Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link
Some Causes and Features of Muscle Weakness

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

Usually other symptoms of nervous system malfunction (such as loss of sensation, loss of coordination, and vision problems)

Weakness that

  • Tends to come and go

  • Sometimes affects different parts of the body

  • Is worse in hot weather

MRI of the brain and sometimes of the spinal cord

Sometimes a spinal tap (lumbar puncture)

Symptoms that occur suddenly:

  • Weakness or paralysis, usually on one side of the body

  • Abnormalities in or loss of sensation on one side of the body

  • Difficulty speaking, sometimes with slurred speech

  • Confusion

  • Dimness, blurring, or loss of vision, particularly in one eye

  • Dizziness or loss of balance and coordination

CT or MRI of the brain

Spinal cord disorders‡

Tingling, numbness, and muscle weakness that

  • Occur rapidly (over hours to a few days)

  • Start in the feet and move upward

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

Blood tests to help identify the cause

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§ o

  • Abscesses (pockets of pus)

  • Hematomas (pockets of blood)

  • Injuries of the neck or back

  • Some cancers

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§

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 other symptoms of nervous system malfunction (such as loss of sensation, loss of coordination, and vision problems)

Weakness that

  • Tends to come and go

  • Sometimes affects different parts of the body

  • Is worse in hot weather

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

  • Often starts in the hands

  • Sometimes affects one side more than the other

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 of the brain and spinal cord (myelography§) 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

Weakness and often loss of sensation that

  • Usually begin in both legs

  • Then progress upward to the arms

When severe, difficulty swallowing and breathing

Electromyography and nerve conduction studies

A spinal tap

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

  • Often begins in both feet

  • Then affects the hands

  • Then progresses up the legs and arms

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

  • Blood and urine tests to check for toxins

  • Blood tests to check for certain antibodies or to measure sugar, vitamin, or drug levels

  • Sometimes a spinal tap

Weakness of the treated muscles or sometimes of all muscles

A doctor's examination alone

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

  • Occurs after muscles are used

  • Disappears when they are rested

  • Recurs when they are used again

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

  • Affects the whole body

  • May come and go

  • Is often accompanied by muscle cramping and twitches

Blood tests to measure the level of potassium and other electrolytes

Weakness that tends to first cause difficulty standing up or lifting the arms overhead

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

  • Duchenne muscular dystrophy

  • Limb-girdle muscular dystrophy

Progressive muscle weakness that

  • May start during infancy, childhood, or adulthood

  • Depending on the type, may progress rapidly, causing early death

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

Muscle biopsy

X-rays of the spine to check for scoliosis

Viral infections that cause muscle inflammation. such as

  • Herpes simplex virus infections

  • HIV infection

  • Mononucleosis

  • Shingles

  • Syphilis

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

§ In the United States, MRI is usually available. However, if MRI is unavailable, myelography Myelography Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more 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.