Patients with multiple sclerosis (MS) have demyelination of the central nervous system; the myelin, which covers the axons of the neurons, becomes damaged due to inflammation. The damage to the myelin causes the signals sent from neuron to neuron to be slowed or blocked. The reason for the inflammation is not known, but theories of the cause of MS include exposure to a virus early in life or genetics. The Merck Manual Home Edition noted that around 5 percent of MS patients have a sibling with the disorder and around 15 percent of MS patients have a close relative with the disorder. Environment may also play a role in the onset of MS: the neurological condition is five times for likely in temperate climates, according to the National Institute of Neurological Disorders and Stroke (NINDS).
The symptoms of MS depend on the type of nerve fibers affected by the demyelination. For example, if a MS patient has demyelination of the nerve fibers that carry motor signals, then that patient can have issues with movement. Symptoms may include weakness in the limbs, muscle spasms, coordination problems and a loss of balance. Some MS patients may have problems walking or moving their arms and limbs. Other symptoms include tremors and stiffness.
The NINDS explained that the first symptoms that MS patients commonly experience are vision problems: about 55 percent of MS patients have optic neuritis, which is inflammation of the optic nerve, and around 15 percent of MS patients experience this issue as their first symptom. With optic neuritis, patients have symptoms usually in one eye, though both eyes may be affected. Symptoms include a loss of color vision, pain, vision loss and seeing flashing lights. MS patients may have uncoordinated eye movements or problems seeing straight ahead.
MS can also cause issues with mood and ]]>cognition]]>. For example, patients may have mood swings, depression, memory loss, or attention problems. If the demyelination affects the nerve fibers that transmit sensory information, patients can experience with sensations.