The patient has injured his upper arm, usually by sleeping
with his arm over the back of a chair, and now presents
holding the affected hand and wrist with his good hand,
complaining of decreased or absent sensation on the radial
and dorsal side of his hand and wrist, and of inability to
extend his wrist, thumb and finger joints. With the hand
supinated (palm up) and the extensors aided by gravity, hand
function may appear normal, but when the hand is pronated
(palm down) the wrist and hand will drop.
What to do:
Look for associated injuries. This sort of nerve injury may
be associated with cervical spine fracture, injury to the
brachial plexus in the axilla, or fracture of the humerus.
Document in detail all motor and sensory impairment. Draw a
diagram of the area of decreased sensation, and grade muscle
strength of various groups (flexors, extensors, etc.) on a
scale of 1-5.
If there is complete paralysis or complete anesthesia,
arrange for additional neurological evaluation and treatment
right away. Incomplete lesions may be satisfactorily
referred for followup evaluation and physical therapy.
Construct a splint, extending from proximal forearm to just
beyond the metacarpophalyngeal joint (leaving the thumb
free) which holds the wrist in 90 degree extension. This and
a sling will help protect the hand, also preventing edema
and distortion of tendons, ligaments, and joint capsules
which can result in loss of hand function after stren~th
returns.
Explain to the patient the nature of his nerve injury, the
slow, rate of regeneration, the importance of splinting and
physical therapy for preservation of eventual function, and
arrange for followup.
What not to do:
Do not be misled by the patient's ability to extend the
inter phalangeal joints of the fingers, which may be
accomplished by the ulnar-innervated interosseus muscles.
Discussion
This neuropathy is produced by compression of the radial
nerve as it spirals around the humerus. Most commonly it
occurs when a person falls asleep, intoxicated, held up by
his arm thrown over the back of a chair. Less severe forms
may befall the swain who keeps his arm on his date's chair
back for an entire double feature, ignoring the growing pain
and paresis.
If the injury to the radial nerve is at the elbow or just
below, there may be sparing of the wrist radial extensors as
well as the radial nerve autonomous sensation. The deficient
groups will be the wrist ulnar extensors as well as the
metacarpophalyngeal extensors. A high radial palsy in the
axilla (e.g., from leaning on crutches) will involve all of
the radial nerve innervations, including the triceps.
