INTRODUCTION
Multiple sclerosis is a chronic inflammatory disease and one of the most common causes of neurological disability in young adults globally.1,2 Many genetic and environmental factors, demyelination, and iron-related abnormalities are the etiological and pathological causes of the MS.3-5
MS can affect all the anatomical parts of the visual system. The most often seen presentations are optic neuritis, brainstem, and spinal cord syndromes.1 Optic neuritis may be the first manifestation of multiple sclerosis.6 Acute demyelinating optic neuritis is the presenting symptom in about 20% of MS patients and affects about half of MS patients at some point in the disease course.7
Computerized tomography has limited applications in optic nerve pathologies because of the ionizing radiation and low resolution of soft tissue. Conventional and non-conventional Magnetic Resonance Imaging (MRI) such as diffusion tensor imaging, diffusion-weighted imaging provide high-resolution images. Whereas it is time-consuming, expensive, less obtainable, and often requires the use of gadolinium contrast. A more practical method is needed to evaluate the optic nerve for the initial diagnosis and follow-up of patients.8-10
Sonoelastography is an advanced sonographic technique and a non-invasive method for evaluating the different elasticity characteristics of tissues. There are two main sonoelastographic techniques that include strain elastography (SE), which display the local strain of a given sample of tissue (relative strain) and compresses the tissues axially, and shear wave elastography (SWE), which uses waves that are generated by transducers and interact with the tissue and a less operator-dependent method. Shear wave elastography can allow visualization and documentation of absolute stiffness in kilopascals or meters per second objectively without a maneuver.10,11
Sonoelastography has been used in the evaluation of internal organ pathology, and more recently, its clinical application to optic nerve tissue has been a growing area of interest.12 As far as we know, there is only one reported study about the sonoelastography of the optic nerve in MS patients in the English medical literature.13
The main purpose of the study is to assess the elasticity features of the optic nerve, optic disc, and perineuronal area using SWE in patients with MS (with or without optic neuritis), compare with healthy volunteers and describe the contribution of SWE findings for visual dysfunction in MS.