Accurate diagnosis key to identifying, managing multiple sclerosis
MS is the most common neurologic disease among young adults. (Fotolia.com / April 17, 2013)
Multiple sclerosis, which led to the recent death of actress Annette Funicello, affects more than 2.5 million people worldwide, according to the National Multiple Sclerosis Society. Because it is the most common neurologic disease among young adults, there's increasing urgency to find a cure.
While anyone can develop MS, there are environmental patterns that identify vulnerable populations. The National MS Society reports that women are diagnosed with MS at least two to three times more often than men, and most are diagnosed between the ages of 20 and 50. Geographically, people who live in more temperate regions, further from the equator, are more likely to develop MS.
Research studies suggest genetic factors and ethnicity may also play a role. The disease is more common in Caucasians, especially those of European descent, but also occurs in African-American, Hispanic/Latino ethnic groups and, more rarely, in Asians.
WHAT IS MS?
MS is an autoimmune demyelinating disease that affects the central nervous system. According to the USC Multiple Sclerosis Comprehensive Care Center and Research Group, "autoimmune diseases are those in which the body's own immune system, which normally targets and destroys substances foreign to the body, mistakenly attacks normal tissues."
In MS, the immune system attacks myelin, the fatty, insulating tissue that wraps around the fingerlike projections from nerve cells called nerve processes, much like the insulation on electrical cords. Nerve processes facilitate communication between the central nervous system and different parts of the body. Damage to myelin makes it difficult for the brain to send and receive messages from the body. This can lead to the many symptoms of MS.
Myelin damage is accompanied by inflammation in the central nervous system, much like the redness and swelling experienced when we cut a finger or scape a knee. Constant inflammation and damage lead to a buildup of scar tissue, or plaques, which can be detected through magnetic resonance imaging (MRI). Early in the disease, damage to myelin may be repaired, but as MS progresses, repaired processes are likely to break down.
MAKING A DIAGNOSIS
According to the Multiple Sclerosis Association of America (MSAA), neurologists most reliably diagnose MS through exams and lab tests. Laboratory tests are especially important because they can rule out other diseases that may have symptoms similar to MS.
Key evaluations include:
1. Medical history and neurologic exam. A physician obtains a medical history from a patient or suitable person who is familiar with the patient. Medical history includes information such as name, birthplace, family history, travel, allergies and other important details about a patient's life. Medical history reports help physicians formulate a diagnosis and provide appropriate medical care.
Physicians can also perform a variety of neurologic exams to evaluate functions such as vision, motor activity (e.g., ability to walk or maintain balance, coordination), sensory modalities (e.g., ability to feel and locate touch and pain), memory, ability to concentrate and mental and emotional health.
"In several cases, medical history, neurologic exams and an MRI may provide sufficient evidence for MS diagnosis. Neurologic exams provide evidence of damage that has occurred or is occurring in the central nervous system, and an MRI may prove this," says Lilyana Amezcua, M.D., assistant professor of clinical neurology, co-chief and medical director of the Multiple Sclerosis Comprehensive Care Center and Research Group at Keck School of Medicine of the University of Southern California (USC). If a diagnosis cannot be confirmed through these criteria, there are additional tests available.
2. Magnetic resonance imaging. MRIs are a diagnostic tool used for scanning internal structures of the body using magnetic fields. The National MS Society suggests MRIs are more useful for evaluating the extent of damage to the myelin, also known as plaques, and areas of inflammation.
Areas where the myelin is damaged may appear as bright white spots or darkened areas on MRI scans. However, it's important to note that these spots or indications of damage can also appear on scans of people who do not have MS -- mainly the elderly.
"MRI is currently our best clinical marker of disease, but clearly it lacks sensitivity in its ability to differentiate other conditions, which is still a problem," says Dr. Amezcua.
3. Evoked Potential tests. These tests record the central nervous system's electrical responses to stimulation of different senses such as hearing and vision. EPs are effective because they can detect evidence of scarring along nerve pathways that might not be evident during a neurologic exam.