Up to 20% of MS diagnoses are wrong, like Christina Applegate's. Here's what doctors say patients should know.

TL;DR

Up to 20% of patients diagnosed with multiple sclerosis (MS) may not actually have the condition.
MS is difficult to diagnose due to its wide spectrum of symptoms and the lack of a single definitive test.
Abnormalities on brain scans, a hallmark of MS, can also be caused by other issues like high blood pressure, smoking, or migraines.
More advanced MRI sequences and spinal fluid analysis can help differentiate MS lesions from those caused by other conditions.
Seeking a second opinion is encouraged for anyone concerned about their MS diagnosis, as it can lead to further investigation or confirmation of the diagnosis.
Conditions like fibromyalgia, migraines, and chronic pain or fatigue syndromes can mimic MS symptoms.
New diagnostic criteria were published in 2025 to reduce the risk of misdiagnosis.

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