Can Brain Imaging Predict Deep Brain Stimulation Outcomes for OCD?

What you need to know

• Deep brain stimulation (DBS) is an emerging treatment for severe obsessive-compulsive disorder (OCD), but patient responses vary
• This study used brain imaging to try to predict which patients would benefit from DBS treatment
• While some brain regions showed correlations with treatment response, the imaging could not reliably predict outcomes for individual patients
• More research is needed to develop brain imaging techniques that can accurately guide DBS treatment decisions for OCD

What is deep brain stimulation for OCD?

Obsessive-compulsive disorder (OCD) is a mental health condition characterized by recurring, unwanted thoughts (obsessions) and repetitive behaviors (compulsions). For some people with severe OCD that does not respond to standard treatments, deep brain stimulation (DBS) may be an option.

DBS involves surgically implanting electrodes in specific areas of the brain and delivering electrical pulses to those regions. For OCD, the electrodes are typically placed in an area called the ventral capsule/ventral striatum (VC/VS). This brain region is involved in the circuits thought to drive OCD symptoms.

While DBS can be very effective for some patients with OCD, responses vary. Some patients experience significant symptom improvement, while others have little or no benefit. Researchers are trying to find ways to better predict which patients are most likely to respond well to DBS treatment.

Can brain imaging help predict DBS outcomes?

Recent studies have used brain imaging techniques, particularly diffusion MRI and tractography, to try to identify brain connection patterns that might predict DBS response. Tractography allows researchers to map out the white matter pathways, or “wiring”, connecting different brain regions.

Some of these studies have suggested that stimulating specific white matter tracts linking the prefrontal cortex to deeper brain structures might lead to better OCD symptom improvement with DBS. However, most of these studies used averaged brain data from healthy people, rather than looking at each OCD patient’s individual brain structure.

This new study aimed to test whether looking at patient-specific brain imaging could reliably predict DBS outcomes for individual OCD patients.

How was this study done?

The researchers studied 8 patients who received DBS treatment for severe OCD. Before DBS surgery, each patient underwent detailed brain imaging, including diffusion MRI scans.

Using the imaging data, the researchers mapped out key white matter pathways in each patient’s brain, focusing on connections between:

• Thalamus and prefrontal cortex regions
• Subthalamic nucleus and prefrontal cortex

They then used computer modeling to estimate which of these pathways would likely be activated by each patient’s specific DBS settings.

The researchers looked at whether activation of particular pathways correlated with:

• Improvement in OCD symptoms (measured by the Yale-Brown Obsessive Compulsive Scale)
• Improvement in depression symptoms (measured by the Montgomery-Åsberg Depression Rating Scale)
• Occurrence of hypomania (a potential side effect of DBS)

Importantly, they used rigorous statistical methods to test whether the brain imaging data could actually predict these outcomes for individual patients, not just show group-level correlations.

What were the key findings?

The study found some correlations between activation of specific brain pathways and DBS outcomes. In particular:

• Activation of pathways connecting the thalamus to the cingulate cortex was associated with greater improvement in both OCD and depression symptoms
• Activation of pathways to the orbitofrontal cortex was linked to worse OCD outcomes

However, when the researchers tested whether these patterns could reliably predict outcomes for individual patients, the results were not accurate enough to be clinically useful. In other words, while there were some overall trends, the brain imaging could not dependably forecast how a specific patient would respond to DBS.

Notably, the study did not find a strong link between activation of subthalamic nucleus pathways and OCD improvement. This contrasts with some previous research suggesting these pathways were important for DBS response.

Why couldn’t the brain imaging predict individual outcomes?

There are a few potential reasons why the patient-specific brain imaging approach did not translate into accurate predictions for individuals:

• Small sample size: With only 8 patients, it’s difficult to develop a reliable predictive model. However, the researchers note that if there were a very strong, consistent effect, it likely would have been detectable even in this small group.

• Brain differences in OCD: Most previous studies used brain imaging from healthy people to create “standard” brain maps. But OCD may cause changes to brain structure and connections. Using patient-specific imaging in this study revealed that there was a lot of variability between OCD patients in their brain wiring patterns.

• Complex factors in DBS response: How a patient responds to DBS likely depends on many factors beyond just brain wiring, such as the specific symptoms they experience, other treatments they receive, and even the expertise of their medical team in adjusting DBS settings.

• Limitations of current imaging: While diffusion MRI and tractography have improved greatly, they still have some accuracy limitations in mapping complex brain connections.

What are the implications of this study?

This research highlights the challenges in developing reliable biomarkers to predict DBS outcomes for psychiatric conditions like OCD. While brain imaging can provide valuable insights into the mechanisms of DBS and OCD, we are not yet at the point of using it to make individual treatment decisions.

The study also emphasizes the importance of using rigorous statistical methods when evaluating potential predictive biomarkers. Showing a correlation between a brain feature and treatment outcome is not the same as proving that feature can accurately forecast results for individual patients.

However, the findings do provide some support for targeting DBS to activate pathways connecting the thalamus and cingulate cortex. This aligns with other research on the brain circuits involved in OCD and cognitive control.

Conclusions

• Patient-specific brain imaging showed some correlations with DBS outcomes for OCD, but could not reliably predict results for individuals
• Activation of pathways between the thalamus and cingulate cortex was linked to greater symptom improvement
• More research is needed to develop brain imaging techniques that can accurately guide DBS treatment decisions
• Future studies should use larger patient samples and combine imaging with other clinical and biological measures

While this study did not find a clear predictive biomarker, it represents an important step in trying to personalize and optimize DBS treatment for OCD. As brain imaging and stimulation technologies continue to advance, researchers will keep working to better understand the neural circuits underlying OCD and how to most effectively target them with DBS. The ultimate goal is to be able to tailor this promising treatment approach to each individual patient.