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What Is the Difference Between Alzheimer’s Disease and MS?

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Updated September 28, 2009

Question: What Is the Difference Between Alzheimer’s Disease and MS?
I have multiple sclerosis (MS) and know that many of my symptoms are caused by "lesions" or "plaques" on different parts of my brain and spinal cord. Recently, I read an article about Alzheimer's disease, where the author referred to "plaques" causing the symptoms and problems related to that disease. Are these plaques the same as my lesions?
Answer: No. Although the lesions in MS are often referred to as "plaques" by some neurologists, these are not the same thing as the plaques in the brains of people with Alzheimer's disease. MS and Alzheimer's have entirely different mechanisms and causes and affect different areas of the central nervous system.

Damage to Different Parts of the Central Nervous System

Alzheimer’s disease results in extensive damage to the gray matter of the brain, which is basically a buildup of proteins in the brain in the form of “plaques” and “tangles,” which are associated with dying or injured neurons.

While MS often also leads to destruction of neural cells, which shows up as atrophy or “black holes,” the damage is not nearly as extensive in the gray matter. MS primarily damages the myelin and the axons underlying the myelin (the white matter) of the entire central nervous system, which is comprised of the brain, the spinal cord and the optic nerves.

Different Causes/Mechanisms of Disease

MS is thought by most experts to be primarily an autoimmune disease, whereby someone’s immune cells begin attacking their myelin. No one is quite sure what causes this to happen, but different theories point to infection with a virus (Epstein-Barr virus is often implicated), problems with metabolizing vitamin D and various genetic and geographic factors.

There are different hypotheses around the cause of Alzheimer’s disease, as well. Risk factors include: family history of Alzheimer’s disease, advanced age and lifestyle factors (smoking, cardiovascular problems, past accidents involving head injuries).

Extra Immune Cells at Work in MS

Interestingly, both MS and Alzheimer’s disease are caused by chronic inflammation in the central nervous system. In both diseases, cells called “microglia” are involved in the inflammation. Microglia are the main immune cells that are normally in the brain and spinal cord and those get over-activated in both Alzheimer’s disease and MS, leading to the formations of lesions, or scars.

However, in multiple sclerosis, the microglia are joined by other immune cells (including B cells and T cells) that have gotten across the blood brain barrier and attack the myelin. These “rogue” immune cells are not present in the central nervous system of people with Alzheimer’s disease.

Other Differences in MS and Alzheimer's Disease

Alzheimer's Disease:
  • continues to progress
  • uUsually diagnosed in older people
  • impacts life expectancy (average years lived after diagnosis is 4 to 7 years, although average age at death is often 90+ years)
Multiple Sclerosis:
  • MS-related cognitive dysfunction does not usually progress
  • usually diagnosed between the ages of 20 and 50
  • does not impact life expectancy significantly

Sources:

Dal Bianco A, Bradl M, Frischer J, Kutzelnigg A, Jellinger K, Lassmann H. Multiple sclerosis and Alzheimer's disease. Annals of Neurology. 2008 Feb;63(2):174-83.

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