Behind a feeling of numbness in the arms, thighs, feet or face can be various causes. Often, a lack of blood circulation or a pinched nerve is responsible for the discomfort. But serious diseases such as a slipped disc or a stroke can also be accompanied by numbness. We inform you about possible causes and give tips on what you can do against the numbness.
Numbness (hypesthesia).
A numb sensation – medically called hypesthesia – is caused by a reduced sensitivity of the skin. If such a numb sensation is present, the sense of feeling is disturbed and no or only limited information about external stimuli can be transmitted to the brain in this way. This includes information about heat and cold, touch and pressure, pain as well as vibrations. A complete loss of the sense of feeling is called anesthesia. Failure of the sense of feeling occurs primarily in the extremities; numbness in the fingers, toes, arms, and legs is particularly common. In contrast, it is rare in the face or trunk. The numb feeling can occur on one side or on both sides. Often, the numbness is accompanied by an unpleasant tingling sensation.
Numbness: causes and diagnosis
A wide variety of causes can lie behind a feeling of numbness. In some cases, the cause is harmless, but a recurring feeling of numbness can also indicate a serious disease. If the numb feeling occurs more frequently, a doctor should definitely be consulted. Possible causes of numbness include:
- Circulatory disorders
- Pinched nerves
- Carpal tunnel syndrome
- Polyneuropathy
- Herniated disc
- Stroke
- Infections
- Vitamin B12 deficiency
- Tumors
Depending on the cause of the numbness, other symptoms may also occur at the same time, such as pain or motor limitations. When making a diagnosis, the first decisive factor for the attending physician is where, since when and in which situations the numbness occurs, whether it is unilateral or bilateral and whether it persists since the first occurrence or disappears on its own. In order to determine possible damage to the nerves, the doctor checks the reflexes as well as various sensory functions – for example, hearing and vision. If there is an initial suspicion, further examinations may be necessary.
Circulatory disorders as a cause
When temperatures are low in winter, our hands and feet may become too cold and we no longer have any feeling in them. The cold causes the blood vessels to contract and blood flow to the extremities becomes poorer. It is not until warmer temperatures that the numbness disappears and sensation returns – this process is often accompanied by an uncomfortable tingling sensation in the fingers and toes. While cold-related, short-term circulatory disturbances are usually harmless, if you experience a circulatory disturbance without an identifiable cause, you should see a doctor immediately. Then serious diseases such as arteriosclerosis or Raynaud’s disease, which primarily affects the arteries in the fingers and toes, may be behind the numbness. In particular, circulatory disorders in the brain as well as in the legs can trigger a numb feeling. Circulatory disorders in the heart, on the other hand, are more likely to make themselves felt by a tightness sensation in the chest.
Pinched nerves as a cause
Numbness in the arms, legs, hands and feet caused by a pinched nerve has probably been experienced by everyone at some time: due to incorrect posture – for example, when sitting or lying down – a nerve is pinched off and the transmission of stimuli is disturbed. As a result, the hand or arm feels numb and usually can no longer be moved voluntarily. Often, a fallen asleep arm or leg is accompanied by an unpleasant tingling sensation on the skin. As soon as we move the body part that has fallen asleep a little, however, the numb feeling usually disappears on its own. If this is not the case or if the numb feeling occurs more frequently, there is probably another cause behind the complaints that should be clarified by a doctor.
Carpal tunnel syndrome as a cause
If there is a constantly recurring feeling of numbness and an unpleasant tingling sensation in the fingers, carpal tunnel syndrome is probably behind the symptoms. In this case, the metacarpal nerve is constricted as it passes through the carpal canal. The causes of carpal tunnel syndrome can be many and varied, including, for example, bony malpositions following fractures or tendon sheath inflammation. Often, however, no direct cause can be determined. By wearing a special splint, the numbness in the fingers can usually be eliminated. If there is no improvement, surgical treatment is performed. In addition to carpal tunnel syndrome, numbness in the fingers and hands can also occur when other nerves, such as the ulnar nerve, are pinched off (ulnar tunnel syndrome). This syndrome is also known as cyclist’s palsy because it is usually caused by gripping the handlebars tightly. However, narrowing of the nerve canals can occur not only in the arms, but also in the legs. A pinched nerve and associated numbness occur particularly often in the thigh. This is called inguinal tunnel syndrome (power tunnel syndrome) or jeans disease. In this case, the femoral cutaneous nerve is damaged by overweight, but also by too tight clothing. Depending on the stage of the syndrome, drug therapy, physical therapy, or surgical therapy may be considered.
