P273 Effect of repetitive transcranial magnetic stimulation on the structural connectome in patients with major depression

Abstract

Introduction Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex (DLPFC) is an FDA-approved treatment for depression. Increasing evidence indicates that depression is accompanied by altered structural connectivity in the white matter. Objective We assess the impact of rTMS treatment for depression on the structural brain connectome. Patients and methods The IRB of Weill Cornell Medical College approved this study. 25 currently treatment-resistant depressed patients (age 21–68) participated in the study. Patients received 10-Hz rTMS over the left DLPFC 5 days/week for 5 weeks. Treatment response was assessed using the 24-item Hamilton Rating Scale for Depression (HAMD-24) at baseline and after the course of TMS. MRIs were acquired within 7 days prior to starting rTMS and within 3 days after the end of treatment. Diffusion tensor images were acquired using a single-shot spin echo imaging sequence. Nodes of the structural brain network were defined as the 96 anatomical brain areas in the Harvard-Oxford atlas. Whole brain deterministic streamline generation was performed using the Euler delta crossings tracking algorithm. A weighted connectivity matrix was generated based on the number of streamlines traversing between pairwise cortical regions. Graph theory metrics were calculated to assess network integration (characteristic path length), distribution (network density), segregation (clustering coefficient, modularity), and nodal influence (nodal degree, betweenness centrality). Results Relative to baseline, no change was observed post rTMS in the global network metrics of density, characteristic path length, and modularity. No group difference was observed between treatment responders and nonresponders on these global network metrics. Fig. 1 shows the distribution of nodes with properties that correlate (p Conclusion A collection of nodes in the frontal pole, frontal medial cortex, subcallosal cingulate, and lateral occipital cortex (LOC) have baseline nodal degree, centrality, and clustering coefficient that are correlated with baseline HAMD-24. The post treatment change in centrality in the LOC and precuneus is correlated with change in HAMD-24, suggesting rTMS selectively modulates the white matter connectivity underlying key areas in the default mode network. Download : Download high-res image (888KB) Download : Download full-size image