Evaluation of Nerve Root Lesions Involving the Upper Extremity

Examination by neurologic level is based on the fact that the effects of pathology in the cervical spine are frequently manifested in the upper extremity (Fig. 1-1). Problems that affect the spinal cord itself or nerve roots emanating from the cord may surface in the extremity as muscle weakness or abnormality, reflex abnormality, and sensory diminution; the distribution of neurologic findings depends on the level involved. Thus, a thorough neurologic testing of the extremity helps determine any involvement of neurologic levels; it may also assist in the evaluation of an assortment of problems originating in the cervical cord or its nerve roots.

The following diagnostic tests demonstrate the relationship between neurologic problems in the upper extremity and pathology involving the cervical nerve roots. For each neurologic level of the cervical spine, motor power, reflexes, and areas of sensation in the upper extremity should be tested, so that the level involved can be identified. We have begun individual nerve root testing with C5, the first contribution to the clinically important brachial plexus. Although C1-C4 are not included in our tests because of the difficulty of testing them, it is crucial to remember that the C4 segment is the major innervation to the diaphragm (via the phrenic nerve).

FIGURE 1-1 The cervical spine.

Testing of Individual Nerve Roots: C5-T1

Neurologic Level C5

Muscle Testing

The deltoid and biceps are the two most easily tested muscles with C5 innervation. The deltoid is almost a pure C5 muscle; the biceps is innervated by both C5 and C6, and evaluation of its C5 innervation may be slightly blurred by this overlap (Fig. 1-2).

FIGURE 1-2 Neurologic level C5.

FIGURE 1-3 Each head of the deltoid and its function.

Deltoid: C5 (Axillary Nerve): The deltoid is actually a three-part muscle. The anterior deltoid flexes, the middle deltoid abducts, and the posterior deltoid extends the shoulder; of the three motions, the deltoid acts most powerfully in abduction (Fig. 1-2). Because the deltoid does not work alone in any motion, it may be difficult to isolate it for evaluation. Therefore, note its relative strength in abduction, its strongest plane of motion (Fig. 1-3).

Primary shoulder abductors (Fig. 1-4):

Supraspinatus C5, C6 (suprascapular nerve)
Deltoid (middle portion) C5, C6 (axillary nerve)

Secondary shoulder abductors:

Deltoid (anterior and posterior portions)
Serratus anterior (by direct stabilizing action on the scapula, because abduction of the shoulder requires a stable scapula).

Stand behind the patient and stabilize the acromion. Slide your stabilizing hand slightly laterally so that, while you stabilize the shoulder girdle, you can also palpate the middle portion of the deltoid.

Instruct the patient to abduct their arm with the elbow flexed to 90°. As the patient moves into abduction, gradually increase your resistance to their motion until you have determined the maximum resistance the patient can overcome (Fig. 1-5). Record your findings in accordance with the muscle grading chart (see page 2).

Biceps: C5-C6 (Musculocutaneous Nerve): The biceps is a flexor of the shoulder and elbow and a supinator of the forearm (Fig. 1-6); to understand its full function, envision a man driving a corkscrew into a bottle of wine (supination), pulling out the cork (elbow flexion), and drinking the wine (shoulder flexion) (Fig. 1-7).

FIGURE 1-4A Shoulder abduction.

FIGURE 1-4B Deltoid.

Origin: Lateral third of clavicle, upper surface of acromion, spine of scapula.

Insertion: Deltoid tuberosity of humerus.

FIGURE 1-4C Supraspinatus.

Origin: Supraspinous fossa of scapula.

Insertion: Superior facet of greater tuberosity of humerus, capsule of shoulder joint.

To determine the neurologic integrity of C5, we shall test the biceps only for elbow flexion. Because the brachialis muscle, the other main flexor of the elbow, is also innervated by C5, testing flexion of the elbow should give a reasonable indication of C5 integrity.

To test flexion of the elbow, stand in front of the patient, slightly toward the side of the elbow being tested. Stabilize his upper extremity just proximal to the elbow joint by cupping your hand around the posterior portion of the elbow. The forearm must remain in supination to prevent muscle substitution, which may assist elbow flexion.

Instruct the patient to flex his arm slowly. Apply resistance as the patient approaches 45° of flexion; determine the maximum resistance that the patient can overcome (Fig. 1-8).

Reflex Testing

Biceps Reflex: The biceps reflex is predominantly an indicator of C5 neurologic integrity; it also has
a smaller C6 component. Note that, because the biceps has two major levels of innervation, the strength of the reflex needs to be only slightly weaker than the strength of the opposite side to indicate pathology. It is essential to compare opposite sides of the body.

To test the reflex of the biceps muscle, place the patient’s arm so that it rests comfortably across your forearm. Your hand should be under the medial side of the elbow, acting as support for the arm. Place your thumb on the biceps tendon in the cubital fossa of the elbow (Fig. 1-9). To find the exact location of the biceps tendon, have the patient flex his elbow slightly. The biceps tendon will stand out under your thumb.

Instruct the patient to relax the extremity completely and to allow it to rest on your forearm, with the elbow flexed to approximately 90°. With the narrow end of a reflex hammer, tap the nail of your thumb. The biceps should jerk slightly, a movement that you should be able to either see or feel. To remember the C5 reflex level more easily, note that when the biceps tendon is tapped, five fingers come up in a universal gesture of disdain (Fig. 1-9).

FIGURE 1-5 Muscle test for shoulder abduction.

FIGURE 1-6A Elbow extension and flexion.

FIGURE 1-6B (continued) Biceps brachii (left).

Origin: Short head from tip of coracoid process of scapula, long head from supraglenoid tuberosity of scapula.

Insertion: Radial tuberosity and by lacertus fibrosus to origins of forearm flexors.

FIGURE 1-6C Brachialis (right).

Origin: Lower two-thirds of the anterior surface of the humerus.

Insertion: Coronoid process and tuberosity of the ulna.

FIGURE 1-7 Various functions of the biceps. (Hoppenfeld, S.: Physical Examination of the Spine and Extremities. Norwalk, CT: Appleton-Century-Crofts, 1976.)

FIGURE 1-8 Muscle test for the biceps.

Sensation Testing

Lateral Arm (Axillary Nerve): The C5 neurologic level supplies sensation to the lateral arm, from the summit of the shoulder to the elbow. The purest patch of axillary nerve sensation lies over the lateral portion of the deltoid muscle. This localized sensory area within the C5 dermatome is useful for indicating specific trauma to the axillary nerve as well as general trauma to the C5 nerve root (Fig. 1-10).

Neurologic Level C6

Muscle Testing

Neither the wrist extensor group nor the biceps muscle has pure C6 innervation. The wrist extensor group is innervated partially by C6 and partially by C7; the biceps has both C5 and C6 innervation (Fig. 1-11).

FIGURE 1-9A Biceps reflex test.

FIGURE 1-9B An easy way to remember that the biceps reflex is innervated by C5 is to associate five fingers with neurologic level C5.

FIGURE 1-10 The sensory distribution of the C5 neurologic level.

FIGURE 1-11 Neurologic level C6.

Wrist Extensor Group: C6 (Radial Nerve)

Radial extensors (Fig. 1-12):

Extensor carpi radialis longus and brevis, Radial nerve, C6

Ulnar extensor:

Extensor carpi ulnaris
C7

To test wrist extension, stabilize the forearm with your palm on the dorsum of the wrist and your fingers wrapped around it. Then instruct the patient to extend his wrist. When the wrist is in full extension, place the palm of your resisting hand over the dorsum of the hand and try to force the wrist out of the extended position (Fig. 1-13). Normally, you will be unable to move it. Test the opposite side as a means for comparison. Note that the radial wrist extensors, which supply most of the power for extension, are innervated by C6, whereas the extensor carpi ulnaris is innervated primarily by C7. If C6 innervation is absent and C7 is present, the wrist will deviate to the ulnar side during extension. On the other hand, in a spinal cord injury where C6 is completely spared and C7 is absent, radial deviation will occur (Fig. 1-14).

Biceps: C6 (Musculocutaneous Nerve): The biceps muscle, in addition to its C5 innervation, is partially innervated by C6. Test the biceps by muscle testing flexion of the elbow. (For details, see page 11.)

FIGURE 1-12A Wrist extension and flexion.

FIGURE 1-12B (continued) Extensor carpi ulnaris (left). Origin: From common extensor tendon from lateral epicondyle of humerus and from posterior border of ulna.

Insertion: Medial side of the base of the 5th metacarpal bone.

FIGURE 1-12C Extensor carpi radialis longus (right).

Origin: Lower third of lateral supracondylar ridge of humerus, lateral intermuscular septum.

Insertion: Dorsal surface of the base of the 2d metacarpal bone.

FIGURE 1-12C Extensor carpi radialis brevis (right).

Origin: From common extensor tendon from lateral epicondyle of humerus, radial collateral ligament of elbow joint, and intermuscular septa.

Insertion: Dorsal surface of base of 3d metacarpal bone.

Reflex Testing

Brachioradialis Reflex: The brachioradialis is innervated by the radial nerve via the C6 neurologic level. To test the reflex, support the patient’s arm as you did in testing the biceps reflex. Tap the tendon of the brachioradialis at the distal end of the radius, using the flat edge of your reflex hammer; the tap should elicit a small radial jerk (Fig. 1-15). Test the opposite side and compare results. The brachioradialis is the preferred reflex for indicating C6 neurologic level integrity.

Biceps Reflex: The biceps reflex may be used as an indicator of C6 neurologic integrity as well
as C5. However, because of this dual innervation, the strength of its reflex need only weaken slightly in comparison to the opposite side to indicate neurologic problems. The biceps reflex is predominantly a C5 reflex.

To test the biceps reflex, tap its tendon as it crosses the elbow. (For details, see page 11.)

FIGURE 1-13 Muscle test for wrist extension.

FIGURE 1-14 Wrist deviation with C6 and C7 injuries.

Sensation Testing

Lateral Forearm (Musculocutaneous Nerve): C6 supplies sensation to the lateral forearm, the thumb, the index finger, and one-half of the middle finger. To remember the C6 sensory distribution more easily, form the number 6 with your thumb, index, and middle fingers by pinching your thumb and index finger together while extending your middle finger (Fig. 1-16).

Neurologic Level C7

Muscle Testing

Although the triceps, wrist flexors, and finger extensors are partially innervated by C8, they are predominantly C7 muscles. All of these motions come together in the throwing motion of a baseball (Fig. 1-17).

Triceps: C7 (Radial Nerve): The triceps is the primary elbow extensor (Fig. 1-18). To test it, stabilize the patient’s arm just proximal to the elbow and instruct the patient to extend his arm from a flexed position. Before the patient reaches 90°, begin to resist the patient motion until you have

discovered the maximum resistance the patient can overcome (Fig. 1-19). Your resistance should be constant and firm, because a jerky, pushing type of resistance cannot permit an accurate evaluation. Note that gravity is normally a valuable aid in elbow extension; if extension seems very weak, you must account for it, as well as for the weight of the arm. If extension seems weaker than grade 3, test the triceps in a gravity-free plane. Triceps strength is important because it permits the patient to support weight bearing on a cane or a standard crutch (Fig. 1-20).