What Causes MS?
Multiple sclerosis (MS) affects women more than men. The disorder is most commonly diagnosed between ages 20 and 40, but can be seen at any age.
MS is caused by damage to the myelin sheath, the protective covering that surrounds nerve cells. When this nerve covering is damaged, nerve impulses are slowed down or stopped.
The nerve damage is caused by inflammation. Inflammation occurs when the body's own immune cells attack the nervous system. Repeated episodes of inflammation can occur along any area of the brain, optic nerve, and spinal cord.
Researchers are not sure what triggers the inflammation. The most common theories point to a virus or genetic defect, or a combination of both. Geographic studies indicate there may be an environmental factor involved.
People with a family history of MS and those who live in a geographical area where MS is more common have a slightly higher risk of the disease.
The major scientific theories about the causes of MS include the following:
Immunologic
It is now generally accepted that MS involves an autoimmune process—an abnormal response of the body’s immune system that is directed against the myelin (the fatty sheath that surrounds and insulates the nerve fibers) in the central nervous system
Environmental
MS is known to occur more frequently in areas that are farther from the equator. Epidemiologists—scientists who study disease patterns—are looking at many factors, including variations in geography, demographics (age, gender, and ethnic background), genetics, infectious causes, and migration patterns, in an effort to understand why.
Infectious
Since initial exposure to numerous viruses, bacteria and other microbes occurs during childhood, and since viruses are well recognized as causes of demyelination and inflammation, it is possible that a virus or other infectious agent is the triggering factor in MS.
Genetic
While MS is not hereditary in a strict sense, having a first-degree relative such as a parent or sibling with MS increases an individual's risk of developing the disease several-fold above the risk for the general population. Studies have shown that there is a higher prevalence of certain genes in populations with higher rates of MS.
Symptoms
Symptoms vary, because the location and severity of each attack can be different. Episodes can last for days, weeks, or months. These episodes alternate with periods of reduced or no symptoms (remissions).
Fever, hot baths, sun exposure, and stress can trigger or worsen attacks.
It is common for the disease to return (relapse). However, the disease may continue to get worse without periods of remission.
Because nerves in any part of the brain or spinal cord may be damaged, patients with multiple sclerosis can have symptoms in many parts of the body.
Muscle symptoms:
- Loss of balance
- Muscle spasms
- Numbness or abnormal sensation in any area
- Problems moving arms or legs
- Problems walking
- Problems with coordination and making small movements
- Tremor in one or more arms or legs
- Weakness in one or more arms or legs
Bowel and bladder symptoms:
- Constipation and stool leakage
- Difficulty beginning to urinate
- Frequent need to urinate
- Strong urge to urinate
- Urine leakage (incontinence)
Eye symptoms:
- Double vision
- Eye discomfort
- Uncontrollable rapid eye movements
- Vision loss (usually affects one eye at a time)
Numbness, tingling, or pain
- Facial pain
- Painful muscle spasms
- Tingling, crawling, or burning feeling in the arms and legs
Other brain and nerve symptoms:
- Decreased attention span, poor judgment, and memory loss
- Difficulty reasoning and solving problems
- Depression or feelings of sadness
- Dizziness and balance problems
- Hearing loss
Sexual symptoms:
- Problems with erections
- Problems with vaginal lubrication
Speech and swallowing symptoms:
- Slurred or difficult-to-understand speech
- Trouble chewing and swallowing
Fatigue is a common and bothersome symptoms as MS progresses. It is often worse in the late afternoon.
Exams and Tests
Symptoms of MS may mimic those of many other nervous system disorders. The disease is diagnosed by ruling out other conditions.
People who have a form of MS called relapsing-remitting may have a history of at least two attacks, separated by a period of reduced or no symptoms.
The health care provider may suspect MS if there are decreases in the function of two different parts of the central nervous system (such as abnormal reflexes) at two different times.
A neurological exam may show reduced nerve function in one area of the body, or spread over many parts of the body.
This may include:
- Abnormal nerve reflexes
- Decreased ability to move a part of the body
- Decreased or abnormal sensation
- Other loss of nervous system functions
An eye examination may show:
- Abnormal pupil responses
- Changes in the visual fields or eye movements
- Decreased visual acuity
- Problems with the inside parts of the eye
- Rapid eye movements triggered when the eye moves
Tests to diagnose multiple sclerosis include:
- Lumbar puncture (spinal tap) for cerebrospinal fluid tests, including CSF oligoclonal banding
- MRI scan of the brain and MRI scan of the spine are important to help diagnose and follow MS
- Nerve function study (evoked potential test)