Christina Applegate, the actor who has been one of the most visible faces of multiple sclerosis since her 2021 diagnosis, made a stunning revelation this week: She does not have MS after all. And her doctors still don\u2019t know what is causing her debilitating symptoms.<\/p>\n
\u201cI\u2019m back at square one,\u201d Applegate told<\/a> fellow actor Jamie Lynn Sigler, who does have MS, on Sigler\u2019s podcast MeSsy<\/a>. \u201cI was not happy at all. Everybody else was so happy.\u201d<\/p>\n It is a harrowing predicament for Applegate, and hopefully her medical team is able to get her the diagnosis and treatment she needs. But the fact is, her experience is not unique. Even as more and more Americans get diagnosed with multiple sclerosis, misdiagnosis remains all too common. According to one meta-analysis, roughly 15 percent of MS diagnoses may actually be false positives<\/a>.<\/p>\n How could such a common medical condition \u2014 roughly 1 million Americans are living with the disease, about one in every 350 people \u2014 remain such a mystery? After Applegate\u2019s announcement, I called some leading experts on MS to ask why diagnosing the disease is such a challenge, and what they want people to know. Here\u2019s what I learned.<\/p>\n Why MS can be challenging to diagnose<\/p>\n Multiple sclerosis<\/a> is an autoimmune condition: The body mistakenly attacks cells meant to protect your brain and spinal cord, and the resulting damage interrupts nerve signals and causes the disease\u2019s telltale symptoms of motor impairment, tingling sensations, and vision problems. Some people experience a rollercoaster of relapses and remissions; others see the disease steadily progress, eventually leading to serious disability.<\/p>\n The reality is, scientists still don\u2019t really know what causes MS to develop, said Dr. Andrew Solomon<\/a>, a neurologist at the University of Vermont who specializes in MS. Smoking is a known risk factor. Obesity and metabolic problems play a role, but we need more research. Even the precise role of genetics remains something of a mystery. \u201cWe don\u2019t really know what causes or triggers the autoimmune response in any given individual,\u201d Solomon said.<\/p>\n And that\u2019s where the challenge in diagnosing it begins.<\/p>\n First, the testing can be imprecise; there is not a single test that reliably diagnoses MS. If a doctor suspects their patient may have MS, they usually undergo an MRI, which their physicians then scour for lesions that are typically associated with the disease. But those scans are still subject to interpretation: Other rare conditions sometimes resemble MS in imaging, as can diseases of blood vessels in the brain. You can also receive a spinal fluid analysis to check for abnormalities in your immune system, which the vast majority of MS patients have.<\/p>\n The nature of MS symptoms adds to the difficulty. They can often be vague early on: brain fog or fatigue or a general malaise. The tingling or vision problems can be similar to symptoms for other conditions that are not MS, and they are easily dismissed if they go into temporary remission, as often happens during the initial phases of the disease.<\/p>\n \u201cNeurological symptoms sometimes can be vague \u2014 numbness, pins and needles \u2014 and it\u2019s usually short-lived,\u201d Dr. Saud Sadiq<\/a>, chief research scientist and director of the Tisch Multiple Sclerosis Research Center of New York, told me. \u201cUnless they\u2019re taken seriously initially, they may be ignored because by the time the patient goes through the healthcare system and is actually referred to a neurologist, the symptoms have abated.\u201d<\/p>\n If your doctor is diagnosing you with MS, ask directly: What\u2019s the evidence?<\/p>\n One 2025 study by Solomon and his colleagues found that 40 percent of people who had later been diagnosed with multiple sclerosis were initially misdiagnosed<\/a> with a different disease.<\/p>\n \u201cBecause it\u2019s so heterogeneous, it doesn\u2019t present in the same way in everybody and can have varying severity, it can be hard to diagnose sometimes,\u201d Solomon said.<\/p>\n Lastly, when people are experiencing debilitating symptoms, there is pressure to deliver some diagnosis \u2014 and that may push some doctors to leap to MS even if they are not sure, Solomon said. The recent advent of effective treatments that help manage the disease\u2019s symptoms, especially when it is caught early, may add to that pressure, even if the better course would be to continue monitoring the person before they start a medication.<\/p>\n \u201cThere may be a lot of clinicians who, if they can\u2019t find a better explanation than MS, may be inclined to diagnose MS, even if they don\u2019t really meet our diagnostic criteria, because they\u2019re worried about missing a window of opportunity to treat somebody,\u201d Solomon said.<\/p>\n There is reason to hope the MS misdiagnosis problem could get better. The National Multiple Sclerosis Society released new diagnostic criteria in 2024<\/a> that Solomon said more physicians should become familiar with to better distinguish MS from problems like migraines or vascular disease. And because imaging is involved in diagnosis, there is optimism that AI could be a powerful new tool in delivering more accurate results.<\/p>\n What everyone should know about MS symptoms and diagnosis<\/p>\n The good news is that MS, when diagnosed properly, is a treatable condition these days. \u201cThe prognosis with new drugs is extremely good for long-term care,\u201d Sadiq told me. \u201cIf patients stick to treatment at a good MS center, you can look forward to a life without disability in 2026.\u201d<\/p>\n So it is worth being vigilant and talking to your doctor if you experience any concerning symptoms. You should seek care if you have numbness or pins and needles that persists for more than 24 to 48 hours, Sadiq said, or have motor problems, like one hand won\u2019t work as you try to play piano. Dr. Annette Langer-Gould<\/a>, who develops and evaluates programs for MS care at Kaiser Permanente, said numbness in your abdomen, chest or back, as opposed to your extremities, is a particular cause for concern. If one eye has normal vision and the other is blurred, that\u2019s another good reason to get checked out.<\/p>\n If you do get tested, make sure the actual images of your MRIs end up being reviewed by an expert in MS. \u201cThe most common reasons the disease is still misdiagnosed are related to the providers\u2019 lack of expertise usually in reading MRI scans,\u201d Langer-Gould said. The spinal tap may sound scary, and doctors sometimes don\u2019t recommend them because their insurance reimbursement is low \u2014 but they add to the confidence of a diagnosis. They are worth it, she said.<\/p>\n \u201cAmerican patients are very afraid of the spinal tap,\u201d Langer-Gould said. \u201cMy message to patients is: Listen, just get the spinal. This way we\u2019ll be sure.\u201d<\/p>\n