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Numbness

By

Michael C. Levin

, MD, College of Medicine, University of Saskatchewan

Last full review/revision Aug 2021| Content last modified Aug 2021
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People with numbness may be unable to feel light touch, pain, temperature, or vibration or to know where parts of their body are (position sense). When people do not know where parts of their body are, they have problems with balance and coordination.

Many people mistakenly use the term numbness when they have abnormal sensations such as tingling, prickling, or a pins-and-needles sensation or when a limb feels weak or is paralyzed—perhaps partly because people with numbness often also have such abnormal sensations and symptoms. The presence of other symptoms depends on what is causing numbness.

If numbness has been present a long time, particularly in the feet, it can lead to other problems. People may have difficulty walking and driving and may be more likely to fall. They may not notice infections, foot sores (ulcers), and injuries because they cannot sense pain as well. In such cases, treatment may be delayed.

Pathway for sensation

For a person to feel sensations normally, sensory receptors (specialized ends of sensory nerve fibers in the skin) must detect information in and around the body. These receptors must then send a signal along the following pathway:

For some parts of the body, the pathway includes a plexus or the cauda equina.

Plexuses Plexus Disorders Plexuses (networks of interwoven nerve fibers from different spinal nerves) may be damaged by injury, tumors, pockets of blood (hematomas), or autoimmune reactions. Pain, weakness, and loss... read more are networks of sensory nerve fibers and motor nerve fibers (which carry signals from the brain and spinal cord to muscles and other body parts). In plexuses, these nerve fibers are combined and sorted to serve a particular area of the body. The fibers then branch off from the plexus to become peripheral nerves. There are four plexuses in the torso.

The cauda equina Cauda Equina Syndrome Cauda equina syndrome occurs when the bundle of nerves that extends from the bottom of the spinal cord is compressed or damaged. The most common cause of cauda equina syndrome is a herniated... read more is a bundle of spinal nerve root fibers at the bottom of the spinal cord. This structure resembles a horse's tail, which is what its name means in Latin. It supplies sensation to the thighs, buttocks, genitals, and the area between them, which are called the saddle area because they are the area of the body that would touch a saddle.

Causes of Numbness

Numbness results when one part of the pathway for sensation malfunctions, usually because of a disorder or drug.

Many conditions can cause numbness in various ways. For example, they may

Evaluation of Numbness

Because so many disorders can cause numbness, doctors ask questions systematically, focusing on more likely causes.

Warning signs

In people with numbness, the following symptoms are cause for concern:

  • Numbness that begins suddenly (within minutes or hours)

  • Weakness that begins suddenly or rapidly (within hours or days)

  • Numbness or weakness that rapidly spreads up or down the body, involving more and more parts of the body

  • Difficulty breathing

  • Numbness in the thighs, buttocks, genitals, and the area between them (saddle area) and loss of bladder and bowel control (incontinence)

  • Numbness on both sides below a specific level of the body (such as below the midchest)

  • Numbness of an entire leg or arm

  • Loss of sensation in the face and torso

When to see a doctor

People who have warning signs should go to a hospital immediately. People without warning signs should call their doctor. The doctor can decide how rapidly they need to be seen based on their symptoms.

What the doctor does

Doctors begin by asking which body parts are affected. The pattern of body parts affected by numbness often indicates which part of the nerve pathway is malfunctioning:

Doctors ask the person to describe the numbness. Then doctors may ask specific questions:

  • When numbness began

  • How quickly it began

  • Whether the person also has other symptoms such as abnormal sensations, weakness or paralysis, loss of bowel or bladder control, retention of urine, vision problems, difficulty swallowing, or deterioration of mental function

  • Whether any event, such as pressure on a limb, an injury, sleeping in an awkward position, or an infection, triggered the symptoms

Knowing how quickly numbness and other symptoms began helps doctors determine the type of disorder.

The person is asked about symptoms that may suggest a cause. For example, back and/or neck pain suggests osteoarthritis, a ruptured disk, or another disorder that puts pressure on the spinal cord.

Doctors also ask whether the person has had a disorder that can cause numbness, particularly diabetes, chronic kidney disease, infections (such as HIV infection or Lyme disease), a stroke, or arthritis. Doctors may ask whether any family members have had similar symptoms or have a hereditary disorder that affects the nervous system. They ask the person about use of drugs, including recreational drugs, and about possible exposure to toxins.

The physical examination includes a complete evaluation of the nervous system (neurologic examination Neurologic Examination When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the nervous system. Examination of the nervous system—the... read more ), focusing on testing sensation (whether the person can feel stimuli, such as touch and temperature, normally), as well as reflexes and muscle function.

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Testing

Testing is not needed if the diagnosis is obvious and treatment involves only general measures (such as rest or a splint)—for example, in some cases of carpal tunnel syndrome.

In other cases, tests are done based on where doctors think the problem is:

  • For sensory nerves, plexuses, or spinal nerve roots: Nerve conduction studies and electromyography

  • For plexuses: Nerve conduction studies and electromyography and sometimes magnetic resonance imaging (MRI) after a contrast agent is injected into a vein

  • For the brain or spinal cord: MRI or, if MRI is not readily available, computed tomography (CT)

Nerve conduction studies and electromyography Electromyography and Nerve Conduction Studies 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 Electromyography and Nerve Conduction Studies are often done at the same time. Nerve conduction studies use electrodes or small needles to stimulate a nerve. Then doctors measure how fast the nerve transmits signals. For electromyography, a small needle is inserted into a muscle to record its electrical activity when the muscle is at rest and when it is contracting.

Other tests are then done to identify the specific disorder. For example, if results suggest a polyneuropathy, doctors do blood tests to check for its various causes (such as diabetes, kidney disorders, or vitamin deficiencies).

Treatment of Numbness

The condition causing numbness is corrected or treated when possible.

General measures can help relieve symptoms and prevent additional problems. Precautions to prevent injury are needed because people with numbness are less likely to feel discomfort. If their feet are numb, particularly if circulation is impaired, they should wear socks and shoes that fit well and should check their shoes for pebbles or other foreign material before putting their shoes on. People should inspect their feet frequently for sores and signs of infection, such as redness. If hands or fingers are numb, people should be careful when handling objects that could be hot or sharp.

If people are having difficulty walking or have lost their sense of position (where body parts are), physical therapy can help them learn to walk more safely and to prevent falls Prevention Most falls occur when older people with one or more physical conditions that impair mobility or balance encounter an environmental hazard. Although many people have no symptoms before a fall... read more .

People should be aware that they may have problems driving, and if they do, they should talk to their doctor about the problems.

Key Points

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