CT Scan Multiple Sclerosis Lesions

Multiple Sclerosis (MS)

• MS is an autoimmune demyelinating disorder characterized by distinct episodes of neurologic deficits, separated in time, attributable to white matter lesions that are separated in space.
• The disease may become clinically apparent at any age, although onset in childhood or after age 50 years is relatively rare.
• The frequency of relapses tends to decrease during the course of time, but there is a steady neurologic deterioration in most affected individuals.
• MS will continue to progress with relapses, usually leading to death due to respiratory failure (lung collapse).

Pathogenesis

• The lesions of MS are caused by an autoimmune response directed against components of the myelin sheath.
• The pathogenesis of this disease involves both genetic and environmental factors.
• There is a strong effect from the DR2 extended haplotype of the major histocompatibility complex.
• Genome-wide association studies first identified additional associations with the IL-2 and IL-7 receptor genes.

Demyelinating Diseases

• Demyelinating diseases of the CNS are acquired conditions characterized by preferential damage to myelin with relative preservation of axons.
• Myelin loss will affect the transmission of electrical impulses along axons.
• Several pathologic processes can cause loss of myelin, including immune-mediated, viral infections, and inherited disorders.

Characteristics of MS

• MS is the most common of the demyelinating disorders, having a prevalence of approximately 1 per 1000 persons in most of the United States and Europe.
• Women are affected twice as often as are men.
• MS affects oligodendrocytes.
• The infiltrate in plaques and surrounding regions of the brain consists of T cells (mainly CD4+, some CD8+) and macrophages.

Pathological Features

• Macroscopically, lesions are firmer than the surrounding white matter (sclerosis) and are well circumscribed, somewhat depressed, glassy, gray-tan, irregularly shaped plaques.
• Microscopically, active plaques have abundant macrophages containing lipid-rich, PAS-positive debris, while inactive plaques have little to no myelin found.
• Plaques commonly occur adjacent to the lateral ventricles, and are also frequent in the optic nerves and chiasm, frequently brainstem, ascending and descending fiber tracts, cerebellum, and spinal cord.