Parkinson’s disease is a progressive neurological condition that primarily affects movement. It arises from the degeneration of dopamine-producing cells in the brain, leading to various motor symptoms. Focused ultrasound offers a non-invasive, incision-free treatment option for managing some of these symptoms.
What Focused Ultrasound Is
Focused ultrasound is a medical technology that uses concentrated sound waves to address issues deep within the body without the need for surgical incisions. The principle is similar to using a magnifying glass to focus sunlight onto a single point, where the energy becomes highly concentrated. Multiple low-energy ultrasound beams precisely converge at a specific target location inside the body. Individually, these beams are harmless as they pass through tissues like skin, muscle, and bone.
However, at their focal point, the convergence of these beams generates enough thermal energy to create a tiny, precise lesion in the targeted tissue. Magnetic Resonance Imaging (MRI) plays a crucial role by providing real-time visualization and temperature monitoring, ensuring accurate targeting and controlled energy delivery. This technology has applications in various medical fields.
Targeting Parkinson’s Symptoms
Focused ultrasound specifically addresses certain Parkinson’s disease symptoms by disrupting abnormal neural circuits in the brain. For tremor-dominant Parkinson’s disease, the primary target is often the ventral intermediate nucleus (VIM) of the thalamus. The thalamus acts as a relay station for motor and sensory signals; its abnormal activity contributes to tremors. By creating a lesion in the VIM, focused ultrasound can interrupt these irregular signals, leading to tremor reduction.
Beyond tremor, focused ultrasound can also target other areas for symptoms like rigidity and dyskinesia. The globus pallidus internus (GPi) is a target for treating dyskinesia, bradykinesia (slowness of movement), and rigidity. Some approaches also consider the pallidothalamic tract. The precise thermal ablation aims to normalize the brain activity responsible for these motor manifestations.
Patient Suitability
Not everyone with Parkinson’s disease is a candidate for focused ultrasound treatment. Patient selection involves several considerations. Candidates often include individuals with tremor-dominant Parkinson’s disease who have not responded adequately to medication. The treatment is also approved for dyskinesia and other motor symptoms that are resistant to medication.
Contraindications for focused ultrasound include conditions that prevent a patient from undergoing an MRI, such as certain metal implants like pacemakers. Patients with abnormal bleeding or coagulation disorders are excluded. Skull density can also be a factor, as insufficient bone density hinders the ultrasound waves from effectively reaching the target. Additionally, severe cognitive impairment or poorly controlled medical conditions disqualify a patient.
The Treatment Process
The focused ultrasound procedure involves several steps, beginning with preparation. Before the treatment, the patient’s head is shaved to ensure optimal ultrasound transmission. A stereotactic frame is then attached to the head, providing stability and precise targeting during the procedure. This frame helps to keep the head perfectly still within the MRI scanner.
During the treatment, the patient lies on an MRI bed and is positioned within the MRI machine. The patient remains awake and communicative throughout the procedure, allowing for real-time feedback to the medical team. MRI scans are used to guide the ultrasound beams and monitor temperature changes in the brain. Low-power ultrasound pulses are delivered first to confirm the exact target location and observe any temporary symptom changes, such as tremor improvement, before a permanent lesion is created.
Post-Procedure Expectations
Following the focused ultrasound procedure, patients can expect immediate improvement in the treated symptoms, particularly tremor. Patients are monitored in a recovery area for a few hours before being discharged, often on the same day or the next. The small cuts from the head frame require only simple dressings.
While the procedure is well-tolerated, some temporary effects may occur. Common temporary experiences include mild dizziness, headache, or nausea. Patients might also experience temporary unsteadiness, balance issues, or sensory changes like numbness or tingling in the lips or fingertips. Speech or swallowing difficulties are also possible, but these effects are mild and resolve within days or weeks. Follow-up appointments are scheduled to monitor long-term outcomes and address any lingering effects.