An Anatomical Method Using External Markers for the use of repetitive magnetic stimulation (rTMS)

FACUNDO MANES; JEREMY BOCKHOLT; JAMES BAILEY; ROBINSON ROBINSON

Los Ángeles

Encuentro; 10th Annual Meeting of the American Neuropsychiatric Association; 1999

American Neuropsychiatric Association

Background: Left dorsolateral prefrontal cortex (area 46) stimulation with rTMS can potentially treat depression. Studies are warranted that use MRI-guided anatomical localization of stimulation site to control for differences in brain morphology and skull size. Methods: A swim cap was placed on the patient's head by using reference points. Vitamin E capsules were glued to the cap at the F3 point in relation to International 10-20 System (point A) and at the point of maximum stimulation of the right abductor pollicis brevis muscle (point B). The subjects then had structural 3D MRI scans. On the basis of the 3D reconstruction, we identified area 46 in Talairach coordinates and calculated the "skull area 46" point and its distance from points A and B. Results: We have identified the skull area 46 point and its distance from points A and B in 9 subjects. Intrarater and interrater reliability for identifying the two measured distances to area 46 was high (intraclass correlations 0.95 and 0.99, respectively). The average distance to the skull area 46 from point A was 14.3 mm posterior and 5.1 mm above; the average distance from point B was 5.2 cm anterior. Conclusions: This method offers an objective means of identifying a specific cortical site for rTMS stimulation. It is hoped that site-specific stimulation will lead to more consistent therapeutic response.