55.8 Examining the peripheral nerves

Whenever a patient has injured a limb, especially if he has a penetrating wound, test the function of its nerves and tendons before you anaesthetize him or refer him elsewhere. Test the most distal point supplied by each nerve. The following tests are so quick that you can do them all in a few seconds. Always record your results. It will then be certain that paralysis is not the result of treatment.

QUICK TESTS FOR PERIPHERAL NERVES

Record both power and sensation when you first see a patient, and after each subsequent examination. For the nerves of the hand goto Section 75.1.

AXILLARY (CIRCUMFLEX) NERVE This arises from the posterior cord of the bachial plexus, and winds round the neck of a patient’s humerus to supply his deltoid and the skin over the lower part of this muscle. It is injured in dislocations of the shoulder.

Ask the patient to abduct his arm. Put the palm of your hand over his deltoid as he does so, as in A, Fig. 55-6. Even a flicker of contraction shows that his deltoid is working.

Test sensation with a pin on the outer part of his shoulder, over the insertion of his deltoid. If his axillary nerve has been injured, there will be a small patch of anaesthesia.

MUSCULOCUTANEOUS NERVE If this nerve has been injured there will be anaesthesia along the outer side of his forearm, and he will be almost unable to flex his arm.

SCIATIC NERVE This is sometimes injured by pelvic fractures. Test its peroneal and tibial branches as described below. Test the sensation of the dorsum of his foot.

Figure 55.6: SOME QUICK TESTS FOR PERIPHERAL NERVES. Test the function of an injured patient’s nerves and tendons before you anaesthetize or refer him. Tests for the nerves of the hand are in Section 75.1.

COMMON PFRONFAL BRANCH OF SCIATIC NERVE Paralysis causes foot drop. Can he walk on his heels with his forefoot raised? Test for anaesthesia in the distribution of his deep peroneal nerve in the web between his big and second toe. His common peroneal nerve can be injured by Thomas splints, badly applied skin traction, or blows to the neck of his fibula.

TIBIAL BRANCH OF SCIATIC NERVE Ask him to plantar flex his ankle, or stand on tip toe.

Figure 55.7: IS IT A NERVE OR A TENDON? A nerve is yellowish and flexible, and you can make it lie in various positions. A tendon is bluish white and glistening, straighter and firmer and more difficult to deform by compression than a nerve. Kindly contributed by Peter Bewes.