Snapshot A 25-year-old woman presents to the emergency department for poor vision on the left eye. She reports that her symptoms began approximately 1 week ago and it has progressively worsened. Her visual deficit is associated with eye pain with movement. She denies having these symptoms in the past but recalls having urinary incontinence that self-resolved. Physical examination is only remarkable for a significant visual deficit solely affecting the left eye. The rest of the neurological examination is normal. An MRI of the brain and spinal cord enhanced with gadolinium demonstrate a hyperintense lesion affecting her left optic nerve. There is also enhancing and nonenhancing hyperintense lesions in the spinal cord, suggestive of demyelinating lesions of different ages. She is admitted to the hospital and is started on 3 days of intravenous methylprednisolone. Introduction Definition autoimmune disorder leading to demyelination and neurodegeneration Associated conditions may be seen with other autoimmune diseases (e.g., thyroid disease) Epidemiology Incidence more common in women and young adults Risk factors age 20-40 years of age genetics HLA-DRB1 locus environmental factors infection (e.g., Epstein-Barr virus) poor sun exposure Pathogenesis Believed to be due to a trigger (e.g., infection in a susceptible patient) that results in the migration of autoreactive lymphocytes to affect the central nervous system leading to demyelination decreases nerve conduction, thus impairing nerve function axonal neurodegeneration mediated by CD8+ lymphocytes and macrophages Presentation Clinical presentation depends on where demyelinating plaques are located cerebrum unilateral motor or sensory deficits brain stem diplopia nystagmus intranuclear ophthalmoplegia login to view 1 more bullet vertigo cerebellum nystagmus vertigo impaired coordination spinal cord weakness or sensory changes bowel and bladder dysfunction Lhermitte sign login to view 1 more bullet erectile dysfunction optic nerve symptoms of optic neuritis login to view 3 more bullets Uhthoff phenomenon worsening neurological symptoms in the setting of increased heat (e.g., fever and hot weather) Imaging MRI brain and spinal cord with gadolinium indication the imaging study of choice in the evaluation of multiple sclerosis findings hyperintense lesions in the central nervous system Studies Diagnosis is made based on McDonald 2017 criteria however, to simplify, the diagnosis is based on finding dissemination in time login to view 2 more bullets dissemination in space login to view 5 more bullets Cerebrospinal fluid analysis indication typically used if there is uncertainty in the diagnosis or if one is considering an alternative diagnosis (e.g., neuromyelitis optica) findings elevated IgG index oligoclonal bands login to view 2 more bullets Differential Neuromyelitis optica differentiating factor the presence of aquaporin-4 antibodies on cerebrospinal fluid testing Treatment Medical intravenous methylprednisolone indication login to view 1 more bullet comment login to view 2 more bullets disease-modifying therapy indication login to view 7 more bullets baclofen or tizanidine indication login to view 1 more bullet Complications Increased risk of infection due to being on immunosuppressants Disability