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Bilateral muscle weakness is a common complaint among patients. It can be challenging to evaluate because it has a broad differential diagnosis. Bilateral muscle weakness can be caused by a variety of conditions, including inflammatory myopathies, endocrine disorders, electrolyte imbalances, neurologic conditions, and spinal cord injuries. In some cases, bilateral muscle weakness may be a sign of a serious underlying medical condition, such as a spinal cord infarct or stroke. Therefore, it is important for physicians to conduct a thorough evaluation and differential diagnosis to determine the underlying cause of bilateral muscle weakness in their patients.
| Characteristics | Values |
|---|---|
| Prevalence | Occurs in about 5% of U.S. adults 60 years and older |
| Diagnosis | Distinguish true muscle weakness from subjective fatigue or pain-related motor impairment with normal motor strength |
| Pattern of weakness | Global (bilateral) or focal (unilateral) |
| Possible causes | Neurologic, rheumatologic, endocrine, genetic, medication- or toxin-related, infectious etiologies, inflammatory myopathies, IBM, spinal cord infarction, etc. |
| Symptoms | Muscle atrophy, myalgia, dysphagia, facial weakness, gradual memory loss, etc. |
| Diagnostic tools | Laboratory testing, imaging, electrodiagnostic testing, muscle biopsy, electromyography, etc. |
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What You'll Learn
Inflammatory myopathy
The inflammatory myopathies are a group of rare diseases that involve chronic (long-standing) muscle inflammation, muscle weakness, and, in some cases, muscle pain. Myopathy is a general term used to describe a number of conditions affecting the muscles. All myopathies can cause muscle weakness. Both children and adults can be affected, although it is rare. Children are usually diagnosed between the ages of 5 and 10, and adults between 40 and 50. Women get inflammatory myopathies twice as often as men.
The main classes of idiopathic inflammatory myopathy are polymyositis (PM), dermatomyositis (DM), inclusion-body myositis (IBM), immune-mediated necrotising myopathy (IMNM), and focal autoimmune myositis. The most common inflammatory myopathies are dermatomyositis and polymyositis; however, new inflammatory myopathies are being described all the time. IBM is less common than polymyositis and is characterised by chronic progressive muscle inflammation and weakness. It often goes undiagnosed and untreated. IBM is the most common inflammatory myopathy in individuals over the age of 50.
Inflammatory myopathies cause muscle weakness, usually in the neck, shoulders, and hips. Dermatomyositis can also cause rashes. Inflammatory myopathies may cause problems like weakness when climbing stairs, getting out of a seat, or lifting objects above the head, choking while eating, shortness of breath, cough, or a rash on the knuckles, eyelids, knees, or elbows. Diagnosing inflammatory myopathies starts with a strength exam. A rheumatologist may also perform blood tests, electromyogram (EMG) to measure electrical activity in the muscles, or magnetic resonance imaging (MRI) to look for muscle damage. A muscle biopsy may also be needed. These diseases may be linked to cancer, so tests to rule out cancer may be necessary.
The goal of treatment is to improve activities of daily living and muscle strength. Suppression of immune system activity (immunosuppression) is the treatment strategy. Patients with PM or DM almost always improve to some degree in response to treatment, and many recover fully with maintenance therapy. There is no proven effective therapy for IBM, and most patients will need assistive devices such as a cane, a walking frame, or a wheelchair. The first treatment for inflammatory myopathies is an oral corticosteroid, such as prednisone, at a high dose. Muscle enzymes usually return to normal within 4 to 6 weeks, and strength returns in 2 to 3 months.
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Spinal cord infarction
Bilateral muscle weakness can be caused by inflammatory myopathy, which is a common cause of the condition in adults. One type of inflammatory myopathy is inclusion body myositis (IBM), which is characterised by chronic progressive muscle inflammation and accompanying muscle weakness. IBM is often missed or goes undiagnosed, and it does not respond to treatment as well as other inflammatory myopathies.
The symptoms of spinal cord infarction can vary but often include sudden onset of weakness in the bilateral lower extremities, also known as bilateral extremity weakness. This can include both proximal and distal extremity weaknesses, with the ocular and facial muscles often spared. Other possible symptoms include impaired light touch and pin-prick sensations below the L2 level, impaired voluntary anal contraction, and absent perianal and deep anal sensations. Bilateral knee and ankle jerks may also be reduced.
The treatment for spinal cord infarction aims to prevent complications and maximise recovery. Early rehabilitation is crucial for improving independence and physical function. Standard drug therapy includes aspirin, which can help reduce the risk of recurrent stroke and death. Anticoagulation and antiplatelet agents may also be administered to prevent the extension of the acute ischemic injury and reduce the risk of pulmonary embolism. In some cases, emergency spinal decompressive surgery may be necessary.
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Muscle atrophy
- Remaining immobile for long periods due to illness or injury.
- Bed rest or inability to move certain body parts due to a medical condition.
- Seated jobs, health problems that limit movement, or decreased activity levels.
- Astronauts can experience muscle atrophy after a few days of weightlessness.
In addition, certain medical conditions can cause muscle wasting or make movement difficult, leading to muscle atrophy. These include:
- Arthritis.
- Myositis.
- Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, which affects nerve cells that control voluntary muscle movement.
- Dermatomyositis, which causes muscle weakness and skin rash.
- Multiple sclerosis, an autoimmune condition in which the body destroys the protective coverings of nerves.
- Malnutrition.
The symptoms of muscle atrophy vary widely depending on the cause and severity of muscle loss. The primary symptom is reduced muscle mass, which may be noticeable when comparing one hand, arm, or leg to the other.
Treatments for muscle atrophy depend on the degree of muscle loss and any underlying medical conditions. Treatment may include physical therapy, nutritional intervention, ultrasound therapy, and, in some cases, surgery. Functional electrical stimulation (FES) is another effective treatment.
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Hemiparesis
If you experience sudden hemiparesis in a limb or your face for an unknown reason, you should seek immediate medical attention.
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IBM diagnosis and treatment
Bilateral muscle weakness can be caused by a variety of conditions, including inflammatory myopathies and inclusion body myositis (IBM). IBM is a type of inflammatory myopathy characterised by chronic progressive muscle inflammation and weakness. It is a relatively rare disorder, with a prevalence of 5 to 9 cases per million adults, and it often goes undiagnosed and untreated.
IBM diagnosis:
IBM is a degenerative muscle disease that causes a gradual and painless weakening of muscles. It usually appears after the age of 50 and progresses slowly over several years, eventually becoming disabling. The distinguishing features of IBM from other inflammatory myopathies include asymmetric and distal muscle involvement, an insidious onset, muscle atrophy, and dysphagia. IBM is also characterised by the presence of "inclusion bodies", which are clumps of abnormal proteins inside muscle fibres.
To diagnose IBM, a physician will first take a detailed history and perform a physical examination. Laboratory tests, including blood tests for electrolyte levels, thyroid-stimulating hormone, and creatine kinase, may be ordered. Electrodiagnostic testing, such as electromyography (EMG) and nerve conduction studies (NCS), can also be useful in the diagnostic process. Magnetic resonance imaging (MRI) may be indicated if there is a concern for acute neurological conditions or to guide muscle biopsy.
The definitive test for IBM is a muscle biopsy, which involves taking a tissue sample from an affected muscle. A pathologist will then examine the tissue under a microscope to look for the presence of inclusion bodies. The European Neuromuscular Centre (ENMC) 2011 clinically defined diagnostic criteria have a high specificity of greater than 99% to diagnose IBM, but their sensitivity is low at 57%.
IBM treatment:
Currently, there is no effective treatment or cure for IBM. Unlike other inflammatory and autoimmune conditions, it does not respond well to corticosteroids, immunosuppressant drugs, or other pharmacological therapies. However, physical therapy and regular exercise are crucial for preserving muscle strength and preventing disability. Research studies and clinical trials of medications to treat IBM are currently underway.
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Frequently asked questions
Bilateral muscle weakness is a loss of strength on both sides of the body. It can be differentiated from subjective fatigue or pain-related motor impairment with normal motor strength.
The causes of bilateral muscle weakness vary. It could be due to injury, disease, endocrine disorders, electrolyte imbalances, inflammatory myopathy, or inclusion body myositis (IBM).
Diagnosis begins with a patient history, medication use, and family history. Physical examinations are conducted, including laboratory tests, imaging, and electrodiagnostic testing.
Treatment depends on the underlying cause. In some cases, steroid therapy, physical therapy, or surgery may be recommended. For muscle atrophy, exercise and a healthy diet can help reverse the condition.
