Key Points
- Researchers at Columbia University used focused ultrasound to treat carpal tunnel syndrome, a type of nerve pain in the wrist.
- The group also studied how the technology affects arm nerves.
The research team led by Elisa Konofagou, PhD, the Robert and Margaret Hariri Professor of Biomedical Engineering, Radiology, and Neurological Surgery at Columbia University, recently published results from a clinical study that tested focused ultrasound neuromodulation of the median nerve in healthy participants as well as in a small group of patients with carpal tunnel syndrome (CTS).
A type of neuropathic pain, CTS begins when the median nerve is compressed as it passes through the “carpal tunnel” of the wrist, which is formed by the small bones and ligaments in the joint. CTS causes pain, numbness, and loss of feeling in the hand. About 3–4% of adults develop the condition, but women are three times more likely than men to have it. Focused ultrasound neuromodulation could provide noninvasive pain relief as an alternative to the current treatment options for CTS, which include medication, physical therapy, and surgery.
Nerve damage in the arms or legs is called peripheral neuropathy. The peripheral – or outer nerves away from the spinal cord and brain – sense and process information about pain, temperature, touch, and balance. Combining information from these senses is a form of nerve signal processing is called “somatosensation.” Beyond treating CTS, this study also sought to better understand how to modulate somatosensation with focused ultrasound.
The Investigational Review Board–approved clinical research study enrolled 18 healthy participants plus 6 people (3 male and 3 female) with CTS for a total of 24 subjects. After using ultrasound imaging to locate the median nerve but also map the induced nerve displacement during focused ultrasound, targeting was initiated 7–10 cm from the wrist. The focused ultrasound was applied with a Sonic Concepts transducer driven by the Verasonics Vantage system with customized imaging techniques by the Konofagou lab. An electroencephalography (EEG) cap was fitted onto each participant’s head to evaluate changes in nerve transmission during the focused ultrasound treatment. Researchers collected data on these somatosensory evoked potentials (SSEPs) by measuring pain, stiffness, and numbness as markers of sensation.
Results showed that focused ultrasound significantly reduced the SSEPs in both healthy participants and those with CTS. An average pain reduction of 40.6% was reported in the CTS group. The research team concluded that median nerve displacement-guided focused ultrasound slowed the conduction of nerve signals when the nerve fibers were accurately targeted. The analgesic effects (reduced pain and stiffness) lasted 1–3 days. The opposite was true if the treatment was performed blindly (i.e., no pain reduction was achieved if the nerve was accurately targeted or displaced).
“With a clever study design, these researchers used EEG to show how a pain signal detected at the wrist travels via the spinal cord neurons to reach the brain,” said Hongchae ‘Iris’ Baek, PhD, the Foundation’s neuromodulation program director. “By showing a decrease in amplitude, the EEG provides evidence that focused ultrasound is actively blocking—or at least dampening—the nerve signaling, which explains why the patient feels less pain.”
“We are very excited to demonstrate these initial efficacy results on CTS patients, which included EEG measurements independent of the verbal testimonies of reduced pain sensation with clear differentiation from sham treatments,” said Dr. Konofagou. “More recently, we have demonstrated in preclinical studies that nerve treatment with focused ultrasound also induces anti-inflammatory effects similar to pharmacological treatment but lasting longer. We are excited to demonstrate these effects in a variety of neuropathies, including in an ongoing study in patients with neurofibromatosis type 1.”
This study was funded by the National Institutes of Health (National Institute of Biomedical Imaging and Bioengineering) and the Focused Ultrasound Foundation.
See IEEE Transactions in Biomedical Engineering
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