Quick, Inexpensive Retina Scan Can Predict Brain Damage Caused by MS
Method is one-tenth the cost of an MRI (Oct. 17)
An inexpensive, 5-minute eye scan can accurately assess the amount of brain damage in patients with multiple sclerosis (MS) and may offer clues about how quickly the disease is progressing, according to the results of two studies conducted at the Johns Hopkins University School of Medicine in Baltimore, Md. The studies were published in recent issues of The Lancet Neurology and the Archives of Neurology.
Researchers used optical coherence tomography (OCT) to scan nerves in the back of the eye, and applied special software that is capable of assessing previously immeasurable layers of the light-sensitive retinal tissue. The scan does not use harmful radiation and is one-tenth the cost of magnetic resonance imaging (MRI). The software will soon be available commercially.
In the Lancet paper, Peter A. Calabresi, MD, and his team reported measuring the thickness or swelling of the inner nuclear layer of the retina in 164 patients with MS and in 60 healthy controls. The researchers followed changes in these tissues over 4 years. At the same time, they used brain MRI scans to measure inflammation spots directly, and performed clinical tests to determine disability levels.
The more inflammation and swelling the researchers found in the retinas of the MS patients, the more inflammation showed up in their brain MRIs. The correlation, they said, affirmed the value of the retinal scans as a stand-alone surrogate for brain damage. Having such information easily available could allow physicians to accurately tell how far the disease has progressed, and to better advise patients about how they should proceed with their care.
The researchers also found microcystic macular edema — tiny pockets of fluid typically seen in older, usually diabetic people — in the central part of the retinas of 10 (6%) of the MS patients. While Calabresi cautions that eye scans do not yet have primary diagnostic value for MS, he says that finding a cyst on the eye of a young, healthy patient might be reason to have the patient evaluated for MS.
In the second paper, published in the Archives of Neurology, Calabresi and colleagues looked at eye and brain scans from 84 MS patients and 24 healthy controls. This time, they focused on two other deep retinal layers — the ganglion cell layer + inner plexiform layer (GCL+IPL), and the peripapillary retinal nerve fiber layer (pRFNL). Greater cell wasting in those areas was strongly correlated with more atrophy in the gray matter of the brain, indicating more nerve damage from MS.
Calabresi says this finding is particularly important because neurodegeneration is so difficult to gauge accurately. In a young person with MS, the brain may be atrophying but may cause no symptoms because the brain is able to compensate for what is being lost. Ultimately, however, the loss of brain cells becomes apparent and is irreversible.
Calabresi says his findings could change how researchers approach MS, which is believed to be caused by an immune system that wrongly attacks myelin — the fatty protein that insulates nerves and helps them send electrical signals that control movement, speech, and other functions. The usefulness of the retina scans raises the possibility that there could be something else going on in MS, as there is no myelin deep in the retina of the eye. If the immune system is attacking something else along with myelin, it could help researchers find new medications to target the incapacitating symptoms of MS, such as blurred vision, numbness, and weakness.
Source: Johns Hopkins University School of Medicine, October 17, 2012.