Multiple sclerosis can affect people in different ways, and there is no way to know exactly which symptoms will be experienced or how long they will last. Before understanding what tools and approaches are used by health care professionals to make a diagnosis, it is important to recognize the symptoms of MS and understand the impacts they can cause.

The following sections will help to shape that understanding: 

MS causes a wide range of symptoms

MS is an inflammatory disease (causing inflammation to a part of the body) that attacks the myelin of the central nervous system (CNS). The CNS is the part of the nervous system that controls activities of the body. It includes the brain, brainstem and spinal cord. As a result, the signs and symptoms of MS vary depending on the specific areas of the CNS being affected.

Some early symptoms are often so mild or vague that their presence is difficult to recognize. In some situations, they can be severe and very abrupt.


Some people have very few symptoms, especially in the early stages. The symptoms some people experience may not be the same as someone else’s. What is more, symptoms may vary from one MS relapse (attack or flare-up) to the next. Depending on the area of the CNS that has been affected and the degree of damage, different symptoms may occur.

Some of the more common symptoms of MS are outlined below.


Numbness of the face, body or extremities (arms and legs) is often the first symptom experienced by those eventually diagnosed with MS. The altered sensations (paresthesias)  may be mild or so severe that they interfere with the ability to use the affected part of the body.

Examples include tickling, burning, pricking, or the sensation of “pins and needles” or of a limb “falling asleep.” These symptoms can be chronic (persisting for long periods of time) or transient (lasting for only a short period of time).

Blurred vision or visual loss

A sudden onset of visual blurring or loss of vision in one eye, particularly in the central visual field, is understood as optic neuritis  (an inflammation of the optic nerve). The optic nerve is the specialized cable that transmits what the eye sees to the brain.

In addition to blurring or loss of vision, eye movement may bring on pain, light flashes or other visual symptoms, such as changes in colour vision. 

Double-vision , commonly known as diplopia , occurs when the pair of muscles that control a particular eye movement are not perfectly coordinated due to weakness in one or both pairs of muscles. When the images are not properly fused, the person perceives a false double image.

Double vision may increase with fatigue or overuse of the eyes (e.g., with extended reading or computer work), and improve with rest.

Difficulty walking or staying balanced

Poor coordination in MS results from cerebellar involvement (area in the brain) and can be one of the most disabling symptoms of MS. It often co-exists with tremor and balance difficulties. Errors in rate, range, direction and force of movement are characteristic in these cases, making the simplest of daily activities like walking, pouring liquids, eating and personal hygiene very difficult.

Problems with gait (difficulty walking) are the most common mobility limitations in MS and are related to weakness, spasticity (muscle tightness), loss of balance, fatigue and numbness.

The majority of gait or mobility problems can be helped to some extent by physical therapy (including exercises and gait training), the use of appropriate assistive devices (such as canes, scooters, walkers) and, in some cases, medications for spasticity, fatigue and walking speed.

Spasticity  refers to feelings of stiffness and a wide range of involuntary muscle spasms (sustained muscle contractions or sudden movements), and is one of the more common symptoms of MS.

Spasticity may be as mild as the feeling of tightness of muscles or may be so severe as to produce painful, uncontrollable spasms of extremities, usually of the legs.

The primary tools used for evaluating mobility are known as the Timed 25-foot Walk, Timed Up and Go (TUG) and the Nine-Hole Peg Test.

Weakness or fatigue

Of the many symptoms associated with MS, fatigue is a common and potentially disabling symptom. Fatigue can be a primary symptom (due to active inflammatory disease) or a secondary symptom (the result of other symptoms or conditions such as sleep disorders, depression or muscle weakness), sometimes referred to as lassitude or MS-related fatigue .

Difficulty with bladder or bowel control

Specific bowel dysfunction problems common in MS include constipation, incontinence, loss of muscle control or weakness, slow motility and diarrhea.

Constipation can be caused by nerve damage or be a side effect of medication such as antidepressants or bladder control drugs. Loss of control of bowel movements may be caused by nerve damage or aggravated by constipation. Diarrhea is less common than other bowel function problems in people with MS.

Bladder dysfunction  happens when MS lesions block or delay transmission of nerve signals in areas of the central nervous system (CNS) that control the bladder and urinary sphincters.

A spastic (overactive) bladder that is unable to hold the normal amount of urine, or a bladder that does not empty properly and retains some urine in it can cause symptoms including: inability to empty the bladder completely, incontinence (the inability to hold in urine), frequent nighttime urination, frequency and/or urgency of urination and hesitancy in starting urination.

Challenges with memory or other thinking skills

Thinking skills, or cognition , refer to a range of high-level brain functions, including the ability to learn and remember information, organize, plan and problem-solve, understand and use language, perform calculations and more.

A person may experience difficulties in only one or two areas of cognitive functioning or in several. As with many other symptoms in MS, cognitive problems happen because of damage (lesions or scars) in the brain. The effect that lesions have on the way the brain functions depends on their specific location.

A neurological exam is one of the first things a doctor will do to assess whether or not someone may have MS. A series of tests are used to provide information so the doctor knows what areas may need further evaluation. The exam looks at a person’s cognition, coordination and strength, vision and hearing, and other senses.

Speech problems

Speech disorders are fairly common in people with MS, affecting most at some point. Speech patterns are controlled by many areas in the brain, especially the brainstem. Lesions (damaged areas) in different parts of the brain can cause several types of changes in normal speech patterns. If brain areas that control the tongue, lips, soft palate, cheeks or breathing muscles are affected, speech patterns can become slurred. 

There are two types of speech disorders that occur in MS, dysarthria and dysphagia.

When speech sounds slurred , slow or difficult to understand , it can sometimes be the result of dysarthria. Dysarthria is a term used to describe the weakening of the muscles used to speak.

Difficulty in swallowing can be the result of dysphagia. While more frequent in advanced disease, it can occur at any stage.  A person may cough after drinking liquids, or choke when eating certain foods.

The effect of heat and fatigue on MS symptoms

MS symptoms worsen with exposure to heat — commonly referred to as Uhthoff’s phenomenon.

Why it happens is unclear, but it is believed that heat reduces nerve transmissions along axons that have lost their myelin.

MS symptoms tend to worsen with fatigue.

In general, people with MS feel much better in the morning. As the day wears on they become tired and their symptoms become worse. Fever, depression or feeling stressed can all worsen symptoms significantly.

Relapses and remissions

Most people with MS experience relapses.

In MS, the onset of symptoms is called a relapse or exacerbation . No two relapses are alike, and symptoms vary from person to person and from one relapse to another. A lessening of severity or short-term disappearance of the disease is called a remission.  To be considered a relapse, symptoms must last more than 24 hours. These episodes of symptoms could last between three to 12 weeks, sometimes less, and then go away, either partially or completely – but later return, or relapse.

Some produce only one symptom  (related to inflammation in a single area of the central nervous system) while other relapses cause two or more symptoms at the same time  (related to inflammation in more than one area of the central nervous system).

It is important to let a doctor know if symptoms worsen and if any new ones appear.

pseudo-relapse  is an episode of symptoms occurring due to circumstances, and clearing up when those circumstances change.

For example, becoming overheated or extremely tired may cause some symptoms to appear, which then vanish once a person has rested or cooled down.

Typically they last less than a day.

Relapses cause new symptoms or the worsening of old symptoms.

There is no way to know exactly which symptoms will be experienced or how long they will last. Even so, it is important to know the symptoms that MS can cause, in order to keep track of them if they occur.


Assessing the impact of MS on mobility

“Mobility” means different things to everyone.

For some, it means being able to go on long runs or hikes, while for others it means being able to walk and perform their daily activities just like they always have. No matter what mobility means to different people, the ability to get from A to B is something that is important to all of us.

The primary tools used for evaluating mobility are known as the Timed 25-foot Walk, Timed Up and Go (TUG) and the Nine-Hole Peg Test.


The Timed 25-Foot Walk test is a mobility and function test based on a timed 25-foot walk. An individual will be asked to walk 25 feet on a clearly marked course as quickly and safely as they can.

The time is calculated with a stopwatch, recorded, and the individual is asked to repeat the task immediately, walking back the same distance to the their initial starting point.


The purpose of the TUG test is to identify individuals who are at risk of falling. It can screen for balance and gait problems.

A person is observed as they stand from a sitting position without using their arms for support, then walk 10 feet, turn and return to a chair. Finally, they sit back in the chair without using their arms for suport.

In a follow-up assessment, the individual is asked to stand from a sitting position without using their arms for support, then close their eyes for a few seconds while standing still. The individual is then instructed to walk 10 feet, come to a complete stop, then turn around and return to the chair and sit without using their arms for support.


The Nine-Hole Peg Test  aims to measure arm and hand function. The apparatus is placed on the table so that the side with the pegs is in front of the hand being tested. Pegs are picked up one at a time using only the hand being tested, and put into the holes as quickly as possible.

When all pegs are placed into the holes, the person should then remove them and return them to their container as quickly as possible. The routine is repeated twice with each hand.

Timely and accurate diagnosis

Making the diagnosis of MS as quickly and accurately as possible is important for several reasons:
  1. If someone is living with unfamiliar and distressing symptoms, knowing the reasons contributing to the discomfort could provide reassurance. A diagnosis allows a person to begin the adjustment process and helps to relieve worries about other diseases.
  2. Since we now know that permanent neurologic damage (damage related to the nervous system) can occur even in the earliest stages of MS, it is important to confirm the diagnosis so that the appropriate treatment options can be explored and initiated as early in the disease process as possible.

When MS is considered as a potential diagnosis, an individual’s medical history and neurological exam are the mainstay. With that, a diagnosis of MS must include evidence of disease activity separated in time ( lesions that formed at different points in time) and space (lesions in at least two separate areas of the central nervous system).  

The diagnosis of MS is made only once other potential causes for symptoms have been ruled out, and while this process of exclusion may be very rapid for some individuals, it can take a much longer time – with repeat testing – for others.

MS rating scale (EDSS scale)

The Expanded Disability Status Scale (EDSS) is a tool used to assess mental and physical ability. A trained examiner, such as a doctor or neurologist, will carry out an examination looking at general ability. Specific areas such as visual, sensory and bowel and bladder functions will also be observed. 

The EDSS is a clinical rating scale based on the judgement of the examiner, ranging from 0 to 10 in half-point increments.

The score increases the more your ability is affected. For example, a score of 0 signifies a normal neurological examination, a score of 4 signifies disability but self-sufficient, and 6 means “needing assistance” such as a cane to walk. It is important to remember that 75% of people with MS will never need to use a wheelchair. Few people will ever have a score higher than 6 – in fact, nearly 60% of people with MS will still have an EDSS score of 6 or below, 15 years after diagnosis.

Keeping an eye on symptoms involves being aware of any changes that can be noticed during regular activities that involve a set distance. For example, some people may notice that running errands takes longer than normal, more rests are needed or they feel more tired afterwards.

Reference: Kurtzke JF. Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS).  Neurology. 1983 Nov;33(11):1444-52.  

Any changes in symptoms should be discussed with a doctor.

MS diagnostic tools

When doctors diagnose multiple sclerosis (MS), they may use a few different tests. That is because there is not necessarily one single test that can diagnose MS. The tests help doctors rule out other conditions and zero in on a diagnosis.

The main tests are:

Neurological exam

This is one of the first things a doctor will do to assess whether or not someone may have MS. A series of tests are used to provide information so the doctor knows what areas may need further evaluation.

The exam looks at a person’s cognition, coordination and strength, vision and hearing, and other senses.

Magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI) is the diagnostic tool that currently offers the most sensitive way of imaging the brain, spinal cord or other areas of the body. It is a tool that makes it possible to visualize and understand much more about the underlying progression of the disease.

MRI is the preferred imaging method to help establish a diagnosis of MS and to monitor the course of the disease.

Evoked potentials

Evoked potential (EP) tests measure the electrical activity of the brain to see if sensory pathways are properly functioning. This helps measure any damage the nerves have had from MS.

Evoked potential tests are especially useful when findings on the MRI scan are unexpectedly normal or borderline. No needles or injections are involved and there is no radiation –making it safe to undertake even during pregnancy. 

Cerebrospinal fluid (CSF) examination 

Cerebrospinal fluid (CSF) is a clear, colourless liquid that bathes the brain and spinal cord.

While the primary function of CSF is to cushion the brain within the skull and serve as a shock absorber for the central nervous system, CSF also circulates nutrients and chemicals filtered from the blood and removes waste products from the brain.

In people with MS, this fluid shows specific changes that match up with the presence of inflammation.

The important role of MRI

MRI can enable people to plan their next steps.

Magnetic resonance techniques have had a major impact over the last two decades in understanding and MS. The imaging guidelines for MS are broadly divided into approaches for imaging patients with suspected MS, or for monitoring patients with established MS. 

How it works:

MRI uses very strong magnets, radio signals and computer software to take three-dimensional pictures of the inside of the body. During the test, a person will lie in the MRI machine for 15 to 30 minutes.

The actual device produces a unique sound that might surprise people if they do not know it is coming. A technician will be on hand to notify individuals of what they can expect and help answer any questions they may have.

It may seem a little cramped in the MRI machine. Those who have a difficult time being in confined spaces may wish to consult with their doctor.


Use of contrast materials:

An MRI may sometimes include contrast materials, substances used to improve the image of body organs and tissues. They are often used to visualize certain types of MS disease activity on the MRI. 

Benefits of MRI in MS:

In providing a relatively accurate measure of disease activity, MRI has enhanced our ability to diagnose the disease, which in turn allows for earlier treatment exploration.

Because MRI is also a tool that helps track the progression of the disease, assessing progression can help individuals make informed decisions on treatment options.

Early diagnosis and treatment are important in limiting the impact of MS, helping in the management of early symptoms and prevention of new disease activity.

Treating MS requires a comprehensive approach

People living with MS may have concerns that range from physical to social to emotional. Patient programs and several support groups – such as those coordinated through the Multiple Sclerosis Society of Canada (MSSC) and the Biogen ONE™  Support Program – are available for all types of resources.

To learn more about the Biogen ONE™ Support Program,

Treatment goals

Although there is currently no cure for MS, the good news is there are various treatments that can help reduce the frequency of relapses.

Advances are being made that help us better understand MS and address its symptoms. Effective strategies can help modify or slow the disease course, treat relapses and manage symptoms, while addressing emotional health. Neurologists play an important role within a healthcare team, providing guidance on available treatments and helping to coordinate the best possible treatment plans.

This journey should be a joint effort, but ultimately, those living with MS are the ones who will decide what steps to be taken next.


For over 30 years, Biogen has been a leader in MS research and currently offers the broadest MS therapy portfolio to help people with relapsing forms of MS.