The cause of MS is still unknown. Most researchers believe that it is an autoimmune disorder: for some reason, the immune system malfunctions and attacks myelin, the protective sheath around the central nervous system. Some studies show that MS may be triggered by a common virus and that some people are more vulnerable than others to this disease because of their genetic makeup. There is no proof that MS is a hereditary disease, but a certain number of genes probably contribute to making a person susceptible to multiple sclerosis.
MS attacks the myelin sheath around the nerve fibres in the brain and spinal cord, causing inflammation and often deterioration of the myelin. The resulting “lesions” or “plaques” block or alter nerve impulses. MS symptoms vary depending on the part of the nervous system that is affected.
MS attacks the myelin in the brain and the spinal cord. Most myelin is in the brain, so it is more likely that lesions will be found there. The MRI examination is used to confirm the presence of lesions. The neurologist does not need to see them all to reach a diagnosis of MS. Also, a brain scan takes 30 minutes, while a scan of the spinal cord takes 60 to 90 minutes. If the brain scans are conclusive, it is not necessary to explore the spinal cord.
The symptoms of MS are unpredictable and vary greatly from one person to the next. The list of possible symptoms is long, but you will not have them all:
Visual symptoms (double or blurred vision)
These problems may include diplopia (double vision), optic neuritis (inflammation of the optic nerve), nystagmus (rapid, uncontrolled eye movements), and in very rare cases, blindness (total loss of sight).
Debilitating fatigue that occurs suddenly or is unwarranted for the expended effort: this is one of the most frequent and most troublesome symptoms of MS.
Loss of balance and coordination
These symptoms may include loss of balance, tremors, ataxia (unstable gait), vertigo, awkwardness and lack of coordination.
Muscle stiffness (spasticity)
Altered muscle tone may cause spasticity or stiffness that interferes with mobility. Painful spasms may sometimes occur.
Weak leg muscles may alter gait.
These symptoms can include prickling, “pins and needles” (paresthesia) and a burning sensation in one part of the body. Trigeminal neuralgia, sharp pain in the face, may also be caused by dysfunction of one of the main facial nerves.
Many people with MS are sensitive to heat and their symptoms are intensified in a hot environment.
Difficulties speaking or swallowing
These problems can include slurred speech, poor articulation (dysarthria), changes in the pace of speech, and difficulty in swallowing (dysphagia).
Urinary and bowel problems
Bladder dysfunction may involve a frequent or urgent need to urinate, incomplete voiding of the bladder, or incontinence. Bowel problems may include constipation, and, less frequently, bowel incontinence (loss of bowel control).
These problems may include temporary impotence, reduced libido and altered sensation.
Difficulty remembering recent events and cognitive problems
These symptoms may include difficulty with short-term memory and concentration, and altered judgement or reasoning.
An attack is described as the occurrence of a new symptom or aggravation of an old symptom that lasts a minimum of 24 hours. It generally lasts two to three weeks, but recovery (sometimes partial) may take several months. For more information, see the article entitled MS Attacks: What they are and… what you can do about them.
At first, multiple sclerosis may show up as vague, intermittent symptoms. Many of the signs and symptoms of MS can be attributed to other diseases. This is why MS can sometimes only be diagnosed after a length of time and after a number of medical tests and examinations.
Generally the doctor – usually a neurologist – first makes sure that at least two different areas of the central nervous system are affected and that symptoms appeared at two different times. A diagnosis of MS is still mainly based on clinical examinations, because there is no specific diagnostic test for MS. Nevertheless, the medical history and certain tests are useful for establishing this diagnosis:
The doctor will ask you to describe the symptoms that you have felt so far.
The neurologist looks for any indication of neurological problems, the most frequent of which are vision difficulties, lack of coordination, weakness, lack of balance, altered sensation and reflexes, and speech difficulties.
Visual and auditory evoked potentials
When the nerve fibres lose their myelin, message transmission along the nerves may be slowed. Evoked potentials measure the time (speed of impulses along neurons) the brain takes to receive and interpret these messages. For this test, small electrodes are placed on the patient’s head to record brain waves caused by visual and auditory stimulation. If demyelination has occurred, the response to the stimuli will be delayed. Since this test is external (noninvasive) and painless, hospitalization is not required.
Magnetic resonance imaging (MRI)
MRI, done with a scanner, provides very detailed images of the brain and spinal cord and shows damaged areas (lesions or plaques). However, it cannot be considered conclusive because such plaques may be caused by other diseases. The MRI image, medical history, and results of neurological and other examinations are often used to confirm a diagnosis of MS.
In this examination, cerebrospinal fluid (the fluid that bathes and protects the brain and spinal cord) is sampled to look for specific antibodies. A fine needle is inserted between two lumbar vertebrae to remove a small amount of fluid. Although unpleasant, this procedure is generally not too painful.
Not exactly: there may be few symptoms but several lesions on the MRI, and inversely, there may be severe physical disability with few lesions.
The progression of multiple sclerosis is unpredictable. However, over time, doctors can identify different courses or types of MS. Some people are not affected much by the disease (benign or relapsing-remitting form with no permanent disability), while others are hit hard. Most people are between these two extremes.
The main courses are:
Relapsing-remitting course: characterized by clearly defined attacks, followed by partial or full remission – this is the most common form (70% at the time of diagnosis)
Primary-progressive course: relatively rare (10% to 15% at the time of diagnosis), this form is characterized from onset by almost continuous progression, without any evident remission
Secondary-progressive course: about half of MS patients start with a relapsing-remitting form, then their state begins to worsen within ten years of diagnosis and they risk becoming increasingly disabled
Progressive-relapsing course: relatively rare form in which continuous progression is punctuated by attacks, without remission
Most people with multiple sclerosis start out with relapsing-remitting MS. In some of them, this first manifestation of the disease will gradually change into a secondary-progressive course that can make their disabilities worse. Others will only have light attacks that will not aggravate their condition: they have the benign form of MS.
MS is not a muscle disease, but it can affect the nerve systems that control muscles. The muscles then become weakened, not because they were affected, but because the nerve impulses do not reach them as well or not at all.
MS does not affect fertility in women or men. Some people may experience difficulties with sexual response, but eggs and sperm remain healthy and viable.