Optical coherence tomography: A useful tool for identifying subclinical optic neuropathy in diagnosing multiple sclerosis

Care of patients with multiple sclerosis (MS) has evolved in the last decade to shorten the time to confirm the diagnosis of clinically definite MS and to start disease-modifying drugs as soon as possible to decrease permanent disability and the risk of progressive disease. Such trends have been achieved by improving our understanding of the role of paraclinical tests such as the presence of oligoclonal bands on CSF examination, visual evoked potentials, or MRI imaging of the brain or spinal cord. Recently, the evidence that retinal damage detected with optical coherence tomography (OCT) is a sensitive test for identifying MS-related damage in the anterior visual pathway has been added to the diagnostic armamentarium.^1,2 However, symptomatic or subclinical optic nerve lesion as evidence of dissemination in space has not been included in the 2017 MS diagnostic criteria because the available data concerning the diagnostic specificity and sensitivity were considered to be insufficient to justify its inclusion at that time.³ Despite the fact that optic neuritis is one of the most characteristic findings of MS, the optic nerve has not been designated as a fifth lesion site³ because imaging and other data were unavailable to support its inclusion. Recently, Brownlee et al.⁴ found that the inclusion of symptomatic optic nerve involvement in patients with optic neuritis from their clinically isolated syndrome (CIS) cohort improved the accuracy of 2017 MS diagnostic criteria. This study did not include OCT. Today, evidence of optic neuritis may be confirmed clinically by visual evoked potentials or by imaging with MRI or OCT. Subclinical or oligosymptomatic cases can be confirmed with these complementary tests, and new technologies such as OCT can help to characterize the underlying conditions producing optic neuritis. Further refinement of the diagnosis of optic neuritis is now possible with the introduction of the aquaporin 4, glial fibrillary acid protein, and myelin oligodendrocyte protein antibodies, which help to exclude variants of optic nerve inflammation. Therefore, it is time to re-evaluate the inclusion of optic nerve as a fifth lesion site for dissemination in space for the diagnosis of MS.