Some Causes and Features of Muscle Weakness
Cause | Common Features* | Diagnostic Approach† |
|---|---|---|
Brain disorders | ||
Headaches, personality changes, confusion, difficulty concentrating, drowsiness, loss of balance and coordination, and paralysis or numbness Sometimes seizures | MRI or CT of the brain | |
Multiple sclerosis (affects the brain, spinal cord or both) | Usually other symptoms of nervous system malfunction (such as loss of sensation, loss of coordination, and vision problems) Weakness that
| MRI of the brain and sometimes of the spinal cord Sometimes a spinal tap (lumbar puncture) |
Symptoms that occur suddenly:
| CT or MRI of the brain | |
Spinal cord disorders‡ | ||
Acute transverse myelitis (sudden spinal cord inflammation), often due to
| Tingling, numbness, and muscle weakness that
Usually a bandlike tightness around the chest or abdomen Often difficulty passing urine When an injury is severe, loss of bowel and bladder control and/or reduced sexual response, including erectile dysfunction in men | MRI of the spinal cord, CT myelography§, or both A spinal tap to help identify the cause Blood tests to help identify the cause |
Cauda equina syndrome, caused by pressure on several spinal nerve roots, as may result from
| Weakness in both legs Loss of feeling in the upper inner part of the thighs, the buttocks, bladder, genitals, and the area between them (saddle area) Usually pain in the lower back Loss of bowel and bladder control and/or reduced sexual response, including erectile dysfunction in men | MRI of the spinal cord or CT myelography§ |
Compression of the spinal cord that develops suddenly (acute), as may result from
| Symptoms that develop in hours or days Weakness or paralysis of the legs and sometimes arms and loss of sensation With abscesses or tumors, tenderness to the touch over the compressed area | MRI of the spinal cord or CT myelography§ |
Compression of the spinal cord that develops slowly (chronic), as may result from
| Symptoms that are present for weeks to months When an injury is severe, loss of bowel and bladder control and/or reduced sexual response, including erectile dysfunction in men | MRI of the spinal cord or CT myelography§ |
Compression of a spinal nerve root by a ruptured disk | Weakness, numbness, or both in one leg or arm Usually back or neck pain that shoots down the leg or arm | Usually MRI or CT of the spinal cord Usually electromyography (stimulating muscles and recording their electrical activity) Sometimes nerve conduction studies (measuring how fast nerves transmit signals) |
Multiple sclerosis (affects the brain, spinal cord, or both) | Usually other symptoms of nervous system malfunction (such as loss of sensation, loss of coordination, and vision problems) Weakness that
| MRI of the brain and spinal cord Sometimes a spinal tap |
Disorders that affect the peripheral nerves and the brain or spinal cord║ | ||
Progressive muscle weakness that
Clumsiness, involuntary muscle contractions, and muscle cramps Drooling and difficulty speaking and swallowing As the disorder progresses, difficulty breathing and eventually death | Electromyography and sometimes nerve conduction studies MRI or CT myelography§ of the brain and spinal cord or both to rule out disorders that can cause similar symptoms | |
Muscles that tire easily and progressive muscle weakness Sometimes muscle twitching and loss of muscle tissue In people who have had polio | Electromyography and sometimes nerve conduction studies MRI or CT myelography§ of the brain and spinal cord or both to rule out disorders that can cause similar symptoms | |
Disorders that simultaneously affect many nerves (polyneuropathies) | ||
Weakness and often loss of sensation that
When severe, difficulty swallowing and breathing | Electromyography and nerve conduction studies A spinal tap | |
Hereditary neuropathies (such as Charcot-Marie-Tooth disease) | Muscle wasting (atrophy) Sometimes loss of reflexes Loss of sensation, including the ability to sense position of the limbs, vibration, pain, and temperature | Electromyography and nerve conduction studies Sometimes genetic testing |
Nerve damage caused by
| Muscle weakness that
Loss of sensation, typically before muscles become weak Loss of reflexes | Electromyography and nerve conduction studies Other tests depending on the disorder suspected, such as
|
Disorders that affect the connections between nerves and muscles (neuromuscular junction disorders) | ||
Botulinum toxin when a dose that is too high is used to treat dystonia or other muscle spasms | Weakness of the treated muscles or sometimes of all muscles | A doctor's examination alone |
Botulism (due to the bacteria Clostridium botulinum) | At first, often a dry mouth, drooping eyelids, vision problems (such as double vision), difficulty swallowing and speaking, and rapidly progressive muscle weakness, often beginning in the face and moving down the body When contaminated food is the source, nausea, vomiting, stomach cramps, and diarrhea No changes in sensation | Blood or stool tests to check for toxins produced by the bacteria Usually electromyography Sometimes examination of a stool sample to check for bacteria |
Weak and drooping eyelids, double vision, difficulty speaking and swallowing, and weakness in the arms and legs Excessive weakness of affected muscles that
| Sometimes the ice pack test to see whether cold improves muscle strength after muscles are used Blood tests to check for certain antibodies and/or electromyography | |
Tearing of the eyes, blurred vision, increased salivation, sweating, coughing, vomiting, frequent bowel movements and urination, and weak muscles that twitch | Often a doctor’s examination alone Sometimes blood tests to identify the toxin | |
Disorders that affect muscles (myopathies)║ | ||
Conditions that cause generalized muscle wasting:
| Loss of muscle tissue In people with obvious evidence of the problem | A doctor’s examination alone |
Electrolyte abnormalities due to certain disorders or use of diuretics, such as
| Weakness that
| Blood tests to measure the level of potassium and other electrolytes |
Muscle malfunction due to use of alcohol, corticosteroids, or various other drugs | Weakness that tends to first cause difficulty standing up or lifting the arms overhead Use of a drug or medication that can cause muscle damage (such as a statin) When due to use of alcohol or certain other drugs, muscle aches and pains | Stopping any drug that can cause muscle malfunction Sometimes electromyography Blood tests to measure levels of muscle enzymes that leak from damaged muscles into the blood |
Muscular dystrophies, such as
| Progressive muscle weakness that
In some types, an abnormally curved spine (scoliosis) and weakness of the spinal muscles, which often develop during childhood | A thorough family history to determine whether any family members have had a similar disorder Genetic testing Sometimes muscle biopsy |
Viral infections that cause muscle inflammation. such as
| Muscle aches and pains that are worsened by movement, especially walking Sometimes fever, a runny nose, cough, sore throat, and/or fatigue | Sometimes a doctor’s examination alone Sometimes blood tests to measure levels of muscle enzymes that leak from damaged muscles into the blood Often tests of blood and/or spinal fluid to identify the infection causing the symptoms Sometimes muscle biopsy (removal of a piece of muscle tissue for examination under a microscope) |
* Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present. | ||
† Although a doctor's examination is always done, it is mentioned in this column only if the diagnosis can sometimes be made by the doctor's examination alone, without any testing | ||
‡ Symptoms vary depending on the location (level) of the damage. Areas that are supplied by the parts of the spinal cord below the damaged part are affected (see figure Where Is the Spinal Cord Damaged?). | ||
§ In the United States, MRI is usually available. However, if MRI is unavailable, myelography with CT can be done. In myelography, x-rays of the spinal cord are taken after a radiopaque contrast agent is injected via a spinal tap. | ||
║ Sensation is usually not affected. | ||
CT = computed tomography; MRI = magnetic resonance imaging. | ||