“Who Was I to Know?”

The early signs of multiple sclerosis — and why early diagnosis matters more than ever.

Author: Paola Larrabure, Pharma Content Manager  |  Clinical Reviewer: Julia Kravtsova, PharmD, Head Patient Navigator

Last Reviewed: April 2026

In a 2022 interview with The New York Times, actor Christina Applegate — who was diagnosed with multiple sclerosis in 2021 — reflected on the early warning signs she missed before her diagnosis. She described struggling with balance during a dancing scene on her Netflix show, noticing her tennis game slipping in ways she chalked up to not training hard enough, feeling a little unsteady in her shoes. Each symptom had a reasonable explanation. None of them, on their own, looked like the start of a chronic neurological disease.

As she told the Times: “I wish I had paid attention. But who was I to know?”

That question — who was I to know? — sits at the center of almost every MS diagnosis story. Multiple sclerosis rarely announces itself loudly. It begins with small things that look like a hundred other things: stress, fatigue, aging, dehydration, a bad night’s sleep. Most people who develop MS are not neurologists. Few of us would connect a subtle balance issue to an autoimmune attack on the central nervous system. And yet the medical reality is increasingly clear: the earlier MS is diagnosed, the more treatment options exist, and the better the long-term outcomes tend to be. In 2026, after the most significant update to MS diagnostic criteria in nearly a decade, this has never been more true.

This guide is written for people who have noticed something off and aren’t sure whether to pursue it, for caregivers and family members watching someone they love struggle, and for anyone who has heard of MS but doesn’t know where it begins. It is not a substitute for evaluation by a qualified neurologist. If something here sounds familiar, please bring it to your doctor.

What is multiple sclerosis?

According to the National Multiple Sclerosis Society, MS is a disease of the central nervous system — the brain, spinal cord, and optic nerves — in which the immune system mistakenly attacks a protective coating on nerve fibers called myelin. When myelin is damaged, the signals that travel between the brain and the rest of the body are disrupted. Depending on where that damage occurs, symptoms can range from vision changes to balance problems, numbness, weakness, cognitive changes, or debilitating fatigue.

MS affects approximately one million people in the United States, including an estimated 70,000 military veterans. It is unpredictable by nature. Two people with the same diagnosis can have very different symptoms, progression, and day-to-day experience. The exact cause is not fully understood, though researchers have identified a combination of genetic predisposition and environmental factors, with growing evidence that prior Epstein-Barr virus infection plays a role in triggering the disease in susceptible individuals.

There is no cure for MS. But the treatment landscape has changed dramatically over the past three decades. Since the FDA approved the first disease-modifying therapy for MS in 1993, more than a dozen therapies have followed, and early identification has become one of the most important factors in how someone’s MS journey unfolds.

MS doesn’t care who you are

One of the most persistent misconceptions about multiple sclerosis is that it is a disease of a particular “type” of person — usually imagined as a white woman in her thirties. While MS is more commonly diagnosed in young adults, particularly women between the ages of 20 and 40, the reality is far more varied. MS can appear at almost any age, in any demographic, and in any body.

Pediatric MS

Approximately 3 to 5 percent of all MS cases begin before age 18 — meaning children, adolescents, and teenagers can and do develop multiple sclerosis. Pediatric MS is often missed or misdiagnosed for years because clinicians don’t expect it in young patients. Symptoms in children can be harder to articulate, easier to attribute to growing pains, vision problems, or school stress. For families, a pediatric MS diagnosis can be devastating and disorienting — but it is also increasingly treatable, with growing research support specifically for young patients.

Young adult MS

This is the group most people picture: patients typically diagnosed in their 20s, 30s, and early 40s, most often women. This pattern is real, but it is not the entire story. Men develop MS too, though at lower rates. People across every racial and ethnic background develop MS. And plenty of young adults spend years chasing inconclusive answers before someone finally orders the right MRI.

Late-onset MS

MS can begin in a patient’s 50s, 60s, or even later. Historically, late-onset MS has been underdiagnosed because vascular disease, normal aging changes, and other conditions can produce overlapping symptoms. The 2024 revisions to the McDonald Criteria — the international diagnostic standard for MS — specifically added stricter diagnostic thresholds for patients over 50 precisely to help distinguish MS from look-alike conditions in older adults. Christina Applegate was 49 when she received her diagnosis.

The point of this section is not to make anyone anxious, but to challenge the assumption that MS only happens to a certain type of person. If something feels wrong, your age or demographic profile should not be the reason a provider dismisses your concerns.

Early signs of MS that are often missed

The list of possible MS symptoms is long, because the disease can affect any part of the central nervous system. But certain early symptoms come up repeatedly in patient stories and in the clinical literature. Dr. Paige Sutton, a neurologist specializing in neuroimmunology and multiple sclerosis at OhioHealth, has described the most important early signs to watch for as those that are new, constant, and last for more than 24 hours. Commonly reported early MS symptoms include:

• Vision changes — blurry vision, loss of vision, or pain in one eye (optic neuritis is a frequent first sign of MS, and the 2024 McDonald Criteria now formally recognize the optic nerve as a diagnostic location)
• Balance or coordination problems — difficulty walking, a sudden sense of clumsiness, or trouble with activities that previously felt automatic
• Numbness or tingling — often in the face, arms, legs, or on one side of the body
• Unilateral facial pain or weakness
• Vertigo or dizziness that is persistent and not explained by an ear infection or other cause
• Muscle weakness, especially in the legs or on one side of the body
• Unusual fatigue that is not relieved by rest
• Heat sensitivity — symptoms that worsen in hot weather, during exercise, or in hot showers
• Bladder dysfunction — new urgency, frequency, or difficulty
• Cognitive changes — difficulty with focus, memory, or word-finding

Christina Applegate’s described early signs — trouble with balance during a dance scene, a tennis game that felt suddenly off, a sensation that her shoes were making her feel unsteady — all fit the pattern of early balance and coordination changes. None of them, in isolation, would have made a doctor think “MS.” That’s exactly the problem.

Why MS is so often missed in its early stages

According to Dr. Daniel Ontaneda, a neurologist at Cleveland Clinic’s Mellen Center for Multiple Sclerosis and co-author of the 2024 McDonald Criteria revisions, the average time from symptom onset to MS diagnosis has historically been around two years. He has also noted that approximately 20 percent of people diagnosed with MS may actually have an incorrect diagnosis. Both problems stem from the same underlying difficulty: MS symptoms overlap with many other conditions.

Dr. Nora Lansen, a primary care doctor at Galileo Health, told Healthline that fatigue, anxiety, low mood, decreased focus, and even constipation are symptoms frequently encountered by people with MS — but they are also frequently encountered by people without it. Situational stress, thyroid dysfunction, seasonal affective disorder, PMS, vitamin deficiencies, and dozens of other conditions can produce overlapping symptoms. For a primary care doctor seeing a patient with fatigue and some balance issues, MS is rarely the first thing that comes to mind.

That’s not a failure of medicine — it’s how diagnosis works when a disease has no single confirmatory test and shares symptoms with many common conditions. But it means patients often have to advocate for themselves, especially when symptoms are subtle, intermittent, or don’t fit the stereotype of what MS is “supposed” to look like.

When to talk to a doctor — and which doctor

Not every balance issue or episode of fatigue warrants a trip to a neurologist. But certain symptoms warrant prompt medical evaluation. The National Multiple Sclerosis Society and neurologists specializing in MS generally recommend seeking medical attention for:

• Any new neurological symptom — weakness, numbness, vision change, vertigo — that lasts more than 24 hours
• Symptoms that come and go in a pattern, or that affect one side of the body
• Vision changes in one eye, especially with eye pain
• Balance or coordination problems that don’t resolve
• Any combination of the symptoms listed earlier in this guide

Start with your primary care doctor. If MS is on the list of possibilities, you will likely be referred to a neurologist — ideally one who specializes in MS or neuroimmunology. Ask for that referral by name if you need to. Come prepared: bring a timeline of when symptoms started, how long they lasted, what made them better or worse, and any family history of autoimmune disease. Ask for copies of any imaging reports.

Self-advocacy is not optional in the MS diagnostic process. If you feel you are being dismissed and your symptoms continue, a second opinion from a neurologist specializing in MS is reasonable and often necessary.

How MS is diagnosed today: the 2024 McDonald Criteria

Diagnosing MS has always been complex because no single test confirms it. Instead, neurologists use a combination of clinical evaluation, MRI imaging, and sometimes spinal fluid analysis to demonstrate what the field calls “dissemination in space” (lesions in multiple areas of the central nervous system) and “dissemination in time” (lesions occurring at different points). This diagnostic framework is called the McDonald Criteria, first published in 2001 and revised periodically ever since.

On September 23, 2025, the Lancet Neurology published the most significant update to the McDonald Criteria in nearly a decade — the 2024 revisions. These updates are designed to enable faster, more accurate MS diagnosis than ever before. Key changes include:

• The optic nerve is now a fifth anatomical location for demonstrating dissemination in space. Because optic neuritis is the initial clinical event in about 25 percent of MS cases, this change allows earlier diagnosis in a significant number of patients.
• New MRI biomarkers — the central vein sign and paramagnetic rim lesions — are now recognized as optional diagnostic tools that can help confirm MS with greater specificity.
• A new cerebrospinal fluid biomarker — the kappa free-light chain index — can now substitute for dissemination in time, providing a more accessible alternative to traditional oligoclonal band testing.
• Radiologically isolated syndrome — when MRI shows MS-like lesions in a patient who has not yet had clinical symptoms — can now, under specific conditions, be classified as MS. This means diagnosis can happen before a first clinical attack.
• A unified approach across the lifespan, from pediatric presentations through late-life onset — the first time the criteria have been formally designed to apply to patients of all ages.

For patients, this matters enormously. As Dr. Ontaneda has explained, if highly effective treatment is initiated early, patients with relapsing forms of MS can live relatively normal lives and may not accumulate significant disability. The 2024 revisions make early diagnosis more achievable than at any previous point in the history of MS medicine.

Why early diagnosis matters more than ever

The core reason early diagnosis matters is simple: modern disease-modifying therapies work best when started early. These medications — a class that now includes more than a dozen FDA-approved options — can reduce the frequency and severity of relapses, slow the formation of new lesions, and delay or prevent the accumulation of long-term disability.

Research has shown that patients who begin high-efficacy disease-modifying therapy early in their disease course tend to have better long-term outcomes than those who delay treatment. Early intervention cannot undo damage that has already occurred, but it can substantially change what the future looks like.

This is the medical backdrop against which Christina Applegate’s words should be understood. “I wish I had paid attention” is not a statement of regret for its own sake. It reflects a real clinical truth: the earlier MS is identified, the more options exist, and the more of a patient’s future function can be preserved.

The MS community is fighting for research funding — and winning

Every treatment advance described in this guide — every new disease-modifying therapy, every diagnostic biomarker, every refinement to the McDonald Criteria — exists because of research. And much of that research is supported by federal funding, including through a program called the Multiple Sclerosis Research Program (MSRP), part of the Congressionally Directed Medical Research Programs (CDMRP). The MSRP’s stated vision is “to prevent, cure, reverse, or slow the progression, and lessen the personal and societal impact of multiple sclerosis.” It has been particularly important for the 70,000 veterans living with MS in the United States.

In March 2025, Congress passed a continuing resolution that eliminated funding for the MSRP for fiscal year 2025 — cutting the program entirely. For the MS community, this was devastating. Research projects were paused. Early-career researchers lost funding. The pipeline of innovation slowed.

And then the community responded. According to the National Multiple Sclerosis Society, MS activists held more than 220 meetings with members of Congress and sent more than 16,000 emails and phone calls in support of restoring medical research funding. They organized Hill Day 2025 in Washington. Patients, caregivers, and advocates — many of them living with MS themselves — showed up and made their case.

It worked. The FY26 Defense Appropriations Act restored funding for the Multiple Sclerosis Research Program, and as of early 2026, the CDMRP has announced anticipated funding opportunities for fiscal year 2026. Research into MS prevention, early detection, biomarkers, and treatment — including continued work on the Epstein-Barr virus link — is moving forward again.

This is worth pausing on. Patient advocacy is not ceremonial. When the MS community organized, Congress listened, and funding was restored. Continued engagement — contacting elected officials, supporting advocacy organizations like the National MS Society, participating in MS awareness efforts — remains essential. The research that makes early diagnosis possible exists because people fought for it.

What happens after a diagnosis

Receiving an MS diagnosis is a major life moment, and every patient’s process is different. Some common first steps after diagnosis include:

• Establishing care with an MS specialist — a neurologist who focuses on MS or neuroimmunology. Many large medical centers have dedicated MS clinics.
• Discussing disease-modifying therapy options — your neurologist will review the available classes of medications, their mechanisms, their side effect profiles, and their route of administration (oral, injectable, or infusion).
• Starting treatment — current clinical thinking generally favors starting an effective disease-modifying therapy as early as appropriate, to prevent relapses and slow disease progression.
• Building a care team — beyond your neurologist, you may work with a primary care doctor, an ophthalmologist, a physical or occupational therapist, and a mental health provider.
• Connecting with community — the National MS Society, MS Focus Foundation, MS Society of America, and online patient communities offer resources, support, and connection.

A diagnosis is not an ending. It is the start of a different kind of relationship with your body, your medical team, and your community — and for many patients, the relief of finally having an answer after months or years of uncertainty.

Key takeaways

• Multiple sclerosis rarely announces itself. Early symptoms — balance issues, fatigue, numbness, vision changes — are often missed or attributed to other causes.
• MS can appear at almost any age and in any demographic. Pediatric MS, young adult MS, and late-onset MS are all real. Your age or profile should not be the reason your symptoms are dismissed.
• Christina Applegate’s question — “who was I to know?” — captures the experience of many MS patients. Most people don’t connect subtle symptoms to a serious neurological disease until years later.
• The 2024 revisions to the McDonald Criteria, published in September 2025, enable faster and more accurate MS diagnosis than at any previous point in history.
• Early diagnosis matters more than ever because modern disease-modifying therapies work best when started early.
• The MS community’s advocacy for restored federal research funding in 2025 shows what patient organizing can accomplish. Continued engagement matters.
• If something feels off, trust yourself. Seek evaluation. Ask for referrals. Seek second opinions when needed. Early answers change futures.

Sources and references

1. National Multiple Sclerosis Society. Available at: nationalmssociety.org
2. Montalban X, et al. Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria. Lancet Neurology. 2025;24(10):850-865. Published September 23, 2025.
3. Cleveland Clinic Consult QD. “Revised McDonald Criteria for Multiple Sclerosis: A Big Step Toward Biomarker-Driven Diagnosis.” Interview with Daniel Ontaneda, MD, PhD. Available at: consultqd.clevelandclinic.org
4. Healthline. “Christina Applegate and MS: Warning Signs Key to Early Diagnosis.” Fact-checked. Available at: healthline.com
5. Congressionally Directed Medical Research Programs. Multiple Sclerosis Research Program (MSRP) FY26 Pre-announcement. Available at: cdmrp.health.mil/msrp
6. National Multiple Sclerosis Society. “MSRP Unfunded in FY25 by Congress.” March 2025. Available at: nationalmssociety.org
7. Lancet Neurology. Multiple sclerosis research in 2025: earlier diagnosis and halting progression. 2026;25(1).
8. Applegate C. The New York Times interview, November 2022.
9. Applegate C. Good Morning America interview, May 2023.
10.  Image Courtesy of https://www.brainandlife.org/the-magazine/online-exclusives/christina-applegate-announces-multiple-sclerosis-diagnosis/