Neurosurgery for Intractable OCD 

April 18, 2022


Obsessive-convulsive disorder (OCD) is a common mental disorder, with a 1-year prevalence rate of 2.1-3% [1-3]. Hallmarks of OCD include intrusive and distressing thoughts (obsessions) and repetitive and ritualistic behaviors (compulsions) [3]. Over 90% of people with OCD meet criteria for other psychological disorders, such as depression, anxiety, mood disorders, personality disorders, and schizophrenia [4]. The DSM-5, the official manual for psychiatric illness, no longer classifies OCD as an anxiety disorder, but rather as a category all on its own, further emphasizing the complexity of this disease’s progression and treatment. Pharmacological treatment for OCD mainly consists of selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, sertraline, fluvoxamine, paroxetine, and citalopram [4]. While effective in the short-term, people taking these medications experience a relapse rate from 24 to 89%. Thus, behavioral therapy, namely exposure and response prevention (ERP) therapy, is central to an effective treatment regimen. ERP is effective in 70-80% of cases; however, the remaining ~10% of patients suffer from intractable OCD, which requires neurosurgery [2].  



Sub-caudate tractotomy (SCT) targets white matter tracts ventral to the head of the caudate nucleus, an anatomical region critical not only in planning movement but also in learning, memory, reward, and social interaction [4-6]. In particular, white matter tracts connecting the medial, central and lateral orbitofrontal cortex (OFC) to the thalamus are most affected by SCT [7]. Studies have implicated aberrant OFC activation in OCD; additionally, whereas stimulation of lateral OFC led to a reduced OCD-like phenotype, OFC-ventromedial striatum activation aggravated OCD symptomology [8-10]. Taken together, these studies suggest SCT directed at posteroventral parts of the OFC would be most effective in alleviating clinical OCD symptoms [8]. Several clinical studies reported a 50% efficacy rate (little to no postoperative symptomology) in OCD patients after SCT [11, 12]. Published in 1994, the latest comprehensive review of SCT included over 1300 cases and concluded SCT allowed 40-60% of patients to lead normal lives after neurosurgery. The authors suggested a sudden onset, a good family history, and a prior response to electroconvulsive therapy to be predictors of positive response to the procedure [2, 13]. 



The most widely recognized and practiced procedure in the United States for intractable OCD is anterior capsulotomy (AC), which targets fibers of the internal capsule, a white matter structure connecting the frontal lobes with the thalamus [2]. After craniotomy, thermocoagulation lesions are placed bilaterally using bipolar electrodes in the anterior part of the internal capsule, which is especially important in the processing of emotion, cognition, and decision-making [14]. As reported by a recent literature review, AC has a remission rate of 33% and clinically meaningful results in >75% of patients [15]. In another review, correct placement of right AC lesions was associated with more favorable outcomes than left AC lesions [16]. Two clinical studies suggested reduction of obsessive thoughts is produced by AC lesions to the most ventral part of the internal capsule [17, 18]. AC is considered a safe neurosurgical procedure, with side effects being generally limited to short-term fatigue, apathy, and headache or confusion [2, 17]. Several clinical reviews found a positive response rate of AC in 64-75% of patients [17, 19, 20].  



Intractable OCD causes tremendous suffering to those affected and to their families, while the high prevalence of OCD poses a burden to society as a whole. The literature suggests lesion procedures for the most extreme cases of OCD can provide substantial benefit, with the two most practiced procedures both interrupting connections of orbital and medial prefrontal cortices to the thalamus [2]. Future research in psychiatric neurosurgery is urgently needed for the development and enhancement of safe and effective therapeutic options.  



References 

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