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Paresis is a condition characterised by a weakness of voluntary movement, partial loss of voluntary movement, or impaired movement. Paretic muscles are those that have undergone atrophy, or muscle wastage, and an increase in intramuscular fat, often as a result of stroke. This condition is also referred to as hemiparesis, or muscle weakness on one side of the body, and can cause significant mobility issues, with walking being limited in two out of three patients post-stroke. Paretic muscle atrophy can be observed through imaging techniques such as MRI, DEXA, and CT scans.
| Characteristics | Values |
|---|---|
| Definition | In medicine, paresis is a condition typified by a weakness of voluntary movement, or by partial loss of voluntary movement or by impaired movement. |
| Cause | A neurological impairment or injury. |
| Mechanism | Damage to the corticospinal system, that is, the motor cortical areas, the corticospinal tract, and the spinal cord. |
| Manifestation | Weakness during movement in gravity-eliminated positions, against gravity, and/or against manual resistance. |
| Diagnosis | Magnetic resonance imaging (MRI) is used to determine muscle atrophy. |
| Atrophy | All individual paretic muscles examined had smaller volumes in the non-paretic side, except the gracilis. |
| Atrophy percentage | The average decrease in volume for paretic muscles was 23%. |
| Gracilis volume | The gracilis volume was approximately 11% larger on the paretic side. |
| Non-contractile tissue | Higher in all paretic muscles except the gracilis. |
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What You'll Learn
Hemiparesis
Pusher syndrome is a clinical disorder that occurs in 10.4% of patients with acute stroke and hemiparesis, where patients actively push their weight away from the non-hemiparetic side. This can increase the time needed for physical rehabilitation.
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Paresis and paralysis
Paresis refers to partial or restricted muscle weakness, typically affecting a larger group of muscles. It is often less severe than paralysis and is usually reversible with proper treatment, such as physical therapy. With appropriate intervention, individuals with paresis may regain full muscle function. Paresis can occur due to damage to the upper motor neurons, which are responsible for connecting with the motor cortex and controlling muscle movements. This damage results in partial weakness or impaired movement of the muscles, known as paresis. It can also occur during a stroke and is generally temporary. Different types of paresis include mono paresis, affecting one leg or arm, para-paresis, affecting both legs, and hemi-paresis, affecting an arm and a leg on opposite sides of the body following a stroke. Paresis can also occur in the vocal cords, resulting in voice changes and potentially airway and swallowing difficulties.
Paralysis, on the other hand, refers to complete or very severe muscle weakness, typically affecting fewer muscles or organs. It is more localized than paresis. If the lower motor neurons are damaged, it can result in absolute paralysis of the affected muscle, as these neurons are responsible for muscle contraction. An example of this is motor neuropathy, where degeneration of lower motor neurons occurs, causing the muscle to become flaccid and lose its ability to contract, leading to a significant reduction in muscle tone. Paralysis can also occur in the vocal cords, resulting in a total loss of movement and voice changes.
Both paresis and paralysis can result from various causes, including traumatic injuries, such as brain or spinal cord trauma, and medical conditions. Infections such as Lyme disease, polio, and botulism can lead to paralysis, while nerve damage, trauma, autoimmune disorders, tumours, and certain medications can cause paresis.
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Post-stroke muscle changes
Following a stroke, an individual may experience hypotonicity, or low muscle tone. This can result in partial or complete paralysis of the muscles, and they may feel limp and lack resistance when being stretched or moved. Hypotonia does not always equate to muscle weakness, but the two can often be related. Hypertonicity, on the other hand, is a high amount of muscle tone, resulting in increased tension and resistance when the muscle is stretched. This can cause the muscle to feel tight and be difficult to move or straighten. Hypertonicity can sometimes result in the affected arm being pulled in and flexed toward the body. Spasticity is a specific type of hypertonicity, causing muscles to stiffen when stretched quickly.
Muscle atrophy, or a decrease in muscle size, is also a common post-stroke change. This can affect the overall force-generating capability of the muscle. In addition, the muscle fibres may be replaced with fat and fibrous tissues, altering the mechanical properties of the muscle, such as its stiffness. This can be observed through imaging techniques such as MRI scans. The gracilis muscle, however, has been found to be larger on the paretic side, which may be due to its increased use to compensate for paretic plantar flexor weakness.
Post-stroke gait is often characterised by a range of deficits, including decreased walking speed and asymmetric stance periods. These changes are related to muscle dysfunction and weakness. Exercise interventions can be beneficial in restoring muscle function and improving overall health.
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Paretic muscle atrophy
Paresis is a condition characterised by a weakness of voluntary movement, partial loss of voluntary movement, or impaired movement. Paretic muscle atrophy is a phenomenon observed in patients post-stroke, wherein muscle fibres are lost and replaced with fat and fibrous tissues, resulting in muscle weakness. This condition is also known as hemiparesis, or muscle weakness on the side of the body contralateral to the brain lesion.
Post-stroke, walking is limited in two out of three patients. When ambulation ability is regained, post-stroke gait is characterised by a number of deficits compared to a normal gait, such as decreased walking speed and decreased centre of mass support. Walking performance after a stroke is related to paretic knee extensor strength.
Imaging techniques such as dual-energy X-ray absorptiometry (DEXA) and computed tomography (CT) have confirmed muscle atrophy in post-stroke limbs. Magnetic resonance imaging (MRI) is advantageous in measuring skeletal muscle variations because it overcomes the limitations of DEXA and CT.
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Paretic knee extensor strength
Paresis is a condition characterised by a weakness of voluntary movement, partial loss of voluntary movement, or impaired movement. Paretic muscles, therefore, refer to muscles that have been weakened or impaired due to neurological issues.
Several studies have investigated paretic knee extensor strength and its impact on walking performance and aerobic capacity. One study found that the paretic knee extensors showed exaggerated weakness at short muscle lengths, and the non-paretic knee extensors demonstrated selective strength gains. This can lead to compensatory overuse of the non-paretic leg. To prevent this, clinicians should focus on strengthening the paretic knee extensors near full extension and promoting symmetrical use of the legs.
Another study found that paretic knee extensor strength was a major determinant of peak aerobic capacity in subacute stroke patients, along with gait velocity and fat mass. The study found that therapeutic approaches should focus on improving gait velocity and paretic knee extensor strength in the early stages of stroke recovery.
Overall, paretic knee extensor strength is an important factor in the rehabilitation of stroke patients, as it can impact walking performance and aerobic capacity. Therapeutic interventions should aim to improve strength and promote symmetrical use of the legs to prevent compensatory overuse of the non-paretic leg.
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Frequently asked questions
Paresis is a reduction in muscle strength with a limited range of voluntary movement. Paretic muscles are those that have been affected by paresis.
Paresis is defined by the inability to voluntarily recruit skeletal muscles to generate movement. It is a problem with movement execution and is caused by damage to the corticospinal system.
Paresis can result from a wide range of neurological conditions, such as stroke, multiple sclerosis, cerebral palsy, amyotrophic lateral sclerosis, traumatic brain injury, and spinal cord injury.
The symptoms of paresis can vary depending on the underlying cause and the location of the affected muscles. However, common symptoms include muscle weakness, impaired movement, and partial loss of voluntary movement.
