• A high power photomicrograph of the MS plaque showing
the pallor of the plaque almost devoid of myelin.
There is a decrease in oligodendroglial nuclei and an
increase of astrocyte nuclei characteristic of an older
• Between the nomal myelin and plaque there is an area of milder pallor which is known as a shadow plaque.
•Multiple sclerosis is a demyelinating disease (see loss of myelin with relative preservation of neurons and axons) characterized by remissions and exacerbations which is due to an inborn error of immune reaction to an environmental agent, probably a virus.
•T and B cells through immunological mechanisms still
unknown influence macrophages to strip myelin off
axons in random areas of the white matter during
periods of active disease.
•Oligodendroglia are not
primarily affected and may even multiply to remyelinate
the periphery of the lesion the first time.
•Although with time oligodendroglia and remyelination decreases and astrocytes proliferate to form glial "scar" tissue.
•MS is seen in approximately 1 in 1000 persons in the US.
•However, its prevalance varies with latitude being higher
the farther from the Equator one lives.
•It is related
to exposure to the agent before 15 years of age. People
who migrate from a high to low before 15 take on
the low prevalance whereas, those that migrate from a
high to low area after 15 maintain the high prevalence.
•The concordance in monozygotic twins is 25%.
develop the disease approximately twice as often as men.
•The onset of the disease is between 20 and 40 years of age.
•With the onset of active disease, acute exacerbation,
the patient develops neurological symptoms and signs
such as optic neuritis with unilateral or partial
blindness, hemiparesis, ataxia, and hemisensory defects
depending on where the lesions are in the brain.
weeks the symptoms remit although there is often
•The remission is thought to be due
to decreased edema, remyelination and some ability of
unmyelinated fibers to conduct signals.
•A chronic progressive form of MS is also known.
|General Gross Description|
•The lesions appear as greyish plaques randomly
distributed throughout the nervous system.
•Most commonly they are found periventricularly but can be seen anywhere including predominately grey matter.
|General Micro Description|
•Acute MS plaques appear as areas with many macrophages
filled with lipid and a few perivascular lymphocytes as
well as lymphocytes in the tissue.
•As time passes, the
macrophage reaction decrease and there is proliferation
of reactive astrocytes forming fibers throughout the
•Perivascular and tissue lymphocytes remain for
•With time oligodendroglia and axons decrease in number throughout the plaque for reasons that are not well understood.
• Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 1328.
• Poirer J et.al. Manual of basic neuropathology. Philadelphia: Saunders, 1990, pp.128-129.