Focused ultrasound is a medical technology offering a non-invasive approach to treating various conditions, particularly within the brain. This technique precisely delivers therapeutic energy deep into the body without requiring surgical incisions or implants. It provides an alternative to traditional surgical interventions by targeting specific areas with accuracy. This method allows for the treatment of neurological disorders by modulating or ablating problematic brain activity.
Understanding Focused Ultrasound
Focused ultrasound operates on the principle of concentrating multiple beams of sound energy onto a single, small target deep within the brain. Each individual ultrasound beam passes harmlessly through surrounding tissue, similar to how light rays can be focused by a magnifying glass. At the precise focal point where these hundreds or thousands of beams converge, their combined energy generates a therapeutic effect.
This concentrated energy can be used to create a small, controlled thermal lesion, effectively disrupting abnormal electrical activity in the brain. Unlike diagnostic ultrasound, which uses low-intensity sound waves to create images, therapeutic focused ultrasound employs higher intensities to achieve a desired biological effect, such as tissue ablation or temporary blood-brain barrier opening. The target area typically measures a few millimeters, ensuring precision while sparing healthy adjacent brain tissue.
Neurological Conditions Treated
Focused ultrasound is an approved treatment option for several neurological conditions, primarily movement disorders. It is approved by the U.S. Food and Drug Administration (FDA) for treating essential tremor and certain symptoms of Parkinson’s disease, including tremor, rigidity, and dyskinesia. For essential tremor, the procedure targets the ventral intermediate nucleus (VIM) of the thalamus, a brain region involved in the circuit causing tremor. Creating a small thermal lesion in the VIM can immediately reduce or eliminate the tremor.
In Parkinson’s disease, focused ultrasound can also target the VIM for tremor control. For other motor symptoms like rigidity, slowness, or dyskinesia, the globus pallidus interna (GPi) or the pallidothalamic tract may be targeted. Ablation of these brain regions disrupts the abnormal neuronal networks contributing to these symptoms, offering symptomatic relief. Bilateral treatment of Parkinson’s motor symptoms and dyskinesia is possible through staged procedures.
Beyond movement disorders, focused ultrasound is being explored for other neurological and psychiatric conditions. Clinical trials are investigating its use for obsessive-compulsive disorder (OCD) by creating a lesion in the anterior limb of the internal capsule (ALIC), a pathway connecting the frontal lobe to structures involved in anxiety and mood. Early data from these studies suggest a potential for improvement in OCD symptoms. Research also extends to conditions like brain tumors, degenerative disorders such as Alzheimer’s disease, epilepsy, and neuropathic pain, often by temporarily opening the blood-brain barrier to enhance drug delivery.
The Procedure and Patient Experience
Before a focused ultrasound brain procedure, patients undergo preparation, which typically includes shaving the entire head to ensure optimal ultrasound wave transmission, as hair can interfere with the sound waves. A head frame is then attached to stabilize the head, ensuring precise targeting during the treatment. This frame also connects to the magnetic resonance imaging (MRI) table, which is used for real-time guidance and monitoring.
During the procedure, the patient lies on a treatment bed that moves in and out of an MRI scanner, with their head placed into a helmet-like device filled with cool water. The circulating cool water helps prevent the scalp from overheating during the ultrasound application. The neurosurgeon, working from a control room, uses MRI images to precisely pinpoint the target area within the brain.
Low doses of ultrasound energy are initially delivered, and the patient, who remains awake and alert, provides immediate feedback on symptom improvement or any sensations. This real-time interaction allows the medical team to fine-tune the target location and energy levels. Once the optimal spot is confirmed and symptom reduction is observed, the energy is increased to create a permanent therapeutic lesion. The entire procedure usually lasts a few hours, and most patients experience immediate relief of symptoms. Following the treatment, the head frame is removed, and patients are monitored in a recovery room before being discharged home on the same day.