MR-guided high-intensity focused ultrasound (HiFu) at Norton Neuroscience Institute delivered tremor relief and restored independence in a complex essential tremor case.

Published: September 18, 2025

The patient

A 79-year-old man with essential tremor in the bilateral hands for at least 10 years

Over the years, the severity of the tremor worsened, along with its negative impact on his life.

First-line medications, propranolol and primidone, both were tried, without significant impact on the severity of tremor and the patient’s disability.

Feeding himself and drinking from a cup without spilling, writing, shaving, and performing fine motor tasks around the home were increasingly difficult.

The patient’s medical history is relevant for cognitive impairment, with a Montreal Cognitive Assessment score of 21/30, coronary artery disease and peripheral neuropathy causing gait and balance impairment due to numbness at the feet.

The challenge

While first-line medications weren’t providing relief, the patient and his neurologist felt it was unlikely that medications such as gabapentin, clonazepam and topiramate would provide any better tremor relief.

The patient’s advanced age, cognitive impairment and coronary artery disease placed him at an elevated perioperative risk, as well as risk of worsened cognition and loss of independence from deep brain stimulation surgery.

The solution

A referral to Abigail J. Rao, M.D., stereotactic and functional neurosurgeon with Norton Neuroscience institute, led to a MR-guided focused ultrasound thalamotomy of the left ventral intermediate nucleus (VIM) of the thalamus. The left VIM was targeted because the patient is right-hand dominant.

This surgery allows lesioning the brain in a precise manner, at a location of the surgeon’s choosing, and under highly controlled parameters. The surgical system allows for real-time monitoring of tissue temperature and anatomy, using high-resolution MR images of the patient’s brain and MRI-based thermometry software. The surgical system allows high-frequency (660 kilohertz) ultrasound waves to penetrate the intact skull, obviating the need for an incision or any penetration of the brain by surgical instruments. The energy parameters and focus of the energy are very precisely controlled by the surgeon.

The surgery is performed with the unanesthetized patient in the MRI scanner. This allows the patient to participate in a neurological exam, such that tremor improvement and off-target side effects are assessed. After baseline neurological exams and imaging are performed, the surgeon makes lower-energy temporary lesions, which are reversible, but allow for a few minutes of temporary elevation in brain temperature. During these few minutes, tremor improvement and side effects are tested. Once the surgeon is satisfied with the temporary effect, higher-temperature lesions, allowing for tissue necrosis and this permanency of clinical changes, are created. At the conclusion of the surgery, the tremor improvement is seen immediately.

The result

The patient underwent surgery with no immediate complication. Three lesional sonications were made, achieving maximal temperature of 57 C using about 13,000 joules of energy.

Significant tremor improvement was seen at the conclusion of the surgery, as noted with the handwriting “spiral” sample below. During telephone follow-up the next day, the patient noted the ability to eat and drink independently and without spilling, for the first time in years.

He reported no worsening of gait and balance, known risks of the surgery secondary to off-target edema. At clinic follow-up two weeks later, he described “feeling 100% better” and felt his tremor was completely alleviated. He reported slight residual numbness of the tongue that was not bothersome. He reported no other off-target side effects. He appreciated the improvement in independence with being able to feed himself without spilling or needing assistance from family.

The team