What Brain Areas Should Surgeons Target When Treating Severe OCD With Gamma Knife Surgery?

What you need to know

• For some people with severe OCD that hasn’t improved with standard treatments, brain surgery using focused radiation (gamma knife) can be an effective option
• The surgery targets brain pathways in an area called the internal capsule that connects regions involved in OCD symptoms
• The study found that targeting the middle portion of this area led to better symptom improvement than targeting just the bottom portion

Understanding OCD and Treatment-Resistant Cases

Obsessive-compulsive disorder (OCD) affects 2-3% of people worldwide. It involves intrusive, anxiety-provoking thoughts (obsessions) and repetitive behaviors or mental acts (compulsions) that can be severely disabling. While most people with OCD improve with standard treatments like medication and cognitive behavioral therapy, about 20% continue to have severe symptoms despite trying multiple treatments.

For this smaller group of people with treatment-resistant OCD, neurosurgery may be considered as a treatment option. One such surgical procedure is gamma knife capsulotomy, which uses focused radiation to create small, precise lesions in specific brain circuits involved in OCD.

How Gamma Knife Surgery Works

Gamma knife surgery doesn’t require opening the skull. Instead, it uses many beams of radiation that converge on a specific target in the brain. The target for OCD treatment is an area called the anterior limb of the internal capsule (ALIC). The ALIC contains bundles of nerve fibers that connect parts of the brain involved in OCD symptoms, including the prefrontal cortex, thalamus, and structures called the basal ganglia.

The radiation creates small lesions that interrupt these problematic brain circuits. Originally, surgeons would target the entire height of the ALIC, but more recent approaches focus on just the bottom half, which has shown similar benefits with fewer side effects.

What the Research Found

The researchers analyzed brain scans and symptom improvements in 26 patients who underwent gamma knife surgery for severe OCD. They looked at how the location and size of the lesions related to how much patients’ symptoms improved.

Key findings included:

• 69% of patients had a significant improvement in their OCD symptoms (defined as at least a 35% reduction on a standard OCD rating scale)
• Lesions in the middle portion of the targeted area (closer to the middle of the ALIC) were associated with better symptom improvement compared to lesions in just the bottom portion
• The overall size of the lesions didn’t affect how much symptoms improved

Implications for Treatment

The study suggests that to get the best results, surgeons should target the bottom half of the ALIC rather than just its lowest portion. This ensures the treatment affects the key nerve pathways that need to be interrupted to improve OCD symptoms.

This knowledge could help improve how the surgery is performed and potentially lead to better outcomes. It may also guide the development of less invasive treatments that target the same brain circuits.

The researchers note that each person’s brain is somewhat different, so future work should focus on personalizing the target location based on individual brain anatomy. This “precision medicine” approach could further improve the effectiveness of the treatment.

Conclusions

• Gamma knife surgery remains an effective option for severe OCD cases that haven’t responded to standard treatments
• Targeting the bottom half of the internal capsule appears optimal for symptom improvement
• Future research should focus on personalizing the treatment target for each individual patient
• This knowledge could help develop new, less invasive treatments that target the same brain circuits