What is the medical term for upper body weakness? A guide to causes and diagnosis

According to the National Institute of Neurological Disorders and Stroke, muscle weakness can be a symptom of a wide range of conditions, from temporary infections to chronic diseases. Understanding the precise medical term for upper body weakness is the first step toward getting an accurate diagnosis and effective treatment.

Quick Summary

The medical term for general physical weakness, which can include upper body weakness, is asthenia, though more specific conditions like myopathy or myasthenia gravis also cause muscle weakness. The exact term depends on the underlying cause, which can range from nerve damage to muscular diseases and must be properly diagnosed by a doctor.

Key Points

• Asthenia Defined: The general medical term for weakness or lack of strength is asthenia, which can be localized to the upper body.

• Proximal Weakness: Specifically, weakness in muscles closest to the body's center, like the shoulders and upper arms, is known as proximal weakness and is a sign of myopathy.

• Myopathy vs. Myasthenia Gravis: Myopathy refers to muscle disease, while myasthenia gravis is an autoimmune condition causing fluctuating weakness that worsens with activity.

• Diverse Causes: Upper body weakness can result from nerve damage (neuropathy), muscle disorders (myopathies), systemic diseases, nutritional deficiencies, and side effects of medication.

• Importance of Diagnosis: An accurate diagnosis from a healthcare provider is critical for determining the correct cause and receiving effective treatment, which may include physical therapy, medication, or lifestyle changes.

Understanding the medical terminology for weakness

While "weakness" is a common term, the medical field uses more specific language to describe a loss of strength. The general medical term for a feeling of physical weakness or lack of energy is asthenia. This term can be applied to the entire body or a specific region, such as the upper body. However, for a more precise diagnosis, a doctor will consider additional factors to determine the specific cause.

Asthenia: The general term

Asthenia describes a subjective sensation of physical, emotional, or cognitive tiredness and weakness. It is not a disease itself but a symptom of many possible underlying conditions. For instance, asthenia can be a result of a viral infection like the flu, chronic health issues, or even a nutritional deficiency.

Proximal weakness: A specific type of myopathy

When the weakness is specifically in the muscles closest to the center of the body (e.g., shoulders, upper arms, and hips), it is medically known as proximal weakness. This is a key symptom of a class of disorders called myopathies, which are diseases affecting the muscles themselves. Symptoms of proximal weakness may include difficulty with daily activities such as:

• Lifting objects overhead
• Combing your hair
• Reaching for high shelves
• Getting out of a chair or bathtub

Distinguishing myopathy and myasthenia gravis

It's important to differentiate between myopathy and another condition called myasthenia gravis. Myasthenia gravis is an autoimmune disease where the immune system attacks the communication between nerves and muscles, causing muscle weakness and fatigue. The weakness in myasthenia gravis tends to worsen with activity and improve with rest, which is a key distinguishing feature from other myopathies.

Possible causes of upper body weakness

Upper body weakness can stem from a variety of sources, which can be broadly categorized as follows:

Neurological conditions

• Peripheral Neuropathy: Damage to nerves outside the brain and spinal cord can lead to weakness, numbness, and pain in the limbs. Conditions causing this can include diabetes, infections, and inherited disorders.
• Pinched Nerves: A compressed nerve in the neck or upper spine, perhaps from a herniated disc, can cause weakness, numbness, or tingling in the arm and hand.
• Brachial Plexus Injury: This is damage to the network of nerves that controls the muscles and sensation in the shoulder, arm, and hand. It can result from trauma, inflammation, or tumors.
• Amyotrophic Lateral Sclerosis (ALS): A progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord, leading to widespread muscle weakness.

Muscular disorders (Myopathies)

• Inflammatory Myopathies: These include conditions like polymyositis and dermatomyositis, where chronic muscle inflammation leads to progressive muscle weakness.
• Muscular Dystrophies: A group of inherited disorders that cause progressive muscle weakness and loss of muscle mass.
• Drug-Induced Myopathy: Certain medications, including cholesterol-lowering drugs (statins) and corticosteroids, can cause muscle damage and weakness.

Other systemic diseases and factors

• Nutritional Deficiencies: A lack of certain vitamins, such as vitamin B12 or vitamin D, or electrolyte imbalances can cause muscle weakness.
• Endocrine Disorders: Conditions affecting hormone levels, like thyroid disorders (hyperthyroidism or hypothyroidism), can lead to myopathy and weakness.
• Infections: Some infections, including viral illnesses, can cause myositis (muscle inflammation) and subsequent weakness.

Diagnosing the cause of upper body weakness

An accurate diagnosis requires a thorough evaluation by a healthcare professional. The process typically involves several steps:

Patient history and physical exam

The doctor will ask about the nature of the weakness, its onset, and any other symptoms. A physical exam will assess muscle strength, reflexes, and coordination.

Diagnostic tests

• Blood Tests: These can check for elevated muscle enzymes, hormone imbalances, or nutritional deficiencies.
• Electromyography (EMG) and Nerve Conduction Studies: These tests measure the electrical activity of nerves and muscles to pinpoint nerve or muscle damage.
• Imaging: MRI or CT scans can provide detailed images of the spine, nerves, and muscles to look for structural issues.
• Muscle Biopsy: In some cases, a small sample of muscle tissue is examined under a microscope to identify muscle disorders.

Comparison of myopathy vs. neuropathy

Feature	Myopathy	Neuropathy
Primary Location	Within the muscle fibers themselves	In the nerves that control the muscles
Symptom Type	Often involves symmetrical proximal weakness (shoulders, hips)	Can cause asymmetrical weakness, numbness, tingling, and pain (distal weakness)
Reflexes	Normal or slightly decreased	Often diminished or absent
Sensation	Sensation is typically normal	Sensory loss (numbness, tingling) is a hallmark symptom
Underlying Cause	Genetic, autoimmune, metabolic, inflammatory	Nerve compression, diabetes, trauma, toxicity

Treatment options and management strategies

The treatment for upper body weakness depends entirely on the underlying cause. Once a diagnosis is made, a treatment plan can be developed. For instance, if a thyroid disorder is the cause, treating the thyroid can resolve the weakness. For other conditions, management may be more complex.

• Physical Therapy: Tailored exercises can help strengthen muscles, improve range of motion, and enhance mobility.
• Medications: Anti-inflammatory drugs, corticosteroids for autoimmune issues, or drugs to manage chronic conditions may be prescribed.
• Nutritional Support: Addressing any vitamin or electrolyte deficiencies through dietary changes or supplements is crucial.
• Surgical Intervention: For cases involving nerve compression from a herniated disc or tumor, surgery may be necessary to alleviate pressure.
• Lifestyle Adjustments: Regular exercise, adequate rest, and stress management can help support muscle health and overall well-being.

Conclusion: Seeking expert guidance is key

Weakness in the upper body is a symptom that requires professional medical attention to uncover the underlying cause. The terms asthenia, myopathy, and proximal weakness are all possibilities depending on the specifics of your condition. It is essential not to self-diagnose but to consult with a healthcare provider who can perform the necessary tests and develop an appropriate treatment plan. With a correct diagnosis, many causes of muscle weakness can be effectively managed, leading to improved quality of life.

Visit the NIH website for more information on neurological disorders.

Frequently Asked Questions

What is the medical term for upper body weakness?

The most general medical term is asthenia, which means lack of energy and strength. When the weakness is concentrated in the shoulders and upper arms, it is referred to as proximal weakness, often associated with a myopathy.

Is asthenia the same as fatigue?

While often used interchangeably, asthenia refers more to physical weakness or a lack of strength, whereas fatigue typically implies a feeling of tiredness that can result from physical or mental exertion. You can experience asthenia without feeling tired.

What is the difference between myopathy and myasthenia gravis?

Myopathy is a disease of the muscle tissue itself, whereas myasthenia gravis is an autoimmune disease that affects the communication between nerves and muscles. A key difference is that myasthenia gravis weakness often fluctuates and improves with rest.

Can nutritional deficiencies cause upper body weakness?

Yes, deficiencies in certain nutrients like vitamin D, vitamin B12, and potassium can lead to muscle weakness. Addressing these through diet or supplements, under a doctor's guidance, can help resolve the issue.

What are the common diagnostic tests for upper body weakness?

Doctors may use several tests to pinpoint the cause, including blood tests to check for enzymes and hormones, electromyography (EMG) and nerve conduction studies to evaluate nerve and muscle function, and imaging like MRI or CT scans to look for structural problems.

Can medication cause muscle weakness?

Yes, certain medications, such as statins (for cholesterol) and corticosteroids, are known to cause myopathy and muscle weakness in some individuals. It is important to discuss any medication side effects with your doctor.

When should I see a doctor for upper body weakness?

You should see a doctor if your weakness is persistent, worsening, or interfering with daily activities. Seek immediate medical attention if weakness is accompanied by severe symptoms such as difficulty breathing, sudden paralysis on one side, or confusion, as these could indicate a serious condition like a stroke.