The nerves of our body are its'
'electrical wires.' As such, they are insulated with a thin fatty
material called myelin. Among the many functions of nerves, there are
two that are obvious: (1) they carry electrical impulses from the brain
and spinal cord to make muscles contract, and (2) they carry impulses
back from the skin to the brain, so we can feel. The longest nerves in
the body are those that carry electrical impulses up and down from the
toes to the spinal cord; on average these are more than 40 inches (100
cm) long. Those that reach the fingers are only slightly shorter. The
three major nerves of the arm are the median, the ulnar, and the radial.
The second concept to understand is that the nerves, when running
from the spinal cord to the ends of the toes (or fingers), follow a very
complex path, between and/or under muscle fibers and tendons (which are
like gristle), and often inside a fibrous tunnel. These tunnels are
usually situated at the joints of the body, so that the stretching of
the nerve across the joint as it bends or straightens is protected by
the tunnel. The diagram below is from a very old anatomy text, yet it is
a great illustration of the complex path that the nerves must follow as
they course down the limbs.
However, there are also places where a nerve may be very superficial
(just under the skin) and the two best examples are (1) on the outside
of the leg, just below the knee , where the common peroneal nerve runs
from behind the knee around the head of the fibula bone, and (2) the
ulnar nerve at the elbow, which can also be easily felt, especially in a
thin person. It is this nerve that causes the shooting pain and
tingling in the little finger when a person bumps their "funny bone." If
you bend the elbow to 90 degrees and press in with your finger tips, in
the groove on the inner side of the elbow, you may be able to feel the
ulnar nerve like a piece of spaghetti running around the elbow joint.
It is at this site that the ulnar nerve is most likely to be bruised
or stretched, usually slowly over time with repetitive strain, which
results in the symptoms and signs termed "ulnar neuropathy." Sometimes
the fibrous bands around the elbow joint also may thicken and squeeze
the ulnar nerve-the consequence is the same as the stretching injuries.
There are factors that may predispose or exacerbate the stretching
and bruising of the ulnar nerve at the elbow, such as a previous elbow
fracture or continuously resting the bent elbow on a desk. Diabetes may
also make the nerve less resistant to damage and trauma, and inhibit
healing and recovery.
The first symptom of ulnar neuropathy is usually an insidious
tingling and loss of feeling in the little finger and the inner side of
the hand as far as the wrist. This strange tingling slowly spreads,
often over weeks or months, and involves the side of the ring finger
next to the little finger, but strangely not the side next to the middle
finger. This is because the feeling on the skin of the ring finger is
supplied by two nerves: the ulnar on the inner side and the median nerve
on the outer side. Indeed, the fact that the tingling, numb feeling
"splits" the ring finger is almost solely diagnostic of an ulnar nerve
irritation at the elbow. The area involved is colored blue in this
Much later, perhaps over months, the muscles supplied by the ulnar nerve begin to waste and become weak. The first, somewhat irritating weakness is of the little finger, which seems to develop a mind of its own and tends to spread apart, away from the ring finger. This often results in the little finger getting caught outside when one attempts to put the hand in a pocket. About this time one may detect wasting of specific muscles. This is best appreciated on the back of the hand, where the plump muscle between the thumb and index finger sinks in. In addition, "gutters" appear between the tendons on the back of the hand. Finally, if the problem is allowed to go untreated, the fingers develop a "claw-like" deformity, with the little, ring, and to a lesser extent, the other fingers becoming increasingly bent over (flexed) toward the palm.
The diagnosis is usually straightforward, especially if the numbness
and tingling "splits" the ring finger as explained above. Rarely the
problem may arise in the neck from osteoarthrosis, causing irritation of
a nerve root as it leaves the cervical spinal cord. The most important
part of the diagnosis is to accurately localize the location at which
the ulnar nerve is being stretched or squeezed. In most people this is
in the elbow region. Your doctor will use MRI and/or ultrasound scans of
the elbow region as well as electrical studies of the ulnar nerve
(nerve conduction studies and electromyography). Using these techniques
an experienced neurologist may be able to pinpoint the site of the
trouble. A surgeon may need to operate to release the nerve.
Many doctors will recommend surgery, but the outcome of "surgical
release" is not as predictable or successful as the surgical outcome for
another more common entrapment neuropathy-carpal tunnel syndrome.
Timing of surgery is somewhat of a dilemma in ulnar entrapment
neuropathy. On one hand, a mild case of stretching may improve with
conservative measures that reduce the strain; supportive Velcro-padded
splints serve to reduce the bending of the elbow and provide a degree of
protection against pressure knocks. However, the longer one leaves the
problem without operating, the more severe it may become and hence the
less chance there is of a successful surgical release.
Many patients have a concept of "tennis elbow" - characterized by
pain and discomfort around the elbow, not always with symptoms and signs
of ulnar nerve involvement. Injecting steroids in and around the elbow
joint may provide a degree of symptomatic relief of pain, but it has not
been shown to reverse any bruising or stretching of the ulnar nerve in
the long term.
The final decision about surgical intervention for an ulnar nerve
problem at the elbow will usually be made after your surgeon has
considered (1) the likely cause (including where exactly the pressure or
stretch is localized), (2) the duration, and (3) the severity. The
final decision, of course, will be a mutual one between you and your
doctor after considering all of these factors.
This information was written by Graham Norton FRACP, and is herewith used with permission. It was last updated February 1, 2013.
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