Radial Neuropathy: The Wrist-Drop of Saturday Night Palsy
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 against the bone all night. 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 injury 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