University of Maryland physician-scientists have treated the first patient in the United States with MRI-guided focused ultrasound for neuropathic leg pain as part of a pilot clinical trial.
"If we can interrupt or carefully destroy the nucleus in the brain responsible for processing and amplifying pain signals, then we can disrupt this network and stop the neuropathic pain," says principal investigator Dheeraj Gandhi, MBBS, professor of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine (UMSOM) and director of neurointerventional radiology at the University of Maryland Medical Center (UMMC).
An estimated 100 million Americans suffer from neuropathic pain, a type of chronic pain caused by nerve damage or a malfunctioning nervous system that carries pain signals to the brain. The pain is not precipitated by a physical event such as accidentally hitting your thumb with a hammer. It can be a result of a number of things, including injury, infection, metabolic disease or a traumatic event. People often describe neuropathic pain as burning, tingling, pins and needles, and shooting or stabbing pain.
Chronic neuropathic pain is difficult for doctors to treat because it doesn't respond well to common pain medications. Current treatments include medications, nerve blocks, implantable devices and physical therapy. Approximately $530 billion is spent annually in caring for people with neuropathic pain. It can cause marked disability in some people, with many unable to work or be productive. Patients not only have pain, but they can become depressed, have trouble thinking clearly or falling sleep. The medications prescribed often impact cognition and executive function, and there are significant risks for drug toxicity and addiction. There is an unmet need for safe and more effective pain therapies.
Tammy Durfee of Kansas City, Missouri, woke up one morning with a pain in her hip that was so severe she couldn't get out of bed. Doctors couldn't figure out what was causing the pain, and nothing seemed to relieve it. "I couldn't sit still. I was always fidgeting and moving around to try and get comfortable, but I never could," says the 56-year-old pharmacy supervisor. Over the next eight years, she would try electronic nerve stimulators, cortisone shots, narcotics and other medications. Some treatments didn't work at all; others would work for a little while, and then stop.
An evaluation of her brain activity showed that brainwaves were misfiring, sending phantom pain signals to parts of her body. Her neurosurgeon diagnosed cerebral dysrhythmia as the cause of her neuropathic pain, and recommended a radiation procedure. But after learning her insurance wouldn't cover it, Durfee started researching alternative treatment options. She found a center in Switzerland that treats patients like her with MRI-guided focused ultrasound, and then saw that the University of Maryland Medical Center was recruiting for a clinical trial of the same procedure. "After reading about the Switzerland study and how it was successful there, I just went for it," says Durfee. She travelled to Baltimore and had the focused ultrasound procedure on September 13, 2018.
MRI-guided focused ultrasound is a novel approach to treating neuropathic pain that does not use radiation or invasive surgery. Instead, doctors use acoustic energy to ablate cells within the body. Magnetic resonance imaging (MRI) allows doctors to define the target inside the body and create a heat map so they know exactly where to aim. In this case, doctors guided ultrasound waves through Tammy Durfee's skin and skull to precisely target the central lateral nucleus of the thalamus, which serves as the brain's message relay center.
"We have pioneered a technique for high-resolution structural imaging of the thalamus and brain, which allows us to perfectly localize and target the nucleus responsible for amplifying the neuropathic pain network," says Dr. Gandhi. He notes that every person's skull shape and brain structure is different; for this reason, a personalized approach for every patient is necessary.
Before starting the procedure, Durfee's head was shaved and a metal frame affixed. She laid face up in an MRI machine as the surgical team attached her head frame to the focused ultrasound transducer, which converts sound energy to heat energy. Chilled water circulated around her head to keep it cool during the three-hour procedure. Durfee was awake the entire time. Doctors gradually heated up the target, all the while getting real-time feedback from Durfee to learn whether she was experiencing more or less pain, and to make sure she wasn't having any unwanted side effects.
"Imagine a race where all the runners have different obstacles on their way to the finish, but they all must reach the target at the exact same moment," says Howard M. Eisenberg, MD, professor and chair of neurosurgery at UMSOM and neurosurgeon at UMMC. "That is what we are doing with focused ultrasound."
Once doctors were sure they had identified the exact target, they increased the temperature and created bilateral lesions, effectively destroying the part of the brain responsible for sending pain signals to Durfee's hip and leg.
When the treatment was over, Tammy Durfee got up off of the MRI table and did something she hadn't been able to do in years. She danced. "I feel great," Durfee says. "I'm able to do fun things with my grandkids again, like go to Legoland and the zoo."
Currently, the study is limited to treat certain indications of neuropathic pain, which are radiculopathy (sciatica), spinal cord injury and phantom limb pain. If this study is a success, then the next step is to hold a larger trial and expand to other types of neuropathic pain that are widespread, such as diabetic neuropathy pain.
The clinical trial of focused ultrasound to treat neuropathic pain is currently recruiting qualified patients. UMMC is the only treatment site. The Focused Ultrasound Foundation is funding the study. Dr. Eisenberg is a consultant to Insightec. For more information about the trial, please contact Charlene Aldrich, RN, MSN, clinical research manager, at 410-328-5332.
By: James Ives, MPsych