Many imaging tools are available to study what’s happening in the brain, assisting physicians in better diagnosing diseases such as Alzheimer’s, Parkinson’s, and multiple sclerosis, or MS. The most popular of these tools is magnetic resonance imaging — more commonly known as MRI.
Seema Tiwari-Woodruff, a professor of biomedical sciences in the UC Riverside School of Medicine and an MS expert, and collaborators Andy Obenaus of UC Irvine and Neil Harris of UCLA suggest in a recently published research paper that diffusion tensor imaging, or DTI, which has been around since 2011, is a more efficient imaging technique to examine changes in water flow in the brain. These changes, in turn, provide information about the health of axons — data that is particularly useful in diagnosing MS, the autoimmune and neurodegenerative disease that affects about 2.3 million people worldwide.
“DTI sees ultra-structures and detects remyelination of axons in mice which already had drug-induced demyelinated axons,” Tiwari-Woodruff said. “This technology could be used one day to efficiently detect remyelination in MS patients. DTI can identify changes in myelination that MRI would miss.”
The myelin sheath is a protective covering around the axons of nerve fibers — similar to insulating material around a copper wire. It is essential for the proper functioning of the brain and spinal cord. When myelin is intact, water flow through the axon is uninterrupted and signals travel smoothly. When myelin is damaged or missing, which happens in MS, water in the axons diffuses abnormally. DTI can easily and accurately detect these altered diffusion patterns.
An unpredictable disease that disrupts the flow of information within the brain and between the brain and the body, MS is triggered when the immune system attacks the myelin sheath. The demyelination that follows causes a disruption of nerve impulses. As the protective sheath wears off, the nerve signals slow down or stop, and the patient’s vision, sensation and use of limbs get impaired. Permanent paralysis can result when the nerve fibers are completely damaged by the disease.
In the lab, Tiwari-Woodruff’s team administered Indazole chloride (IndCl), a synthetic compound, to mice with demyelinated axons. (In 2014, a team assembled by Tiwari-Woodruff reported that IndCl can remyelinate damaged axons and alter the immune system.) The researchers were able to see changes in remyelination in the mouse brain using the DTI technology.
“Structural MRI detects lesions that arise due to demyelination, inflammation, and axon damage,” Tiwari-Woodruff said. “It provides no clues, however, to the details of the pathology. DTI, on the other hand, can tell us if, and how well, remyelination is occurring by measuring diffusion of water within the brain’s tissues, thus providing information on these tissues’ structural integrity. As a result, physicians using DTI can more efficiently diagnose MS in patients.”
The research paper, titled “Diffusion tensor imaging identifies aspects of therapeutic estrogen receptor β ligand-induced remyelination in a mouse model of multiple sclerosis,” appears in the journal Neurobiology of Disease. The research was supported by grants to Tiwari-Woodruff from the National Institutes of Health and the National Multiple Sclerosis Society.