Most of us have experienced it. There you are sitting in what seems like a comfortable position, watching tv. All of sudden you notice that you have no feeling in your hand! It has fallen asleep. You move from the all-of-a-sudden awkward position trying to pause the show you are watching but you can’t because you have no feeling. You do the obligatory shaking of the hand trying to get it to wake up. It starts to get some feeling back but really it just feels like someone is jabbing you with thousands of pins and needles. Then you start to flex and extend you fingers. It finally starts to wake up and you are able to reverse back and watch what you missed. Slowly, the hand goes back to normal. You have just experienced paresthesia.
The scenario described is the least serious form of paresthesia. It is usually temporarily caused from either a direct pressure on a nerve or by cutting off blood supply to the nerve. Once you release the pressure or get the blood moving, feeling starts to return. One still needs to be careful in such a situation. I have a patient who tried to walk when, unbeknownst to her, she had a foot that had fallen asleep. When she got up to walk, she fell and shattered that numb foot requiring surgery and a litany of issues. So, be careful!
The bigger issue, however, happens when parasthesia comes on insidiously. In these types of situations, there is something deeper that is irritating the nerve. For the hand, this can happen at the carpal tunnel, at the elbow, at the shoulder, under the pectoralis minor muscle, under the scalene muscles, and at the nerve roots in the neck. Irritation can be caused by swelling of soft tissue (ligaments, muscles or tendons), by bulging discs, by stretched nerves due to poor posture, by a deficiency in blood supply due to a host of conditions, and the list goes on. If your hand consistently falls asleep, you need to figure out the cause. It could be a simple remedy or it could be a sign of something serious. The longer a nerve is injured, the longer it takes for it to heal. In addition, you run the risk of injury to the area the nerve supplies.