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List of All Topics
Muscle Disorders
Also called: Myopathy
Your muscles help you move and help your body work. Different types of muscles have different jobs. There are many problems that can affect muscles. Muscle disorders can cause weakness, pain or even paralysis.
There may be no known cause for a muscle disorder. Some known causes include
- Injury or overuse, such as sprains or strains, cramps or tendinitis
- Genetics, such as muscular dystrophy
- Some cancers
- Inflammation, such as myositis
- Diseases of nerves that affect muscles
- Infections
- Certain medicines
Problems can occur anywhere along this route. If the brain, spinal cord, or nerves are damaged or diseased, the electrical signal may not be generated or get through. If muscles are inflamed or abnormal, they may not be able to respond properly to a nerve impulse.
In persons with muscle weakness, nerve impulses are usually able to reach the muscles without a problem, but the muscles are unable to respond in a normal way due to disease.
Many things can cause muscle weakness to occur, a few of which include:
- Inflammation of the muscles
- Inherited conditions, especially muscular dystrophies
- Problems with certain hormones that affect muscle function
- Chemical imbalances in the body
- Drugs and toxic substances
- Infections
DERMATOMYOSITIS AND POLYMYOSITIS — Dermatomyositis and polymyositis cause inflammation of the muscles. They are rare disorders, affecting only about one in 100,000 people per year. More women than men are affected. Although the peak age of onset is in the 50s, the disorders can occur at any age. The two diseases have similar symptoms, though there are different mechanisms that cause the muscle inflammation.
Signs and symptoms — Patients with dermatomyositis and polymyositis often notice muscle weakness that worsens over several months, though in some cases symptoms develop suddenly. The affected muscles are typically close to the trunk (as opposed to in the wrists or feet), involving the hip, shoulder, or neck muscles. Muscles on both sides of the body are equally affected. In some cases, muscles are sore or tender. There may be muscle atrophy (loss of muscle) in more advanced disease.
Some patients have involvement of the muscles of the pharynx (throat) or the esophagus (the tube leading from the throat to the stomach), causing problems with swallowing. In some cases, this leads to food being misdirected to the lungs, which can cause pneumonia.
In dermatomyositis there is a rash, although sometimes the rash resolves before muscle problems occur. A number of different types of rash can occur, including rashes on the fingers, the chest and shoulders, or on the upper eyelids . In rare cases, the rash of dermatomyositis appears but myopathy never develops.
Other problems sometimes associated with these diseases include fever, weight loss, arthritis, cold-induced color changes in the fingers or toes (Raynaud phenomenon), and heart or lung problems.
Diagnosis — In addition to a careful history and physical exam, a number of tests are useful in diagnosing these conditions. Blood tests typically show evidence of muscle damage. An electromyogram (EMG) shows abnormal muscle electrical activity. Muscle biopsy is the definitive test in establishing the diagnosis, as careful analysis of the cells will reveal the typical inflammation seen in each disorder. However, in patients with typical dermatomyositis, EMG and muscle biopsy are not always used to make the diagnosis.
Electromyography — Electromyography (EMG) is a test that evaluates the health of muscles and the nerves associated with the muscles by measuring the electrical activity. It is used to aid in the diagnosis of most types of muscular dystrophy.
A small needle is inserted through the skin into a muscle in several locations (usually the arms and legs). The needle is connected to a recording device that displays the muscle's electrical activity at rest and in response to contraction. The electrical activity may also be heard as a static-type noise through a speaker.
The size and pattern of electrical activity recorded from different muscles is analyzed by the physician who supervises the EMG test in order to determine whether the muscles and nerves are affected by any disease such as muscular dystrophy.
A patient may feel some discomfort as the needle is inserted, and the muscle may feel sore or bruised for several days. The test generally takes about 30 minutes.
Muscle biopsy — A muscle biopsy is a procedure that removes one or more small piece(s) of muscle in order for a pathologist to examine it with a microscope. The biopsy can also help distinguish between muscle weakness that is caused by problems in the muscle or problems in the nerves.
The biopsy is done by making a small incision and removing a piece of muscle. This can be done surgically or by using a special needle. A single sample is typically removed surgically while several pieces of tissue are taken when the needle biopsy approach is used. The type of biopsy used will depend upon the physician's preference. Both types of biopsy can be done without the need for a hospital stay. It is often done using local anesthesia (medication is injected to numb the area).
After the area is numb, the patient should feel no pain during the biopsy. The procedure usually takes between 15 and 30 minutes. The area will feel sore for several days after the biopsy. Patient who have a surgical biopsy may have stitches or staples that will need to be removed. The muscle biopsy results are usually available within two to three weeks.
Magnetic resonance imaging (MRI) can be useful in evaluating patients with these disorders because it can assess large areas of muscle and is not invasive (like muscle biopsy and EMG). In many cases, MRI has replaced EMG and muscle biopsy in the evaluation of these conditions.
Treatment of DM and PM — Treatments for dermatomyositis and polymyositis are intended to suppress the immune system, which is though to be the cause of myopathy. However, DM and PM are rare disorders and an optimal treatment regimen has not been determined. Further study is needed. Until data are available, treatment is guided by the severity of an individual's symptoms and their complications.
Glucocorticoids — Glucocorticoids, also known as corticosteroids, are typically used as a first-line treatment in dermatomyositis and polymyositis. The optimal dose and length of treatment has not been established, and is therefore based upon an individual's signs and symptoms. Treatment with prednisone is usually started with a low dose, slowly increased, and then slowly decreased very slowly after the patient has improved. Patients are careful monitored for side effects of prednisone, which commonly include skin changes (thinning, development of small red spots), cataracts, heart disease, gastrointestinal problems, and fluid retention, among others.
Methotrexate or azathioprine — Some patients are given other medications to potentially decrease or eliminate the progression of dermatomyositis and polymyositis. Methotrexate or azathioprine may be given if glucocorticoids are not helpful or cannot be used, or may be given at the same time as glucocorticoids in patients with severe disease.
Patients who fail to improve with steroids, methotrexate, or azathioprine may try other options, include intravenous immune globulin, cyclosporine, tacrolimus, or a number of other regimens. However, there is little data about the benefit and effectiveness of these treatments for PM and DM.
Other treatments — In addition to medications, patients should take several precautions to prevent complications related to myositis and its treatments. These precautions include:
- Osteoporosis prevention — A calcium supplement (1500 mg) with vitamin D (800 mg), and a calcium anti-resorptive agent such as alendronate (Fosamax®), risedronate (Actonel®), etidronate (Didronel®), ibandronate (Boniva®), pamidronate (Aredia®) or calcitonin are recommended, especially for postmenopausal women and those on high-dose glucocorticoids.
- Exercise — Physical therapy and rehabilitation should begin soon after the diagnosis of dermatomyositis or polymyositis to prevent contractures (shortening of the muscle that can limit joint motion). Patients who become bed or chair bound should move or be repositioned frequently to avoid pressure sores.
- Avoidance of sunlight – Patients with dermatomyositis and rash should protect themselves from the sun with sunscreen or by sitting in a shaded area.
- Preventing aspiration — Patients who have difficulty swallowing must take care to avoid inhaling (aspirating) foods and drinks. This may be done by elevating the head, using thickened drinks, or in severe cases, by placing a feeding tube.
Patients with dermatomyositis or polymyositis tend to have better outcomes if they are treated promptly, have mild weakness, have no difficulty swallowing, and have no signs of disease in other organ systems such as the heart and lungs.
INCLUSION BODY MYOSITIS — Inclusion body myositis (IBM) differs in a number of ways from polymyositis and dermatomyositis. It affects more men than women, and the age of onset is almost always after age 60, though it can affect persons between 30 and 90 years.
Symptoms — Typically, symptoms come on very slowly, over an average period of six years. The first area to be affected by weakness is usually the hips and upper legs. Some patients with inclusion body myositis have weakness in the hands or feet. Weakness is accompanied by muscle pain in 40 percent of patients. In 10 to 15 percent of cases, one side of the body is affected more than the other. Facial muscles may be involved, though the eye and mouth muscles are usually not affected.
Muscle atrophy often progresses along with the weakness. Some patients may have profound atrophy of the upper arms or upper legs. Between one-third and one-half of patients have difficulty swallowing due to weakness in the throat muscles.
Diagnosis — Blood tests may be done to look for signs of muscle damage, but may be normal or only mildly elevated. Electromyography (EMG) usually shows abnormal electrical activity, and MRI may reveal abnormalities in some cases (see "Electromyography" above). Muscle biopsy shows the definitive diagnostic features of this disorder, which are abnormal structures in the muscle cells (filamentous inclusions and vacuoles); these are seen in over 90 percent of affected patients (see "Muscle biopsy" above).
Diagnosis of inclusion body myositis is usually based upon signs and symptoms of progressive muscle weakness and results of a muscle biopsy. Blood testing and MRI may be helpful in establishing the diagnosis.
Treatment of IBM — Unlike dermatomyositis and polymyositis, inclusion body myositis often does not improve with standard treatments to suppress the immune system. Muscle strength usually responds minimally, if at all, to corticosteroids and other treatments. Despite this, corticosteroids are generally used first, with methotrexate or azathioprine used in some cases. Intravenous immune globulin has been used, though studies show mixed results.
Prognosis — Patients with inclusion body myositis may become progressively weaker if not treated or if treatment is not successful. Progression is usually more rapid in older patients.
Information obtained from National Institute of Health