Introduction: Although recent studies have demonstrated the efficacy of deep brain stimulation (DBS) for the treatment of debilitating and treatment refractory obsessive-compulsive disorder (OCD), no standardized stimulation target exists for this disorder. We have performed meticulous micro-anatomical post-mortem brain dissections to clarify the three-dimensional neuroanatomy and important fiber pathways that are potentially important in OCD DBS.
Methods: Ten hemispheres from adult formalin-fixed cadaver brain specimens were dissected using meticulous microneurosurgical technique and recorded in numerous photographs. We carefully investigated the anatomy of various targets for OCD DBS including nucleus accumbens (NAcc), anterior limb of internal capsule (ALIC), subthalamic nucleus (STN), inferior thalamic peduncle (ITP), and adjacent structures and fiber pathways.
Results: ALIC and NAcc are the most common targets for OCD DBS. ALIC is comprised of the anterior thalamic peduncle and frontopontine fibers. The anterior thalamic peduncle, which conveys fibers connecting the prefrontal and orbitofrontal cortices to the mediodorsal thalamic nucleus, was identified medial to the frontopontine fibers. Based on anatomical relationships, stimulation in the region of the NAcc may impact adjacent structures including: nucleus basalis of Meynert (posterior to NAcc), septal nucleus (posterior, medial, superior), bed nucleus of stria terminalis (posterior, superior), diagonal band of Broca (posterior, medial) and the olfactory stria (inferior). The medial forebrain bundle and the lateral hypothalamic nucleus were identified medial to the anterior aspect of the STN. The ITP, carrying primarily amygdalo-fugal fibers, was identified posterolateral to the column of the fornix. The anterior commissure serves as a useful landmark to localize these structures.
Conclusions: DBS is a promising therapy for severe, treatment refractory OCD, however, the optimal target for stimulation and the mechanism of effect of this therapy remain unclear. An improved understanding of the three-dimensional neuroanatomy involved is a critical first step toward developing a standardized neurosurgical procedure with consistently good outcomes.
Patient Care: DBS is a promising therapy for patients with severe, treatment refractory OCD, however, neither the optimal target for stimulation nor the mechanism of action of this treatment is well delineated. A necessary first step in the development of a better understanding of OCD DBS is a solid characterization of the three-dimensional neuroanatomy in the region of stimulation. This will enable precise anatomic DBS lead localization relative to the potentially important neuroanatomical structures, which will in turn allow a more meaningful analysis of their potential mechanistic importance in OCD DBS.
Learning Objectives: The participants should be able to 1) Describe the neuroanatomical relationships of structures that are potentially relevant to OCD DBS, and 2) Understand the current neurosurgical approaches to OCD.