Introduction: Bilateral anterior capsulotomy (BAC) is an effective surgical procedure for patients with major depression (MD). The anterior limb of the internal capsule (ALIC) carries circuits associated with emotion, and cognition. Here, we analyzed the connectivity of the BAC lesions to identify ‘fingerprints’ associated with clinical outcomes.
Methods: We retrospectively analyzed ten patients following BAC. These patients were divided into good or poor outcome based on the Beck depression inventory (BDI) score at one-year follow-up. These patients were matched with 10 subjects obtained from a neuroimaging sample. The lesions were segmented and transferred to the native space of the matched subjects to generate group-averaged probabilistic ‘fingerprints’ associated with a given outcome. We also generated the major fibers of the ALIC (mesocortical, mesolimbic, and anterior thalamic radiations[ATR]) and analyzed if the lesion overlap with each of these fibers correlated with outcome.
Results: Six patients had good outcome (>50% improvement), four patients had poor outcome (25-50% improvement). The good-outcome map showed significant connections with limbic areas including ventromedial prefrontal, anterior cingulate, lateral orbitofrontal, and medial prefrontal cortex. The poor-outcome map showed significant connections with the same limbic areas and also significant stronger connectivity to associative areas including the dorsolateral prefrontal, ventrolateral prefrontal, and lateral orbitofrontal cortex. Nonparametric tests showed that in the good-outcome group, the involvement of the associative circuit was significantly less than the limbic circuit (p=.002). Conversely, in the poor-outcome group, there was no significant difference between the involvement of these circuits (p=.099). Finally, there was no significant difference in the involvement of the mesocorticolimbic tracts compared to the ATR in the two outcome groups (p=.134, p=.347).
Conclusions: Good outcome following BAC surgery is associated with interruption of key limbic areas and preservation of associative regions. Tractography would be helpful in identifying those fibers within the ALIC that need to be destroyed or preserved.
Patient Care: Improving treatment strategies
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Identify the functional segmentation of the ALIC based on associative and limbic circuits. 2) Describe the major pathways of the ALIC based on the connection with the dopaminergic nuclei or thalamus. 3) Identify key circuits associated with good outcome following BAC surgery for depression