Peering into the eyes to determine brain health

Patients with multiple sclerosis often display decreased brain volume, a consequence of brain-cell breakdown brought on by the disease. MRI can detect the change, but it is costly and time-consuming. Researchers led by Dr. Peter Calabresi of Johns Hopkins University in Baltimore have found that screening for the disease with optical coherence tomography (OCT) may be less expensive than using MRI.

The scientists assessed nerve fiber thickness by imaging the retinal nerves of 40 patients with multiple sclerosis and of 15 healthy patients using a Carl Zeiss OCT device. They measured the volume of patients’ brain matter and fluid with a Philips Medical Systems MRI scanner.

Images of three patients’ brains show increasing degradation of brain tissue (left to right). Retinal fiber layer thickness in the right (OD) and left (OS) eyes decreases correspondingly. Courtesy of Eliza Gordon-Lipkin, Johns Hopkins University.

In the 20 patients with relapsing remitting multiple sclerosis, the most common form of the illness, thinning of the optical nerve typically accompanied loss of brain volume. Results from the remaining participants with either secondary or primary progressive multiple sclerosis — less common, more severe types of the disease — showed a weaker but still significant correlation. OCT and MRI data displayed an insignificant relationship in patients unaffected by multiple sclerosis. The work is detailed in the Oct. 16 issue of Neurology.

According to the researchers, these results show the potential of OCT for detecting damage to the nerves from multiple sclerosis. Because the nerve fibers frequently degrade before the brain volume decreases, the technique may help catch the disease in its earlier, less detrimentalstages. Furthermore, when multiple sclerosis affects primarily the spinal cord, as in secondary progressive multiple sclerosis, MRI images of the brain may provide little useful information. OCT may be a more convenient screening option, requiring about one-tenth the time and money needed for an MRI scan.

The researchers stress, however, that optical nerve degradation revealed by OCT could indicate problems other than multiple sclerosis. Thus, the procedure may be used best for screening prior to more detailed analyses. Longer-term studies should help clarify variable correlation of nerve fiber thickness and brain volume data, among other issues, allowing clearer definition of the method’s exact role in prognosis. The researchers have begun a three-year investigation to determine whether OCT changes can forecast brain atrophy and disease. Other applications of OCT are highlighted in a feature on page 46 of this issue.