Why do our legs fall asleep?

We have all experienced a sensation of tingling and numbness in one of our lower limbs. This occurs when we have been sitting in the same position for a while and we are pressing one leg with the other. When we get up from the sofa or chair, we try to put our foot down, but it doesn't seem to respond and we say that "our leg has fallen asleep".

The numbness and tingling are normally accompanied by prickling, but little by little all the symptoms fade and after a few minutes they end up disappearing completely.

This sensation is quite common and is known as paresthesia, but contrary to popular belief, it does not depend on the lack of irrigation and has more to do with the nervous system. Leg numbness, known as paresthesia in the medical field, is caused by nerve compression or its inflammatory state.

In this article we will explain the different possible causes of leg numbness, including pathological and non-pathological.

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What is paresthesia of the legs?

Paresthesia of the legs is described as the numbness and tingling sensation experienced in the lower limbs. This is normally not serious and disappears within a few minutes of appearing, but sometimes it can be caused by another condition, usually pathological.

When we put too much pressure on the nerves when sitting with one leg on top of the other, they stop working properly, this translates into the impossibility of moving the leg; however, by relieving the pressure, normally, everything works correctly again and we regain mobility.

When sitting cross-legged for a long time, the pressure exerted can compress the nerves of the leg. This prevents the brain and the nerves that end in the lower limbs from communicating correctly, the nerve impulses do not arrive. The main nerves affected by paresthesia of the legs originate in the torso and lower back, and reach the toes.

If paresthesia is the main cause of numbness in the legs, it can also be accompanied by burning, tingling, and a burning sensation in the skin (as if it will "crawl"), in addition to temporary immobility characteristic.

By changing the posture, the numbness and all the symptoms that accompany the paresthesia should disappear. Postural paresthesia can be avoided and prevented by changing position often and avoiding sitting cross-legged or with one leg over the other.

This condition can be non-pathological and originate from pregnancy; in this case there are different origins of paresthesia, which not only have to do with the system nervous, but also with the hormonal and bodily changes that are experienced during the process of gestation.

But sometimes, paresthesia can derive from other more or less serious conditions.. In some cases, numbness in the legs may be caused by an underlying disease, such as multiple sclerosis, diabetes or fibromyalgia, where symptoms include numbness in the legs.

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The main causes of paresthesia in the legs

Normally, the origin of numbness and tingling in the legs is postural. However, if this condition occurs frequently and has no apparent cause, it may indicate an underlying disease.

The most common causes of paresthesia include the following.

1. The lesions

Some injuries are likely to cause pressure on the nerves that go to the legs, and cause sensory disturbances; for example, sciatica is usually caused by a problem in the spine. The most common injuries that can put pressure on the nerves and causing the feet and legs to go numb, occur in the torso, lower back, legs, ankles, and feet.

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2. diabetes

Some diabetes patients develop a type of nerve damage called diabetic neuropathy. Diabetic neuropathy causes numbness, tingling, and pain, usually in the feet, but in its most severe form it can spread and cause the same symptoms throughout the leg.

3. Peripheral arterial disease

The legs are one of the body parts most affected by peripheral arterial disease. People with peripheral arterial disease experience pain and cramps in the lower part of the body. (usually legs and hips) when they perform some type of physical effort such as walking or climbing stairs. Some people affected with the disease also experience numbness and weakness in the legs as symptoms of the condition.

Peripheral arterial disease (PAD) is caused by narrowing of the peripheral arteries in the legs, arms, and stomach. The constriction of the arteries decreases their pumping ability and reduces blood flow.

Symptoms of peripheral arterial disease usually go away after a few minutes of rest., after the practice of physical exercise.

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4. tumors

The growth of benign (noncancerous) tumors, cysts, abscesses, and nodules can put pressure on the brain, spinal cord or any part of the legs and feet.

This pressure restricts blood flow to the legs and feet, causing paresthesia.

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5. Alcohol consumption

Alcohol is toxic, this means that it can cause damage to our body. Alcohol affects the nervous system, and can affect the nerves responsible for numbness symptomsespecially on the feet

Chronic alcohol use lowers levels of B vitamins, such as B-1 (thiamin), B-9 (folate), and B-12. Reduced levels of these vitamins are related to nerve damage that causes paresthesia.

6. fibromyalgia

Fibromyalgia is a disease considered chronic or long-term. Fibromyalgia patients experience widespread body pain, discomfort, and tenderness. Some affected people also report experiencing numbness and tingling in the extremities, both upper and lower.

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7. sciatica

Low back problems, such as lumbar rupture or herniation, can compress the nerves that originate in the spinal cord and communicate with the lower limbs. This pressure can cause numbness or sensory disturbances.

Among the most common neuralgic (affecting the nerves) conditions is sciatica, which describes irritation or pinching of the sciatic nerve. The sciatic nerve is the longest nerve in the body, it originates in the lower back and reaches the feet, passing through the buttocks and legs. Like other nerves, if it becomes irritated or compressed due to other conditions or trauma, the person may experience numbness or tingling in the legs and feet.

8. tarsal tunnel syndrome

tarsal tunnel syndrome results from compression or injury of the posterior tibial nerve, which runs down the back of the leg and innervates the heel and sole of the foot.

The tarsal tunnel corresponds to a narrow channel or tunnel located on the inside of the ankle. Tarsal tunnel syndrome causes numbness, tingling, prickling, and sometimes burning sensations in all parts of the foot, including the ankles and heels.

9. Paresthesia and pregnancy

Paresthesia is common and frequent in pregnant people. In most cases, the numbness and tingling of the legs that occur during pregnancy are the result of hormonal and bodily changes produced to meet the needs of the fetus and prepare the body for childbirth. In some cases, it may be a pinched nerve, as in sciatica or meralgia paresthetica (the latter origin is much less frequent).

Although most cases of numbness and tingling in pregnancy are normal, there are some more serious conditions that include numbness and tingling as symptoms. Therefore, it is important to consult your doctor about any manifestation of paresthesia, especially if it is accompanied by other symptoms such as abdominal pain or severe swelling, among others.

conclusion

Paresthesia of the legs is common. The tingling and numbness experienced from poor posture is not serious and normally all its manifestations disappear after a few minutes. However, paresthesia that occurs chronically and there is no apparent cause, can sometimes be the consequence of the pinching of a nerve that goes to the legs, as in the case of sciatica or metacarpal tunnel syndrome, and in other cases it may be indicative of the presence of a pathological condition underlying. Among the most frequent pathological conditions of leg numbness are: diabetes, alcohol use, abnormal growths such as tumors, fibromyalgia, and arterial disease peripheral.

In pregnancy, due to bodily and hormonal changes that are experienced, paresthesia usually appears during the second or third trimester. Leg numbness during pregnancy is common and if it is not accompanied by other symptoms, it is not serious. although it is always advisable to consult with the doctor about any changes that are experienced during the course of pregnancy.