<p>Evaluating optic nerve diameter as a possible biomarker for disability in patients with multiple sclerosis</p>

Abstract

Background and purposeThe development of new biomarkers for multiple sclerosis (MS) is of paramount importance to improve our ability to predict disease progression and disability. The aim of this study was to evaluate the potential role of the optic nerve diameter (OND) measured by ultrasonography as a biomarker of early disability in patients with relapsing-remitting multiple sclerosis (RRMS).MethodsForty-nine RRMS patients, 23 with a history of optic neuritis (MS-ON) and 26 without a history of optic neuritis (MS N-ON), and 50 age- and sex-matched healthy control subjects were included in the study. The OND and optic nerve sheath diameter (ONSD) were measured by transorbital sonography (TOS), and the retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) thicknesses were measured by optical coherence tomography (OCT) using the Optovue RTVue™ system (Optovue, Inc., Fremont, CA, USA).ResultsThere was no significant difference between the patient (whether ON or N-ON eyes) and control groups in either the OND (p=0.979) or the ONSD (p=0.911). However, patients with an expanded disability status scale (EDSS) score >2 had a significantly lower OND and RNFL thicknesses (p=0.014, p=0.010 respectively) than patients with an EDSS score ≤2. Statistical logistic regression revealed that OND was an independent predictor of EDSS>2 (p=0.044, OR =0.000, 95% CI=0.000–0.589).ConclusionThe OND, as measured by ultrasonography, could be potentially used as a biomarker for the detection of early disability in RRMS patients.

Evaluation of transorbital sonography measures of optic nerve diameter in the context of global and regional brain volume in multiple sclerosis

“…The lack of correlation between OND and other disease parameters (disease duration, EDSS) was an unexpected result, since previous studies 15,31,38,39 have shown an inverse correlation between these values, which is to be expected since atrophy is continuous during the course of the disease. Results are, however, conflicting: a study reported no associations between OND and disease duration but showed that OND and EDSS correlate 47 .…”

“…Studies that investigate this association between optic nerve parameters and conventional MS-related markers report conflicting results and are few in number, mainly focusing on the relationship between the optic nerve sheath diameter, disease parameters and altered brain structure 39 . Bare optic nerve diameter, however, might be more representative of axonal loss, therefore it might reflect structural brain alterations more accurately 15 .…”

“…It has high intra-and interobserver reproducibility 13,14 , and it is used extensively in the examination of the anterior visual pathway. OCT has proven to be reliable in detecting the atrophy of retinal fibres, which correlates well with axonal loss 15 , brain atrophy [16][17][18] as well as the degree of disability 17,[19][20][21] and visual impairment [22][23][24] in MS patients 15,20,[25][26][27][28][29] . Furthermore, previous studies have shown that there is close correlation between retinal nerve fibre layer (RNFL) thickness and optic nerve diameter suggesting that by measuring OND, one can indirectly assess axonal loss as well 30,31 .…”

Outcome measures assisting treatment optimization in multiple sclerosis

“…For each 1-year increase in the duration of disease, there was an associated decrease of 0.2% in the superficial vascular plexus; and overall, lower density was associated with higher EDSS scores [ 104 ]. In addition, optic nerve diameter and RNFL thickness were significantly lower in individuals with an EDSS score > 2 than in those with an EDSS score ≤ 2 [ 105 ]. Moreover, researchers have shown correlations between diminished RNFL thickness on OCT and MRI volumetric degeneration of the corpus callosum [ 106 ] and brain parenchymal fraction and cerebrospinal fluid (CSF) volume [ 107 ] and correlation between rates of ganglion cell + inner plexiform layer and whole brain atrophy [ 108 ].…”