The myelin sheath, which covers the axon of the neuron, performs important functions for neural communication. In the central nervous system, or the brain and spinal cord, oligodendrocytes make up the myelin sheath, while Schwann cells make up the myelin sheath in the peripheral nervous system, the nerves in the rest of the body. The myelin sheath insulates the neuron, helping messages pass down to other neurons. Demyelinating diseases damage the myelin sheath, disrupting communication between the brain and the rest of the body.
Multiple Sclerosis
Jerry W. Swanson, MD, a neurologist at the Mayo Clinic, explains that multiple sclerosis is the most common disease of the myelin sheath. MedlinePlus adds that multiple sclerosis commonly starts in people ages 20 to 40, with a higher rate of incidence in women.
The nerve damage from multiple sclerosis gets worse over time. Patients' immune systems attack the nerve cells, causing symptoms such as a loss of balance and problems walking.
Multiple sclerosis can also cause double vision, constipation and a frequent need to urinate. Other symptoms include slurred speech, depression and memory loss.
Neuromyelitis Optica
Also called Devic's syndrome, neuromyelitis optica affects the spinal cord and optic nerves. The National Institute of Neurological Disorders and Stroke explains that women are four times more likely that men to have neuromyelitis optica, with symptoms starting either during childhood or during adulthood around age 40.
Symptoms include blindness in one or both eyes, which occurs quickly, and paralysis in the arms and legs. Patients with neuromyelitis optica might develop other demyelinating diseases, such as optic neuritis or transverse myelitis.
Optic Neuritis
Patients with optic neuritis have an inflammation of the optic nerve, which affects vision. MedlinePlus points out that 20 percent of optic neuritis patients develop myelin inflammation problems elsewhere in their bodies.
Patients can experience pain when moving their eyes or a loss of vision in one eye, which can last up to a few hours. Other symptoms of optic neuritis include a loss of color vision and a change in the pupil's reaction to bright light.
Transverse Myelitis
When patients have transverse myelitis, inflammation occurs in specific areas of the spinal cord. The National Institute of Neurological Disorders and Stroke notes that in the United States, doctors diagnose about 1,400 new cases each year.
Patients can have lower back pain, sensory loss and partial or complete paralysis. Other symptoms of transverse myelitis include muscle spasms and bladder or bowel dysfunction.
Leber's Hereditary Optic Neuropathy
The Merck Manual Home Edition explains that Leber's hereditary optic neuropathy commonly occurs in men, with symptoms starting in people ages 15 to 35. Patients can experience partial blindness with Leber's hereditary optic neuropathy.
Acute Disseminated Encephalomyelitis
Caused by an infection, acute disseminated encephalomyelitis occurs in children more often than adults, according to the Cleveland Clinic. Common symptoms of acute disseminated encephalomyelitis include unsteadiness, falling, tingling and numbness.
Patients can occasionally have double vision or blurred vision. Other symptoms include confusion, trouble swallowing and drowsiness.
Adrenomyeloneuropathy and Adrenoleukodystrophy
Two rare metabolic disorders, adrenomyeloneuropathy and adrenoleukodystrophy affect boys. The Merck Manual Home Edition notes that adrenomyeloneuropathy affects adolescents, while adrenoleukodystrophy affects boys ages 4 through 8, though a milder form of the disorder occurs in men in their 20s and 30s.
Both hereditary disorders, they cause hearing, behavioral and vision problems. Other symptoms include spasticity, mental deterioration and blindness.
Tropical Spastic Paraparesis
Caused by the human T-cell lymphotropic virus, tropical spastic paraparesis or HTLV-associated myelopathy affects the spinal cord. The damage from tropical spastic paraparesis becomes progressively worse. The Merck Manual Home Edition lists spastic weakness, urinary incontinence and bowel problems as symptoms.
References
- MayoClinic.com: Demyelinating Disease -- What Causes It?
- MedlinePlus Medical Encyclopedia: Multiple Sclerosis
- National Institute of Neurological Disorders and Stroke: Neuromyelitis Optica Information Page
- MedlinePlus Medical Encyclopedia: Optic Neuritis
- National Institute of Neurological Disorders and Stroke: Transverse Myelitis Fact Sheet
