Friday, June 19, 2009

Saturday Night Palsies or Why You Shouldn't Put Pressure On Your Nerves

By Jonathan Blood Smyth

It is a common scenario played out in every city and town in the land on Friday and Saturday nights. After getting showered, aftershaved and dressed up the young guy goes out to meet his mates in a pub he typically frequents. He starts the drinking which will continue for the next five or six hours at least as he has a few pints with his friends and then follows them into the nightclub until early in the morning. Leaving there they are all hungry so they go round to the take-away and have a kebab, heading to the one of their houses to watch a film, plus a few more drinks.

It's all pretty much going as expected so far. He won't be surprised when he wakes up with a hangover tomorrow, but what he doesn't realise is the effect his next actions are going to have. Sitting in the chair he hangs his arm over the back of the chair as he watches the television, but the late hour and the alcohol mean he falls asleep like that too. He wakes up several or many hours later in the same position, with his arm over the back of the chair, only to find he cannot move it and it feels odd, a bit like waking up with a dead arm at night.

The real problem here was not so much the odd posture adopted in the chair when he fell asleep but the fact that he was drunk. If he had been sober the discomfort in the arm would have either woken him or made him move the arm at some point to a different position. The armpit tissues have had to endure a significant weight on them for a long time and the result is an arm which is almost paralysed. Our young man has tried to shake it back to life but it has not responded to this.

Our nerves are a reactive tissue, that's what they are designed for. But they won't take too much pressure for too long a time without reacting in a negative manner. One of the things nerves don't like is direct pressure. If subjected to undue pressure for too long, also referred to at times as honeymooners' palsy which is due to the tendency for one person to rest their head on the arm of the other whilst sleeping, the blood supply to the nerve becomes interrupted and the nerve develops a neurapraxia.

There are three broad categories of nerve damage classification: axonotmesis, neurapraxia and neurotmesis, with neurapraxia being the least severe nerve damage. There is no division of the nerve or a break of the nerve fibre axon in neurapraxia, meaning the nerve does not have to regenerate but just needs time to recover. The damaged area interrupts the impulse flow in the nerve, resulting in paralysis of the muscles and perhaps some sensory changes. The avascular state produced by the long period of pressure may be what damages the nerve.

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.

Once the paralysis has occurred the arm will need to be supported by a sling to prevent shoulder problems and the person taught to check the arm regularly if there is any sensory loss. Sensory loss means that the arm can be damaged without the person realising it, so they have to be vigilant in looking after the limb until it recovers. Other ways of getting this kind of nerve trauma is in sport, by leaning against a solid edge for a long time or by falling asleep on the toilet for some hours. - 14130

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