How Does Deep Brain Stimulation Affect Brain Regions in OCD Patients?

What you need to know

• Deep brain stimulation (DBS) is an experimental treatment for severe obsessive-compulsive disorder (OCD) that does not respond to other therapies
• This study examined which brain areas are affected by DBS targeting the bed nucleus of stria terminalis in OCD patients
• The stimulation affected several nearby brain regions involved in OCD, suggesting multiple targets may produce similar effects
• More research is needed to determine the optimal brain target and stimulation parameters for DBS in OCD

Understanding obsessive-compulsive disorder and deep brain stimulation

Obsessive-compulsive disorder (OCD) is a mental health condition characterized by recurring, intrusive thoughts (obsessions) and repetitive behaviors or mental acts (compulsions) that a person feels compelled to perform to relieve anxiety. While many people with OCD benefit from standard treatments like medication and cognitive-behavioral therapy, about 10% continue to have severe symptoms that significantly impair their quality of life.

For these treatment-resistant cases, an experimental therapy called deep brain stimulation (DBS) is being investigated as a potential option. DBS involves surgically implanting thin wire electrodes into specific areas of the brain. These electrodes deliver electrical pulses that can help regulate abnormal brain activity.

DBS is already an established treatment for movement disorders like Parkinson’s disease. Researchers are now exploring its use for severe psychiatric conditions like OCD. However, there are still many open questions about the optimal way to use DBS for OCD, including which exact location in the brain to target.

Examining the effects of DBS in OCD patients

This study aimed to better understand how DBS affects the brain in OCD patients. The researchers looked at 11 patients who received DBS targeting an area called the bed nucleus of stria terminalis (BNST). This is one of several brain regions being investigated as potential DBS targets for OCD.

Using advanced brain imaging and computer modeling techniques, the researchers mapped out which parts of the brain were being affected by the electrical stimulation in each patient. They also looked at whether stimulation of particular areas was associated with greater improvement in OCD symptoms.

Key findings on brain areas affected by DBS

The main areas affected by the electrical stimulation included:

• Anterior limb of internal capsule (ALIC)
• Bed nucleus of stria terminalis (BNST)
• Globus pallidus externa (GPe)
• Fornix
• Nucleus accumbens
• Internal capsule

Interestingly, the researchers found that stimulation affecting the ventral (lower) part of the ALIC and the front part of the GPe was associated with greater improvement in OCD symptoms at the 12-month follow-up. However, this link was not statistically significant after adjusting for multiple comparisons, so it should be interpreted cautiously.

The brain areas affected were very similar at both 12 months and 24 months after DBS implantation. There were no major differences in the affected brain regions between patients who responded well to the treatment versus those who did not.

Implications for understanding DBS targets in OCD

One of the key insights from this study is that DBS targeting the BNST affects multiple brain areas that have been investigated as potential stimulation targets for OCD. As the authors note, many of the proposed DBS targets for OCD are anatomically very close to each other.

This suggests that stimulating different nearby targets may produce similar effects by influencing overlapping brain circuits. The authors propose that DBS of the ALIC, nucleus accumbens, and BNST may essentially be stimulating the same overall brain network involved in OCD.

This has important implications for interpreting and comparing studies of different DBS targets for OCD. It highlights the need to look beyond just the primary intended target and consider the broader network of brain regions being influenced.

Limitations and future directions

There are some important limitations to keep in mind when interpreting this study:

• The sample size was small (11 patients), making it difficult to draw firm statistical conclusions.
• The electrode placements were very similar across patients, limiting the ability to compare different stimulation locations.
• The study only looked at one specific DBS target (the BNST). Similar analyses of other targets would be valuable for comparison.

Future research with larger patient groups and varied electrode placements could help clarify which specific brain areas and networks are most important to target with DBS for OCD. Studies directly comparing different targets within the same patients would also be informative.

Additionally, more work is needed to understand why some patients respond well to DBS while others do not, even when similar brain areas are being stimulated. Factors beyond just the stimulation location, such as individual brain anatomy or OCD subtypes, likely play a role.

Conclusions

• DBS targeting the bed nucleus of stria terminalis affects multiple brain regions involved in OCD circuits
• The brain areas stimulated largely overlap with other proposed DBS targets for OCD
• Stimulation of the ventral anterior limb of internal capsule and anterior globus pallidus externa may be particularly important for symptom improvement
• More research is needed to determine the optimal brain target(s) and stimulation parameters for DBS in treatment-resistant OCD
• Understanding the broader brain networks affected by DBS, rather than just individual targets, is crucial for advancing this experimental therapy