)=0.659, p=0.521). The mean EMG and OM MT estimates were (61.8% (sd=7.25) and 63.1% (sd=9.05). There was no effect for the interaction between estimation method and experience level (F(1,13)=0.036, p=0.851) on MT estimates. The mean distance between the MT sites and the hand knob was 21.25 (sd=8.98), while the mean distance between the treatment sites and F3 was 36.16 (sd=12.15). The wide range of MT estimates and motor scalp locations reveals several problems with the MT procedure for the OM and EMG methods. The standard EMG or OM methods along with the 5 cm rule may position the coil posterior and medial to the intended treatment location. This study shows that nurses with minimal MT training can determine the MT and localize the treatment site as effectively as experienced TMS operators. Information obtained from this study can be used to establish MT protocols and to institute training programs that test each participant's ability to master the TMS procedure.

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All rights reserved. Copyright is held by the author.

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