In pediatric patients, what is a distinguishing feature of acute disseminated encephalomyelitis (ADEM) compared with multiple sclerosis?

• A. ADEM is typically post-infectious or post-vaccination, presents with multifocal deficits and encephalopathy in children, and is usually monophasic; MS is relapsing.
• B. ADEM is relapsing; MS is monophasic and non-inflammatory.
• C. ADEM never involves the optic nerve; MS always involves the optic nerve.
• D. ADEM occurs only in adults.

Answer: (B)

In children, the main distinction comes from how the disease behaves over time after a triggering event. Acute disseminated encephalomyelitis (ADEM) usually presents as a single, self-limited episode after a viral infection or vaccination, with multifocal neurologic deficits and often encephalopathy (altered consciousness or behavior). This monophasic course contrasts with multiple sclerosis, which is typically relapsing-remitting and inflammatory—attacks recur over time and are separated by periods of stability, rather than being a one-and-done event.

So the key point is: ADEM tends to be monophasic and post-infectious/post-vaccination, while MS tends to be relapsing. This distinction helps explain why ADEM can look dramatic initially but often resolves completely or nearly so, whereas MS represents a chronic, recurrent disease process. Additional context: optic neuritis can occur in both conditions, but encephalopathy is more characteristic of ADEM, and MS is more likely to show oligoclonal bands in CSF and discrete, year-to-year evolving MRI lesions.