Neurodegeneration is difficult to accurately gauge, says Peter A. Calabresi, MD, a professor of neurology at the Johns Hopkins University School of Medicine (Baltimore, MD). But a good method for assessment could make a difference in how physicians approach treatment for their patients with multiple sclerosis (MS). And optical coherence tomography (OCT) seems to provide that method.
Calabresi and his colleagues have authored two papers describing the use of OCT to scan nerves deep in the back of the eye, applying software they co-developed that can assess previously immeasurable layers of the light-sensitive retinal tissue.
In one paper, the team reports measuring thickness or swelling of the retina's inner nuclear layer in MS patients and controls, and following tissue changes over four years.1 They also used brain MRI to measure inflammation spots directly, and performed clinical tests to determine disability levels. The more retinal inflammation and swelling the researchers found in the MS patients, the more inflammation showed up in their brain MRIs. The correlation, they said, affirms the value of the retinal scans as a stand-alone surrogate for brain damage.
The team also found microcystic macular edema in the central retinas of some MS patients. While Calabresi cautions that eye scans do not yet have primary diagnostic value for MS, finding such a cyst on a young, healthy person might be reason to have her evaluated for the disorder.
In the other paper, the team looked at eye and brain scans of MS patients and controls, this time focusing on two other deep retinal layers: the ganglion cell layer + inner plexiform layer (GCL+IPL), and the peripapillary retinal nerve fiber layer (pRFNL).2 Greater cell wasting in those areas was strongly correlated with more atrophy in the gray matter of the brain, signifying more nerve damage from MS.
Besides providing a helpful guide for personalized treatment, Calabresi says these findings could shift how researchers approach MS. The scans indicate that MS may incite autoimmune attack of something other than myelin, which has been the traditional suspect. Incidentally, OCT uses no harmful radiation and is one-tenth the cost of an MRI. The software will soon be widely available commercially.
1. S. Saidha et al., Lancet Neurol., 11, 11, 963 (2012).
2. S. Saidha et al., Arch Neurol., 1–10, doi:10.1001/archneurol.2013.573 (2012).