OCT detects asymptomatic optic nerve involvement in clinically isolated syndrome

Identifying asymptomatic optic nerve lesions in clinically isolated syndrome requires a lower intereye retinal thickness difference threshold than previously reported, according to findings published in Neurology.

Clinically isolated syndrome is classified as “one of the MS disease courses,” according to the National Multiple Sclerosis Society. The syndrome is an initial episode of neurologic symptoms that lasts for at least 24 hours and is the result of inflammation or demyelination in the central nervous system. Individuals who experience clinically isolated syndrome with brain lesions detected through MRI that are similar to those seen in MS have a 60% to 80% change of a second neurological event and an eventual diagnosis of MS, according to the organization.

Olivier Outteryck, MD, PhD, of the University of Lille in France, and colleagues performed a cross-sectional study of patients who had presented with clinically isolated syndrome (CIS) in the preceding 4.5 months. All patients underwent optical coherence tomography (OCT) and brain/optic nerve MRI.

The researchers defined optic nerve involvement clinically by whether or not the patient had an episode of optic neuritis (ON) and radiologically as optic nerve hypersignal on 3D double inversion recovery. They examined the sensitivity and specificity of previously published intereye retinal thickness difference thresholds and reported “the observed optimal thresholds for identifying symptomatic optic nerve involvement but also for identifying asymptomatic optic nerve involvement (optic nerve hypersignal without ON history).” Outteryck and colleagues defined ganglion cell–inner plexiform layer (GC-IPL) and peripapillary retinal nerve fiber layer intereye retinal thickness difference (IETD) as the primary outcomes.

The final study cohort included 130 patients.

Outteryck and colleagues found that, among patients presenting with CIS and ON, 3D double inversion recovery demonstrated a hypersignal in all 41 symptomatic optic nerves and in 11 asymptomatic optic nerves. In the CIS cohort who did not have ON, a unilateral optic nerve hypersignal was present in 22 patients and a bilateral optic nerve hypersignal was present in 7 patients, according to 3D double inversion recovery. GC-IPL IETD performed better in the detection of both symptomatic and asymptomatic optic nerve lesions, with optimal thresholds of 2.83 µm (sensitivity, 88.2; specificity, 83.3%) for symptomatic lesions and 1.42 µm (sensitivity, 89.3%; specificity, 72.6%) for asymptomatic lesions.

“Detection of asymptomatic optic nerve lesions in CIS requires lower IETD thresholds than previously reported,” the researchers wrote. “GC-IPL IETD represents an alternative biomarker to MRI for the detection of asymptomatic optic nerve lesions. This study provides Class I evidence that OCT accurately identifies asymptomatic optic nerve involvement in patients with CIS.”

References:

• National Multiple Sclerosis Society. Clinically isolated syndrome (CIS). https://www.nationalmssociety.org/What-is-MS/Types-of-MS/Clinically-Isolated-Syndrome-(CIS). Accessed September 8, 2020.