Can Deep Brain Stimulation Help Treat Obsessive-Compulsive Disorder?

What you need to know

• Deep brain stimulation (DBS) is being explored as a treatment for severe obsessive-compulsive disorder (OCD) that doesn’t respond to other therapies.
• Recent research has focused on identifying specific brain networks involved in OCD that could be targeted with DBS.
• While promising, more research is needed to determine the best way to use DBS for OCD and predict which patients will benefit most.

What is deep brain stimulation?

Deep brain stimulation (DBS) is a neurosurgical procedure that involves implanting electrodes in specific areas of the brain. These electrodes deliver electrical pulses that can help regulate abnormal brain activity. DBS has been used successfully to treat movement disorders like Parkinson’s disease. Now, researchers are exploring its potential to treat psychiatric conditions like obsessive-compulsive disorder (OCD).

OCD is a mental health condition characterized by recurring, unwanted thoughts (obsessions) and repetitive behaviors (compulsions). For some people with severe OCD, standard treatments like medication and psychotherapy are not effective. DBS offers a potential alternative for these treatment-resistant cases.

Targeting brain networks in OCD

Early approaches to DBS for OCD focused on stimulating individual brain regions thought to be involved in the disorder. However, our understanding of the brain has evolved. We now know that mental processes rely on the coordinated activity of networks of brain regions, rather than isolated areas.

Recent research has attempted to identify the specific brain networks involved in OCD that could be targeted with DBS. This “connectomic” approach looks at the connections between different brain regions, rather than just the regions themselves.

The ACC-STN pathway

Several studies have highlighted a particular brain pathway that may be important in OCD. This pathway connects two regions:

1. The anterior cingulate cortex (ACC): This is an area in the front of the brain involved in cognitive control - our ability to regulate our thoughts and behaviors.

2. The subthalamic nucleus (STN): This is a small structure deep in the brain that helps coordinate movement and is also involved in cognitive processes.

The pathway connecting these two regions seems to be particularly relevant for OCD symptoms. It’s thought that abnormal activity in this “ACC-STN pathway” might contribute to the persistent, intrusive thoughts and repetitive behaviors characteristic of OCD.

Interestingly, both the ACC and STN have been targets of DBS or other neurosurgical treatments for OCD in the past. The fact that a pathway connecting these regions has emerged as potentially important provides some support for the relevance of this network in OCD.

Challenges in DBS research

While the focus on brain networks is promising, there are still challenges in using this approach to guide DBS treatment. A study by Widge and colleagues, discussed in the research highlight, points out some important considerations:

1. Individual differences: Most studies have used “normative” brain data - information averaged across many healthy individuals. However, there can be significant differences in brain structure and connectivity between individuals. Using patient-specific data might be more accurate for planning DBS treatment.

2. Prediction vs. correlation: Finding a correlation between stimulation of certain brain areas and symptom improvement is a good start. However, to be truly useful for treatment planning, we need to be able to predict which patients will benefit from stimulating specific brain regions or networks.

3. Statistical rigor: It’s important to use robust statistical methods to validate findings, especially when dealing with small sample sizes common in DBS studies.

The role of the anterior cingulate cortex

Despite these challenges, both the studies by Baldermann and colleagues and Widge and colleagues highlight the potential importance of the anterior cingulate cortex (ACC) in OCD. Understanding the role of the ACC could provide insights into how DBS might help treat OCD:

1. Cognitive control: The ACC is crucial for cognitive control - our ability to regulate our thoughts and behaviors based on our goals and the current situation.

2. Decision-making: When functioning normally, the ACC helps us allocate mental resources appropriately. It signals when we need to engage in more careful, controlled decision-making, and when we can rely on faster, more automatic processes.

3. OCD symptoms: If the ACC is not functioning properly, it might persistently signal the need for careful consideration of stimuli that are no longer relevant. This could manifest as the persistent, intrusive thoughts and repetitive behaviors seen in OCD.

Future directions: Personalized treatment

The emerging focus on brain networks in DBS research points towards a more personalized approach to treating psychiatric disorders. Instead of treating all cases of OCD the same way, we might be able to target specific aspects of brain function that are impaired in individual patients.

For example:

• Patients with primarily cognitive control deficits might benefit from stimulation targeting the ACC and its connections.
• Patients with issues related to reward sensitivity might benefit from stimulation of other regions, like the orbital or ventral prefrontal cortex.

This approach aligns with the Research Domain Criteria (RDoC) framework, which aims to classify mental disorders based on dimensions of observable behavior and neurobiological measures, rather than traditional diagnostic categories.

Conclusions

• Deep brain stimulation shows promise as a treatment for severe, treatment-resistant OCD.
• Recent research has focused on identifying specific brain networks involved in OCD that could be targeted with DBS.
• The pathway connecting the anterior cingulate cortex and subthalamic nucleus appears particularly relevant for OCD symptoms.
• Future research may lead to more personalized DBS treatments targeting specific aspects of brain function impaired in individual patients.
• While promising, more research is needed to determine the best way to use DBS for OCD and predict which patients will benefit most.