REIDER PART 2
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316 Chaptkr8_Cervical and Thoracic Spine

rests thc base of the vibrating fork on the bony prominence and asks thc patient to report when thc vibration stops (scc Fig. 8-28D). The examiner then stops the vibration sud-denly with the free hand (sec Fig. 8-28E). Normally, thc patient identifies the cessation of vibration quite readily. Vibration scnse should never be abscnt in the fingers or bony prominenccs. Some elderly individuals may, however, lose vibration sense distally. Otherwise, loss of vibration sense is associatcd with injury to the posterior columns of the spinał cord or pcripheral nerves.

Proprioception. Loss of proprioception, also a sign of posterior column dysfunction, may be associated with aging, injury, or cerebellar dysfunction. To assess proprioception, the patient is instructed to close his or her eyes and the examincr grasps one of the patients fingers or toes. The examiner then alternatcly flexes and extend$ the digit several times, randomly stopping in flexion or extension (see Fig. 8-28Fand G). The patient should be able to identify whether thc digit cnds the maneuver in extension or flexion.

Two-Point Discrimination. The most sensitive means of assessing sensory loss in the upper extremities is two-point discrimination testing. This is most useful for deficits in the C6, the C7, or the C8 dcrmatomes. A sub-ject with normal sensation should be able to distinguish points 5 mm apart on the fingertips. The tcchnique for assessing two-point discrimination is described in Chapter 1, Terms and Techniques.

Sensory Dermatomes. The approximate areas of sensory innervation from the cervical and thoracic nerve roots arc shown in Figurę 8-29. Thcre is considerable overlap in the sensory dermatomes, and the cxact distribution of each dermatome varies somewhat from one individual to another. Sensory deficits are usually sought by evaluating sensation in relatively smali areas that can reliably be expected to correspond to specific dermatomes in most individuals. The C4 nerve root is most effectivcly assessed by testing the lateral neck (Fig. 8-30A). The C5 nerve root can be evaluatcd by testing sensation over thc middle del-toid (Fig. 8-30B). The C6 nerve root supplies the dorsum

Figurę 8-28, eont'd. Pand E, Yibration. Fand G, Proprioception.

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