Multiple sclerosis often looks like a sudden diagnosis, but researchers are finding that the disease starts working silently years before it is recognized. Using an animal model, scientists at the National Institute of Neurological Disorders and Stroke built a four-dimensional brain map that flagged brain regions at risk of MS lesions weeks before any damage appeared on standard MRI.
The pattern reaches even further in humans. A study published in JAMA Network Open in August 2025 tracked healthcare use in 2,038 people who later developed MS and more than 10,000 who did not, finding vague symptoms and doctor visits climbing as much as 15 years before the first recognized MS event.
MS is an autoimmune disease in which the immune system attacks the myelin coating that protects nerve fibers, disrupting signals between the brain and body. NIH's StatPearls chapter on multiple sclerosis puts the US caseload at around 400,000, with 2.5 million people affected worldwide.
Early symptoms tend to flare and fade, which is exactly why they get chalked up to stress, poor sleep or aging. Here are eight signs that neurologists and NIH-linked resources highlight as potential early indicators.
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8 early warning signs
1. Blurred or painful vision in one eye. Optic neuritis, inflammation of the optic nerve, causes sudden vision loss in one eye, often with pain on eye movement and washed-out color perception. NIH's StatPearls entry on optic neuritis notes that about half of all people with MS experience at least one episode of optic neuritis within 15 years, and it is the first inflammatory event of MS in 15 to 20 percent of patients.
2. Numbness or tingling in the face or limbs. StatPearls lists numbness and tingling among the most common neurological presentations of MS, sometimes affecting one side of the body or a single limb.
3. Unexplained fatigue that does not lift with rest. Fatigue is one of the earliest and most frequent complaints in MS. In the JAMA Network Open cohort, fatigue and general feelings of being unwell showed up in medical records up to 15 years before MS onset.
4. Weakness in an arm or leg. StatPearls describes MS motor symptoms as ranging from focal weakness in a single limb to weakness on one side of the body, sometimes with tremor or spasticity.
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5. Balance and walking problems. Spasticity and coordination trouble can leave the legs feeling heavy or make gait unsteady, especially after any exertion.
6. Bladder or bowel changes. Urgency, hesitation and constipation are recognized MS symptoms and can appear early, according to StatPearls.
7. Trouble with memory or concentration. Cognitive impairment is a known feature of MS, and problems with thinking and focus also turned up years before diagnosis in the JAMA Network Open records.
8. Persistent low mood or anxiety. Mental health visits rose sharply in the years before MS was diagnosed, with psychiatric consultations climbing 12 to 14 years ahead of the first MS event.
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When to see a neurologist
Early MS often follows a relapsing and remitting pattern. New symptoms surge, then ease over days or weeks, which is one reason they get dismissed. StatPearls advises patients to contact their clinician promptly if new neurological symptoms last more than 24 hours. Anyone noticing several of these signs, especially vision changes in one eye or new numbness that will not go away, should ask for a neurology evaluation.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.