Multiple Sclerosis
A 19-year-old woman has 5 days of blurred vision with pain on moving the right eye and 2 weeks of left leg numbness and weakness. Three months earlier she had double vision for 10 days. Right visual acuity is 6/36, with reduced left leg pinprick sensation and an extensor plantar response. MRI shows multiple periventricular and juxtacortical T2-hyperintense lesions, one enhancing with gadolinium. What is the most likely diagnosis?
- A.Functional neurological disorder
- B.Neuromyelitis optica spectrum disorder
- C.Acute disseminated encephalomyelitis
- D.Multiple sclerosisCorrect
Explanation
Multiple sclerosis is defined by demyelinating events disseminated in space and time, and this young woman has both: previous diplopia, current optic neuritis, and a left corticospinal and sensory long-tract syndrome, with MRI showing periventricular and juxtacortical lesions of which one enhances (an active lesion) while the others do not (older lesions). Optic neuritis with painful eye movement and a relative afferent pupillary defect is one of the commonest presenting syndromes, and MS is two to three times more common in women, typically presenting between 20 and 40 years. The pathology is immune-mediated demyelination of central nervous system white matter with relative axonal preservation, producing conduction block that worsens transiently with heat (Uhthoff phenomenon). Supportive tests are oligoclonal bands in cerebrospinal fluid not matched in serum, and spinal cord MRI. Neuromyelitis optica spectrum disorder causes severe often bilateral optic neuritis with longitudinally extensive transverse myelitis spanning three or more vertebral segments and is confirmed by aquaporin-4 IgG; small ovoid periventricular lesions are not typical. Acute disseminated encephalomyelitis is usually monophasic, follows an infection or vaccination, occurs mostly in children, and features encephalopathy with large, poorly demarcated lesions that all enhance at the same stage. A functional disorder cannot explain an objective afferent pupillary defect, an extensor plantar response, or gadolinium-enhancing MRI lesions. Acute relapses are treated with high-dose methylprednisolone and long-term control with disease-modifying therapy.
Why each option
- A.
- Objective signs such as a relative afferent pupillary defect, an extensor plantar response and enhancing MRI lesions exclude a functional cause.
- B.
- Neuromyelitis optica typically causes severe bilateral optic neuritis and longitudinally extensive myelitis with aquaporin-4 antibodies, not scattered small ovoid brain lesions.
- C.
- Acute disseminated encephalomyelitis is monophasic and post-infectious with encephalopathy and lesions all of the same age.
- D.
- Correct. Relapsing optic neuritis and long-tract signs with periventricular white matter lesions of differing ages satisfy dissemination in space and time.
Reference: McDonald Criteria (Lancet Neurology, 2018); UpToDate 2025, Evaluation and diagnosis of multiple sclerosis in adults
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