Demyelinating Diseases

Demyelinating diseases constitute a diffuse group of diseases ranging from those with uncertain cause (e.g., multiple sclerosis, where genetic, epidemiologic, and immunologic factors are probably all involved and interferon-beta appears to be a promising treatment^[652] ) to those that follow infection, vaccination (e.g., Guillain-Barré syndrome), or antimetabolite treatment of cancer. Therefore, demyelinating diseases can have very diverse symptoms. Apparently, there is a risk of relapse of these diseases immediately after surgery. ^[653] Because relapse may occur as a result of rapid electrolyte changes in the perioperative period, such changes might be avoided. In addition, perioperative administration of steroids has been advocated as a protective measure.^[279] Multiple sclerosis and demyelinating diseases in general are the most common cause of nontraumatic disability in young adults. The age-adjusted survival rate is 80% of that of unaffected individuals, or put another way, the average patient with multiple sclerosis ages 1.2 years for every year that they have the disease. However, the variability of the disease makes this average rate of aging almost meaningless. Thus far, no mode of treatment has been shown to alter most of these disease processes, although ACTH, steroids, interferon-beta, glatiramer acetate (Copaxone), and plasmapheresis may ameliorate or abbreviate a relapse, even alter disease progression, especially progression of multiple sclerosis and (if started within 2 weeks of onset) Guillain-Barré syndrome.^[654] Such an effect is consonant with the hypothesis of an immunologic disorder being the cause of these diseases.

Sleep apnea may be considered a demyelinating or degenerative CNS disease or a peripheral disease of obesity, depending on its etiology. Both types (central and peripheral etiologies) appear to be increasingly common and are present in more than 5% of elderly African-Americans. Because sleep apnea poses many problems for postoperative pain control, we now recommend using only nonsteroidal anti-inflammatory drugs for pain relief if we cannot monitor these patients in a second-stage recovery unit.^{[655] [656] [657]} Preprocedure and preoperative identification of patients and therapy for sleep apnea are discussed in the earlier section "Obesity."