What Is Multiple Sclerosis (MS)? Symptoms, Diagnosis and Treatment

Created: 27.05.2024 · Last Updated: 17.08.2026 · Category: Neurology · Prepared by the Academic Hospital Web and Editorial Board.

What Is Multiple Sclerosis?

Multiple sclerosis (MS) is a chronic neurological condition associated with an abnormal immune response against structures within the central nervous system.

MS can affect the brain, spinal cord and optic nerves. Inflammation can damage the myelin surrounding nerve fibres, and the nerve fibres themselves can also become damaged over time.

This can interfere with nerve signalling and cause a wide range of neurological symptoms.

Does MS Always Cause Relapses?

No. MS does not always follow a relapsing course.

Many people initially have relapsing-remitting MS, in which neurological symptoms occur during attacks followed by periods of partial or complete recovery.

Some people later develop secondary progressive MS, in which gradual neurological worsening becomes more prominent.

A smaller proportion have primary progressive MS, with gradual progression from the beginning rather than clearly defined relapses.

The course of MS varies considerably between individuals. Symptoms, relapse frequency and the rate of progression cannot be assumed to be the same for every patient.

What Are the Symptoms of MS?

  • Reduced or blurred vision in one eye
  • Double vision
  • Numbness or tingling
  • Weakness in an arm or leg
  • Muscle stiffness or spasms
  • Balance and coordination problems
  • Difficulty walking
  • Dizziness
  • Significant fatigue
  • Bladder or bowel problems
  • Sexual dysfunction
  • Problems with concentration, information processing or memory
  • Pain in some people

No single symptom is specific to MS, and similar symptoms can occur in many other neurological or medical conditions.

How Can MS Affect Vision?

Optic neuritis can be one of the first manifestations of MS.

It may cause reduced vision in one eye, reduced colour perception and pain during eye movement.

MS can also affect pathways controlling eye movements and cause double vision or involuntary eye movements.

At What Age Does MS Begin?

MS most commonly begins in young adulthood, with symptoms frequently starting between 20 and 40 years of age.

However, MS can also begin during childhood or adolescence and can first present after the age of 50.

What Causes MS?

The exact cause of MS is not known.

Genetic susceptibility, immune-system mechanisms and environmental factors are thought to interact in the development of the condition.

MS is not inherited in a simple direct pattern, although having a family member with MS can modestly increase risk.

How Is MS Diagnosed?

There is no single blood test, MRI finding or other investigation that independently confirms MS in every patient.

Assessment can include:

  • Detailed neurological history
  • Neurological examination
  • Brain MRI
  • Cervical and thoracic spinal MRI when appropriate
  • Cerebrospinal fluid analysis
  • Evoked potentials in selected patients
  • Blood tests to investigate conditions that can mimic MS

White-matter lesions on MRI alone do not establish a diagnosis. Their location, morphology and clinical context must be consistent with MS, and alternative explanations must be considered.

What Are the 2024 McDonald Criteria?

The internationally used McDonald criteria provide a structured framework for diagnosing MS.

The 2024 revisions, published in 2025, expanded previous diagnostic criteria to improve accuracy and allow an earlier diagnosis in appropriate patients.

Important changes include:

  • The optic nerve can now serve as a fifth anatomical location.
  • The central vein sign can provide supportive evidence in selected situations.
  • Paramagnetic rim lesions may increase diagnostic specificity in appropriate cases.
  • CSF kappa free-light chains can provide supportive evidence when available.
  • The criteria provide a more unified approach to relapsing and progressive presentations.
The McDonald criteria are not a single diagnostic test. They are applied by neurologists using clinical history, examination, imaging and laboratory findings while ensuring there is no better explanation for the presentation.

How Is MRI Used in MS?

MRI is one of the most important investigations in MS diagnosis and follow-up.

It can assess the location, number and characteristics of lesions in the brain and spinal cord and can help determine whether new disease activity has developed over time.

Is a Lumbar Puncture Always Needed?

No. Cerebrospinal fluid analysis is not required in every patient, but it can provide important supporting evidence when the diagnosis remains uncertain.

CSF can be examined for oligoclonal bands indicating immune activity within the central nervous system.

Under the 2024 McDonald criteria, CSF kappa free-light chains may also provide supportive diagnostic information in appropriate circumstances.

What Is an MS Relapse?

An MS relapse involves new neurological symptoms or a clear worsening of previous neurological symptoms associated with new inflammatory disease activity.

Infection, fever or heat can temporarily worsen old MS symptoms without representing new inflammatory activity. This is sometimes described as a pseudo-relapse.

How Is MS Treated?

There is currently no treatment that completely cures MS, but modern treatments can reduce disease activity, prevent or reduce relapses and slow disability progression in appropriate patients.

Management can be divided into:

  1. Treatment of acute relapses
  2. Disease-modifying treatment
  3. Symptom management and rehabilitation

Significant relapses affecting daily function may be treated with high-dose corticosteroids. These can accelerate recovery from the relapse but do not replace long-term disease-modifying therapy.

What Are Disease-Modifying Therapies?

Disease-modifying therapies (DMTs) target the immune processes responsible for MS disease activity.

Depending on the treatment and form of MS, DMTs can reduce relapses, reduce the development of new MRI lesions and slow disability progression.

They are available as injectable, oral and infusion therapies.

Treatment selection considers disease activity, MRI findings, previous relapses, age, other medical conditions, pregnancy plans and the potential risks and benefits of each therapy.

What Is the Role of Rehabilitation?

Rehabilitation is an important component of MS management.

Depending on individual needs, it can include physiotherapy, strengthening, balance training, gait rehabilitation, spasticity management, occupational therapy, speech and swallowing therapy and cognitive rehabilitation.

Regular physical activity adapted to individual capacity can help maintain strength, mobility and overall function and can assist with fatigue management.

Living With MS

Regular neurological follow-up and adherence to the agreed treatment plan are important.

Physical activity, avoiding smoking, balanced nutrition, good sleep, infection prevention and appropriate management of heat sensitivity can form part of long-term MS care.

Which Symptoms Require Urgent Assessment?

Sudden symptoms such as:

  • One-sided facial, arm or leg weakness
  • Sudden speech difficulty
  • Sudden severe visual loss
  • Sudden severe loss of balance or coordination
  • Altered consciousness

should be assessed urgently because stroke and other neurological emergencies can cause similar symptoms.

Early and Regular Follow-up Matters in MS

The course and activity of MS differ between individuals. Clinical assessment and MRI follow-up can help create an individualised treatment and monitoring programme.

Frequently Asked Questions

What is multiple sclerosis (MS)?
Multiple sclerosis is a chronic neurological condition associated with an abnormal immune response against structures within the central nervous system. It can affect the brain, spinal cord and optic nerves.
Does MS always cause relapses?
No. Many people initially have relapsing-remitting MS, but secondary progressive and primary progressive forms of MS can also occur.
At what age does MS usually begin?
MS most commonly begins between ages 20 and 40, although it can begin in childhood, adolescence or after the age of 50.
Can MS be diagnosed from MRI alone?
No. Diagnosis is not based on MRI alone. Clinical history, neurological examination, MRI findings and, when needed, cerebrospinal fluid and other investigations are considered together while excluding better alternative explanations.
What changed in the 2024 McDonald criteria?
The 2024 McDonald criteria added the optic nerve as a fifth anatomical location. In appropriate situations, the central vein sign, paramagnetic rim lesions and CSF kappa free-light chains can also provide supportive diagnostic evidence.
Is there a cure for MS?
There is currently no treatment that completely cures MS. Disease-modifying therapies can reduce relapses and disease activity and can slow disability progression in appropriate patients.
Can people with MS exercise?
Yes. Regular exercise and rehabilitation adapted to individual ability can help with strength, balance, mobility and fatigue management.
Does fever or hot weather cause an MS relapse?
Fever, infection or excessive heat can temporarily worsen previous MS symptoms in some people. This does not always represent new inflammatory MS activity and may be considered a pseudo-relapse.
Academic Hospital note: MS cannot be diagnosed from a single MRI finding or laboratory test. Clinical history, neurological examination, imaging and appropriate laboratory investigations are interpreted together. Modern disease-modifying therapies aim to reduce MS activity and limit future neurological damage. You can book an appointment.

References

  1. Academic Hospital. Multiple Sclerosis
  2. The Lancet Neurology / PubMed. Diagnosis of Multiple Sclerosis: 2024 Revisions of the McDonald Criteria
  3. ECTRIMS. McDonald Diagnostic Criteria
  4. National Institute of Neurological Disorders and Stroke. Multiple Sclerosis
  5. MS International Federation. Treatments and Therapies