A buildup of sodium in the brain detected by magnetic resonance imaging (MRI) may be a biomarker for the degeneration of nerve cells that occurs in patients with multiple sclerosis (MS), according to a new study published online in the journal Radiology.
The study found that patients with early-stage MS showed sodium accumulation in specific brain regions, while patients with more advanced disease showed sodium accumulation throughout the whole brain. Sodium buildup in motor areas of the brain correlated directly to the degree of disability seen in the advanced-stage patients.
"A major challenge with multiple sclerosis is providing patients with a prognosis of disease progression," said Patrick Cozzone, Ph.D., director emeritus of the Center for Magnetic Resonance in Biology and Medicine, a joint unit of National Center for Scientific Research (CNRS) and Aix-Marseille University in Marseille, France. "It's very hard to predict the course of the disease."
In MS, the body's immune system attacks the protective sheath (called myelin) that covers nerve cells, or neurons, in the brain and spinal cord. The scarring affects the neurons' ability to conduct signals, causing neurological and physical disability. The type and severity of MS symptoms, as well as the progression of the disease, vary from one patient to another.
Dr. Cozzone, along with Wafaa Zaaraoui, Ph.D., research officer at CNRS, Jean-Philippe Ranjeva, Ph.D., professor in neuroscience at Aix-Marseille University and a European team of interdisciplinary researchers used 3 Tesla (3T) sodium MRI to study relapsing-remitting multiple sclerosis (RRMS), the most common form of the disease in which clearly defined attacks of worsening neurologic function are followed by periods of recovery. Sodium MRI produces images and information on the sodium content of cells in the body.
"We collaborated for two years with chemists and physicists to develop techniques to perform 3T sodium MRI on patients," Dr. Zaaraoui said. "To better understand this disease, we need to probe new molecules. The time has come for probing brain sodium concentrations."