Radiologically isolated syndrome refers to lesions consistent with MS but with no past or current neuro symptoms.

• A. Clear MS diagnosis with multiple relapses.
• B. Lesions consistent with MS but no current or past neuro symptoms.
• C. Lesions in spinal cord only.
• D. CIS that has progressed to PPMS.

Answer: (B)

Radiologically isolated syndrome is when MRI shows lesions that look like multiple sclerosis, but the person has no past or current neurological symptoms. That combination of MS‑typical imaging without any clinical manifestations is what sets RIS apart from active MS, which requires clinical events along with the imaging features.

The other descriptions describe scenarios that involve actual clinical MS activity or different patterns of disease. One option implies clear MS with relapses, which means there are neurologic symptoms; RIS by definition has none. Another implies lesions confined to the spinal cord, whereas RIS typically refers to brain lesions that resemble MS on imaging, with no symptoms. The last implies a progression from a clinically isolated syndrome to a progressive clinical course, which again involves prior symptoms and a defined disease trajectory, not a silent imaging finding.