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Objective: Motor evoked potential (MEP) is the minimum potential that can produce motor response. It gives excitability of the motor tracts. In this study, we aimed to determine the relationship between the response of rTMS treatment and motor evoked potential, which is an indicator of cortical excitability.
Methods: rTMS response of 42-depression patients, who were diagnosed in a university hospital according to DSM IV-R, were measured Motor Threshold (MT) of each patient was obtained. M abductor pollicis brevis was used to for site of measurement. The minimal intensity required to elicit an evoked potential of at 50-100 µV with 50% probability in a fully relaxed muscle was the resting motor threshold. MT represents the excitability of the tracts. 50% or more decrease in Hamilton depression scale was accepted as a response to TMS.
Results: Mean MT of the patients was 57.76±13.28%. It was 57.40±4.11% in the control group. The differences were similar (p>0.05). While MT scores were 52.60±10.18% in patients, who gave response to rTMS treatment, it was 59.92±14.20% in patients who did not.
Conclusion: The lower motor excitation threshold would lead to easy neural stimulation. Therefore effectiveness of stimulation increases. Lower thresholds suggest better response to rTMS treatment.