Egypt J Neurol Psychiat Neurosurg. │Jan 2010 │ Vol 47 │ Issue 1 497 Study of the Retinal Nerve Fiber Layer Thickness in Multiple Sclerosis by Using Optical Coherence Tomography Azza A. Ghali 1 , Tarek R. Hussein 2 Departments of Neuropsychiatry 1 , Ophthalmology 2 , Tanta University; Egypt ABSTRACT Background: Multiple sclerosis (MS) is being increasingly recognized as a complex neurodegenerative disorder of the brain and spinal cord Objective: to study the role of optical coherence tomography (OCT) in assessment of RNFL thickness as a structural biomarker for axonal loss in multiple sclerosis (MS). Methods: This study enrolled 15 patients (30 eyes) with remitting relapsing MS, 8 patients with secondary progressive MS, and 16 age and sex-matched healthy controls. Patients were divided into 2 subgroups: group I which included MS patients without optic neuritis (MS-N-ON). Group II included MS patients with history of optic neuritis (MS-ON). All patients underwent neurologic assessment by Expanded Disability Status Scale (EDSS) and ophthalmic examination that included visual acuity, visual field examination, and OCT to measure retinal nerve fiber layer (RNFL) thickness. Results: RNFL thickness measured by OCT for all MS patients was significantly reduced compared with the control (p =0.000). RNFL thickness was significantly reduced in MSON eyes compared to healthy controls and MS-N-ON eyes. Although MS ON eyes demonstrate the greatest reductions in RNFL thickness, MS|-N- ON eyes are also abnormal including fellow eyes of MS patients with a history of unilateral optic neuritis. Reduction of average RNFL also showed a correlation with disease duration and neurological disability in MS-N-ON and MS-ON unaffected eyes. Conclusion: The results support potential usefulness of OCT for MS patient monitoring and research applications. [Egypt J Neurol Psychiat Neurosurg. 2010; 47(3): 497-504] Key Words: Retinal nerve fiber layer, Multiple sclerosis, Optical coherence tomography INTRODUCTION Multiple sclerosis (MS) is being increasingly recognized as a complex neurodegenerative disorder of the brain and spinal cord that involves autoimmune mechanisms that target both white and gray matter elements 1 . Manifestations of MS are heterogeneous and include visual, motor, sensory, cognitive, functional, and emotional symptoms 2 . Although MS has long been considered a primary demyelinating disease, axonal loss is of critical importance since this pathologic change appears to correlate with a patient's ultimate disability. Axonal loss is increasingly thought to occur early in the disease course and to be associated with, and predictive of neurologic deficits progressing to permanent disability 2,3 . Current techniques used to measure axonal loss in MS primarily nonconventional magnetic resonance imaging (MRI)-based sequences, have notable limitations of sufficient resolution to assess specific white matter tracts in the brain and spinal cord in a time-sensitive, cost-efficient protocol. 2 Correspondence to Azza Abbas Ghali, Department of Neuropsychiatry, Tanta University Hospital; Egypt Tel.: +20127984473. Email: azzaghali_4@hotmail.com The RNFL is of particular interest in MS, firstly, because optic neuritis (ON) is often the pivotal event in establishing the diagnosis 4 . Secondly, the retinal nerve fiber layer (RNFL) is composed of unmyelinated axons of retinal ganglion cells 5,6 . Measurements of the RNFL should, therefore, give relatively direct measures of the number of axons present without the confounding variable of tissue loss due to demyelination 6 . Moreover, it is estimated that nearly 20% of all patients with MS present initially with ON, and an additional 40% will have ON at some point in their disease course and. Preliminary studies have found a loss of RNFL thickness in ON, likely due to axons that are destroyed in the optic nerve. 7 Unlike MRI measures of brain or optic nerve atrophy, OCT provides a unique opportunity to measure a structure within the central nervous system that consists of isolated axons (because axons within the RNFL are not myelinated) 8,9 . Optical coherence tomography is an imaging technology that uses light to create high-resolution, quantitative, real-time, cross-sectional images of biological tissues 10 . It has been used to image intraretinal layers, including the macular, peripapillary, and optic nerve head regions. The imaging technology of OCT has been compared to that of ultrasonography, but OCT utilizes light, not Original Article