Years ago as an engineer, I learned about using ultrasound to evaluate structures in the body. Ultrasound uses tuned sound waves and their reflections from structures to study a variety of things. In the body, one can look at various soft tissues from the heart, to the unborn infant, to nerves, muscles and a variety of tissues using ultrasound technology. In physical therapy, ultrasound can be used to provide deep tissue heating. Outside of the body, it is used in non-invasive testing of many materials including airplanes, looking for stress fractures and locations of potential failure. The overall unique feature is that sound waves are being used safely, without radiation to look at the body.

Going on to the next level of thinking, sound waves are interesting since they act like any other wave. That means waves that are exact opposites of each other can cancel each other out when they meet; this process is used in noise cancelling headphones. Combining waves from several sources can also enlarge sound waves. Sophisticated computer techniques then can focus a number of beams in one point and at this location all the energy could cause the area to heat up. For years I thought about the potential of being able to focus ultrasound beams. Now with some very sophisticated equipment, this is finally beginning to be tried on an experimental basis.

Concentrated Ultrasound and Pain

A medical trial has begun at the University of Maryland to focus beams of ultrasound to a small area in the brain in order to treat certain conditions, including neuropathic pain. Other conditions being treated are movement disorders like the tremors caused by Parkinson’s Disease. The specific pains being treated are suppose to be caused by central damage to the nervous system and must include problems in the central processing of sensory signals in the brain. The pain must be from documented damage to nerves, the spinal cord, or into the neurons in the brain. Furthermore, all people in the study currently must have failed conventional techniques, it will be given only to five patients, and they must have had phantom limb pain from an amputation, a spinal cord injury or pain that does not respond to neurosurgery.

For now, the patients are placed in a special apparatus within an MRI scanner, and over 1,000 elements focus ultrasound beams to a discreet 5-6 millimeter area of brain that is then burned and destroyed. This treatment of pain is pretty unique. At this time we have not clearly identified a region in the brain that is definitely responsible for ongoing difficulties with chronic neuropathic pain. In the past, physicians have tried to cut out various areas in the brain and even place electrodes in the brain to pace out possibly abnormal signals causing pain. Surgeons have cut nerves in all kinds of places to prevent people from having painful sensations and have even cut off body parts in attempt to solve pain problems.

However all these solutions have found very limited use and usually failed over time to be successful. The main reason is pain is a extremely complex event far beyond just electrical signals from a damaged location in the body. Pain is a perceptual event involving an emotional response to some sort of signal that can be very diffuse in the body. Destroying a part of the brain is not a reversible event especially since we have no definite way to determine if a specific location in the brain just controls all the pain signals.  

The concept of focusing an ultrasound beam to one place in the brain to stop chronic neuropathic pain is intriguing. Pausing for a second and realizing that the process destroys a segment of brain makes one review our history of other tissue destroying attempts to cure pain. Chronic pain is extremely complex. Pain physicians know from experience that there is rarely a simple solution for most patients. We have a long history of failed destructive techniques to treat pain. No matter how intriguing this may sound, until we can absolutely determine that there is an definitive correlation to pain and a specific area in the brain and that this area is causing the pain, destroying parts of the brain appears to be ill-advised. Often the less we do as physicians, the better off it is for the patient. Or as part of the Hippocratic Oath says, “do no harm.”