• Posted November 10, 2025

Multiple Sclerosis Explained: Symptoms, Risk Factors & How It’s Treated

Multiple sclerosis (MS) is one of the most common autoimmune diseases affecting the brain and spinal cord, with 2.9 million people estimated to be living with the disease worldwide.

As MS is an autoimmune disease, damage is caused by inappropriate actions of the body’s infection-fighting (immune) cells. 

The damage typically involves myelin, the outer covering of the cells that reside in the brain and spinal cord. This impedes the electrical signals necessary for the brain and spine to function properly.

The damage can lead to both sudden “flares” of inflammation and a slow worsening of symptoms over time. Historically, MS has been broken down into specific subtypes, as detailed below. But the reality of the disease may be better understood as a spectrum that likely started even before symptoms were noticed.

Relapsing and remitting MS is:

• The most common subtype (85% of cases) 

• Characterized by flares of inflammation, known as “relapses”

• Separated by periods, known as “remissions,” when patients feel relatively normal 

Primary progressive MS is: 

• The less common subtype (10% to 15% of cases) 

• Characterized by consistent worsening of symptoms over months to years 

• Not characterized with clear “flares” or periods of stability 

Secondary progressive MS: 

• Initially follows a course like that of relapsing and remitting MS 

• Evolves over time, with patients noting a consistent worsening of symptoms in the absence of any clear “flares”

What are the symptoms of multiple sclerosis?

Since MS can affect any part of the brain or spinal cord, patients can present with a wide variety of symptoms, depending on where the damage has taken place.

In patients with the most common subtype, relapsing and remitting, these symptoms will typically come on over days and improve over weeks to months.

Common initial symptoms include: 

• Painful loss or blurred vision

• Double vision 

• Face drooping on one side  

• Slurring words 

• Room-spinning dizziness and unsteadiness 

• Weakness in arms and/or legs 

• Numbness and tingling in arms and/or legs

• Difficulty with fine motor tasks (such as typing, buttoning a shirt and eating)

• Difficulty walking, possibly leading to falls 

• Electric shock-like sensation down the spine when touching chin to chest (“Lhermitte’s sign”) 

• Tight, squeezing sensation around the chest or belly (“MS hug”)

What are the causes and risk factors of multiple sclerosis?

There is no single cause of multiple sclerosis. It likely results from interactions between genetic and environmental risk factors. 

• Inherited factors (genetics) 

  • Risk of developing MS is higher in patients who have a family history of the disease 

  • Risk is not associated with any single gene but with more than 200 genetic contributors 

• Environmental factors 

  • Exposure to the virus that causes infectious mononucleosis (Epstein-Barr virus)

  • Low vitamin D

  • Low UV exposure  

  • Childhood obesity/increased weight 

  • Tobacco use

How is multiple sclerosis diagnosed? A diagnosis of MS generally requires a doctor to pursue several different tests during the initial evaluation. These tests help rule out other possible causes and provide evidence that supports a diagnosis of MS. 

• Blood work

  • To look for evidence of other diseases (including infection, inflammation, vitamin deficiencies, for example)

• Imaging: MRI of the brain and spine 

  • To look for characteristic lesions/scars from prior inflammation 

  • May be done with contrast (such as gadolinium) given through an IV to look for active inflammation 

• Procedure: Lumbar puncture 

  • Looks for evidence of inflammation in the fluid that surrounds the brain and spine

A neurologist may also recommend evaluations by additional medical providers. This can include an ophthalmologist (eye doctor) who can look for evidence of MS affecting the optic nerve that connects the eye to the brain.

This can be achieved through non-invasive testing, such as optical coherence tomography (OCT), which examines the thickness of the nerves at the back of the eye, or visual evoked potentials (VEPs), which assess the function of the optic nerve.

How is multiple sclerosis treated?

MS treatment is provided on two fronts: 1) Treatment of active inflammation. 2) Prevention of new inflammation and damage to the brain and spine. 

If a patient is having active inflammation due to MS (“flare”), a provider will typically recommend treatment with steroids. Steroids quickly reduce inflammation in the body to speed recovery. This is generally administered by IV infusion over three to five days.

To avoid recurrent “flares” and the side effects of frequent steroid use, however, the key to MS treatment is prevention.

Preventive medications in MS are referred to as disease-modifying therapies (DMTs). These medications should be started as early as possible to limit damage to the brain and spine. 

The U.S. Food and Drug Administration (FDA) has approved many DMTs for relapsing-remitting MS. Each medication can vary in effectiveness, side effects and how it is administered (pills, injections or infusions). 

Ultimately, the choice of treatment is an individualized discussion between the patient and provider. There are fewer options for secondary and primary progressive MS. A single medication (Ocrevus) is currently FDA-approved to treat this subtype of MS.

What is it like living with multiple sclerosis? 

Living with MS has changed dramatically as more effective treatments have been developed, with patients generally acquiring less disability and limitations over time.

However, many people with MS can continue to struggle with “day-to-day” symptoms that require additional treatment. Possible “day-to-day” symptoms include: . 

• Fatigue 

• Slowed processing speed and memory impairments 

• Issues with mood (depression, anxiety) 

• Problems with urination and bowel movements 

• Tingling and burning sensations 

• Muscle tightness and cramping 

• Walking difficulties and instability 

• Heat intolerance 

Given the variety of symptoms one can face with MS, a patient’s neurologist will work with other medical providers to optimize care.

Additional team members could include physical therapists, occupational therapists, speech therapists, physiatrists, mental health care providers, and specialists in the areas of eye, bladder, GI and sleep.

Together, the health care team will work with the patient to prevent and treat the complications of MS, allowing patients to live life as they want.

About the expert

Dr. Aaron Bower is an Assistant Professor of Neurology at the Yale School of Medicine. He is a board-certified neurologist and completed fellowship training in Multiple Sclerosis and Neuroimmunology. He specializes in treating patients with inflammatory disorders of the central nervous system such as Multiple sclerosis, Neuromyelitis Optica, Autoimmune encephalitis, MOG-associated disease, and the neurologic sequelae of systemic Rheumatologic disease.