MULTIPLE SCLEROSIS

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS). Symptoms may be relatively mild, such as paresthesia of the extremities, or they may be severe, such as blindness or paralysis.¹

MS is an illness diagnosed in more than 400,000 persons in the United States today.² It is a demyelinating disease typically diagnosed between the ages of 20 and 40. In MS, myelin is lost in multiple areas, leaving scar tissue called sclerosis. These damaged areas are also known as plaques or lesions. Sometimes the nerve fiber itself is damaged or broken. There is such wide diversity in those afflicted that the final severity for any one individual cannot be determined at the initial onset of symptoms. A number of factors in combination are probably involved in MS.³ The four major theories of causes of MS are: environmental, genetic, immunologic, and viral.¹

Environmental

Those who are born in an area with a high incidence of MS and then move to an area with a lower risk appear to acquire the new risk, but only if the move occurs before the approximate age of puberty. It is possible that exposure to some environmental agent encountered before puberty may predispose a person to develop MS later in life. This currently is an area of active research.

Genetic

Although MS is known not to be hereditary per se, having a close relative with MS does increase one’s risk of developing the disease. Some researchers believe that MS may develop as a result of a genetic predisposition that also requires a reaction to an environmental antigen (which makes this actually an autoimmune response).

Immunologic

Most professionals agree that MS is primarily an autoimmune-modulated disease directed toward the myelin in the CNS; the exact antigen is unknown, but more data is continually acquired. As the myelin sheath is damaged or destroyed, the nerve impulses are altered—they are slowed or interrupted, leading to the symptoms of MS.

Viral

Some viruses of typical childhood exposure are known causes of demyelination and inflammation, so it is possible that a virus is the triggering factor in some cases of MS. Many viruses, including measles and herpes, have been evaluated to determine whether they might be associated with the development of MS, but at present, none have been proven as causative.

Worldwide, for as yet unknown reasons, MS occurs with much greater frequency in latitudes above 40 degrees north. In the United States specifically, MS occurs more frequently in states that are above the 37th parallel than in states below it. For informational purposes, the 37th parallel extends from approximately the southern border of Virginia to just south of San Francisco, California. It follows the northern border of North Carolina to the northern border of Arizona. The prevalence rate for those above the 37th parallel is approximately 125 cases per 100,000 persons, whereas below the 37th parallel, it is only around 70 cases per 100,000. MS is also two to three times as common in women as in men.¹

Even though local anesthetics exert their effect on nerves and nerve transmission, there are no particular concerns with the administration of local anesthetics in patients with MS. Likewise, inhalation sedation with nitrous oxide and oxygen, enteral (oral) minimal or moderate sedation, parenteral moderate sedation, and general anesthesia are all acceptable in the outpatient dental office. Stress may negatively influence this disease, so all efforts to minimize or ideally eliminate stress are encouraged; of course, this includes all properly performed sedative and anesthetic procedures.

MUSCULAR DYSTROPHY

Muscular dystrophy is not one disease, but a family of genetically transmitted diseases, each of which encompasses degeneration of musculature but with no definable nerve disturbances. The most common form is Duchenne muscular dystrophy (DMD) (also known as pseudohypertrophic).⁴ It was first described by the French neurologist Guillaume Benjamin Amand Duchenne in the 1860s. Until the 1980s, however, little was known about the cause of any of the muscular dystrophies.

DMD occurs when a specific gene on the X chromosome does not manufacture a protein called dystrophin; therefore the disease affects only male subjects. Women may be carriers of the disease. The course of DMD is fairly predictable. Signs of muscle weakness may be seen as early as age 3.⁵ Within the next 10 years, the heart and muscles of respiration can also be affected. Nearly all children with DMD lose the ability to walk sometime between ages 7 and 12.

Myotonic muscular dystrophy (DM, MMD, or Steinert disease) is the most common adult form of muscular dystrophy, affecting more than 30,000 Americans. It is caused by a repeated section of DNA on either chromosome 19 or chromosome 3.⁶ This form of muscular dystrophy is quite unusual in that it may trigger many other unrelated symptoms such as hormonal problems, cataracts, heart disease, and myotonia (delayed relaxation of a muscle). Researchers have identified a new genetic form of MMD, a mutation of a gene called ZNF9, that may shed light on the nature of mutations causing this and perhaps other diseases.

Muscular Dystrophies

Duchenne Muscular Dystrophy (DMD) (also known as pseudohypertrophic)

Onset: 2 to 6 yr of age

Symptoms: generalized weakness and muscle wasting affecting limb and trunk muscles first; the calves are often enlarged

Becker Muscular Dystrophy (BMD)

Onset: adolescence or adulthood

Symptoms: almost identical to DMD, but often much less severe; can be significant heart involvements

Emery-Dreifuss Muscular Dystrophy (EDMD)

Onset: childhood to early teens

Symptoms: weakness and wasting of shoulder, upper arm, and shin muscles; joint deformities common

Limb-Girdle Muscular Dystrophy (LGMD)

Onset: childhood to middle age