When vision suddenly turns cloudy in one eye and an arm or leg feels unexpectedly weak, many patients immediately fear a stroke. While sudden visual changes or one-sided paralysis require urgent evaluation, these symptoms in young adults aged 20 to 40—especially when developing over several hours to days and persisting for more than 24 hours—may signal a central nervous system inflammatory condition like multiple sclerosis (MS).
Soonchunhyang University Bucheon Hospital highlighted the importance of evaluating central nervous system inflammatory diseases when young patients present with vision loss, limb weakness, gait difficulty, or urinary dysfunction. "An accurate diagnosis is especially critical when these neurological symptoms recur or persist over an extended period," said Kim Ji-eun, a professor of neurology at the hospital.
Multiple sclerosis is a chronic autoimmune disease in which the immune system mistakenly attacks myelin, the protective insulation surrounding nerve fibers in the brain, spinal cord, and optic nerve. Much like damaged electrical wiring, myelin degradation disrupts nerve signals. Over time, recurrent inflammation leaves sclerotic lesions and scars across multiple regions. Symptoms depend on lesion location: optic nerve involvement causes monocular blurriness; spinal cord lesions impair limb strength, sensation, and walking; while brainstem involvement can trigger double vision, dizziness, urinary dysfunction, severe fatigue, and cognitive decline.
Approximately 85% of patients initially present with relapsing-remitting multiple sclerosis (RRMS). Symptoms appear, resolve over weeks or months, and then reemerge unexpectedly. However, the temporary disappearance of symptoms does not mean the disease has halted; silent lesions can continue to form on MRI scans, accumulating nerve damage that leads to long-term disability.
Differentiating Multiple Sclerosis from Related Rare Diseases
While MS is less prevalent in South Korea than in Western nations—where the disease affects an estimated 2.9 million people globally—recent national data highlights its burden. A hospital-based registry study published in Neurology surveyed patients receiving follow-up care across 47 South Korean hospitals from January to March 2025. Among patients visiting outpatients within six months, 1,799 were diagnosed with multiple sclerosis.
The study also identified significant populations with related central nervous system inflammatory disorders: 1,616 patients with neuromyelitis optica spectrum disorder (NMOSD) and 781 with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), bringing the total across all three conditions to 4,196.
Because MS, NMOSD, and MOGAD cause inflammation across the brain, spinal cord, and optic nerves, their clinical presentations overlap significantly. However, accurate differential diagnosis is vital due to distinct therapeutic requirements:
Multiple Sclerosis: Typically causes monocular optic neuritis with relatively favorable recovery. Aquaporin-4 (AQP4) and MOG antibodies are absent.
NMOSD: Frequently involves bilateral or severe vision loss, extensive spinal cord lesions spanning three or more vertebral segments, and intractable hiccups or nausea lasting days. Most patients test positive for AQP4 antibodies.
MOGAD: Commonly presents with bilateral optic nerve involvement or optic disc swelling, and may cause acute disseminated encephalomyelitis (ADEM) in pediatric patients. Diagnosis relies on positive MOG immunoglobulin G (MOG-IgG) antibody tests.
Clinicians utilize the 2024 revised McDonald diagnostic criteria, which incorporates the optic nerve as a fifth anatomical region for identifying MS lesions. Diagnosis requires demonstrating dissemination in space and time using brain, spinal cord, and optic nerve MRI, alongside blood tests and cerebrospinal fluid (CSF) analysis for oligoclonal bands.
Environmental Risk Factors and Long-Term Management
The onset of multiple sclerosis involves a complex interplay between genetic susceptibility and environmental factors. Notably, strong epidemiological links connect MS to previous Epstein-Barr virus (EBV) infection, though most infected individuals never develop the disease. Additional established risk factors include cigarette smoking, adolescent obesity, and low vitamin D levels. "Because smoking adversely affects both disease onset and progression, smoking cessation is essential," Professor Kim advised.
While a permanent cure remains elusive, modern disease-modifying therapies (DMTs) effectively reduce relapse rates and prevent disability accumulation. Acute relapses causing functional impairment are managed with high-dose intravenous corticosteroid therapy or plasmapheresis (plasma exchange). Long-term management relies on disease-modifying agents—including injectable, oral, and monoclonal antibody therapies—with growing consensus favoring early, highly effective treatments.
"Multiple sclerosis can cause vision impairment and paralysis in young adults, leading to permanent disability if unmanaged," said Professor Kim Ji-eun. "While a complete cure is difficult, consistent medication can effectively prevent relapses. Patients should never alter or stop their treatment independently, but rather maintain close communication with their neurology specialists."
