Multiple Sclerosis (MS)

What happens in multiple sclerosis

Nerve fibers carry electrical signals like wires. Myelin, a fatty insulating layer, lets signals travel quickly. In MS, immune cells cross into the central nervous system and attack myelin, leaving inflamed patches called lesions or plaques. Over time these become scarred (sclerosis means hardening), and the nerve fibers themselves can be damaged.

Where the lesions form determines the symptoms. A lesion in the optic nerve blurs vision. One in the spinal cord causes numbness or weakness in the legs. One in the brainstem causes double vision or vertigo. Because lesions occur in different places at different times, MS symptoms vary widely between people.

The nervous system can partly repair myelin and reroute signals, which is why many early relapses recover well.

Early signs and symptoms of MS

Common first symptoms:

• Optic neuritis: blurred or dim vision in one eye, faded colors and pain when moving the eye
• Sensory symptoms: numbness, tingling, pins and needles or a tight band feeling around the trunk or limbs
• Weakness in one or both legs, or clumsiness of a hand
• Balance problems and unsteady walking
• Double vision
• Lhermitte's sign: an electric-shock sensation down the spine or into the limbs when bending the neck forward

As MS progresses, other symptoms can appear:

• profound fatigue, one of the most common and disabling symptoms
• muscle stiffness and spasms (spasticity)
• bladder urgency, frequency or incomplete emptying; constipation
• sexual problems
• problems with memory, attention and processing speed
• depression and anxiety
• pain, including nerve pain and trigeminal neuralgia
• tremor and slurred speech
• heat sensitivity: symptoms temporarily worsen with a hot bath or fever (Uhthoff phenomenon)

Types of MS

Doctors also describe MS as active (relapses or new MRI lesions) or not active, and as progressing or stable. See clinically isolated syndrome for what a first episode means.

Causes and risk factors

The exact cause is unknown. MS appears to result from a combination of genes and environmental triggers:

• Epstein-Barr virus (EBV): infection with EBV, the cause of mononucleosis, is strongly linked to later MS. Almost everyone with MS has had EBV, although most people with EBV never develop MS.
• Low vitamin D and little sun exposure. MS is more common farther from the equator.
• Smoking, which also speeds progression.
• Obesity in adolescence.
• Genetics: having a parent or sibling with MS raises the risk, though most people with MS have no affected relative. The HLA-DRB1 gene variant is the strongest known genetic factor.
• Sex and age: women aged 20 to 40 are at highest risk of relapsing MS. Primary progressive MS affects men and women more equally and starts later.

MS is not contagious and is not directly inherited.

How MS is diagnosed

There is no single test. A neurologist diagnoses MS using the McDonald criteria, which require evidence of damage in at least two areas of the central nervous system occurring at different times, with other causes excluded.

• Neurological examination: vision, strength, reflexes, sensation, coordination and walking.
• MRI of the brain and spinal cord: shows lesions in typical locations. Contrast dye (gadolinium) highlights active inflammation. MRI can show both old and new lesions on a single scan, which can satisfy the "different times" requirement.
• Lumbar puncture (spinal tap): oligoclonal bands in the spinal fluid, but not in the blood, show inflammation within the nervous system.
• Evoked potentials: measure how quickly nerves carry signals from the eyes or limbs.
• Optical coherence tomography (OCT): an eye scan that measures nerve fiber loss after optic neuritis.
• Blood tests to rule out conditions that mimic MS, including vitamin B12 deficiency, lupus, Lyme disease and sarcoidosis, and antibody tests for neuromyelitis optica (AQP4) and MOG antibody disease, which need different treatment.

Multiple sclerosis treatment

Treating relapses

A relapse is a new or worsening neurological symptom lasting more than 24 hours, at least 30 days after the last one, without fever or infection. Mild relapses may not need treatment. Disabling relapses are treated with:

• High-dose corticosteroids, usually methylprednisolone for 3 to 5 days by vein or by mouth. They shorten the relapse but do not change long-term outcome.
• Plasma exchange for severe relapses that do not respond to steroids.

Disease-modifying therapies (DMTs)

DMTs reduce relapses, new MRI lesions and disability progression. They do not repair existing damage, so early treatment matters. Options include:

• Injections: interferon beta, glatiramer acetate, ofatumumab
• Pills: dimethyl fumarate, diroximel fumarate, teriflunomide, fingolimod, siponimod, ozanimod, ponesimod, cladribine
• Infusions: ocrelizumab and ublituximab (anti-CD20 antibodies), natalizumab, alemtuzumab

Ocrelizumab is the first drug approved for primary progressive MS. Siponimod is approved for active secondary progressive MS.

Choosing a DMT involves balancing effectiveness against risks such as infections, liver effects and, with natalizumab and some others, a rare brain infection called PML. Plans for pregnancy also affect the choice. Many neurologists now favor starting a high-efficacy therapy early in people with active disease. Regular MRI and blood tests monitor response and safety.

Treating symptoms

• Spasticity: stretching, physical therapy, baclofen, tizanidine, botulinum toxin
• Walking: dalfampridine can improve walking speed in some people
• Fatigue: energy pacing, exercise, treating poor sleep and depression, cooling strategies
• Bladder: timed voiding, medicines for urgency, self-catheterization for incomplete emptying
• Pain: nerve pain medicines such as gabapentin or duloxetine
• Mood and cognition: counseling, antidepressants, cognitive rehabilitation

Rehabilitation

Physical, occupational and speech therapy help maintain strength, balance, independence and safety. Regular exercise, including aerobic and strength training, is safe in MS and improves fatigue, mood and mobility.

Recovery from relapses, including weakness on one side

Weakness of one arm and leg on the same side (hemiparesis), or rarely near-complete paralysis on one side (hemiplegia), can occur in an MS relapse when a lesion affects the motor pathways in the brain or upper spinal cord. Any sudden one-sided weakness still needs emergency assessment to rule out stroke.

Recovery from an MS relapse usually starts within a few weeks. Improvement is often fastest in the first 2 to 3 months and can continue for 6 to 12 months. Many early relapses recover fully; others leave some residual weakness, numbness or stiffness. Steroids speed recovery, and early physical and occupational therapy helps regain strength, walking and hand use. Recovery tends to be less complete with age and with repeated relapses in the same area.

Living with MS

• Stay active with exercise you enjoy, adjusted to your energy levels.
• Stop smoking, which is linked to faster progression.
• Check vitamin D levels and supplement if low, on your doctor's advice.
• Manage heat: cooling vests, cool showers and avoiding hot tubs reduce heat-related symptoms.
• Stay up to date with vaccines, ideally before starting immune-suppressing treatment. Live vaccines are avoided with some DMTs.
• Pregnancy: relapses usually decrease during pregnancy and may rise in the first months after birth. Plan pregnancy with your neurologist to choose a suitable treatment.
• Treat infections promptly, because they can trigger pseudo-relapses and real relapses.

Outlook

MS affects nearly 1 million people in the US. Its course varies greatly. Many people with relapsing MS treated early remain fully active and working for decades. Life expectancy is close to normal, a few years shorter on average, and the gap has narrowed with modern treatment. Factors linked to a better outlook include younger age at onset, female sex, sensory or optic nerve first symptoms, good recovery from early relapses, few MRI lesions and early effective treatment.

Frequently asked questions

What are usually the first signs of MS?

The most common first signs are blurred or painful vision in one eye (optic neuritis), numbness or tingling in part of the body, weakness or clumsiness of a limb, balance problems and double vision. Symptoms typically develop over hours to days, last days to weeks, and then improve.

How is multiple sclerosis diagnosed?

A neurologist combines your history and examination with an MRI of the brain and spinal cord, which shows typical lesions. A spinal tap that finds oligoclonal bands and evoked potential tests can support the diagnosis. Blood tests exclude conditions that mimic MS. The McDonald criteria guide the final diagnosis.

Can you recover from hemiplegia caused by MS?

Often, yes. One-sided weakness from an MS relapse usually starts improving within weeks, with most recovery in the first 2 to 3 months and further gains up to a year. Steroids and early rehabilitation help. Some people recover fully, while others are left with mild weakness or stiffness.

Is MS fatal?

MS itself is rarely fatal. Most people with MS have a near-normal life expectancy, on average a few years shorter than the general population. Severe disability can raise the risk of complications such as infections and swallowing problems, but modern treatments reduce the chance of reaching that stage.

What triggers an MS relapse?

Relapses often occur without a clear trigger. Infections, the months after childbirth and stopping a disease-modifying therapy can increase the risk. Heat, stress and fatigue can temporarily worsen existing symptoms without causing new damage, which is called a pseudo-relapse.

Can diet or vitamin D cure MS?

No diet or supplement cures MS. Correcting low vitamin D, eating a balanced, mostly plant-based diet, keeping a healthy weight and not smoking support general and brain health and may help the disease course. They work alongside, not instead of, disease-modifying therapy.