Merck Manual

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Some Causes and Features of Numbness

Some Causes and Features of Numbness

Cause

Common Features*

Tests

Numbness in both limbs (arm and leg) on one side of the body

Disorders that affect the outer layer of the cerebrum (the largest area of the brain), such as

Loss of sensation on the same side of the face and body that is affected by the disorder and loss of the ability to recognize items by touch

Usually weakness, loss of coordination, and other symptoms indicating malfunction of the nervous system

MRI or CT of the brain

Disorders that affect the upper part of the brain stem, such as

Loss of sensation on the same side of the face and body that is affected by the disorder

Often double vision

MRI or CT of the brain

Disorders that affect the lower part of the brain stem, such as

  • Stroke

  • Tumors

  • Degenerative brain disorders

Loss of sensation on one side of the face and on the opposite side of the body affected by the disorder

Often vision problems and difficulty chewing, swallowing, and speaking

MRI of the brain

Numbness in the limbs or torso on both sides

Disorders that affect the width of the spinal cord, such as

Loss of sensation and usually weakness below a certain level of the body

No loss of sensation in the face

Usually retention of urine, loss of bowel and bladder control (incontinence), and/or reduced sexual response, including erectile dysfunction in men

MRI of the spinal cord

Cauda equina syndrome, caused by pressure, as may result from

  • A ruptured or herniated disk

  • Spread of cancer to the spine

Numbness mainly in the thighs, buttocks, bladder, genitals, and the area between them (saddle area)

Usually pain in the lower back

Often retention of urine, loss of bowel and bladder control, and/or reduced sexual response, including erectile dysfunction in men

MRI of the spinal cord

Polyneuropathies (simultaneous malfunction of many peripheral nerves throughout the body), as may result from

Numbness and abnormal sensations in about the same areas on both sides of the body, mainly in the feet and hands

Sometimes weakness and loss of reflexes

Nerve conduction studies (measuring how fast nerves transmit signals) and electromyography (stimulating muscles and recording their electrical activity)

Other tests depending on the disorder suspected

Demyelinating disorders (disorders that cause nerves to become inflamed and lose their outer layer, called the myelin sheath), such as

  • Multiple sclerosis

Often weakness or clumsiness and abnormal sensations (such as tingling or numbness)

Sometimes changes in vision or speech

MRI of the brain and spinal cord

Spinal tap (lumbar puncture) to examine a sample of cerebrospinal fluid (the fluid that surrounds the brain and spinal cord)

Numbness in part of one limb

Disorders that affect a spinal nerve root such as

Pain that

  • Sometimes shoots down an arm or a leg

  • May feel like an electric shock

  • May be worsened by moving the spine, coughing, or doing a Valsalva maneuver (forcefully trying to exhale without letting air escape through the nose or mouth)

Often weakness and/or reduced or absent reflexes in the area supplied by the nerve root

A doctor's examination

Sometimes MRI or CT of the spinal cord

Sometimes nerve conduction studies and electromyography

Disorders that affect a plexus (a network of nerve fibers), such as

  • An injury such as a stabbing

  • Cancer that spreads to organs near a plexus

  • Brachial neuritis (sudden malfunction of the plexus in the neck and shoulder)

Numbness, pain, and/or weakness in a relatively large area of a limb

Nerve conduction studies and electromyography

MRI

Mononeuropathy (malfunction of one peripheral nerve), as occurs in

Numbness with or without pain

Often weakness and reduced or absent reflexes in an area supplied by one nerve

A doctor's examination

Sometimes nerve conduction studies and electromyography

*Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present.

CT = computed tomography; MRI = magnetic resonance imaging.