You may be familiar with the picture, either personally or from a story somebody told you. A young man goes out for the evening, all dressed up and smelling of aftershave. He meets his mates in the pub and has a few beers, starting off the process of intoxication which continues most of the night. After the pub there is the nightclub and more drinking until it’s time to roll out and round to the kebab house to have a snack. After a bit more hanging about he goes home or to one of his mates’ houses to watch television, chat and perhaps drink a little more.
There is nothing exceptional in the story so far and our young man will not be shocked at all by the fact that he is very likely to feel hung over tomorrow. The surprise is due to what happens when he is watching the TV and he falls asleep. However, he has placed his arm over the back or the arm of the chair he is half lying in and that’s the position in which he stays for some hours as he sleeps soundly. When he awakes he finds himself still in the chair with his arm over the back or the side, however he can’t move his arm properly like he has slept on it and got a dead arm.
If we adopt an odd or stressful position when we sleep the increasing discomfort in the part wakes us up or we naturally just move to a better posture. When we are drunk however we may not do this and this was the problem which allowed the bodily structures in his armpit to suffer significantly increased stresses for perhaps some hours before he finally woke. The arm will hardly move at all and he becomes concerned when it does not respond to shaking and rubbing by recovering its movement.
Nervous tissue is designed to react to stimuli but give them too much input for too long and there will be a negative reaction in terms of nerve function. Direct blows or pressure for a significant length of time are both potential hazards, for example by one member of couple using their partner’s arm as a pillow to sleep, the resulting nerve problem being called honeymooners’ palsy. Continual pressure on a nerve can interrupt the blood supply and damage nerve function in a condition known as neurapraxia.
Nerve damage is classified into three categories: axonotmesis, neurotmesis and neurapraxia. Neurapraxia is the mildest variety of nerve trauma and there is internal biochemical damage to the nerve but no break in the internal axon or the nerve itself. The nerve being intact, it does not need to regenerate but recover. Nerve impulse conduction is disrupted by the area of nerve trauma and gives paralysis of the muscle with some difference in feeling. Compression may cause avascular damage to the nerve, resulting in inflammatory changes.
An inability to move the arm and the loss of function can persist for a variable time. Even though it may resolve relatively quickly, even in hours, a typical time for full resolution of the injury is 6-8 weeks. Muscle power is mostly the ability which is affected and the sensory and circulatory/sweating control nerve conduits may continue to work fairly well. A doctor should examine the person to make sure the injury is no more serious than a neurapraxia and explain the length of time which it is likely to take until recovery. Looking after the arm is important, especially if the feeling is affected.
The non-functional arm will need to be supported as its muscles are paralysed, with a sling keeping the shoulder protected and holding the arm in a safe position. Loss of sensibility in the arm can mean that the person can damage it against something like a hot object without knowing, so they need to be advised to look after it. Activities such as sport can produce these kinds of injuries as can related palsies such as falling asleep whilst sitting on a toilet.
