Conditions We Treat
Muscle Weakness
Overview
Muscle weakness is a loss of strength in one or more muscles, and it can develop suddenly or gradually. It happens when your best effort does not produce the normal, expected movement.
The brain sends signals through the spinal cord and nerves to the muscles, telling them to contract. Weakness can come from a problem anywhere along that path, in the brain, the spinal cord, the nerves, the muscles, or the connections between them. Common causes include stroke, spinal cord injury, and nerve and muscle disorders.
Many people use the word weakness to describe feeling tired, but true weakness is different from fatigue. Weakness that has no clear explanation, or that does not go away, should be checked by a neurologist, because it can be a sign of an underlying condition that needs attention.
Symptoms
What real weakness looks like
True muscle weakness is a loss of strength, not just tiredness. Signs include:
- Trouble with everyday tasks like writing, grooming, or lifting
- Loss of balance or frequent falls
- Muscle twitching, cramps, or spasms
- Numbness, tingling, or a burning feeling
Weakness is different from fatigue, which is a feeling of low energy. Telling them apart helps point to the cause.
Causes
What can cause weakness
Weakness comes from a problem somewhere between the brain and the muscles. Causes include:
- Stroke, the most common cause in older adults
- Spinal cord injury
- Nerve and muscle (neuromuscular) disorders
- Infections, certain medications, or electrolyte imbalances
Some causes, such as a medication side effect or an electrolyte imbalance, are reversible once identified.
Emergency
Stroke: call 911
Sudden weakness can be a stroke. Remember F.A.S.T. and call 911 right away if you notice:
- Face drooping on one side
- Arm weakness or numbness, often on one side
- Speech that is slurred or hard to understand
- Time to call 911, even if symptoms pass
A stroke is a medical emergency. Fast treatment can save brain tissue and lives.
Diagnosis
How weakness is evaluated
Because the causes are so varied, finding the source is the priority:
- A detailed history and a physical exam
- Checking reflexes and comparing muscle strength and size on both sides
- EMG/NCV to test nerve and muscle function
- Imaging such as MRI when a stroke or spinal cause is suspected
Treatment
How weakness is treated
Treatment targets the underlying cause, and some causes are quickly reversible:
- Adjusting a medication or correcting an electrolyte imbalance
- Physical rehabilitation to rebuild strength, such as after a stroke
- Treating the underlying nerve or muscle condition
- Ongoing therapy and support to protect function
Our Approach
How we help
Because weakness has so many possible causes, the goal is to find the specific one. Our providers take a careful history, examine and measure your muscle strength, and use testing such as EMG/NCV and imaging when needed. Treatment then targets the cause, which may be as simple as adjusting a medication, or may involve rehabilitation after a stroke or ongoing care for a nerve or muscle condition.
On-Site Testing
Testing that may help with diagnosis
Good to Know
Muscle Weakness: Frequently Asked Questions
What is muscle weakness?
Muscle weakness is a true loss of muscle strength caused by a problem in the nerves, the muscles, or the connection between them. It can affect a single muscle or a whole group, and it may come on suddenly or gradually.
What is the difference between weakness and fatigue?
Weakness is the inability to perform a movement at normal strength. Fatigue is a feeling of exhaustion or low energy, often from stress, poor sleep, or overwork. Both are symptoms rather than diagnoses, and telling them apart helps your neurologist find the cause.
What causes muscle weakness?
Causes include neurological conditions such as stroke, spinal cord injury, multiple sclerosis, and myasthenia gravis, as well as infections, certain medications, and electrolyte imbalances. In older adults, stroke is the most common cause.
What are the warning signs of a stroke?
Use F.A.S.T.: Face drooping, Arm weakness, Speech difficulty, Time to call 911. Other signs include sudden numbness, confusion, trouble seeing or walking, and a severe headache. A stroke is an emergency, so call 911 right away, even if the symptoms go away.
How is muscle weakness diagnosed?
Your neurologist starts with a detailed history and a physical exam, checking reflexes and comparing muscle strength and size on both sides. Depending on the suspected cause, testing may include EMG/NCV and imaging such as MRI.
How is muscle weakness treated?
Treatment depends entirely on the cause. Some causes are straightforward to reverse, such as stopping a medication or correcting an electrolyte imbalance. Others, such as weakness after a stroke, are treated with physical rehabilitation to restore strength and function.
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