Neurology · Demyelinating Diseases
The facts most likely to be tested
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Multiple Sclerosis is a demyelinating disease of the central nervous system characterized by dissemination in space and time.
Optic neuritis presenting as unilateral eye pain and afferent pupillary defect is often the initial clinical manifestation.
Internuclear ophthalmoplegia is a classic finding caused by a lesion in the medial longitudinal fasciculus.
Lhermitte sign, an electric shock-like sensation radiating down the spine upon neck flexion, indicates cervical cord involvement.
MRI of the brain and spine with gadolinium contrast is the diagnostic test of choice, revealing periventricular plaques known as Dawson fingers.
Lumbar puncture findings in Multiple Sclerosis typically show oligoclonal bands in the cerebrospinal fluid that are absent in the serum.
High-dose intravenous corticosteroids are the first-line treatment for acute exacerbations, while disease-modifying therapies are used for long-term management.
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A 28-year-old woman presents with a 3-day history of blurred vision in her right eye and pain with extraocular movements. She reports a previous episode of transient numbness in her left leg that resolved spontaneously 6 months ago. Physical examination reveals a right afferent pupillary defect and impaired adduction of the right eye during lateral gaze. MRI of the brain demonstrates multiple hyperintense periventricular lesions.
What is the most likely diagnosis?
Multiple Sclerosis
The patient exhibits clinical evidence of dissemination in space and time (optic neuritis and prior sensory symptoms) combined with characteristic MRI findings, confirming the diagnosis of Multiple Sclerosis.
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Etiology / Epidemiology
Autoimmune demyelination in young women (20-40y). Associated with HLA-DR2 and vitamin D deficiency.
Clinical Manifestations
Optic neuritis (painful monocular vision loss) and Uhthoff phenomenon (worsening with heat).
Diagnosis
MRI with gadolinium showing dissemination in space and time (lesions in different areas/times).
Treatment
Methylprednisolone for acute flares; Ocrelizumab or Interferon beta for disease modification.
Prognosis
Relapsing-remitting is most common (~85-90%); 10-15% have a primary progressive course from onset, while many relapsing-remitting patients later convert to secondary progressive MS.
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Epidemiology & Etiology
Prevalent in temperate climates and Caucasian populations. Strong genetic link to HLA-DR2 haplotype. Environmental triggers include Epstein-Barr virus exposure and smoking.
Pertinent Anatomy
Central nervous system white matter tracts. Demyelination occurs in the optic nerves, brainstem, and spinal cord, leading to focal neurological deficits.
Pathophysiology
T-cell mediated inflammatory response against myelin basic protein. This results in focal areas of demyelination known as plaques, causing slowed or blocked nerve conduction.
Clinical Manifestations
Classic presentation includes optic neuritis (painful vision loss, afferent pupillary defect) and Lhermitte sign (electric shock sensation down spine with neck flexion). Patients report Uhthoff phenomenon, where symptoms worsen with heat exposure. Red flags include bowel/bladder incontinence and severe motor weakness.
Diagnosis
MRI of brain and spine is the gold standard, demonstrating hyperintense white matter lesions. Diagnosis requires dissemination in space and time (DIT/DIS). Lumbar puncture may show oligoclonal bands in CSF.
Treatment
Acute flares are managed with high-dose IV methylprednisolone. Disease-modifying therapy (DMT) includes Ocrelizumab or Interferon beta. Live vaccines are contraindicated while on immunosuppressive DMTs.
Prognosis
Most patients follow a relapsing-remitting course. Secondary progression occurs in many patients over 10-20 years. Monitor for depression and cognitive decline.
Differential Diagnosis
Neuromyelitis optica: positive for anti-aquaporin-4 antibodies
Acute disseminated encephalomyelitis: follows viral infection in children
Lyme disease: history of tick bite and erythema migrans
Neurosyphilis: positive VDRL/RPR and Argyll Robertson pupils
B12 deficiency: subacute combined degeneration with macrocytic anemia