The Wrist-Drop of Saturday Night Palsy
Gary E Cordingley, MD, PhD
The magic and menace of Saturday night are invoked to account for a variety of
phenomena, but one of the less appreciated examples is how a night of debauchery on
Saturday can produce weakness of the wrist and fingers on Sunday morning.
So here's the scenario. It's Saturday night and I've had a long week. I hit the bars and tip back one or two too
many. Stumbling out of the last bar, I find I can't make it past the city park without landing on my nose, so I plop
onto a park bench. Slinging an arm over the back of the bench to stabilize myself, I fall into a deep slumber.
Now it's Sunday morning and the sun is shining, the birds are singing and I've got a splitting headache. My arm
is where I left it last night, slung over the back of the bench. I haul it back in front of me, but something is wrong.
When I try to extend (cock up) my wrist, it doesn't go anywhere. In fact, it droops downward. Moreover, I can't
straighten my drooping fingers, either. As I investigate further, I find that the skin on the back of my hand is
numb. What gives?
The problem is that I have injured the arm's radial nerve. As a result, the muscles it controls and the
skin-sensation it manages are out of commission. On its course from the spinal cord in the neck to the forearm
and hand, the radial nerve -- a bundle containing many individual nerve-fibers -- spirals around the
humerus-bone of the upper arm. The nerve is particularly vulnerable to injury near the mid-portion of the
humerus, in this case by allowing the hard edge of the park-bench to compress it all night against the bone.
The weakness produced by this condition is usually more impairing than the numbness that is also present.
With "palsy" as another word for weakness this kind of injury to the radial nerve is called "Saturday night palsy."
Of course, injury to the radial nerve can occur on any other night of the week, as well, and the setting does not
have to be a park-bench. The usual common denominators are that alcohol or other drugs are involved, and
because of the deep, drug-induced slumber, the arm is kept in the same position all night long.
This part of the radial nerve can also be injured by off-course injection-needles intended for the shoulder
muscle above it (the deltoid muscle). When this occurs, the pattern of weakness and numbness is the same,
but instead of going by the name of "Saturday night palsy," the nerve-injury is sometimes called "law suit."
In either case, the nerve and its functions usually recover over a time-frame that can vary from days to longer
than a year. The faster recoveries mean that the nerve-fibers within the nerve-bundle were sick but not dead.
In more severe injuries, the nerve-fibers at the site of the injury and beyond have actually died, and their
surviving stumps need to send out sprouts to replace the missing parts. This is a slow process. The growing
sprouts reach the upper forearm (where the wrist-straightening muscles are located) before reaching the
mid-forearm (where the finger-straightening muscles are located). As a result, the muscles that straighten the
wrist usually recover before those that straighten the fingers.
People with Saturday night palsy often exercise their arms by squeezing rubber balls or similar objects.
Unfortunately, this activity exercises the wrong muscles. The radial nerve and its muscles have nothing to do
with flexing the hand muscles. These functions are instead served by the arm's median and ulnar nerves which
were not injured in the first place. In order to be useful, an exercise would need to focus on cocking up the wrist
and straightening the fingers.
But this, too, might be futile because the paralyzed muscles have no incoming nerve-messages to activate
them. Until the damaged nerve-fibers reconnect with the muscle-fibers, the most useful exercise is a passive
one in which the other hand does the work by stretching out the weak muscles at least daily. Using passive
"range-of-motion" exercises, people with nerve-injury can avoid shortening of tendons and freezing of joints
that might otherwise occur as complications while waiting for the nerve to recover.
What else can be done? Unfortunately, there is a dearth of scientific evidence in the form of randomized,
controlled trials -- the gold-standard for judging a treatment -- to go by. All we have to go on is collective
"clinical experience" and common sense. In order to properly heal and grow, nerve-fibers need a good supply
of nutrients, so healthy eating -- perhaps supplemented by a multiple vitamin or two each day -- can give the
nerve the building-blocks it needs to properly recover. Avoidance of alcohol might prevent a second injury.
Because alcohol can also produce a direct toxic effect on the body's peripheral nerves, abstinence would
additionally prevent this barrier to recovery. In cases of prolonged weakness, electrical stimulation of the
affected muscles via probes applied to the skin might keep the muscle-tissue healthier until they can receive
more normal activation through their nerves.
While waiting for the nerve to heal, the wrist can be splinted in a neutral position with a device that leaves the
fingers free to move. The fingers are more functional when the wrist is straight. One can prove this to himself or
herself by flexing the wrist and trying to do something useful with the fingers, like write a sentence or pick up a
coin. However, use of a splint does not preclude the need for at least daily, passive, range-of-motion exercises.
(C) 2005 by Gary Cordingley