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Year |
2001 |
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Question Number |
196 |
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Category |
Select |
Question
Which of the following is considered the most sensitive sensory test for detecting early carpal tunnel syndrome?
1. Light touch sensation
2. Pinprick sensation
3. Two-point discrimination
4. Moving two-point discrimination
5. Semmes-Weinstein monofilament
Figures
Answer (click for answer)
Correct Answer: 5
The tests mentioned above can basically be separated into two categories: threshold tests and innervation/density tests. Innervation density tests measure multiple overlapping peripheral receptive fields and densities of innervation in the region being tested. These tests are highly dependent on cortical integration of peripheral impulses. As such they may be normal in compressive neuropathies in that all that is needed is that a few fibers conduct normally to the correct cortical endpoints to give a normal result. These tests are better for nerve repairs than for compressive neuropathies.
Threshold tests evaluate single nerve fibers innervating a receptor or group of receptor cells. These tests better show gradual and progressive change in value as a greater proportion of nerve fibers are lost while others maintain proper central connections. In the above question, only #5 is a threshold test.
The article referenced is actually pretty interesting. In it they measured sensibility testing using 7 different methods as well as EMG studies. Briefly, in it they found that following order for most reliability for these tests:
1. Vibratory 120 Hz vibrometer – 87% accurate
2. Semmes Weinstein Monofilament – 83%
3. 256 cycles/sec tuning fork – 70%
4. Phalen’s test – 70%
5. Tourniquet test – 70%
6. Nerve percussion – 61%
7. Weber static 2 point discrimination – 22%
Reference: Szabo, Gelbermen, Dimick: Sensibility testing in patients with carpal tunnel syndrome; JBJS American 1984;66:60-64