Actor Christina Applegate recently shared that she was misdiagnosed with multiple sclerosis after years of believing she had the condition. Medical experts note that her experience reflects a wider issue within neurology, where diagnostic errors occur more frequently than many patients realize.
According to Dr. Marwa Kaisey, an associate professor in the department of neurology at Cedars-Sinai Medical Center, almost one in five people told they have multiple sclerosis do not actually have the disease. Large studies examining the risk of misdiagnosis have similarly shown that between 15% and 20% of patients diagnosed with MS are found to have other conditions upon further review.
Unlike many medical conditions, multiple sclerosis has no single definitive test. The disease involves the immune system attacking the central nervous system, and symptoms vary significantly from person to person while progressing in different ways, according to the National Multiple Sclerosis Society.
Dr. Josef Gutman, director of NYU Langone’s Long Island Comprehensive MS Care Center, explained that the wide spectrum of symptoms associated with MS makes diagnosis particularly challenging. Unlike diabetes, which can be confirmed with a single blood test, diagnosing MS requires combining a patient’s medical history with MRI imaging and biomarkers such as spinal fluid analysis.
When a misdiagnosis occurs, the root cause is frequently the misinterpretation of brain scan abnormalities. While brain lesions are considered a hallmark of multiple sclerosis, they can also stem from other medical issues, including migraines, high blood pressure, or smoking. Dr. Robert Brumel, director of the Mellon Center for MS at Cleveland Clinic, noted that advanced MRI sequences can help differentiate between MS lesions and those caused by other conditions.
Misdiagnoses are most commonly uncovered when patients seek a second opinion because their symptoms are not improving. Brumel noted that while most standard MS treatments are safe and unlikely to endanger a patient’s health, an incorrect diagnosis can significantly sidetrack care. When a misdiagnosis is identified, physicians investigate alternative causes, such as autoimmune conditions, fibromyalgia, migraines, or chronic pain and fatigue syndromes. In some cases, patients may have multiple overlapping disorders rather than a single root cause.
Applegate noted on her podcast that learning she had the wrong diagnosis left her back at square one, as she still lacks an explanation for the debilitating symptoms affecting her daily life and mobility since 2021.
To address diagnostic challenges, an international panel of experts published new multiple sclerosis diagnostic criteria in 2025 designed to be more specific, particularly regarding the interpretation of brain lesions. Specialists emphasize that patients concerned about their diagnosis should feel comfortable seeking a second opinion, especially from multidisciplinary centers or MS specialists who have access to advanced testing and deeper familiarity with conditions that mimic the disease.
