Why do arms go numb at night?

What are the causes of arm numbness?

When we talk about arms going numb, we aren’t talking about the numbness that occurs when we fall asleep on our hands. This is legitimate hand numbness that seems to recur most nights that also wakes you up from your sleep. It only gets relieved after you rub your arm. Many people mistakenly believe that these symptoms occur due to a lack of blood flow in the arm or hand. But in reality, it’s because of the transient compression of the nerve supplying blood to the hand. If the nerve is just compressed briefly or occasionally, simply removing the head or changing the position will relieve the numbness.

However, if the hand or arm numbness occurs repetitively while sleeping, then it’s not normal. The symptoms may even recur during the day while working for long hours or while keeping the arms raised above the shoulder level for long periods of time. The nerves involved can be radial, ulnar and median and may lead to Saturday night palsy, Honeymoon palsy or carpal tunnel syndrome.

ln Saturday night palsy, there is a compression of the radial nerve at the spiral groove of the humerus. It may be due to the compression of the nerve against the bone when the arm is pressed upon for long. In Honeymoon palsy, the weight of a sleeping partner’s head may compress the nerve closer to the shoulder, which leads to numbness and weakness at the wrist. Pressure on the ulnar nerve during sleep, or working long hours on the computer may also contribute to numbness of the inner side forearm and hand (ulnar neuropathy).

Carpal tunnel syndrome is the most common neuropathy affecting the median nerve, characterised by compression as it passes through the wrist and into the hand. Inflammation or swelling within this passageway may lead to symptoms affecting the hand at night.

A neurologist, after examining such a patient, subjects him/her to nerve conduction studies, which would be abnormal. The common causes of such numbness are obesity, thyroid dysfunction, diabetes, rheumatoid arthritis, pregnancy, etc. A tendency to suffer from pressure palsies may also be hereditary. If the arm becomes numb at night, the symptoms will resolve just by rubbing. But with chronicity, symptoms persist during the day with extreme pain and dropping of objects. Regular exercises, splinting of the forearm and hand, especially while sleeping, or keeping the arm over a pillow may relieve the hand numbness.

lf conservative techniques are ineffective, then surgery may be the next best option. It is important that the upper extremity is comfortably supported during sleep. The wrist and elbow should be neither flexed nor extended for prolonged periods during sleep.

(The author is a senior consultant, neurology, Paras Hospitals)