Found this somewhere:
The symptoms that you describe - numbness and/or tingling after waking from sleep which rapidly improves - are typically caused by pressure on a nerve which stretches it, or which temporarily cuts off the blood supply to the nerve.
This is quite common in the arms. The nerves which are being damaged are a group of large nerves passing from the lower part of the cervical spine in the neck, across the shoulder and down the arm into the hand. While this group of nerves run together they are known as the brachial plexus. But as they go down the arm they divide into individual nerves which control different arm muscles and different areas of skin sensation.
The brachial plexus is probably affected
if all the muscles in your arm are affected, and numbness is widespread rather than limited to certain sides or areas of your arm, then it is likely that it is the brachial plexus which is giving you problems rather than just one nerve.
Injuries to the brachial plexus are common, especially in falls when the shoulder is pushed downwards away from the neck or when there is a blow to the side of the neck which stretches the nerves as they pass through.
In your case it is likely that when you are asleep, the position you lie in stretches the brachial plexus on that side. This could be aggravated by your weight which adds extra downward pressure on the shoulder. This may not happen on your right side because the nerves there may follow a slightly different course which makes them less vulnerable to being stretched.
Cervical rib
an alternative explanation is an unusual abnormality of the spine where there is a small extra rib on vertebrae above the normal first rib, often only on one side of the body. This abnormality is known as a cervical rib, and it can press on the lower part of the brachial plexus to cause the one-sided symptoms you describe.
See your doctor
this sort of nerve compression rarely leads to any permanent damage. Changing your sleeping position and losing weight may help stop the problem.
But you should check it out with your gp, who can look for rarer causes of arm numbness and may arrange an x-ray for a cervical rib (these may be surgically removed if symptoms are severe).
If you have any other symptoms such as loss of movement in your legs, dizziness, headache or blurred vision you should seek urgent medical attention.
The symptoms that you describe - numbness and/or tingling after waking from sleep which rapidly improves - are typically caused by pressure on a nerve which stretches it, or which temporarily cuts off the blood supply to the nerve.
This is quite common in the arms. The nerves which are being damaged are a group of large nerves passing from the lower part of the cervical spine in the neck, across the shoulder and down the arm into the hand. While this group of nerves run together they are known as the brachial plexus. But as they go down the arm they divide into individual nerves which control different arm muscles and different areas of skin sensation.
The brachial plexus is probably affected
if all the muscles in your arm are affected, and numbness is widespread rather than limited to certain sides or areas of your arm, then it is likely that it is the brachial plexus which is giving you problems rather than just one nerve.
Injuries to the brachial plexus are common, especially in falls when the shoulder is pushed downwards away from the neck or when there is a blow to the side of the neck which stretches the nerves as they pass through.
In your case it is likely that when you are asleep, the position you lie in stretches the brachial plexus on that side. This could be aggravated by your weight which adds extra downward pressure on the shoulder. This may not happen on your right side because the nerves there may follow a slightly different course which makes them less vulnerable to being stretched.
Cervical rib
an alternative explanation is an unusual abnormality of the spine where there is a small extra rib on vertebrae above the normal first rib, often only on one side of the body. This abnormality is known as a cervical rib, and it can press on the lower part of the brachial plexus to cause the one-sided symptoms you describe.
See your doctor
this sort of nerve compression rarely leads to any permanent damage. Changing your sleeping position and losing weight may help stop the problem.
But you should check it out with your gp, who can look for rarer causes of arm numbness and may arrange an x-ray for a cervical rib (these may be surgically removed if symptoms are severe).
If you have any other symptoms such as loss of movement in your legs, dizziness, headache or blurred vision you should seek urgent medical attention.
