Multiple Sclerosis

Biology 12 Nervous System Project

Overview

Multiple Sclerosis (MS) is a progressive and unpredictable disorder that affects the central nervous system.

Figure 1: The central nervous system is comprised of the brain and spinal cord.

What is a relapse?

An attack, worsening or flare up of the disease.

Worsening of symptoms.

Medical providers call an attack a relapse if:

Old symptoms become worse or new symptoms appear.

Symptoms least at lease 24 hours.

Occurs at least 30 days after last relapse.

There is no other explanation for symptoms (ie. Flu)

4 Types of MS

Type Characteristics

Relapsing-Remitting MS (RRMS) This is the most common form of multiple sclerosis. About 85% of people with MS are initially diagnosed with RRMS. People with RRMS have temporary periods called relapses, flare-ups or exacerbations, when new symptoms appear.

Secondary-Progressive MS (SPMS) In SPMS, symptoms worsen more steadily over time, with or without the occurrence of relapses and remissions. Most people who are diagnosed with RRMS will transition to SPMS at some point.

Primary-Progressive MS (PPMS) This type of MS is not very common, occurring in about 10% of people with MS. PPMS is characterized by slowly worsening symptoms from the beginning, with no relapses or remissions

Progressive-Relapsing MS (PRMS) A rare form of MS (5%), PRMS is characterized by a steadily worsening disease state from the beginning, with acute relapses but no remissions, with or without recovery.

Table 1: Types of MS.

Image 2: Relapses and progression of symptoms dictate classification of the type of MS.

Cause

The cause of MS is not know, despite extensive research.

It is likely that MS is an auto-immune disease. A healthy immune system defends the body against disease. Auto-immune diseases cause the immune system to mistake healthy cells for intruders, and therefore, attack them.

Cause: Contributing Factors Lifestyle, environmental, genetic and biological factors could all

contribute to a person’s susceptibility to the disease.

It is not thought that genetic mutations cause MS. Instead, the perfectly healthy genes could have very subtle variations that do not fit together properly. The immune system, the brain and the spinal cord would be most impacted.

MS is known to occur more frequently in areas that are farther from the equator.

This could be explained by the growing evidence that suggests that vitamin D plays an important role. People who live near the equator are exposed to greater amounts of sunlight, allowing them to naturally produce more vitamin D, which is important for immune system function.

Another theory is that a common virus could act as a stimulus by entering the brain and influencing the immune system.

Structures of Nervous System that MS Disrupts/Destroys

MS a result of damage to the myelin.

Myelin is the sheath that covers (usually) the axon in a neuron. Myelin insulates and protects the axon and helps speed nerve transmission.

Myelin is present in both the central nervous system and peripheral nervous system. Central nervous system and peripheral nervous system myelin is different chemically, but serves the same function. However, only the central nervous system is affected by MS.

When the myelin is damaged, the messages from the brain to other bits of the body are affected.

It is believed that the immune system attacks the myelin.

Image 3: Healthy nerve cell vs. nerve cell damaged by MS

Symptoms

There is great variety and inconsistency in symptoms. There is no typical case.

Symptoms can include:

Balance/Dizziness

Bladder or bowel dysfunction.

Cognitive Impairment

Depression

Fatigue

Gait (difficulty in walking)

Optic neuritis (Inflammation of the optic nerve)

Paroxysmal Symptoms (cluster of symptoms – if they occur over several days, it could be a MS relapse.)

Sensory Impairment,

Numbness / Tingling

Sexual Dysfunction

Spasticity

Tremor

Uhthoff's Phenomena (Heat Intolerance)

Weakness

Image 4: MS often causes numbness, which usually originates in the limbs.

Treatment There is no cure for MS, but there are a variety of treatments.

Treatment name Method

Disease-modifying therapies (DMTs) Medication that works on relapses and progression.

Relapse management therapies Steroid medications. If used over the long term there are severe side effects. Work to reduce inflammation in specific areas of central nervous system, and therefore, reduce the severity of relapses.

Symptom management therapies Help ease symptoms, rather than alter disease itself

Alterative medicine Includes acupuncture, naturopathy, homeopathy and others.

Rehabilitation and Physical Therapy Aims to improve and strengthen physical function.

Table 2: Treatments for MS.

Image 5: Physical therapy.

Image 6: Acupuncture, an alternative therapy.

Number of People Affected

It is estimated that more than 2.3 million people are affected by MS worldwide. (National MS Society)

Because diagnosis is difficult and symptoms vary, it is difficult to know an exact number.

Mortality Rate

There is difficulty in collecting data relating to death due to MS because of data collected in different places, at different time. Therefore, data varies.

MS reduces life expectancy in patients compared to the general population by 7-14 years, according to a 2013 study.

MS is the main cause of death in ≥50% of patients, according to the same study.

In people affected by MS, the suicide rate is significantly higher than the general population.

Image 7: Mortality Rates for MS.

Further Enquiries

Learning about the impact on the neurons was very interesting!

It was challenging to come to clear conclusions since so little is know about the causes.

The exciting aspect of learning about MS is that there is so much ongoing research and areas for further enquiry. In the future, I would like to learn more about how environmental and genetic factors can influence susceptibility to the disease.

Bibliography

MS International Federation. (n.d.). Retrieved November 30, 2015, from http://www.msif.org

Multiple Sclerosis FAQs. (n.d.). Retrieved November 30, 2015, from http://www.nationalmssociety.org/What-is-MS/MS-FAQ-s#question-What-are-the-typical-symptoms-of-MS

Multiple Sclerosis Society of Canada. (n.d.). Retrieved November 30, 2015, from https://beta.mssociety.ca

Multiple sclerosis. (2015, October 1). Retrieved November 30, 2015, from http://www.mayoclinic.org/diseases-conditions/multiple-sclerosis/home/ovc-20131882

Myelin. (n.d.). Retrieved November 30, 2015, from http://www.nationalmssociety.org/What-is-MS/Definition-of-MS/Myelin

Scalfari, A., Knappertz, V., Cutter, G., Goodin, D. S., Ashton, R., & Ebers, G. C. (2013). Mortality in patients with multiple sclerosis. Neurology, 81(2), 184–192. http://doi.org/10.1212/WNL.0b013e31829a3388