REIDER PART 2
59

Charter 8__Cervical and Thoracic Spine 319

of thc first web space and the index finger (Fig. 8-30C), the C7 nerve root supplics thc long finger (Fig. 8-30D), and the C8 nerve root supplies the Iittle finger and the ulnar aspect of the hand (Fig. 8-30£). The Tl nerve root can be evaluated by testing the medial arm about the elbow (Fig. 8-30F), and the T2 nerve root supplies the upper medial arm adjacent to the axilla and a contiguous portion of the chest (Fig. 8-30G). The other thoracic nerve roots supply sensation to successive strips of skin across the trunk. Remembering that the nipples identify the T4 der-matome and the umbilicus, the T10 dermatome helps the examiner identify thc approximate level of sensory deficit in the distribution of the thoracic nerve roots.

Motor Examination

There is considerable overlap in the motor dermatomcs of muscles supplied by the cervical nerve roots. In generał, one or two muscles or muscle groups are selected to test each nerve root. These muscles or groups are usually chosen for their ease of examination or purity of inner-vation.

C5 Newe Root The C5 nerve root, which exits the spine through the C4-C5 neuroforamen, is best assessed by testing deltoid strength. The patient is seated in a comfortable upright position and asked to abduct thc arm with thc elbow flcxed. The examiner then exerts downward pressure on the elbow while the patient tries to resist with a pure abduction force (Fig. 8-31). In most normal patients, the examiner is not able to break the deltoid strength. The C5 nerve root also contributes to the biceps brachii. Because the innervation of the biceps is shared with C6, substantial neurologie dysfunction must be present before biceps weakness is perceived.

C5

Figurę 8-31. Assessing C5 motor function (deltoid strength).

Even in the face of a complete C5 motor deficit, moder-ate or normal biceps strength remains because of this dual innervation.

C6 Newe Root. The C6 nerve root, which exits the spine through the C5-C6 neuroforamen, innervates the biceps brachii and the wrist extensors. To test the biceps, the examiner supports the patients flcxed elbow with one hand and grasps the patient s wrist with the other. The examiner then attempts to passively extend the elbow while the patient attempts to keep it flexed (Fig. 8-32A). In most normal patients, the examiner is unable to over-come the patients biceps strength. Owing to the biradic-ular innervation of the biceps noted previously, evcn a complete C6 motor deficit may not lead to total biceps paralysis.

Figurę 8-32. Assessing C6 motor function. A, Biceps. B, Wrist extensors.