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 inability to adduct the eye on lateral gaze with a demyelinating lesion affecting the ipsilateral medial longitudinal fasciculus vertigo cerebellum nystagmus vertigo impaired coordination spinal cord weakness or sensory changes bowel and bladder dysfunction Lhermitte sign paresthesias that radiate down the arms or trunk with neck flexion erectile dysfunction optic nerve symptoms of optic neuritis vision loss pain with eye movement dyschromatopsia (altered color perception) 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 having ≥ 2 multiple sclerosis attacks at different times e.g., having ≥ 2 demyelinating lesions of different ages on MRI dissemination in space having multiple sclerosis lesions in 2 of 4 multiple sclerosis-specific regions, which are periventricular juxtacortical infratentorial spinal cord 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 a serum study should also be sent non-specific finding Differential Neuromyelitis optica differentiating factor the presence of aquaporin-4 antibodies on cerebrospinal fluid testing Treatment Medical intravenous methylprednisolone indication treatment of choice for an acute multiple sclerosis attack comment steroids hasten recovery but it does not improve outcomes preferred over oral prednisone in acute multiple sclerosis attacks with optic neuritis disease-modifying therapy indication these are steroid-sparing agents used to suppress the immune system, in hopes to prevent a future multiple sclerosis attack there are multiple medications, such as beta interferons fingolimod natalizumab associated with the development of progressive multifocal leukoencephalopathy testing for antibodies against JC virus is recommended before starting this medication baclofen or tizanidine indication first-line therapy for spasticity Complications Increased risk of infection due to being on immunosuppressants Disability