THE DIAGNOSIS OF MULTIPLE SCLEROSIS

The diagnosis of Multiple Sclerosis, known as the disease of the thousand faces due to the diversity of its symptoms, is very complex and usually requires a certain time.

Currently the basic “rule” to make a diagnosis of Multiple Sclerosis requires the two following two conditions have to met:

• Objective evidence of at least two areas of myelin loss, or demyelination lesions, that appear in two different neurological zones and separated in time. This means that the lesions are present in different places and different times within the brain, the spinal cord, or the optic nerve.
• Ruling out of other diseases that can cause similar neurological symptoms.

These two conditions, called McDonald’s Criterion, allowed in 2005 to agree on the medical practice in the diagnosis of Multiple Sclerosis and to establish an earlier diagnosis of the pathology. However, it can take months to obtain such a diagnosis, since sometimes, the tests must be repeated several times in order to gather the necessary information in different areas and at different times. All this without taking into account that, if the affected person comes to the consultation with an outbreak, if it decrease before having an established diagnosis, sometimes years pass until other symptoms or another attack confirm that the disease is suffered.

To confirm the diagnosis of Multiple Sclerosis, two types of tests are needed:

• Physical exam
• Diagnostic tests

PHYSICAL EXAM

When the patient visits the doctor with symptoms compatible with Multiple Sclerosis which are not explained for other reasons, the usual procedure is to develop a detailed clinical history, including all the symptoms of the person, both past and present . For this, the doctor will perform a series of physical exams to check if there are signs that can explain the symptoms or indicate the existence of a disease that could be unknown to the person.

The signs are not the same as the symptoms. The signs are signs of the disease that are objectively determined by a doctor. Some signs may explain a person’s symptoms, but others do not have an associated symptom.

The most common signs that a doctor can detect during a physical examination and that may signal neurological abnormalities, are:

• An altered eye movement and an abnormal reaction of the pupils
• Subtle changes in speech
• Alteration of reflexes
• Coordination problems
• Sensory alterations
• Signs of spasticity or weakness in the arms or legs

The physical examination may consist of the following:

• Examination of the eyes, which could reveal the existence of damage to the optic nerve.
• A check of muscle strength, pulling and pushing firmly on the patient’s arms and legs.
• Measurement of  the coordination, usually with a test in which the patient is asked to touch the nose with the index finger quickly, first with the eyes open and then closed.
• An examination of the sensitivity of the body surface, which is done with a pin and with the touch of a feather or a delicate touch.
• A vibration sensitivity test, performed with a diapason that is applied against a joint so that the patient experiences a buzzing or vibrating sensation.
• A test of the reflections, using a small rubber hammer.

DIAGNOSTIC TESTS

The physical examination is complemented with diagnostic and laboratory tests. The most determining test, capable of detecting plaques or scars that could be caused by multiple sclerosis, is magnetic resonance imaging (MRI). MRI allows very precise images of the brain to be obtained non-invasively and has been a key advance in the diagnosis of this neurodegenerative disease.

Magnetic resonance does not use radiation, but magnetism and radio waves. Potent magnetic fields interact with the hydrogen atoms of water contained in all the tissues and fluids of the organism. The radio frequency signals cause these hydrogen atoms to release energy, and the computers translate the changes into cross sectional images.

It is a very sensitive scanning procedure and can produce images of injuries or damaged areas that would go unnoticed with a scanner.

However, like all diagnostic tests, MRI has limitations. Thus, an abnormal MRI does not necessarily imply that Multiple Sclerosis exists. There are other conditions that cause brain injuries very similar to those that cause MS. Conversely, an MRI with a normal result does not rule out the existence of Multiple Sclerosis completely. In 5% of patients in whom the diagnosis of Multiple Sclerosis has been confirmed based on other criteria, MRI does not show lesions in the brain. These people may have spinal cord injuries or they may even have lesions that can not be detected by MRI.

Therefore, to establish a clear diagnosis, it is necessary to evaluate three parameters:

• the symptoms and signs,
• the results of an MRI, and
• exclude other neurodegenerative pathologies through complementary diagnostic tests.

Supplementary tests

If after carrying out the physical examination and MRI there are still doubts regarding the diagnosis, other complementary tests can be carried out, such as those of evoked potentials and the extraction of cerebrospinal fluid and blood.

Evoked potential tests (PE or EP) are electrical diagnostic tests that can show if there has been a decrease in the flow of messages in various parts of the brain. They often reveal the presence of scars along the nerve pathways that can not be detected in any other way.

The cerebrospinal fluid, extracted by means of a lumbar puncture, is examined in order to detect the levels of certain proteins of the immune system and the presence of antibodies called “oligoclonal bands“. These bands indicate an immune response in the central nervous system and are found in the cerebrospinal fluid from 90% to 95% of people with Multiple Sclerosis. However, they are also present in other diseases and, therefore, the oligoclonal bands per se can not be considered as a definitive proof of the existence of MS, being only a complement of the aforementioned tests.

There is no specific biochemical marker associated with multiple sclerosis that can be detected in a blood test, however, these tests do serve to positively rule out other causes of similar neurological symptoms, such as Lyme disease, a group of conditions known as “collagen-vascular diseases”, certain rare hereditary disorders and AIDS. Therefore, blood tests are used as an exclusion test, as discussed above.