Researchers have developed a highly sensitive imaging method that directly visualizes the protective myelin sheath around nerve cells, a breakthrough that could transform the diagnosis and treatment of neurodegenerative diseases. This novel magnetic resonance imaging (MRI) procedure overcomes the fundamental limitations of current technology, providing a more accurate and quantitative map of myelin health. The technique, developed by a team at ETH Zurich and the University of Zurich, has been successfully tested in healthy adults and promises to give clinicians a clearer window into the damage caused by conditions like multiple sclerosis. By capturing signals previously too fleeting to detect, the new approach can directly measure the fatty and protein-based substance of myelin, rather than relying on indirect water-based estimates that have limited diagnostic precision for decades.
The central challenge in monitoring diseases such as multiple sclerosis (MS) has been the inability to accurately assess the state of myelin, the insulating layer essential for fast and efficient nerve signal transmission. Standard MRI technology is optimized to detect signals from hydrogen atoms in water; however, myelin is composed primarily of fats and proteins. Conventional scans therefore create an indirect picture by measuring the water trapped between the layers of the myelin sheath, a method that provides a fuzzy and often inadequate proxy for the sheath’s actual condition. This new technology solves that problem by directly imaging the myelin itself, offering the potential for earlier MS detection, more precise monitoring of disease progression, and a more effective tool for developing new therapeutic drugs.
The Challenge of Visualizing Myelin
Myelin acts as the primary insulator for nerve fibers, or axons, in the central nervous system, much like the plastic coating on an electrical wire. This fatty sheath enables the rapid conduction of electrical impulses, facilitating everything from thought to movement. In diseases like MS, the body’s own immune system mistakenly attacks and degrades this protective layer, disrupting nerve signaling and leading to a range of debilitating neurological symptoms, including vision problems, muscle weakness, and coordination difficulties. Worldwide, MS affects approximately 2.9 million people.
For decades, physicians have relied on MRI to monitor the brains of MS patients. While powerful, these conventional scanners have a significant blind spot. An MRI works by using strong magnetic fields and radio waves to generate signals from the body’s hydrogen atoms, which are overwhelmingly located in water molecules. Since myelin is comprised of lipids and proteins with very little water, standard MRIs cannot see it directly. Instead, they produce images based on the “myelin water” held between the sheath’s concentric layers. This indirect measurement has been a persistent obstacle, preventing clinicians from accurately quantifying myelin loss or repair and forcing them to rely on proxies for disease activity.
A Novel Imaging Approach
The research team, led by Markus Weiger and Emily Baadsvik of the Institute for Biomedical Engineering, engineered a system that can capture the elusive signals generated directly by the hydrogen atoms within the myelin tissue itself. This required rethinking the hardware and physics of the imaging process to detect signals that are not only weaker but also dramatically shorter-lived than those from water. The result is a method that moves beyond inference to provide direct, quantitative evidence of the myelin sheath’s integrity.
Capturing a Fleeting Signal
The physical properties of hydrogen atoms in different molecular environments are key to the new technique’s success. According to Weiger, hydrogen atoms within the dense, semi-solid structure of myelin tissue are less mobile than those in the more fluid myelin water. This restricted movement means they generate extremely brief signals that vanish within a few microseconds—a millionth of a second. Conventional MRI scanners are not fast enough to capture these ephemeral signals before they disappear, which is why their images are dominated by the more persistent signals from water molecules. The Zurich-based researchers overcame this by developing a specialized MRI head scanner with more powerful magnetic field gradients, allowing for much faster and more sensitive signal detection.
Specialized Hardware for Precision
The new system employs a custom-built head scanner that contains especially powerful magnets. These components allow the device to generate the strong magnetic field gradients necessary to record the position and state of hydrogen atoms at a much higher speed than standard clinical machines. This speed is the critical factor that enables the capture of the short-lived myelin signals. As lead author Emily Baadsvik explained, a greater change in magnetic field strength allows for faster recording of the positional information of hydrogen atoms. This hardware innovation is what finally makes the direct measurement of myelin possible, providing a level of detail previously unattainable.
From Indirect Estimates to Quantitative Maps
The new method’s output represents a significant leap forward in neurological imaging. Instead of producing images that require interpretation to infer myelin damage, the technique generates quantitative myelin maps. These images display the myelin content as a numerical value, showing the percentage of myelin present in a specific location relative to a maximum possible value. For instance, a low value on the map would indicate a significant thinning or degradation of the myelin sheath in that area of the brain.
This quantitative data allows for a much more objective and precise assessment of the disease state. Doctors can compare scans taken over time to track the progression of myelin loss with high accuracy or to determine if a particular therapy is successfully promoting myelin repair. This direct measurement eliminates the ambiguity of older techniques and provides a standardized metric for evaluating the physical state of nerve fibers.
Implications for Disease Research and Treatment
The ability to directly and accurately map myelin has profound implications for multiple sclerosis and other neurodegenerative disorders. For MS, it could lead to earlier and more precise diagnoses, as subtle myelin damage might be detected before significant clinical symptoms appear. It would also serve as an invaluable tool for monitoring the effectiveness of new drugs designed to slow or reverse myelin destruction, providing clear evidence of their biological impact.
Beyond MS, the technology could advance the understanding of myelin’s role in aging, brain trauma, and other neurological conditions. Furthermore, the researchers suggest the method’s ability to visualize solid tissue types could be extended to other areas of the body, such as imaging connective tissue, tendons, and ligaments with greater clarity.
The Path Toward Clinical Use
The new MRI procedure has been successfully demonstrated in proof-of-concept experiments on healthy adults, where it produced accurate myelin maps with a resolution of less than two millimeters. The next crucial step is to further refine the technology and test it on MS patients to validate its clinical utility. The researchers acknowledge that the system has limitations, including a lengthy scan time of around 90 minutes, which could be challenging for some patients. Despite this, the team is optimistic about its potential and hopes to collaborate with industry partners to implement the technology and eventually bring it to market for widespread clinical use. This innovation represents a pivotal step toward making the invisible damage of neurological diseases visible, heralding a new era in diagnostics and therapeutic development.