Report Touts New Nerve Imaging Technique
A new technique for taking pictures of nerves inside the human body may revolutionize the diagnosis of nerve damage, particularly injuries that have previously been difficult or impossible to locate, according to researchers at UCLA and the University of Washington.
Using the pictures minimized surgical damage and speeded healing in patients by guiding surgeons directly to the site of nerve injuries, the researchers said. In some cases, it allowed surgical treatment for injuries that could not be found with conventional techniques, they report Thursday in the Journal of Neurosurgery.
“This is the first time we have had a specific way to look at the nervous system,” said Dr. John Mazziotta of UCLA, who was not involved in the research. “It’s as if you could look into a building and just see the wiring. . . . Clinically, we can determine if a nerve is severed or just stretched, if it has been infiltrated by a tumor or is just being compressed. It will really have diagnostic importance.”
The researchers first reported three years ago that they had modified conventional magnetic resonance imaging (MRI) scanners so they could, for the first time, view individual nerves.
Thursday’s report on the first 242 patients studied suggested that the imaging process will have broad utility in the future, said Dr. Aaron G. Filler of UCLA, one of the technique’s developers.
The technique reduces the number of exploratory surgeries performed to locate damaged nerves, he said, and allows surgical treatment for patients who would otherwise receive only palliative treatment at a pain center.
The new approach may be especially valuable for individuals who have nagging pain whose source defies conventional diagnostics. “There are certain times when you can’t find the site of a nerve injury,” said Dr. Mark Hallett, clinical director of the National Institute of Neurological Diseases and Stroke in Bethesda, Md. “This would be very useful to have” in those cases.
The technology is already in use at UCLA, the University of Washington and St. George’s Hospital Medical School in London, Filler said, and other medical centers are beginning to adapt their MRI scanners as well. “Within five years, this may be used on hundreds of thousands of patients annually,” Hallett predicted.
MRI is a relatively recent technique that has substantially improved physicians’ ability to look inside the body. In MRI, the patient is immersed in a strong magnetic field and bursts of radio-frequency energy are used to stimulate water molecules. Water molecules in different tissues respond differently to the signal, and that response is detected by monitoring the magnetic field, producing highly detailed pictures.
In conventional MRI scanners, the images of nerves are hidden, overwhelmed by the signals from nearby bone and muscle. The team at the University of Washington modified the computer programming and detectors in a scanner so it ignores these signals. Images of other tissues virtually disappear, Filler said, leaving behind a three-dimensional picture of the nerve “like the smile of the Cheshire cat in ‘Alice in Wonderland.’ ”
Not only do the nerves appear, but areas of damage are readily apparent, showing up as a bright spot in the case of a compressed nerve or as a narrowed spot in the case of a pinched nerve, the team reported.
Previous diagnostic techniques often could assign the damage only to a general area, and surgeons would have to expose the nerve and explore its entire length in that area to locate a lesion. Now, they can proceed directly to the site with minimal surgery. In some cases, they even use remote, TV-guided surgical techniques to minimize surgical incisions further, allowing patients to be released from the hospital in as little as a day.
For example, in damage to the brachial plexus--the nerve net that spreads from the spinal cord to the armpit--the normal procedure is a six- to eight-hour operation in which the surgeon physically traces all the nerves looking for the problem. The new technique, called MR neurography, can image the entire brachial plexus and easily identify the lesion, the team reported.
“This technique may well have a significant impact on . . . health care costs, since it may eliminate the need for other investigations” and tests, said Dr. Richard Winn of the University of Washington. The ability to locate the source of nagging pains, Mazziotta added, could greatly reduce not only medical costs, but the costs of time lost from work. “Nerve compressions are a major economic issue,” he said.
