Multiple sclerosis does not directly cause strokes, but it significantly raises the risk of having one. A 2024 meta-analysis in the Journal of Neurology found that people with MS are nearly three times more likely to have an ischemic stroke (the type caused by a blood clot) compared to the general population, with a relative risk of 2.79. They also face roughly 2.3 times the risk of a hemorrhagic stroke, the type caused by bleeding in the brain.
The connection is real, even if the mechanism is indirect. The chronic inflammation that defines MS, the reduced physical activity that often accompanies it, and even some of the medications used to treat it all contribute to a higher stroke risk.
How MS Increases Stroke Risk
MS is fundamentally a disease of chronic inflammation. The immune system attacks the protective coating around nerve fibers, but that inflammatory process doesn’t stay neatly confined to nerve tissue. Over time, widespread inflammation can damage blood vessel walls, making them stiffer and more prone to plaque buildup. This is the same process, atherosclerosis, that leads to stroke in the general population. In people with MS, it simply gets a head start.
Beyond the disease itself, the way MS changes daily life plays a role. Fatigue and mobility problems make regular exercise harder. People with MS have higher rates of hypertension and high cholesterol, both major stroke risk factors. Smoking, which is more common among people with MS and worsens the disease course, independently raises stroke risk. A study published in the International Journal of Preventive Medicine found that hypertension was the single most common stroke risk factor among MS patients who had strokes, present in 30% of cases.
The Role of MS Medications
Some treatments for MS carry their own vascular risks, which is an important and sometimes overlooked part of the equation. High-dose steroids, frequently used to treat acute MS relapses, can increase the likelihood of stroke, heart attack, and blood clots in the brain’s veins. This risk is highest with large or frequent doses.
Certain disease-modifying therapies also appear to matter. Some older injectable treatments (interferon-beta and glatiramer acetate) have been linked to a meaningfully higher stroke incidence compared to newer medications like natalizumab and fingolimod. One review in Health Science Reports noted that the relative stroke risk with these older therapies was roughly 10 to 50 times higher than with the newer options, though these are comparative figures between drug classes, not absolute risk numbers.
Alemtuzumab, a potent infusion therapy, has been associated with stroke and poor neurological outcomes after at least two treatment courses. The connection may run through blood pressure: alemtuzumab can cause significant spikes in systolic blood pressure, which is why frequent blood pressure monitoring is standard during and after treatment. Fingolimod, while generally associated with lower stroke risk than some alternatives, has rare reports of causing reversible narrowing of blood vessels in the brain, typically at doses above the standard 0.5 mg daily.
Both Stroke Types Are More Common
The increased risk applies to both major categories of stroke. Ischemic strokes, where a clot blocks blood flow to part of the brain, are the more common type. The pooled prevalence of ischemic stroke among MS patients is about 2.1%. Hemorrhagic strokes, caused by a ruptured blood vessel bleeding into the brain, occur in roughly 0.6% of MS patients. Both rates are elevated compared to the general population.
The hemorrhagic stroke finding is particularly notable because it suggests the vascular damage in MS goes beyond simple clot formation. The relative risk of 2.31 for brain hemorrhage points to broader blood vessel fragility, likely driven by the same chronic inflammatory processes that characterize the disease.
Telling a Stroke Apart From an MS Relapse
This is one of the most practical things an MS patient can know: strokes and MS relapses feel very different in how they begin. A stroke hits suddenly, with symptoms appearing in seconds to minutes. One moment you’re fine, the next you have weakness on one side, difficulty speaking, or vision loss. An MS relapse, by contrast, builds over hours to days, typically reaching its worst point within a few days and then slowly improving over about eight weeks.
If neurological symptoms appear suddenly, treat it as a stroke until proven otherwise. The classic signs, facial drooping, arm weakness, speech difficulty, apply to people with MS just as they do to everyone else. The fact that you already have a neurological condition does not make sudden symptoms less urgent.
Brain imaging can also create confusion. On MRI, MS plaques and stroke lesions can look similar to an untrained eye. MS lesions are typically small, oval-shaped spots oriented perpendicular to the brain’s fluid-filled chambers. Stroke lesions tend to follow the territory of a specific blood vessel. Radiologists use diffusion-weighted imaging, a type of MRI sequence that detects freshly damaged tissue, to distinguish new stroke damage from older MS plaques. Occasionally, large or unusual MS lesions (called tumefactive lesions, greater than 2 cm with swelling) can mimic a stroke on initial imaging, requiring careful interpretation.
Reducing Your Stroke Risk With MS
The most impactful thing you can do is manage the standard cardiovascular risk factors aggressively. That means keeping blood pressure in a healthy range, monitoring cholesterol, not smoking, and staying as physically active as your symptoms allow. These factors are modifiable, and they account for a large share of the excess stroke risk in MS.
Pay attention to how your MS treatments affect your cardiovascular health. If you’re on a therapy that can raise blood pressure or has vascular side effects, regular monitoring becomes more important. Diet also plays a role: anti-inflammatory eating patterns that emphasize fruits, vegetables, and healthy fats may help address both MS inflammation and cardiovascular risk simultaneously.
The overall stroke risk for any individual with MS remains relatively low in absolute terms. A 2.1% prevalence of ischemic stroke means the vast majority of people with MS will never have one. But the elevated relative risk is real, and it’s driven by factors that are largely within your control or your treatment team’s awareness.