Team limits ultrasound power in addiction trial after participant suffers brain hemorrhage

Team limits ultrasound power in addiction trial after participant suffers brain hemorrhage

On 14 August, WIRED reported on a trial in which focused ultrasound is directed at the nucleus accumbens, a deep brain region involved in addiction. After one participant was injured, the team suspended the study for eight months and changed the exposure protocol.

Over the course of his career, neurosurgeon Ali Rezai has performed more than three thousand deep brain stimulation procedures, a surgical treatment in which electrodes are implanted directly into a specific brain region. His group is targeting the nucleus accumbens, a deep part of the reward system involved in responses to opioids and stimulants. In a 2025 experiment in rats trained to prefer a chamber where they received fentanyl, stimulation of this region reduced that preference.

Focused ultrasound concentrates the energy of sound waves at a single point inside the brain, while MRI is used to aim the focus at the nucleus accumbens. In the ongoing trial, participants with opioid addiction or another substance use disorder undergo both active and sham procedures. During each session, they are shown substance-related images intended to induce craving and are asked to rate its intensity. The researchers then monitor them for adverse effects from the procedure over four months.

In an open-label study of eight people with severe opioid use disorder, the authors reported that cue-induced opioid craving fell by an average of 91 percent over 90 days. Urine tests detected no illicit substances during this period in five participants. In another published case, a person with methamphetamine use disorder reported a reduction in craving from 9 out of 10 to zero at five visits over 90 days.

A 44-year-old participant was injured while the power was being increased. He stopped responding to questions, and scans showed small hemorrhages near the nucleus accumbens. The team described the case in a letter to the journal Brain Stimulation, suspended the trial, and introduced an automatic power limit after consulting the FDA, independent specialists, and the device manufacturer. When the device reaches a specified power threshold, it reduces the output. If the threshold is exceeded for too long, the device shuts down.

The method now requires a power and exposure duration protocol that can reach the deep target without damaging brain tissue.