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Proximal muscles are those closest to the body's core, including the upper legs, hips, upper arms, shoulders, and the core itself. Proximal muscle diseases can present with mild and seemingly unrelated symptoms, such as difficulty climbing stairs or getting out of a chair. Proximal muscle weakness can be a sign of acute flaccid myelitis (AFM), a rare but serious neurological condition that can lead to permanent paralysis. Proximal myopathy, also known as proximal paralysis, is a condition that weakens the limb muscles and affects mobility. It can be caused by long-term use of certain medications, such as statins and corticosteroids, as well as alcohol consumption. Duchenne's and Becker's muscular dystrophies are the most prevalent forms of hereditary proximal myopathies.
| Characteristics | Values |
|---|---|
| Definition | Proximal myopathy or proximal paralysis is a condition that weakens the limb muscles and affects mobility. |
| Causes | Long-term use of certain medications, disorders, alcohol, thyroid disease, osteomalacia, idiopathic inflammatory myopathies (IIM), hereditary myopathies, malignancy, infections, sarcoidosis, and viral infections. |
| Symptoms | Muscle pain, tenderness, cramps, fatigue, muscle atrophy, loss of strength, difficulty in breathing, and difficulty in performing daily tasks. |
| Diagnosis | Initial evaluation includes simple tests like creatine kinase, thyroid function, and (25)OH vitamin D levels. Further evaluation may include neurophysiological studies, muscle imaging, and muscle biopsy. Genetic tests can confirm if a disease is inherited. |
| Treatment | Treatment focuses on managing symptoms and slowing progression through physical therapy, adaptive devices, medications, and surgery in some cases. |
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What You'll Learn
Proximal myopathy
Hereditary or congenital myopathies, such as limb girdle muscular dystrophies, facioscapulohumeral muscular dystrophy, Duchenne and Becker muscular dystrophy, and proximal myotonic myopathy, can also lead to proximal myopathy. Glycogen storage diseases like McArdle's disease can cause rapid exhaustion, myalgia, and muscle cramping. Lipid deposition myopathy, a hereditary metabolic myopathy, causes lipids to accumulate in skeletal muscle fibres, leading to lesions and degeneration.
Viral infections, including HIV, dengue virus, influenza virus, hepatitis B and C, and SARS-CoV2, are associated with muscle weakness and may also contribute to proximal myopathy. Sarcoidosis, an inflammatory disease, can manifest as muscle weakness and myalgia. Additionally, inflammatory myopathies, such as polymyositis, dermatomyositis, inclusion body myositis (IBM), and Systemic Lupus Erythematosus (SLE), are associated with moderate to severe muscle weakness. IBM is the most prevalent acquired myopathy in individuals over the age of 50.
Diagnosing proximal myopathy can be challenging due to the various ways it can present. A comprehensive approach is necessary to reach an accurate diagnosis. Clinical assessment aims to distinguish proximal myopathy from other conditions with similar symptoms. Early identification is crucial for patients with cardiac, respiratory, or pharyngeal muscle involvement.
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Proximal paralysis
Proximal muscles are those that are closest to the body's midline or torso, such as the shoulder blade (scapula). Proximal paralysis, or proximal myopathy, is a condition that weakens these limb muscles and affects mobility. It is characterised by muscle weakness, pain, tenderness, cramps, and fatigue. Walking, climbing stairs, and lifting objects become challenging for people suffering from this condition.
The causes of proximal paralysis are varied and include certain disorders and medications. Long-term use of certain medications has been linked to proximal myopathy. For example, statins, commonly prescribed for lowering cholesterol, can induce myopathy. Corticosteroids, used for their anti-inflammatory properties, can lead to muscle weakness by altering skeletal muscle protein metabolism. Alcohol consumption can also be a factor, as it can disrupt the balance between protein synthesis and degradation, contributing to muscle damage.
Myopathy is a well-known side effect of long-term statin use, with symptoms including proximal muscle pain, weakness, tenderness, cramps, and fatigue. Individuals around the age of 65 years are more likely to develop myopathy and rhabdomyolysis than younger people. The risk of statin-induced myopathy is associated with various variables, including patient characteristics (age, demographics, co-morbidities, genetics), pharmacological characteristics, and drug interactions.
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Proximal muscle weakness
Proximal muscles refer to the muscles of the trunk, shoulders, and thighs. Proximal muscle weakness is a common symptom among patients with central or peripheral nervous system diseases, muscular and/or neuromuscular diseases, and rheumatologic diseases. It is also a symptom of inflammatory myopathies.
Proximal myopathy is a well-known side effect of long-term statin use, with symptoms including proximal muscle pain, weakness, tenderness, cramps, and fatigue. The risk of statin-induced myopathy is associated with patient characteristics such as age, genetics, and pharmacological factors. Individuals around 65 years of age are more likely to develop myopathy.
Hereditary or congenital myopathies, including limb-girdle muscular dystrophies, facioscapulohumeral muscular dystrophy, Duchenne and Becker muscular dystrophy, and proximal myotonic myopathy, can result in proximal muscle weakness. Glycogen storage diseases, such as McArdle's disease, can also cause fast exhaustion, myalgia, and cramping in working muscles.
In children, proximal muscle weakness can be a sign of acute flaccid myelitis (AFM), a rare but serious neurological condition that can cause muscle weakness and potentially lead to permanent paralysis. AFM often initially presents as sudden limb, neck, or trunk weakness.
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Proximal muscle testing
Two simple and reliable tests for proximal muscle function are the "1 kg arm lift" test and the "30-second chair stand" test. The 1 kg arm lift test assesses upper limb function by having the patient lift a 1 kg weight with their arm. The 30-second chair stand test evaluates lower limb function by timing how long it takes for the patient to stand up from a chair 30 times in 30 seconds. These tests have been found to be highly reliable and responsive to changes in disease activity, offering advantages over other muscle function tests.
Additionally, the Oxford Scale, also known as the Medical Research Council Manual Muscle Testing scale, is a commonly accepted method for evaluating muscle strength. This scale grades muscle strength from 0 to 5 based on the patient's ability to resist the examiner's force. This method allows for a systematic evaluation of important spinal nerve roots and provides valuable information during the patient's physical exam.
In conclusion, proximal muscle testing is a critical component of clinical practice, aiding in the diagnosis and management of various conditions affecting proximal muscles. Through simple and reliable tests, healthcare professionals can assess muscle strength, identify weaknesses, and develop effective treatment plans for their patients. Proximal muscle testing plays a vital role in maintaining and improving patients' quality of life.
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Proximal muscle treatments
Proximal muscles are those closest to the centre of your body, such as the muscles in your shoulders, upper arms, hips, and thighs. Proximal myopathy is a disease that affects these muscles, causing weakness and pain that can disturb everyday life. The most common pattern of this weakness is symmetric weakness, which affects both sides of the body.
There are various treatments for proximal myopathy, depending on the cause. Myopathy is a general term for diseases that affect the muscles connected to bones (skeletal muscles). It is often hereditary or congenital but can also be acquired later in life.
Hereditary or Congenital Myopathies
Hereditary or congenital myopathies include limb-girdle muscular dystrophies, facioscapulohumeral muscular dystrophy, Duchenne and Becker muscular dystrophy, and proximal myotonic myopathy. Glycogen storage diseases such as McArdle's disease can also cause fast exhaustion, myalgia, and cramping in working muscles. In this case, lipid deposition myopathy causes lipids to accumulate in skeletal muscle fibres, leading to lesions and degeneration.
Acquired Myopathies
Acquired myopathies can be caused by various factors, including:
- Toxins: Alcohol and toluene (found in spray paint) can interfere with muscle structure and function, leading to toxic myopathy.
- Medications: Certain drugs, such as checkpoint inhibitor immunotherapy, corticosteroids, cholesterol-lowering statins, and antivirals, can induce myopathy.
- Endocrine Disorders: Hormonal imbalances, such as hypothyroidism, hyperthyroidism, hyperparathyroidism, and adrenal dysfunction, can contribute to endocrine myopathies.
- Infectious Agents: Some infections can affect muscle function, leading to infectious myopathies.
- Inflammatory Conditions: Sarcoidosis, an inflammatory disease, can manifest as proximal muscle weakness and myalgia. It is treated with corticosteroid medication to prevent the generation of cytokines and reduce granulomatous lesions.
- Statin-Associated Myopathy: Long-term use of statins can lead to myopathy, with symptoms including proximal muscle pain, weakness, tenderness, cramps, and fatigue.
It is important to consult a medical professional for an accurate diagnosis and tailored treatment plan for proximal myopathy.
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Frequently asked questions
Proximal muscles are those closest to the core of the body, including the upper legs, hips, upper arms, shoulders, and the core itself.
Proximal muscle diseases can present with mild and seemingly unrelated symptoms. Some signs and symptoms include:
- Muscle pain
- Muscle weakness
- Fatigue
- Cramps
- Morning headaches
- Difficulty breathing
- Difficulty climbing stairs or getting out of a chair
Proximal muscle diseases can be caused by a variety of factors, including:
- Long-term use of certain medications such as statins and corticosteroids
- Alcohol consumption
- Genetic factors
- Viral causes such as HIV, dengue virus, influenza virus, hepatitis B and C, and SARS-CoV-2
- Hereditary or congenital myopathies
Doctors can diagnose proximal muscle disease through a combination of methods, including:
- Reviewing the patient's medical history
- Physical examinations to identify muscle weakness or atrophy
- Blood tests to detect muscle damage or illness
- Electromyography (EMG) to record muscle electrical activity
- Biopsies to analyse muscle tissue
