Evaluation of the Relationship Between Optic Nerve Diameter and Optic Nerve Sheath Diameter Measured by Transorbital Sonography With Clinical, Radiological, and Electrophysiological Parameters in Multiple Sclerosis Patients

Evaluation of the Relationship Between Optic Nerve Diameter and Optic Nerve Sheath Diameter Measured by Transorbital Sonography With Clinical, Radiological, and Electrophysiological Parameters in Multiple Sclerosis Patients

The primary aim of this study is to evaluate the reliability of optic nerve diameter (OND) and optic nerve sheath diameter (ONSD) measurements made with transorbital sonography (TOS) and magnetic resonance imaging (MRI) in patient groups that may progress with subclinical optic atrophy over time, such as those with multiple sclerosis (MS). The secondary aims of this study are to compare the relationship of TOS with visual evoked potentials (VEP) and optical coherence tomography (OCT) parameters used in the assessment of the afferent visual pathway in MS and its clinical subtypes and to evaluate the potential of TOS as a diagnostic and monitoring tool for detecting optic nerve atrophy, subclinical axonal loss, and clinical disability in MS.

The study included 102 patients with MS-81 with relapsing-remitting MS (RRMS), 19 with secondary progressive MS (SPMS), and 2 with primary progressive MS (PPMS)-as well as 34 healthy controls, all selected according to the inclusion and exclusion criteria. Demographic data for all participants, and clinical characteristics of the MS patient group, were recorded. Expanded Disability Status Scale (EDSS) measurements were performed for the patients. Then, TOS, orbital MRI, VEP and OCT examinations were applied to the individuals in the patient group on the same day for each eye. Measurements recorded included OND and ONSD by TOS and MRI, P100 latency and amplitude by VEP, and peripapillary retinal nerve fiber layer (pRNFL) thickness by OCT. In the healthy control group, OND and ONSD were measured using only transorbital TOS to establish normal measurement ranges.

Inclusion Criteria:

• Being between the ages of 18-65
• Having been diagnosed with Multiple Sclerosis
• Undergoing disease-modifying therapy (DMT) for more than 6 months
• EDSS score ≤ 7

Exclusion Criteria:

• Patients whose Multiple Sclerosis diagnosis is uncertain
• Having ocular pathology that may affect optic nerve measurements (e.g., glaucoma, high myopia, history of ocular surgery)
• Having major systemic diseases that may affect optic nerve measurements (e.g., diabetes mellitus, hypertension)
• EDSS score > 7
• Having experienced a clinical relapse or optic neuritis within the last 6 months.