Multiple Sclerosis

Description

Diagnosis

Multiple sclerosis is characterized by recurring neurologic episodes that are due to multiple lesions (injured areas) in different locations in the central nervous system. The diagnostic challenges in multiple sclerosis are two fold:

• Making an initial diagnosis as early as possible in order to slow down the disease progression. Most patients first seek medical help after an initial inflammatory event (known as a clinically isolated syndrome) originating from demyelination in the eye, the spinal cord, or the brain. About 30% of these individuals will develop progressive MS within the year. At this time, however, experts cannot predict who among these patients are at highest risk for rapid progression.
• Predicting the severity of the disease. Once MS has been diagnosed, the pattern of the disease is uncertain. It can be very benign to rapidly progressive and severe. Although magnetic resonance imaging (MRI) is able to detect lesions in the brain indicating MS. The severity of the disease does not appear related to the number of lesions, the rate of their appearance, or their location. Researchers are hoping to identify some biologic marker, possibly certain antibodies, that will enable physicians to accurately determine the onset and severity of the problem once a diagnosis has been made.

The McDonald Criteria. There is no single test that can accurately diagnose MS and a number of other conditions may mimic its symptoms. Some physicians use a set of factors, called the McDonald criteria, for diagnosing multiple sclerosis in early stages. The criteria include the presence of specific symptoms, spinal fluid evaluation, and magnetic resonance imaging techniques for detecting lesions within the central nervous system and tracking them over time. The criteria are showing high reliability in identifying MS in patients with a variety of disease stages or states, including having only one episode, having a typical relapsing-remitting course, or having a slow insidious progression without clear attacks or remissions. Depending on the MRI and other findings, the patient is then categorized as having MS, possible MS, or no MS.

Ruling Out Other Disorders

The symptoms of MS are similar to a number of other diseases, which must be ruled out. These include stroke, alcoholism, emotional disorders, Lyme disease, chronic fatigue syndrome, fibromyalgia, AIDS, and certain other autoimmune disorders (e.g., hypothyroidism, scleroderma, Sjgren's syndrome, and systemic lupus erythematosus).

Expanded Disability Status Scale

Presently physicians and investigators generally use a test called the Expanded Disability Status Scale (EDSS) to rate the severity of symptoms. It is also used after a diagnosis to gauge the status of the disease, and score the effectiveness of treatments. The scale ranges from zero to ten with higher scores indicating more severe symptoms. These are subjective ratings that require physician observation skills.

Objections to the use of the EDSS are that it assesses only limp and walking problems and does not assess other important complications, including fatigue, sexual function, and mental function.

Laboratory Tests

No reliable single laboratory procedure or test can establish the diagnosis of multiple sclerosis. Several are necessary before a diagnosis can be made.

Analysis of Cerebrospinal Fluid (CFS). Obtaining a sample of spinal fluid requires a lumbar puncture, or spinal tap. Testing spinal fluid is becoming increasingly important for detecting abnormal proteins, tiny fragments of myelin, or specific white blood cells that can help in making a diagnosis. For example, high levels of the immunoglobulin IgG is useful for making a diagnosis and may be a marker for disease progression. (Immunoglobulins are protein chains that are part of the immune system.)

A lumbar puncture, or spinal tap, is a procedure to collect cerebrospinal fluid to check for the presence of disease or injury. A spinal needle is inserted, usually between the 3rd and 4th lumbar vertebrae in the lower spine. Once the needle is properly positioned in the subarachnoid space (the space between the spinal cord and its covering, the meninges), pressures can be measured and fluid can be collected for testing.

Evoked Potential (EP) Test. This is a simple and painless electrical test of nerve function that assesses how long it takes nerve impulses from the eye, ear, or skin to reach the brain.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) scans are important diagnostic tools in MS and are used for diagnosing multiple sclerosis, tracking changes over time, and helping to determine treatment effectiveness.

Click the icon to see an image of a brain MRI.

Making a Diagnosis and Tracking the Disease. Magnetic resonance imaging (MRI) scans can detect bright patches that indicate injured tissue (lesions) caused by MS. (Such lesions may also indicate other conditions such as infections, migraines, or clots.) Importantly, a very sensitive MRI technique using enhancement by an agent called gadolinium can indicate recent activity by showing if the blood-brain barrier has been broken down (the first step in the development of MS lesions). Detecting lesions and treating MS early in the disease process may help reduce progression. Many experts therefore now advocate performing a brain MRI as soon as symptoms appear.

Once diagnosed, periodic follow-up MRIs can be used to track the disease and effectiveness of treatments in two ways:

• By distinguishing new lesions from old ones.
• Revealing increasing or decreasing numbers of lesions within the central nervous system over time.
• Unfortunately, neither the rate nor the number of new or growing lesions necessarily predicts whether symptoms will worsen or if the patient will develop secondary progressive MS.

Measuring Atrophy in Brain and Spinal Cord. As myelin, axons, oligodendrocytes, and neurons are destroyed, the brain begins to shrink. Processing MRI images to determine brain volume may be a useful way to monitor progression and treatment effects. MRI can also detect shrinkage in the spinal cord, which is proving to be a very strong marker of disease progression. A variation of MRI, magnetic resonance spectroscopy (MRS), provides information on the biochemistry of the brain, and may be particularly helpful in detecting this destructive aspect of MS.

Detecting Black Holes.Severe disease progression can be gauged by the presence of so-called "black holes. These are lesions in the brain that emit very low signals on an MRI scan. Some evidence suggests that they may represent iron deposits in the brain.

Investigative Laboratory Tests

Researchers are continuously searing for biologic markers that might help make an accurate diagnosis, predict outcome, or both. A promising marker is an autoantibody that targets myelin oligodendrocyte glycoprotein (MOG), which is found in the oligodendrocyte--the specialized cell that makes up myelin. The autoantibody targeting MOG has been identified in active MS lesions and experts hope it will eventually help predict whether the disease will progress.