How Does Neurosurgery for OCD Affect Brain Function?

What you need to know

• Neurosurgical procedures for severe OCD can effectively reduce symptoms with minimal side effects
• These procedures target brain circuits connecting the prefrontal cortex to other regions
• Studying the effects helps us understand how the brain’s networks function in OCD and normal cognition
• New techniques like deep brain stimulation allow more precise and adjustable treatments

Understanding OCD and Its Treatment

Obsessive-compulsive disorder (OCD) is a challenging mental health condition that affects 2-3% of people. It involves intrusive, unwanted thoughts (obsessions) and repetitive behaviors or mental acts (compulsions). For some people with severe OCD, standard treatments like therapy and medication are not enough to control their symptoms. In these cases, neurosurgical procedures may be considered as a last resort treatment option.

This article reviews what researchers have learned about brain function from studying the effects of neurosurgical treatments for OCD over the past several decades. While the primary goal of these procedures is to help patients, they also offer a unique opportunity to examine how altering specific brain circuits impacts cognition and behavior.

The Brain Circuits Involved in OCD

Research using brain imaging and other techniques has shown that OCD involves problems in the functioning of circuits connecting areas of the prefrontal cortex (the front part of the brain) with deeper brain structures like the striatum and thalamus. These circuits are involved in regulating emotions, making decisions, and controlling behaviors.

In people with OCD, there appears to be excessive activity in some of these brain circuits. This may contribute to getting “stuck” in repetitive thought and behavior patterns. Neurosurgical treatments aim to modulate the activity in these circuits to bring it closer to normal levels.

Types of Neurosurgical Procedures for OCD

Several different neurosurgical approaches have been developed to treat severe OCD:

Cingulotomy: This procedure targets the anterior cingulate cortex, a region involved in emotion regulation and cognitive control. Small lesions are created in the white matter tracts connecting this area to other regions.

Capsulotomy: This targets the internal capsule, a bundle of nerve fibers connecting the prefrontal cortex to deeper brain structures. Lesions interrupt some of these connections.

Deep brain stimulation (DBS): Rather than creating permanent lesions, DBS involves implanting electrodes to deliver adjustable electrical stimulation to specific brain areas. Common targets include regions of the internal capsule and nearby structures.

Effects on OCD Symptoms

Studies have found that these procedures can lead to significant improvements in OCD symptoms for 50-70% of patients who undergo them. Importantly, the benefits often develop gradually over weeks to months after the procedure. This suggests the brain is adapting and rewiring itself in response to the changes.

While not a cure, many patients experience enough symptom relief to substantially improve their quality of life and daily functioning. However, the procedures do not work for everyone, and some patients have only partial improvement.

Cognitive and Behavioral Effects

One of the most striking findings is how little these procedures seem to impact overall cognitive abilities and personality, despite targeting important brain regions. Most studies have found minimal changes on standard neuropsychological tests of memory, attention, and general intelligence.

Some specific effects that have been observed include:

• Mild difficulties with verbal fluency (generating lists of words)
• Some challenges with cognitive flexibility and planning complex actions
• Subtle changes in emotional responsiveness or social behavior

However, these effects are generally mild and often improve over time. Many patients are able to return to work and other activities.

Interestingly, some positive cognitive changes have also been reported. For example, improvements in decision-making ability have been seen in some studies. This may relate to reduced anxiety allowing more rational choices.

What This Teaches Us About Brain Function

The limited side effects of these procedures, despite altering major brain pathways, highlights the adaptability and resilience of the human brain. It suggests many cognitive functions rely on widely distributed networks that can compensate when some connections are disrupted.

The gradual emergence of benefits also demonstrates the brain’s capacity to rewire and optimize its functioning over time in response to changes. This neuroplasticity is likely key to the therapeutic effects.

Studying which circuits, when altered, lead to symptom improvement helps clarify their role in OCD. For example, the benefits of targeting connections between the orbitofrontal cortex and striatum support theories that these regions are central to OCD symptoms.

New Frontiers: Deep Brain Stimulation

While traditional lesioning procedures have provided valuable insights, deep brain stimulation (DBS) opens up exciting new possibilities. Some key advantages of DBS include:

• It is adjustable and reversible, unlike permanent lesions
• It allows testing effects of stimulating different brain areas
• Electrodes can record brain activity as well as stimulate

Early studies of DBS for OCD have shown promise, with response rates similar to lesioning procedures. Interestingly, DBS can sometimes produce rapid mood elevation or even episodes of hypomania when stimulation parameters are adjusted. This provides clues about the brain circuits involved in regulating mood.

Researchers are now working on developing “closed-loop” DBS systems. These could automatically adjust stimulation based on a patient’s brain activity and symptoms. This personalized approach may lead to better outcomes.

Conclusions

• Neurosurgical procedures for OCD reveal the brain’s capacity to adapt and compensate for alterations in major circuits
• Studying their effects advances our understanding of the brain networks underlying OCD and normal cognitive functions
• New techniques like DBS offer more precise ways to modulate brain activity and study its effects
• Continued research may lead to more targeted, personalized treatments for severe psychiatric disorders

While these procedures remain a last resort for severe, treatment-resistant OCD, studying their effects provides valuable insights into brain function. As techniques become more refined, they may offer hope for more patients while expanding our knowledge of the brain’s workings.