Can Focused Ultrasound Brain Surgery Help Treat Severe OCD and Depression Without Harming Cognition?

What you need to know

• Magnetic resonance-guided focused ultrasound capsulotomy (MRgFUS-AC) is a new non-invasive brain surgery technique for treating severe obsessive-compulsive disorder (OCD) and depression.

• This study found that MRgFUS-AC did not cause any significant cognitive decline in patients with severe OCD or depression.

• Some patients even showed improvements in certain cognitive abilities after the procedure.

• Improvements in OCD and depression symptoms were associated with patients reporting better executive functioning in daily life.

A new surgical option for severe psychiatric disorders

For people with severe obsessive-compulsive disorder (OCD) or depression that doesn’t respond to standard treatments, brain surgery may be considered as a last resort option. However, there have been longstanding concerns that these surgeries could potentially harm cognitive abilities.

A new study published in Translational Psychiatry examined whether a cutting-edge form of non-invasive brain surgery called magnetic resonance-guided focused ultrasound capsulotomy (MRgFUS-AC) affects cognition in patients with severe OCD or depression. The results suggest this procedure can treat psychiatric symptoms without causing cognitive decline, and may even lead to some cognitive improvements in certain patients.

How focused ultrasound capsulotomy works

MRgFUS-AC uses highly focused beams of ultrasound energy to make small lesions in a specific area of the brain called the anterior limb of the internal capsule. This region contains nerve fibers connecting parts of the brain involved in OCD and depression.

The procedure is done while the patient is awake inside an MRI machine. No incisions or radiation are involved. The neurosurgeon uses MRI imaging to precisely target the internal capsule and create small lesions on both sides of the brain.

The goal is to disrupt abnormal brain circuits involved in OCD and depression symptoms. Unlike older surgical techniques, MRgFUS allows very precise, real-time control over the size and location of the lesions.

Studying cognitive effects in OCD and depression patients

The researchers studied 10 patients with severe OCD or depression who underwent MRgFUS-AC. The patients completed a battery of cognitive tests before surgery and again at 6 months and 12 months after.

The tests assessed various cognitive domains including:

• Executive function (complex reasoning and problem-solving)
• Memory
• Processing speed
• Decision-making

The study aimed to determine if MRgFUS-AC caused any cognitive decline, and whether changes in psychiatric symptoms were linked to changes in cognitive performance.

Key findings on cognitive function

Overall, the study found no evidence of cognitive decline following MRgFUS-AC:

• No patient showed a significant decline (defined as 2 or more standard deviations worse) on any cognitive test at 6 or 12 months after surgery.

• At the group level, scores on cognitive tests were generally stable or showed mild improvements after surgery.

• 8 out of 10 patients actually demonstrated significant improvement (2 or more standard deviations better) on at least one cognitive test after surgery.

• Improvements were seen across various cognitive domains including processing speed, memory, and executive function.

The researchers note this cognitive safety profile appears better than that seen with older surgical techniques for OCD and depression. They suggest the precise, controlled nature of the MRgFUS lesions may allow disruption of abnormal circuits while minimizing effects on cognitive networks.

Links between symptom improvement and cognitive changes

The study also examined whether improvements in OCD or depression symptoms correlated with changes in cognitive test scores.

Interestingly, greater symptom improvement was associated with patients reporting better executive functioning in their daily lives on a self-report questionnaire. However, symptom changes did not correlate significantly with performance on objective cognitive tests.

The researchers suggest a few potential explanations for this finding:

1. Reducing OCD/depression symptoms may lead to secondary improvements in a person’s ability to engage executive skills in real-world situations.

2. Successfully altering the targeted brain circuits may improve both psychiatric symptoms and certain executive abilities.

3. As patients’ clinical symptoms improved, it may have positively influenced their perception of their own cognitive abilities.

More research is needed to clarify the complex relationships between symptom changes, objective cognitive performance, and subjective cognitive experiences after this type of procedure.

How the lesions affect brain circuits

To understand why MRgFUS-AC appears cognitively safe, it’s helpful to consider the brain circuits involved.

The internal capsule contains nerve fibers connecting the prefrontal cortex to deeper brain structures. Different prefrontal regions send fibers through different parts of the internal capsule:

• Fibers from areas involved in OCD/depression symptoms (like the orbitofrontal cortex) tend to run through the bottom part of the internal capsule.

• Fibers involved in executive function (from the dorsolateral prefrontal cortex) tend to run through the upper part.

By precisely targeting lesions to the lower part of the internal capsule, MRgFUS-AC aims to disrupt the circuits driving psychiatric symptoms while minimizing effects on executive function circuits.

The researchers suggest there may be a “sweet spot” for lesion size - large enough to improve symptoms, but small enough to avoid cognitive side effects. Future studies could investigate whether slightly larger but still precisely placed lesions might lead to even better symptom outcomes.

Limitations and future directions

While promising, this study had some important limitations:

• The sample size was small (10 patients), so larger studies are needed to confirm the findings.

• There was no control group, so some improvements could potentially be due to practice effects from repeat testing.

• Only 4 out of 10 patients were classified as “responders” in terms of symptom improvement, limiting the ability to thoroughly analyze links between symptom and cognitive changes.

The researchers call for additional studies with larger sample sizes and control groups to more comprehensively assess the cognitive effects of MRgFUS-AC.

They also suggest future research could investigate whether slightly larger lesion volumes might improve symptom response rates while still maintaining cognitive safety.

Conclusions

• MRgFUS capsulotomy appears to be a cognitively safe treatment option for severe OCD and depression, with no evidence of cognitive decline in this study.

• Some patients may experience improvements in certain cognitive abilities following the procedure.

• Larger studies are still needed, but these results are encouraging for the cognitive safety profile of this novel treatment approach.

• For patients and clinicians considering surgical options for severe psychiatric disorders, these findings provide reassurance about the cognitive risks of MRgFUS capsulotomy.