Excerp from eMS News, the electronic Newsletter of the Rocky Mountain MS Center
Active multiple sclerosis (MS) outside of the optic nerve is associated with significant and rapid thinning of the retinal nerve fiber layer (RNFL), according to a new study published in the January 2013 issue of Neurology. If results can be replicated in other studies, RNFL analysis may provide a new way of tracking the effectiveness of neuroprotective MS treatments.
To measure the RNFL, study researchers used Spectral Domain Ocular Coherence Tomography (SD-OCT). OCT places an optical beam across the retina to produce high-resolution images of the internal retinal structure. The RNFL is the innermost lay of the retina and is comprised of the nerve fiber bundles that will compose the optic nerve.
In multiple studies, researchers have demonstrated that RNFL loss occurs in the MS patients regardless of their disease subtype or history of optic neuritis. Studies also show that increased thinning of RNFL is evident in both untreated and treated MS patients, regardless of their clinical symptoms. This suggests that retinal thinning occurs regardless of inflammation and disease activity within the optic nerve (optic neuritis).
If RNFL loss occurs outside of disease activity in the optic nerve, then RNFL measurement by OCT would be an ideal marker of the effectiveness of potential neuroprotective treatments in the brain. The effectiveness of current MS therapeutics is determined by disease activity, which is combination of relapse rate, disability accrual, and MRI lesions. Neural loss on the other hand, is more accurately measured by brain volume. This study suggests that RNFL thinning may be an important additional marker.
“A neuroprotective treatment, by definition, protects neurons independent of their mechanism of injury,” explains Dr. Jeffrey L. Bennett, M.D., Ph.D., Professor of Neurology & Ophthalmology at the University of Colorado Denver. “Therefore, OCT may provide a unique tool to identify neural preservation independent of other measures of disease activity. More research is needed however, to determine if OCT can replace or supplement current clinical measures of MS activity. If approved by the FDA as a biomarker of MS activity, OCT may facilitate MS clinical research by decreasing the time and cost of clinical trials.”
John N. Ratchford, MD, from the Johns Hopkins University School of Medicine in Baltimore, and colleagues conducted OCT scans every six months on 223 study participants for an average follow-up period of 21.1 months. Contrast-enhanced brain magnetic resonance imaging (MRI) scans were performed at the beginning of the study to establish a baseline for comparison, and were performed annually.
Researchers observed a 42% faster thinning of the RNFL in patients with MS relapses compared to MS patients with no relapses.
In addition, researchers reported:
• MS patients with gadolinium-enhancing lesions (inflammatory lesions) had 54% faster thinning
• MS patients with new T2 lesions had 36% faster thinning than MS patients without
• Participants whose level of disability got worse during the study had 37% more thinning, compared to patients whose level of disability did not change
• Participants who had the disease less than five years showed 43% faster thinning compared to those who had the disease more than five years
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