Objective: Electromagnetic brain stimulation techniques are under investigation for a variety of neuropsychiatric disorders such as depression. Magnetic stimulators work by inducing brief electromagnetic currents in the brain. The magnetic field passes freely through surrounding tissue and an alternating magnetic field induces an electric field that activates both the cortical neurons and their corresponding neural circuits. Limbic circuits involved in depression are activated and “upregulated” by a course of dominant dorsolateral prefrontal cortical stimulation. Overall, rTMS for depression has been found to be a safe and effective procedure, although response rates vary widely from study to study. This study aimed to test modifications to increase effectiveness of the procedure.
Design: Our study varied the stimulus parameters in a systematic fashion if no response was observed to the initial stimulus pattern to see if increased length of stimulation or increased stimulus intensity (Motor Evoked Potential, %MEP) would improve efficacy. 42 subjects with treatment resistant major depression were recruited. Roughly one half received rTMS alone, and one-half received rTMS while on antidepressant augmentation. Patients were referred initially for ECT (Electroconvulsive Therapy) treatments but chose to participate in the rTMS trial first, and would go on to ECT if not responsive to rTMS. No placebo group was used due to ethical concerns about withholding treatment for such severe illness. The sample ranged from 27-94y/o, mean age 60.7, with 47% of over age 60. 67% of the sample was female. Only the elderly response rates will be presented, although no statistical difference in response was observed by age.
Materials and Methods: We utilized the MagStim Super Rapid Rate Unit consisting of a 1x rapid unit, 4 booster modules, 1 PC controller with control software, and a double 70mm coil with air cooling. The unit is capable of frequency responses from 1 to 50 Hz. Treatments were given 3 times per week up to 12 treatments in a series. 30second intertrain intervals were used for safety.
Results: 52% of subjects with rTMS alone showed full or partial improvement as compared to 71% full or partial response rates for subjects receiving rTMS plus medication. No subjects showed significant improvement at the initial treatment parameters of 100%MEP, 20, 5-second trains of stimulation at 10Hz. Response to the lowest, starting level of stimulation often used in previously published studies showed the poorest response. About equal numbers of responders responded to longer trains of stimulation or higher stimulation levels (%MEP). Only minor complaints of discomfort under the coil occurred. No serious adverse events occurred for either group.
Conclusion: This study demonstrates that improved response is possible with modification of the treatment parameters, and especially with medication augmentation during treatment. Theoretically, improvement may also be seen by stimulating the orbitofrontal area which has traditionally been more highly associated with affective lability and affective disturbance.
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