Some of nerves have a protective covering around them called myelin. Myelin is important as it increases the speed of the signals that your nerves send. Therefore, diseases that destroy the myelin sheath or interferes with its metabolism will interrupt those signals. This can happen as a result of autoimmune diseases, errors in metabolism or infections.
Multiple Sclerosis
Multiple sclerosis (MS) is called an autoimmune disease because instead of your immune system attacking foreign substances, it attacks your body. Your immune system destroys the nerve cells in your central nervous system. It is a demyelinating disease which means it destroys the myelin. As Michael Aminoff, M.D., writes in "Current Medical Diagnosis & Treatment," there are several forms of MS, but all will likely share the characteristics of weakness, double vision, urinary problems, problems with bowel movements, tremors, tingling and numbness.
Guillain-Barre
Guillain-Barre is also an autoimmune disease, but in this disorder, your immune system destroys the myelin in the nerve cells of your peripheral nervous system. This is the part of your nervous system composed of your peripheral nerves, the nerves outside of your brain and spinal cord. Like MS, you will have weakness. But, as Elizabeth Corwin, PhD writes in "Handbook of Pathophysiology," it will start in your legs and progress upwards. You will also have paralysis in your legs that likewise will progress upwards. Hospitalization is required because the paralysis could affect your breathing and heart.
Metachromatic Leukodystrophy
This is a hereditary disease in which there are abnormalities in the metabolism of myelin. According to Ramzi Cotran, M.D. in "Robbins Pathologic Basis of Disease," published in 2004, people with this disease have an insufficient amount of an enzyme called arylsulfatase A. How the lack of this enzyme affects the metabolism of myelin and causes it to break down is not well understood. There are two forms of this disorder. Children affected by 2 years of age will have slurred speech and vision problems. Older children will have speech and personality problems.
Krabbe's Disease
Cotran also noted that Krabbe's is another hereditary disease in which myelin breaks down. In this condition, however, infants will show symptoms a few months after birth. They will be very irritable, experience seizures and have eating, eye and muscle problems.
Progressive Multifocal Leukoencephalopathy
According to Vicente Corrales-Medina, M.D. in "Current Medical Diagnosis & Treatment," progressive multifocal leukoencephalopathy is a rare disease in which myelin is destroyed. It is caused by a virus called JC. After your first infection, the virus stays dormant. When it is reactivated, it infects the cells that make myelin in your central nervous system. You will have visual problems and paralysis or weakness on your entire right or left side.
Osmotic Demyelination Syndrome
Cotran writes that demyelination occurs in this disorder if you have low sodium levels in your blood and the levels are corrected too rapidly. Within a few days or weeks, you will have problems with speech and swallowing, as well as paralysis. The damage can progress and eventually cause "locked-in syndrome." In this condition, you will be awake and able to think, but your body will be paralyzed.
References
- "Current Medical Diagnosis & Treatment 2009"; Stephen McPhee, M.D., Maxine Papadakis, M.D.; 2009
- "Handbook of Pathophysiology"; Elizabeth Corwin, MSN, PhD, FNP; 2000
- "Robbins Pathologic Basis of Disease"; Ramzi Cotran, M.D., Vinay Kumar, M.D., Stanley Robbins, M.D.; 2004
