• Written By: Michael Vaphiades, DO

    This prospective, cross-sectional study published in March by PLoS ONE evaluated retinal nerve fiber layer (RNFL) thickness using optical coherence tomography (OCT) in patients presenting with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS). The results indicate that axonal damage measured by OCT is present in any type of CIS, even in myelitis forms and not only in optic neuritis (ON), as previously seen.

    The authors believe this to be the first study to demonstrate early retinal axonal layer thinning detected by OCT in patients with any type of CIS, including those with isolated myelitis. As expected, this thinning was mild but identifiable with Stratus OCT software.

    Consecutive patients presenting at a neurology department with a single episode of CIS suggestive of MS were recruited for the study. Twenty-four patients (eight optic neuritis, six spinal cord syndromes, five brainstem symptoms and five sensory and other syndromes) participated and underwent OCT within one month of the onset of the clinical episode.

    Thirteen patients had decreased RNFL thickness in at least one quadrant. Mean RNFL thickness was 101.67 ± 10.72 mm in retrobulbar ON eyes and 96.93 ± 10.54 in unaffected eyes. Three of the six patients with myelitis had at least one abnormal quadrant in one eye.

    Eight patients fulfilled dissemination in space (DIS) MRI criteria. The presence of at least one quadrant of an optic nerve with an RNFL thickness at a P < 5% cut-off value had a sensitivity of 75 percent and specificity of 56 percent for predicting DIS MRI.

    The authors conclude that OCT can detect axonal damage in very early disease stages and seems to have high sensitivity and moderate specificity for predicting DIS MRI. However, they say that the relationship between RNFL thinning in CIS and progression to MS is still unclear.

    Prospective studies with long-term follow-up are necessary in order to establish the prognostic value of baseline OCT findings and the capacity of this technology to predict conversion to clinically definite MS. They note that OCT could represent a potential tool for detecting and monitoring axonal protective effects of new neuroprotective therapies.