A 14-year-old with headaches, unilateral weakness, and prior episodes; neurology would order which test to diagnose multiple sclerosis?

A 14-year-old with headaches, unilateral weakness, and prior episodes; neurology would order which test to diagnose multiple sclerosis?

• A. Lumbar puncture.
• B. Electroencephalogram (EEG).
• C. Magnetic resonance imaging (MRI).
• D. Positron emission tomography (PET).

Answer: (C)

Imaging that directly shows the underlying problem—demyelinating plaques in the central nervous system—is what makes MRI the test of choice when MS is suspected in a teenager. MRI can visualize the characteristic white matter lesions scattered in different areas of the brain and spinal cord, especially in periventricular, juxtacortical, callosal, brainstem, and cerebellar regions. It also allows assessment of active inflammation with gadolinium enhancement, helping establish dissemination in time (new or enhancing lesions over time) and dissemination in space (lesions in multiple typical locations). This combination—visible lesions and evidence of activity—fits the diagnostic criteria for MS and often avoids more invasive testing. Lumbar puncture can provide supportive information, such as oligoclonal bands in the CSF, but these bands are not specific and may be absent early in disease. EEG does not reveal MS-specific pathology and is not diagnostic for MS. PET is not a standard tool for diagnosing MS and lacks the specificity needed for this purpose. Therefore, the imaging choice that best clarifies the diagnosis in this clinical scenario is MRI.

Imaging that directly shows the underlying problem—demyelinating plaques in the central nervous system—is what makes MRI the test of choice when MS is suspected in a teenager. MRI can visualize the characteristic white matter lesions scattered in different areas of the brain and spinal cord, especially in periventricular, juxtacortical, callosal, brainstem, and cerebellar regions. It also allows assessment of active inflammation with gadolinium enhancement, helping establish dissemination in time (new or enhancing lesions over time) and dissemination in space (lesions in multiple typical locations). This combination—visible lesions and evidence of activity—fits the diagnostic criteria for MS and often avoids more invasive testing.

Lumbar puncture can provide supportive information, such as oligoclonal bands in the CSF, but these bands are not specific and may be absent early in disease. EEG does not reveal MS-specific pathology and is not diagnostic for MS. PET is not a standard tool for diagnosing MS and lacks the specificity needed for this purpose. Therefore, the imaging choice that best clarifies the diagnosis in this clinical scenario is MRI.