Why Numb Arms Feel Like They Do Not Belong to Us

Most of us have experienced the sensation of not being able to feel our arm after falling asleep on it, followed by the prickling feeling. The most common cause of this is the pressure on the nerves in the arm due to staying in the same position for a long time.So, what exactly is happening in our arm during this time?Numbness in the arm, leg, or hand is often experienced when sleeping on a limb, sitting, or staying in a certain position for a long time. It's commonly believed that this is due to a cut-off in blood flow. However, neurology researcher Martin Syvertsen Mykland from NTNU states that the condition usually doesn't stem from the blockage of a major artery. It is thought that the pressure affects the blood flow within the nerve itself.The nerves in our arms carry two types of fibers together: Sensory Nerve Fibers: They transport sensations from different parts of the body to the brain. Motor Nerve Fibers: They send movement signals from the brain to the muscles.Therefore, in a numbed hand, both sensation and movement ability can be lost simultaneously. When a nerve is pinched, the signals are temporarily blocked. What will happen inside depends on how long and how strong the pressure is.'It's still unclear whether the main cause of the loss of sensation is the blood flow within the nerve or the direct mechanical pressure on the nerve itself.' Martin Syvertsen Mykland, NTNU.This condition is medically referred to as paresthesia. Nerves require fresh oxygen and nutrients to function properly. When these are unable to reach the nerve fibers due to pressure, the flow of sensory information to the brain is disrupted. Some people describe a sensation of not being able to 'locate' their arm in space upon waking from a deep sleep.'In paresthesia, it's as if a part of the nerve has short-circuited. Some sensory signals from the arm can't return to the brain as they normally would,' explains Naomi Kleitman from the National Institute of Neurological Disorders and Stroke in the USA.There could be several processes behind the subsequent sensation of pins and needles: Spontaneously Firing Nerves: Some nerves start sending signals on their own, leading to irregular stimuli reaching the brain. Mixed Signals: When signals from nerves that perceive different stimuli get mixed up, the brain interprets these as prickling, heat, or numbness. Blood Return: As the position of the arm changes and blood starts flowing again, this confusion can intensify for a few more minutes.'Some of the nerves start to discharge spontaneously. This sends a chaotic storm of stimuli to the brain,' says Robert LaMotte from Yale University.According to Mykland, the exact reason why tingling occurs is still not fully understood. However, it is thought to be related to changes in nerve signals, such as the speed of signal transmission.You may have noticed that your hand or arm tends to fall asleep more easily after a heavy night of drinking. This phenomenon is referred to as 'Saturday night palsy'. The nerve that is compressed in this scenario is the radial nerve, one of the three main nerves in the upper arm. The radial nerve, which wraps around the upper arm bone, is particularly exposed when you sleep on your arm at night, leading to both numbness and weakness.'Alcohol makes you more susceptible. You sleep deeper and often for a longer period when your arm is in an awkward position,' says Martin Syvertsen Mykland from NTNU.In the case of short-term pressure, it's likely that only the outer layer of the nerve is affected. If the nerve is compressed for a longer period, it can take several weeks for sensation to return to normal. However, as the nerve doesn't suffer permanent damage, its normal function eventually returns.There are also some suggestions related to sleep position: Elbow: It is recommended to avoid sleeping with the elbow bent more than 90 degrees. The ulnar nerve, which passes through the inner part of the elbow, controls the sensation in the little and ring fingers. Wrist and Fingers: When sleeping on your side, it is advised to place a pillow in front of you to support the whole arm and keep the wrist and fingers straight. Sleeping on Your Back: Sleeping on your back with your arms at your sides or on pillows keeps the elbow and wrist in an ideal position.If the numbness doesn't go away, leads to weakness, or is bothersome, it may be beneficial to see a doctor.

Why Do We Feel Like Our Arm Does Not Belong to Us When It Falls Asleep?

When your arm goes numb, the issue is often not with the blood vessels, but with the nerves that are under pressure.

When a nerve is under pressure, it can't transmit signals to the brain properly, which leads to numbness and tingling.

Sleeping on your arm after consuming alcohol can result in numbness that lasts for weeks.

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