Man, 46, With Wrist Laceration

With our case patient, a small glass cut at the volar wrist crease did not cause tendon lacerations or flexor deficits. The patient complained only of mild tingling to the fingers, and a detailed hand-and-finger examination was not performed to isolate further nerve injury.⁴

Although most nerve injuries result in a loss in sensory function, motor function must also be evaluated.⁵ With partial nerve lacerations, subtle loss of motor or sensory function can be missed by the examiner.⁴ It is imperative to conduct a thorough hand examination (outlined in Tables 1 and 2) to decrease the likelihood of missing a significant nerve or tendon injury.

Sensory testing basics

Nerve laceration vs nerve compression disorder. It is important to distinguish sensory testing for a nerve injury or laceration from testing for a nerve compression disorder, such as carpal tunnel syndrome. When examining compression neuropathies, light touch, tuning fork vibration, and monofilament testing are used. When a nerve injury or laceration is suspected, light touch and 2-point discrimination are used.⁵ Static 2-point discrimination (also known as the Weber static test) will be immediately abnormal if a nerve is lacerated. In a nerve compression disorder, 2-point discrimination is decreased progressively.⁵

Sensory testing evidence

Comparing light touch, monofilament, and 2-point discrimination. As seen with our case patient, testing dull-sharp discrimination using the cotton-tip applicator for “dull” and the broken end of the wooden applicator stick for “sharp” may not be the most complete way to assess sensation in the hand and fingers. The physical examination should include light touch and 2-point discrimination.⁵

In one study, tests for sensation compared the gauze test (light touch), the static 2-point discrimination, the moving 2-point discrimination (m2PD; also known as the Weber dynamic test),⁶ and the monofilament test. The static and m2PD tests were statistically superior to the gauze and monofilament tests (see Table 3).⁷ Two-point discrimination abnormalities are detected immediately after a nerve is lacerated.⁵ This suggests performing 2-point discrimination, either moving or static, is superior to dull-sensation testing alone (gauze or cotton-tip applicator). This should be included in the motor and sensory examinations of the hand and fingers seen in Tables 1 and 2.

Continue to: Moving 2-point discrimination test