Dominic Stone
Muscle atrophy is the wasting or thinning of muscle mass, causing muscles to look smaller than normal. It can be caused by nerve damage, which can be induced by disease or trauma. When nerves are damaged, they cannot trigger the muscle contractions needed to stimulate muscle activity. As a result, the body starts breaking down the muscles, causing them to decrease in size and strength. This is known as neurogenic atrophy, and it can develop sooner depending on the individual's health condition.
| Characteristics | Values |
|---|---|
| Definition | Wasting or thinning of muscle mass or tissue |
| Causes | Neurogenic conditions, nerve problems, nerve diseases, nerve injuries, physical inactivity, immobilisation of joints, malnutrition, age, genetics, neuromuscular diseases, metabolic disorders, nervous system disorders, muscular dystrophies, myositis, genetic disorders, mitochondrial dysfunction, polio, arthritis |
| Symptoms | Loss of movement, loss of strength, reduced muscle mass, muscle weakness, impaired movements, involuntary muscle twitches, sensory disorders, neuropathic pain, hampered motor function, difficulty swallowing or speaking, trouble walking or balancing |
| Diagnosis | Nerve conduction studies, CT scans, MRI scans |
| Treatment | Physical therapy, ultrasound therapy, surgery, exercise, healthy diet, functional electrical stimulation, EMG-triggered stimulation, low-frequency electrical currents |
| Complications | Muscle fibrosis, atrophy, extensive depolarization of the sarcolemma, calcium imbalance, oxidative stress, inflammation, mitophagy, atrophic fibrosis, muscle breakdown, bone damage |
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What You'll Learn
- Neurogenic atrophy is caused by nerve-impacting injuries or diseases
- When nerves are damaged, they can't trigger muscle contractions?
- Denervation causes calcium imbalance, oxidative stress, and inflammation
- Nerve damage can lead to bone abnormalities and muscle fibrosis
- Nerve damage-induced atrophy is associated with elevated myofibrillar protein synthesis
Neurogenic atrophy is caused by nerve-impacting injuries or diseases
Muscle atrophy is the wasting or thinning of muscle mass. It can be caused by nerve-impacting injuries or diseases, also known as neurogenic atrophy. Neurogenic atrophy occurs when an injury or disease affects the nerves that connect to the muscles. When these nerves are damaged, they cannot trigger the muscle contractions needed to stimulate muscle activity. As a result, the muscles stop contracting because they no longer receive signals from the nerves. This leads to a decrease in muscle size and strength.
Neurogenic atrophy can be caused by various conditions and diseases that impact the nerves. Some examples include Amyotrophic Lateral Sclerosis (ALS), Guillain-Barre Syndrome, Carpal Tunnel Syndrome, spinal cord injuries, and Multiple Sclerosis. These conditions damage the nerves that control muscle movement, leading to muscle atrophy. The time it takes for muscles to atrophy depends on age, fitness level, and the underlying cause. Neurogenic atrophy, due to nerve damage, tends to occur more rapidly than physiologic atrophy caused by disuse.
The treatment options for neurogenic atrophy are limited because of the physical damage to the nerves. While disuse atrophy can often be treated with exercise and improved nutrition, neurogenic atrophy typically cannot be reversed. However, physical therapy, including electrical stimulation, and ultrasound therapy may help maintain muscle mass and promote healing. In some cases, surgery may be required to correct contractures caused by muscle atrophy.
It is important to note that muscle atrophy can also be caused by factors other than nerve damage, such as malnutrition, age, genetics, lack of physical activity, and certain medical conditions. These factors can contribute to muscle wasting and atrophy, and the treatment options may vary depending on the underlying cause.
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When nerves are damaged, they can't trigger muscle contractions
Muscle atrophy refers to the wasting or thinning of muscle mass. It can be caused by disuse of muscles, malnutrition, age, genetics, lack of physical activity, or certain medical conditions. One such medical condition that can cause muscle atrophy is nerve damage, also known as neurogenic atrophy.
Neurogenic atrophy occurs when there is an injury or disease affecting the nerves that connect to the muscles. When these nerves are damaged, they can no longer transmit signals to the muscles, resulting in a loss of muscle contractions. This lack of muscle contractions sends a signal to the body that the muscles are no longer needed, leading to muscle breakdown and a decrease in muscle size and strength.
Diseases and conditions that can cause nerve damage and subsequent muscle atrophy include Amyotrophic Lateral Sclerosis (ALS), Guillain-Barre Syndrome, Carpal Tunnel Syndrome, spinal cord injuries, and Multiple Sclerosis. Additionally, peripheral nerve damage can be caused by trauma, resulting in neuropathic pain, hampered motor function, and skeletal muscle atrophy.
The treatment for muscle atrophy depends on its type and cause. Disuse or physiologic atrophy can often be treated with regular exercise and improved nutrition. Neurogenic atrophy, on the other hand, is more challenging to reverse due to the physical damage caused to the nerves. However, functional electrical stimulation (FES) has been shown to strengthen muscles in patients with various forms of muscle atrophy, including neurogenic atrophy.
It is important to note that muscle atrophy can cause a loss of movement or strength, and its symptoms can vary depending on the underlying cause. Seeking medical advice and a proper diagnosis is crucial to determine the appropriate treatment plan for managing muscle atrophy.
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Denervation causes calcium imbalance, oxidative stress, and inflammation
Denervation is any loss of nerve supply, which can occur due to nerve damage or injury, or as a symptom of a disorder like amyotrophic lateral sclerosis (ALS) or Guillain-Barré syndrome. It can also be caused by certain medical procedures, infections, inflammation, or trauma to the spine or a peripheral nerve. Intentional denervation is sometimes used as a valuable surgical technique for treating specific medical conditions.
Denervation affects the muscle activation process, which involves the development and propagation of an action potential and the subsequent release of calcium. Changes in the sarcoplasmic reticulum's morphology and structure lead to increased calcium reuptake, resulting in decreased amplitude and velocity of impulse conduction, along with increased muscle spike duration. This disruption in calcium homeostasis is one way that denervation contributes to muscle atrophy.
Denervation also induces oxidative stress in skeletal muscles. Oxidative stress occurs due to an increase in reactive oxygen species (ROS), which can act as signalling molecules at low levels but can be harmful in higher concentrations. While denervation-induced oxidative stress contributes to the activation of the response to denervation, it is not solely responsible for oxidative damage or neurogenic muscle atrophy. Nonetheless, oxidative stress is a factor in the complex process of muscle atrophy following denervation.
Additionally, denervation can lead to inflammation and tissue dysfunction. This inflammatory response is a component of the overall pathological process that can result in muscle atrophy. The specific mechanisms by which denervation causes inflammation and the subsequent atrophy require further investigation.
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Nerve damage can lead to bone abnormalities and muscle fibrosis
Muscle atrophy is the wasting or thinning of muscle mass. It can be caused by nerve damage, which inhibits the muscle contractions needed to stimulate muscle activity. When muscles don't contract, they start to break down, leading to a decrease in size and strength. This is known as neurogenic atrophy.
Nerve damage can also lead to bone abnormalities. Paget's disease of bone, for example, can cause bone overgrowth, which compresses and damages nerves, resulting in pain, weakness, or tingling sensations. The disease can lead to bone deformities, fractures, and osteoarthritis. Additionally, nerve damage can cause gross bone and cartilage formation abnormalities, such as vertebral bone fusion and rib duplications.
Furthermore, nerve damage plays a role in skeletal muscle fibrosis. In the kidney, nerve-derived Calcitonin Gene-Related Peptide (CGRP) upregulates TGF-B and Connective Tissue Growth Factor (CTGF), inducing fibrosis. TGF-B promotes the expression of collagens, fibronectin, and myofibroblast α-smooth muscle actin, leading to an expansion of the myofibroblast population. These findings suggest that nerve damage releases profibrogenic factors that contribute to fibrosis.
The sources of myofibroblasts in skeletal muscle fibrosis are not fully understood, but they may include resident fibroblasts, muscle-derived stem cells, nerve-associated cells, and inflammatory or perivascular cells. While the functional effects of fibrosis in skeletal muscle are well-studied, the cellular and molecular mechanisms are less defined.
In summary, nerve damage can lead to muscle atrophy by disrupting muscle contractions and breaking down muscle tissue. It can also cause bone abnormalities, such as Paget's disease of bone and bone formation issues, and contribute to skeletal muscle fibrosis through the release of profibrogenic factors and the activation of myofibroblasts.
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Nerve damage-induced atrophy is associated with elevated myofibrillar protein synthesis
Muscle atrophy is the wasting or thinning of muscle mass. It can be caused by disuse of muscles or neurogenic conditions. In the case of nerve damage-induced atrophy, nerves connecting to the muscles are injured or diseased, which inhibits the triggering of muscle contractions that stimulate muscle activity. As a result, the muscles do not contract, and the body interprets this as a sign that these muscles are no longer needed, leading to their breakdown and subsequent decrease in size and strength.
Neurogenic atrophy, specifically, is caused by damage to the nerves that connect to and stimulate the muscles. This damage can be a result of various diseases and conditions, including Amyotrophic Lateral Sclerosis (ALS), Guillain-Barre Syndrome, Carpal Tunnel Syndrome, Spinal Cord injuries, and Multiple Sclerosis. The time it takes for muscle atrophy to develop following nerve damage depends on age, fitness level, and the specific cause of the atrophy.
Several studies have investigated the relationship between nerve damage-induced atrophy and myofibrillar protein synthesis rates. Despite expectations of a decrease in myofibrillar protein synthesis (MPS) rates, research has consistently found that nerve damage-induced atrophy is associated with elevated MPS rates. This finding contradicts the typical assumption that muscle loss is accompanied by a decrease in protein synthesis and an increase in protein breakdown.
One particular study by Langer et al. examined the impact of nerve damage on muscle atrophy using a stable isotope tracer method and analysis of changes in muscle mass. They observed substantial muscle loss in the rat tibialis anterior, extensor digitorum longus, and soleus muscles due to nerve damage. However, despite the atrophy, they found that myofibrillar protein synthesis rates were increased rather than decreased.
Another study by Cegielski et al. used a novel stable isotope tracer method to simultaneously quantify skeletal muscle protein synthesis and breakdown in nerve-damaged muscles. They discovered that nerve damage-induced atrophy was associated with elevated myofibrillar protein synthesis rates, supporting the notion that muscle protein synthesis may reflect muscle remodeling rather than changes in muscle mass.
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Frequently asked questions
Muscle atrophy is the wasting or thinning of muscle mass, resulting in reduced muscle strength.
Nerve damage can cause muscle atrophy by disrupting the nerve signals that trigger muscle contractions. This can be due to an injury or disease affecting the nerves connected to the muscles. When the muscles don't receive signals from the nerves, they stop contracting, and the body starts breaking them down, leading to a decrease in muscle size and strength.
Treatment options for muscle atrophy caused by nerve damage include physical therapy, functional electrical stimulation, ultrasound therapy, and in some cases, surgery. Exercise and a healthy diet can also help slow muscle loss and improve muscle strength.
