Brain surgery has come a long way. In ancient times, trephination was the standard way for surgeons to access to the brain. The procedure was extremely invasive for the patient. Centuries later, surgeons are able to perform advanced interventions that are much less invasive and safer for the patient; however, today most brain surgeries still require burr holes or opening of the skull.
With rising costs in resources and increasing risk to human lives including healthcare-associated infections, it may be time to rethink the surgical use of a scalpel. Technological advancements are giving us to tools that allow surgeons to operate without actually touching the patient and ablative energies that do not require large surgical incisions. Moreover, MR scanners provide high resolution imaging of the patient anatomy and thermometry. So why are we still cutting?
Focused ultrasound guided by MRI provides a technique that makes incisionless surgery feasible. While sound waves can target and ablate deep within the brain through an intact skull, MR imaging provides the necessary thermal feedback.
The first clinical indication approved by the FDA for focused ultrasound in the brain is medication-refractory essential tremor. While people live with this condition for many years, the uncontrollable shaking when performing everyday tasks progresses impacts a person's ability to function in the workplace and live an independent and active lifestyle. While this condition is typically treated with medications, many patients do not get satisfactory tremor relief.
Focused ultrasound uses sound waves, which pass safely through the skull to ablate the targeted area deep in the brain. The focused ultrasound thalamotomy begins by taking MR images to plan the treatment. Then the Vim of the thalamus is identified for targeting. Low energy is first applied to cause transitory tremor relief. Since the patient is fully awake, they can provide feedback such as potential side effects enabling fine-tuning of the target. The energy is gradually increased. After each application of energy, testing is done to evaluate the patient’s safety and improvement of the tremor. The energy causes a rise in temperature until the tissue is thermally ablated, resulting in the therapeutic effect, reduction of the hand tremor.
The treatment is performed in an MRI suite often on an outpatient basis and patients usually return home that same day. Immediately after the treatment, many patients demonstrate improved hand tremor and their ability to perform daily tasks is returned. Research shows that essential tremor patients treated with focused ultrasound maintain improvement in tremor severity and daily living one year following the procedure.
Not only is MR-guided focused ultrasound being used to treat medication-refractory essential tremor, but it is being evaluated in many clinical trials. This critical research is to assess the potential for future applications of MRgFUS in the treatment of challenging disease areas such as Parkinson’s disease.
In May 2018, the first Parkinson’s patient was treated in a pivotal FDA study addressing advanced Parkinson's disease in patients who have not responded to medication. The study, being conducted at ten international medical centers with leading Parkinson's investigators, is evaluating focused ultrasound to improve motor function and reduce dyskinesia in Parkinson's disease patients.
While millions of dollars have been spent on Alzheimer drug research, to-date available medical treatments have been relatively ineffective in slowing the cognitive decline in patients. One of the reasons is the blood brain barrier (BBB), which while preventing toxins and infectious agents from diffusing into the brain tissue, also blocks 97% of potentially beneficial medications from reaching their target. Focused ultrasound is also being researched to temporarily open the BBB and may unlock new possibilities for treating Alzheimer's disease and potentially delivering targeted drug therapy to the brain.
In July 2018, the FDA approved the initiation of a clinical trial to evaluate the disruption of the BBB in patients with Alzheimer’s disease. This follows the successful completion of a Phase I study at Sunnybrook Hospital in Toronto, which demonstrated that focused ultrasound can safely and temporarily open the BBB for patients with early stage Alzheimer’s disease.
MR-guided focused ultrasound is transforming healthcare today and holds promise to become a standard of care in the future. This disruptive technology has the potential to allow surgeons to deliver effective, gentler patient care by performing brain surgery without surgical incisions. On the horizon, brain surgery may no longer require cutting - with the new sound of surgery– focused ultrasound.