Multiple Sclerosis

Risk: Since MS is 5 times more common in temperate zones (such as the northern US, Canada, and Europe) than in the tropics, environment may also play a part. Living the first 15 years or more in a high-risk area seems to increase the risk, suggesting that environmental factors acquired during this early period of life may be responsible for a susceptible person later developing the disease. There may be a protective effect of vitamin D intake, as those taking multivitamins containing vitamin D have a 40% lower risk of MS (Munger).

MS generally occurs in persons between 15 and 45 years of age; the average age at diagnosis is 25 years in women, and 28 years in men (Scott).

Women outnumber men at a ratio of 2:1; this ratio is more balanced among those who develop symptoms at a later age. Whites are afflicted more than twice as often as other races. It is more common in whites of northern European descent. MS is essentially unknown among Eskimos, Gypsies, and Bantus, and rare among Native North and South Americans and Asian people.

Incidence and Prevalence: MS is the most common chronic neurological disease causing disability, with more than 1.5 million people affected worldwide (Neuhaus). In high-risk areas, and for white Americans, the prevalence is about 1 per 1000 people; blacks have a prevalence of 0.33 per 1000, and Japanese Americans have a prevalence of 0.25 per 1000 (Wilson). There are approximately 350,000 to 450,000 individuals with MS in the US (Frohman), and 25,000 new cases are diagnosed each year (Lazoff). Prevalence in northern Europe and Japan is 2 per 1000, although in Scotland prevalence is 2.5 per 1000 (Wilson). The remaining population has a prevalence of 1 per 1,000,000 (Lazoff).

History: Because MS can disrupt function in any area of the central nervous system (CNS), symptoms are varied, numerous, and of differing severity and duration. Approximately 50% of individuals will present with visual problems (including blurred or double vision, red-green color distortion, loss of vision in one eye, or optic nerve inflammation (called optic neuritis). Other common symptoms include severe fatigue; muscle weakness in the extremities; numbness, tingling, and loss of sensation (paresthesias); unsteady or abnormal limb movements and positioning; loss of coordination; loss of balance or equilibrium; a characteristically slow, short stride; impaired dexterity; urinary problems; disturbed speech patterns; mental disturbances; impaired thermal sensation; muscle stiffness and spasms; tremor; and dizziness. Up to 90% of individuals with MS will report fatigue that worsens with high temperatures or exercise (Scott). More than 80% of individuals will have genitourinary tract dysfunction or impotence (Wilson).

Cognitive problems with attention span, concentration, memory, and judgment may be noted at any time during the course of the disease, and 43% of individuals will exhibit cognitive impairment (Wilson). Depression is common, and over the course of the disease 5% to10% of individuals with MS will develop overt psychiatric disorders such as manic-depression (bipolar) or paranoia. Symptoms can last from several days to weeks.

MS can be characterized by a series of attacks followed by a period during which the symptoms of the disease lessen or disappear (complete or partial remission). After a period of stability, the next attack may not occur for several years and recur with new symptoms. In some persons, the disease progresses by gradual clinical decline with no distinct periods of remission. In females, relapses are common in the first 2 to 3 months following pregnancy. Diagnosis is often a considerable challenge because of the potential for an infinite array of signs and symptoms. After exclusion of all other causes, criteria for diagnosis must include at least two neurologic events separated in time by at least a month, occurring in more than one location within the central nervous system.

Physical exam: Physical findings are variable depending on which region of the central nervous system (CNS) is involved. Clumsiness, muscle weakness, and unsteady gait may be due to damage to the white matter in the brain. When the inflammation occurs in the portion of the brain involved with vision, the eye's pupillary response to light is often diminished. Involuntary movements of the eye (nystagmus) may be present. Inflammation of the spinal cord can cause extremity weakness or stiffness (spasticity). Urinary incontinence indicates that the nerve fibers to the bladder may be involved. Heat may cause symptoms to temporarily worsen. In later stages, bladder and bowel control may be lost.

Tests: There is no specific diagnostic test for MS, but the accuracy of the diagnosis can be improved with several indicators. A spinal tap to obtain a sample of cerebrospinal fluid may be used to confirm the presence of an inflammatory lesion or to rule out other possible CNS diseases or infections. Recording nerve responses to various visual or auditory stimuli (evoked potentials) are routinely employed; absence of response or an abnormality in response is useful in detecting and localizing lesions in the CNS. Laboratory studies used to rule out other types of diseases include a complete blood count (CBC), serum glucose and serum electrolyte levels, blood clotting ability (coagulation studies), and urinalysis. Study of brain waves (electroencephalogram, or EEG) is abnormal in about one-third of the individuals who have MS.

Two types of magnetic resonance imaging (T1 MRI and T2 MRI) are used to both diagnose and monitor the disease. MRI will reveal the presence of demyelinating plaques in 95% of individuals with MS (Fertikh). They can also be helpful in excluding other CNS disorders, and can be more sensitive and specific in diagnosing MS than other imaging studies. The T2 MRI can identify the presence of MS lesions, while the T1 MRI with a pre-scan injection of gadolinium distinguishes "active" new lesions from old ones. MRI findings often support a preliminary diagnosis (50% will progress to clinically definite MS within 2 years); however, 5% of suspected individuals with normal MRI findings will similarly progress to MS. Periodic testing and close monitoring, generally for years, is necessary.