Multiple sclerosis causes a breakdown of the protective cover around nerves in the brain and spinal cord. This can affect various body systems, resulting in difficulties with thinking, vision, mood, and movement, among other symptoms.

Multiple sclerosis (MS) is an episodic or progressive and demyelinating immune condition. It’s caused by a breakdown of the protective cover (myelin sheath) around the nerves in the brain and spinal cord. This interferes with nerve messages in the brain and spinal cord, making it hard for the brain and spinal cord to send and receive messages with each other and the rest of the body.

The exact cause of MS is still unknown, and there’s no cure. The resulting symptoms and their severity can vary from person to person.

Read on to learn more about the effects of MS on the body.

Multiple sclerosis effects on the body infographicShare on Pinterest
Medical Illustration by Bailey Mariner

Early MS symptoms tend to appear in adults ages 20–40. People assigned female at birth are more likely to develop MS than people assigned male at birth.

The exact cause of MS is unknown, and there’s currently no cure. But treatments help manage the symptoms, reduce the number of relapses, and delay the disease progressing (worsening).

MS directly affects the nervous system as the body’s immune cells attack myelin in the brain and spinal cord. The symptoms can impact other body systems and cause nervous system symptoms, such as pain and weakness.

Primary symptoms of MS are those that occur due to damage to the myelin sheath and the nerves within. Doctors may treat these symptoms with medications to prevent MS attacks and slow demyelination. This can include:

  • vision loss
  • weakness
  • sensory changes
  • trouble concentrating

Secondary symptoms of MS are complications that arise due to the direct effects of MS. Examples include urinary tract infections that result from weak bladder muscles and a loss of muscle tone that results from an inability to walk. Doctors may treat secondary symptoms with medication and other therapies.

In some cases, slowing the progression of MS can prevent secondary symptoms.

As the immune system damages the myelin sheath, nerves are exposed. If the nerves become damaged, scar tissue known as plaques may form in the central nervous system.

The result is that the nerves within the brain do not communicate efficiently with each other. This can cause nervous system symptoms that include:

  • dizziness
  • vertigo
  • confusion
  • memory problems
  • mood or personality changes

People may also experience depression as a result of MS or from the difficulty of coping with the disease.

Though less common, in advanced cases, MS can cause tremors, seizures, and cognitive problems that closely resemble other neurodegenerative conditions such as dementia.

The impaired nerve signaling between the brain and the organs, muscles, tissues, and cells served by the damaged nerves affects many body systems.

Vision and hearing loss

For many people, vision problems are the first sign of MS and can begin suddenly, affecting one or both eyes. They can include:

  • double vision (diplopia)
  • blurriness or dimness
  • pain
  • loss of color vision
  • shaking of the eyes (nystagmus)

These vision problems are usually temporary and likely result from nerve inflammation or eye muscle fatigue.

Although some people with MS experience permanent vision problems, most can be effectively treated with steroids and other short-term treatments, such as special lenses.

Though rare, some people with MS may experience hearing loss or deafness caused by damage to the brainstem. These types of hearing problems usually resolve when the MS flare improves. But they can be permanent in some cases.

Speaking, swallowing, and breathing

According to the National MS Society (NMSS), 25%–40% of people with MS experience speech problems at some point. These can include:

  • slurring words, or difficulty articulating
  • disrupted speech pattern
  • trouble with volume control
  • stuttering
  • changes in pitch
  • nasal voice
  • hoarseness or breathiness

These effects often occur during relapses or times of fatigue. Treatment may include speech therapy.

People with MS can develop breathing difficulties brought on by demyelination that can impact nerves that control muscles in the chest. Difficulty controlling these muscles can begin early in the disease and worsen as it progresses. Difficulty breathing is a dangerous yet uncommon complication of MS. It often can be improved through work with a respiratory therapist.

Swallowing problems (dysphagia) can also develop. If demyelination weakens the muscles involved in swallowing or hinders the body’s ability to control them, it can cause swallowing problems. When proper swallowing is disrupted, food or drink can be inhaled into the lungs, increasing the risk of infections like pneumonia.

Coughing and choking when eating and drinking may occur if you have swallowing problems and should be evaluated immediately. Speech or language therapists can often help with trouble swallowing.

Muscle weakness and balance issues

Demyelination in areas of the brain and spinal cord that control sensation, movement, or balance results in weakness or balance impairment of the limbs or trunk. This may occur when the brain has trouble sending signals to the nerves and muscles. Symptoms can include:

  • pain
  • tingling
  • numbness
  • trouble with hand-eye coordination
  • muscle weakness
  • balance issues
  • walking difficulties

These effects may start gradually and worsen as demyelination progresses. Many people with MS first feel “pins and needles” and have difficulty with coordination or fine motor skills.

Over time, limb control and ease of walking may be disrupted. In these cases, canes, wheelchairs, and other assistive technologies can aid in muscle control and strength.

People with MS are at higher risk of developing low bone density (osteoporosis) due to common MS treatments (steroids) and inactivity. Weakened bones can make individuals with MS susceptible to fractures and breaks, which can add risk if you also have balance and coordination problems.

Osteoporosis can be prevented or slowed through:

  • physical activity
  • diet
  • supplements

Research suggests that vitamin D deficiencies may play an important role in the development of MS. Although its exact effect on individuals with MS isn’t yet well understood, vitamin D is vital to skeletal health and immune system health. More studies are needed to determine whether and how much vitamin D supplements may benefit people with MS.

MS is thought to be an immune-mediated disease. This means that the body’s immune system mistakenly damages healthy nerve tissue, causing damage to the myelin sheath. Immune system activity seems to result in the inflammation responsible for many MS symptoms. Some symptoms may flare up during an MS attack and resolve when the episode ends.

Some MS treatments involve medications and infusions that affect immune cells to help slow the progression of the disease. However, drugs that suppress the immune system may make people more vulnerable to infection.

Problems with bladder and bowel functions commonly occur with MS. This can include:

  • constipation
  • diarrhea
  • loss of bowel control

In some cases, diet and physical therapy or self-care strategies can reduce the impact of these problems on daily life. Other times, medications or other interventions may be necessary.

This is because nerve damage affects how much urine those with MS can comfortably hold in the bladder. MS can cause:

  • difficulty holding in urine (incontinence)
  • difficulty urination when you want to (retention)
  • voluntary or involuntary release of small amounts of urine (spasticity)

This can result in complications such as:

  • spastic bladder infections
  • urinary tract infections (UTIs)
  • kidney infections

These problems can make urination painful and very frequent, even overnight or when there’s little urine in the bladder. The use of a catheter may occasionally be necessary.

Doctors can help people with MS effectively manage bladder and bowel problems and avoid complications. But if untreated or unmanaged, they can result in serious infections.

MS can cause an increased risk of infertility in people assigned male and female at birth.

MS doesn’t increase the risk of pregnancy complications compared to people without MS.

Pregnant people with MS may experience fewer relapses during the second and third trimesters of pregnancy. The NMSS also notes that exclusive breastfeeding may protect against postpartum relapses.

However, sexual dysfunction, such as difficulty experiencing arousal or orgasm, can occur with MS. This can result from demyelination or other MS symptoms, such as fatigue, pain, or depression.

MS symptoms can sometimes make sexual intimacy feel awkward. But, in many cases, sexual problems can be managed successfully through medication, over-the-counter aids, or counseling.

People with MS may have a greater risk for cardiovascular disease, according to a 2022 review of research. This can include:

  • coronary artery disease
  • heart attack (myocardial infarction)
  • heart failure
  • atrial fibrillation

Treatment to manage MS symptoms, along with heart-healthy behaviors, such as eating a balanced diet and getting regular physical activity, can reduce an individual’s risk.

The following includes common questions about the effect of MS on the body.

What happens to your body when you have MS?

When you have MS, your immune system damages the protective covering around nerves in your brain or spinal cord. This inflammation causes demyelination, which may result in nerve damage and symptoms that affect different body systems.

These symptoms can include tingling and numbness, vision changes, muscle cramping and weakness, and problems with bladder and bowel function.

What is the life expectancy of a person with MS?

MS does not significantly alter a person’s life expectancy, according to the National Institute of Neurological Disorders and Stroke (NINDS).

The NMSS notes that life expectancy may be 7 years less than people without MS due to complications that can potentially be prevented or managed and other health conditions. Depending on the type of MS you have and the severity of your symptoms, you may experience some disability.

What part of the body does MS affect first?

MS directly affects the nervous system as the body’s immune cells attack the myelin in the brain and spinal cord. The impaired nerve activity can impact different body systems, causing symptoms such as muscle weakness, loss of bladder control, and vision changes.

While there’s no cure for multiple sclerosis, a wide variety of treatment options can manage symptoms and modify the disease by preventing its progression and overall effects on your body.

MS affects everyone differently. Each person has a unique set of symptoms and responses to treatments.

You can work with a doctor or healthcare team to customize a treatment plan that addresses your symptoms and helps prevent relapses and disease progression. This can make MS more manageable.