Afferent visual pathways in multiple sclerosis: a review

Multiple sclerosis (MS) is a disease of the central nervous system that involves inflammation and demyelination at multiple sites and causes a wide variety of clinical presentations with variable neurological deficits. The visual pathways are frequently involved with either visual or motor dysfunction. Optic neuritis (ON) is one the most common and best characterized presentations of the disease, but there are many other manifestations depending on the site of the lesion. Eyes that have never had ON show slow progressive loss of axons and retinal ganglion cells. Previously unrecognized optic radiation lesions may be associated with residual latency delays on visual evoked potentials. Both anterograde and retrograde degeneration may occur along the visual pathway. This review covers the features of MS in the anterior and posterior visual system and describes advances that have been made with newer techniques such as retinal optical coherence tomography (OCT), magnetic resonance imaging (MRI) with diffusion tensor imaging and probabilistic tractography (DTI) and multifocal visual evoked potentials (mfVEPs). We report on the inter-relationship between these measures of structure and function, and how they may be used as biomarkers for the disease.