Multiple sclerosis (abbreviated MS, also known as disseminated sclerosis or encephalomyelitis disseminata) is a disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms. Disease onset usually occurs in young adults, and it is more common in females
The person with MS can suffer almost any neurological symptom or sign, including changes in sensation (hypoesthesia and paraesthesia), muscle weakness, muscle spasms, or difficulty in moving; difficulties with coordination and balance (ataxia); problems in speech (dysarthria) or swallowing (dysphagia), visual problems (nystagmus, optic neuritis, or diplopia), fatigue, acute or chronic pain, and bladder and bowel difficulties. Cognitive impairment of varying degrees and emotional symptoms of depression or unstable mood are also common. Uhthoff's phenomenon, an exacerbation of extant symptoms due to an exposure to higher than usual ambient temperatures, and Lhermitte's sign, an electrical sensation that runs down the back when bending the neck, are particularly characteristic of MS although not specific. The main clinical measure of disability progression and symptom severity is the Expanded Disability Status Scale or EDSS.
Symptoms of MS usually appear in episodic acute periods of worsening (called relapses, exacerbations, bouts, attacks, or "flare-ups"), in a gradually progressive deterioration of neurologic function, or in a combination of both. Multiple sclerosis relapses are often unpredictable, occurring without warning and without obvious inciting factors with a rate rarely above 1 and a half per year. Some attacks, however, are preceded by common triggers. Relapses occur more frequently during spring and summer. Viral infections such as the common cold, influenza, or gastroenteritis increase the risk of relapse. Stress may also trigger an attack. Pregnancy affects the susceptibility to relapse, with a lower relapse rate at each trimester of gestation. During the first few months after delivery, however, the risk of relapse is increased. Overall, pregnancy does not seem to influence long-term disability. Many potential triggers have been examined and found not to influence MS relapse rates. There is no evidence that vaccination and breast feeding, physical trauma, or Uhthoff's phenomenon are relapse triggers.
MS affects the ability of nerve cells in the brain and spinal cord to communicate with each other. Nerve cells communicate by sending electrical signals called action potentials down long fibers called axons, which are wrapped in an insulating substance called myelin. In MS, the body's own immune system attacks and damages the myelin. When myelin is lost, the axons can no longer effectively conduct signals. The name multiple sclerosis refers to scars (scleroses—better known as plaques or lesions) in the white matter of the brain and spinal cord, which is mainly composed of myelin. Although much is known about the mechanisms involved in the disease process, the cause remains unknown.Theories include genetics or infections. Different environmental risk factors have also been found. Most likely MS occurs as a result of some combination of genetic, environmental and infectious factors. Epidemiological studies of MS have provided hints on possible causes for the disease. Theories try to combine the known data into plausible explanations, but none has proved definitive.
Different environmental factors, both of infectious and non infectious origin have been proposed as risk factors for MS. Although some are partly modifiable, only further research—especially clinical trials—will reveal whether their elimination can help prevent MS. MS is more common in people who live farther from the equator, although many exceptions exist. Decreased sunlight exposure has been linked with a higher risk of MS. Decreased vitamin D production and intake has been the main biological mechanism used to explain the higher risk among those less exposed to sun. Severe stress may also be a risk factor although evidence is weak. Smoking has also been shown to be an independent risk factor for developing MS. Association with occupational exposures and toxins—mainly solvents—has been evaluated, but no clear conclusions have been reached. Vaccinations were also considered as causal factors for the disease; however, most studies show no association between MS and vaccines. Several other possible risk factors, such as diet and hormone intake, have been investigated; however, more evidence is needed to confirm or refute their relation with the disease. Gout occurs less than would statistically be expected in people with MS, and low levels of uric acid have been found in MS patients as compared to normal individuals. This led to the theory that uric acid protects against MS, although its exact importance remains unknown.
Many microbes have been proposed as potential infectious triggers of MS, but none has been substantiated.
Multiple sclerosis can be difficult to diagnose since its signs and symptoms may be similar to other medical problems. Clinical data alone may be sufficient for a diagnosis of MS if an individual has suffered separate episodes of neurologic symptoms characteristic of MS. Since some people seek medical attention after only one attack, other testing may hasten and ease the diagnosis. The most commonly used diagnostic tools are neuroimaging, analysis of cerebrospinal fluid and evoked potentials. Magnetic resonance imaging of the brain and spine shows areas of demyelination (lesions or plaques). Gadolinium can be administered intravenously as a contrast to highlight active plaques and, by elimination, demonstrate the existence of historical lesions not associated with symptoms at the moment of the evaluation. Testing of cerebrospinal fluid obtained from a lumbar puncture can provide evidence of chronic inflammation of the central nervous system. The cerebrospinal fluid is tested for oligoclonal bands of IgG on electrophoresis, which are an inflammation marker found in 75–85% of people with MS. The nervous system of a person with MS responds less actively to stimulation of the optic nerve and sensory nerves due to demyelination of such pathways. These brain responses can be examined using visual and sensory evoked potentials.
The prognosis (the expected future course of the disease) for a person with multiple sclerosis depends on the subtype of the disease; the individual's sex, age, and initial symptoms; and the degree of disability the person experiences. The disease evolves and advances over decades, 30 being the mean years to death since onset.
Female sex, relapsing-remitting subtype, optic neuritis or sensory symptoms at onset, few attacks in the initial years and especially early age at onset, are associated with a better course.
The life expectancy of people with MS is 5 to 10 years lower than that of unaffected people. Almost 40% of patients reach the seventh decade of life. Nevertheless, two thirds of the deaths in people with MS are directly related to the consequences of the disease. Suicide is also a much more important risk of death than in the healthy population, while infections and complications are specially hazardous for the more disabled ones.
Although most patients lose the ability to walk prior to death, 90% are still capable of independent walking at 10 years from onset, and 75% at 15 years.
Although there is no known cure for multiple sclerosis, several therapies have proven helpful. The primary aims of therapy are returning function after an attack, preventing new attacks, and preventing disability. As with any medical treatment, medications used in the management of MS have several adverse effects. Alternative treatments are pursued by some patients, despite the shortage of supporting, comparable, replicated scientific study.
During symptomatic attacks, administration of high doses of intravenous corticosteroids, such as methylprednisolone, is the routine therapy for acute relapses. Although generally effective in the short term for relieving symptoms, corticosteroid treatments do not appear to have a significant impact on long-term recovery. Oral and intravenous administration seem to have similar efficacy. Consequences of severe attacks which do not respond to corticosteroids might be treated by plasmapheresis.
Disease-modifying treatments are expensive and most of these require frequent (up-to-daily) injections. Others require IV infusions at 1–3 month intervals.
As of 2009, five disease-modifying treatments have been approved by regulatory agencies of different countries for MS. Interferon beta-1a (trade names Avonex, CinnoVex, ReciGen and Rebif ) and interferon beta-1b (U.S. trade name Betaseron, in Europe and Japan Betaferon). A third medication is glatiramer acetate (Copaxone), a non-interferon, non-steroidal immunomodulator. The fourth medication, mitoxantrone, is an immunosuppressant also used in cancer chemotherapy. The fifth is natalizumab (marketed as Tysabri). The interferons and glatiramer acetate are delivered by frequent injections, varying from once-per-day for glatiramer acetate to once-per-week (but intra-muscular) for Avonex. Natalizumab and mitoxantrone are given by IV infusion at monthly intervals.
All five kinds of medications are modestly effective at decreasing the number of attacks in relapsing-remitting MS (RRMS) while the capacity of interferons and glatiramer acetate is more controversial. Studies of their long-term effects are still lacking. Comparisons between immunomodulators (all but mitoxantrone) show that the most effective is natalizumab, both in terms of relapse rate reduction and halting disability progression. Mitoxantrone may be the most effective of them all; however, it is generally not considered as a long-term therapy, as its use is limited by severe secondary effects.The earliest clinical presentation of RRMS is the clinically isolated syndrome (CIS). Treatment with interferons during an initial attack can decrease the chance that a patient will develop clinical MS.
Treatment of progressive MS is more difficult than relapsing-remitting MS. Mitoxantrone has shown positive effects in patients with secondary progressive and progressive relapsing courses. It is moderately effective in reducing the progression of the disease and the frequency of relapses in patients in short-term follow-up. No treatment has been proven to modify the course of primary progressive MS.
As with any medical treatment, these treatments have several adverse effects. One of the most common is irritation at the injection site for glatiramer acetate and the interferon treatments. Over time, a visible dent at the injection site, due to the local destruction of fat tissue, known as lipoatrophy, may develop. Interferons produce symptoms similar to influenza; some patients taking glatiramer experience a post-injection reaction manifested by flushing, chest tightness, heart palpitations, breathlessness, and anxiety, which usually lasts less than thirty minutes. More dangerous but much less common are liver damage from interferons, severe cardiotoxicity, infertility, and acute myeloid leukaemia of mitoxantrone, and the putative link between natalizumab and some cases of progressive multifocal leukoencephalopathy.
As with most chronic diseases, alternative treatments are pursued by some patients, despite the shortage of supporting, comparable, replicated scientific study. Examples are dietary regimens, herbal medicine, including the use of medical cannabis, hyperbaric oxygenation and self-infection with hookworm.
Disease-modifying treatments reduce the progression rate of the disease, but do not stop it. As multiple sclerosis progresses, the symptomatology tends to increase. The disease is associated with a variety of symptoms and functional deficits that result in a range of progressive impairments and disability. Management of these deficits is therefore very important. Both drug therapy and neurorehabilitation have shown to ease the burden of some symptoms, though neither influences disease progression. Some symptoms have a good response to medication, such as unstable bladder and spasticity, while management of many others is much more complicated. As for any patient with neurologic deficits, a multidisciplinary approach is key to improving quality of life; however, there are particular difficulties in specifying a ‘core team’ because people with MS may need help from almost any health profession or service at some point. Multidisciplinary rehabilitation programmes increase activity and participation of patients but do not influence impairment level.