Modern neurosurgery did not really begin until the late 19th century, when surgeons opened the meninges to operate directly on the brain. But these first years were difficult ones: the survival rate for any surgical procedure that involved opening the skull was only 10%!
from The Brain from Top to Bottom Blog

Operating directly on the brain is not without some risk, though the practice of neurosurgery has made extraordinary progress since the late 1800s. Obviously, the less invasive the procedure, the fewer physical risks of collateral damage to neighboring structures, and the lower the chances of infection, post-surgical swelling or inflammation, and pain during recovery.

However, even an incisionless (no cutting, no hole drilling in the skull) is still doing something within the brain that could affect something besides the target. There are 100 billion neurons (specialized brain cells that transmit and process messages) packed into an organ that weighs a mere 3 pounds, so it requires enormous precision to treat even a tiny part of the brain without putting something else at risk.

MRI-guided Focused Ultrasound for Essential Tremor

Essential tremor (ET) is a condition that is created by abnormal brain transmissions from the cerebellum to the motor cortex. These signals are funneled along a tremor pathway that leads to a “relay station” in a central part of the brain called the thalamus, and from there they continue to the motor cortex. We now know that by accurately shutting down the relay area that receives the dysfunctional signals, they are stopped in their tracks—and the tremors stop.

Focused Ultrasound is a way of channeling ultrasound technology so it can deaden the relay station. The procedure is guided by real-time MRI scanning, which is why it is called MRI-guided Focused Ultrasound (MRgFUS). One of the amazing features of the treatment is that the ultrasound waves—over 1000 of them beamed from different direction toward the thalamus—penetrate the scalp, the skull, and the brain without causing any harm along the way. That’s right, a single wave of ultrasound is perfectly harmless, so no other tissues are injured during the ultrasound beam’s journey. However, when all the waves meet (converge) at the target, they generate enough heat to destroy tissue.

This raises the question, does MRgFUS for ET cause nearby tissue damage that might affect the patient’s ability to think, remember, or solve problems? A new study answers that question.

MRgFUS is safe for cognitive ability

A neurosurgical research team from Seoul, Korea published a 2018 paper on the effect of MRgFUS for ET in terms of cognition (including memory and problem-solving functions) and quality of life.ⁱ The authors evaluated 20 patients whose dominant hand was treated in order to control the tremors. They used recognized screening/testing tools to assess both their cognitive function and the postoperative change in quality of life. The patients were treated between March 2012-September 2014, when MRgFUS was still quite new. As an aside, at 1 year after treatment, the total tremor improvement score was 67.3%.

In terms of cognition, any observed decline was described as “minimal” and was statistically insignificant, but memory function was “much improved.” Not surprisingly, quality of life was also better.

The authors concluded that, given the deep penetration into the brain, MRgFUS has a positive safety profile in terms of not damaging cognitive function (or, as we might say, they gave it a thumb up). A second thumb up was merited by the much-improved quality of life. Given these two “thumbs up,” the research team’s summary was that MRgFUS for ET is a “new, favorable surgical treatment.”

ⁱ Jung NY, Park CK, Chang WS et al. Effects on cognition and quality of life with unilateral magnetic resonance-guided focused ultrasound thalamotomy for essential tremor. Neurosurg Focus. 2018 Feb;44(2):E8. doi: 10.3171/2017.11.FOCUS17625.