Progression and Complications of Multiple Sclerosis (MS)


What is multiple sclerosis?

Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system. With MS, the immune system attacks the protective shell (myelin) of nerve fibers throughout the body. Scar tissue then accumulates around the nerves, which eventually causes nerve damage. Once the nerves are damaged with scar tissue, they cannot receive signals sent from the brain to properly operate. Since the nervous system controls every movement of the body, MS can cause vision issues, movement and muscle control problems, balance issues, and other health complications. The exact cause of multiple sclerosis is not yet clear.


Eighty-five percent of individuals diagnosed with multiple sclerosis are initially diagnosed with relapsing-remitting multiple sclerosis (RRMS). RRMS is characterized by flare-ups of symptoms (relapses) followed by times when symptoms are reduced or not present (remission).

Approximately 60 to 70 percent of people who are initially diagnosed with RRMS are eventually diagnosed with secondary-progressive multiple sclerosis (SPMS). With SPMS, symptoms steadily progress and cause problems with mobility.

Fifteen percent of those diagnosed with MS are diagnosed with primary-progressive multiple sclerosis (PPMS). With PPMS, symptoms steadily progress without remission or relapse.

While some people may only have mild symptoms, about 30 percent of individuals with MS experience significant disability after approximately 20 to 25 years with the condition.


Individuals with multiple sclerosis may develop physical, cognitive or emotional complications of the disease. Both MS symptoms and MS complications are highly individualized.

Bladder and bowel issues

Multiple sclerosis can cause interruptions in signals between the brain and the urinary tract and bowel systems. This can lead to constipation, diarrhea, urinary incontinence, urinary retention or urinary hesitancy. Recurrent urinary tract infections can occur when the bladder is affected.

Mobility issues
  • Foot drop
    Muscle weakness caused by multiple sclerosis can lead to a complication called “foot drop.” The nerves that send signals to the muscles that flex the ankle are damaged; therefore, the ankle is unable to lift the foot high enough to take a proper step. Walking often becomes difficult when foot drop is an issue.
  • Falls
    Falls can occur due to various symptoms of multiple sclerosis, including muscle weakness, balance issues, vision problems, dizziness, numbness and fatigue. Falls can break bones, and with MS, the risk of breaking a bone increases by more than 50 percent in comparison to those without MS.
  • Pressure sores
    Pressure sores can develop when mobility is severely limited. Sitting or lying in one position for too long can cause pressure sores to form. They typically occur in areas where bone is close to the skin, such as the heels, tailbone, shoulder blades, etc.
  • Paralysis
    Paralysis can occur with advanced, severe multiple sclerosis; however, two-thirds of people with MS remain mobile. Some individuals require a walking aid, such as a cane or crutches. Others may need a wheelchair or scooter due to weakness, fatigue or balance issues.
Vision changes

Multiple sclerosis can cause temporary or permanent vision changes, such as blurry vision, double vision or vision loss. Vision changes can occur as early symptoms of MS, but vision issues can also develop as the disease progresses.

  • Optic neuritis occurs due to inflammation of the optic nerve. The optic nerve is the conduit between the eye and the brain. Symptoms can occur in one or both eyes and include blurred vision, eye pain, impaired color vision and loss of peripheral vision. Optic neuritis can occur as a single episode or frequently recur.
  • Diplopia is more commonly known as double vision. Double vision occurs when the eyes are misaligned and do not aim at the same focal point at the same time. With MS, this can occur due to lesions on the brain stem or the cerebellum.
  • Nystagmus involves uncontrolled, quick, repetitive eye movements. With MS, nystagmus is caused by damaged nerves and brain structures that control eye movement.
  • Internuclear ophthalmoplegia involves faulty horizontal eye movement. With MS, it usually occurs in both eyes. Symptoms of internuclear ophthalmoplegia include double vision, blurred vision, dizziness and feelings of instability. Similar to nystagmus, it is caused by damaged brain structures.
Swallowing problems

Difficulty swallowing can become an issue when dealing with multiple sclerosis. The act of swallowing is actually a complex process that involves six cranial nerves in the brain controlling over 30 pairs of muscles. With MS, difficulty swallowing, or dysphagia, can arise due to the coordination/timing involved with swallowing or damaged/weak swallowing muscles.

Respiratory issues

Brain and spinal lesions associated with multiple sclerosis can affect lung function due to the lesions affecting signals from the brain to the lungs. This can reduce the ability to inhale and exhale efficiently.

  • Pneumonia
    Multiple sclerosis can cause breathing problems by reducing the ability to cough effectively or fully exhale. This can increase the risk for pneumonia.
  • Sleep apnea
    Sleep apnea causes sudden awakening with shortness of breath, chest pain at night, insomnia, daytime sleepiness and improved shortness of breath while sitting in an upright position. If the muscles that typically keep airways open become slack due to brain lesions, obstructive sleep apnea can occur.
  • “MS hug”
    Cervical spine lesions can cause the "MS hug," which includes the sensation of shortness of breath. The MS hug is caused by spasms of the muscles between the ribs.
  • Muscle weakness and spasticity can cause an inability to breathe deeply, which can decrease oxygen levels in the blood.
Cognitive complications

Cognitive complications include forgetfulness, memory loss, and slow intellectual processing. These changes are likely due to the brain lesions caused by multiple sclerosis.

Emotional complications

Individuals may experience emotional complications, such as depression, anxiety or mood swings. They may also experience unexpected or exaggerated sudden shifts in emotion, such as uncontrollable laughing or crying. This is known as pseudobulbar affect.

Sexual complications

Multiple sclerosis can cause damage to the nerves that carry messages from the brain to sexual organs. Reduced libido, erectile dysfunction or reduced vaginal lubrication can result from MS. The most common sexual complication from MS is erectile dysfunction. Hypersensitivity and reduced sensation are possible in the genital region, causing difficulty with orgasm.

Multiple sclerosis can also indirectly interfere with sexual function due to fatigue, depression and pain. Emotional impacts of MS often interfere with sex due to lowered self-esteem. Bladder and bowel issues can also interfere with sexual intimacy.