Vibration Threshold Increased with Chronic Arm or Wrist Pain
In this study, blood flow and vibratory sense were measured in three groups. Group one was adults ages 18 to 65 years old with chronic upper limb pain disorder (ULPD).

Group two were slightly older with carpal tunnel syndrome (CTS). Group two had wrist and hand pain, numbness, or loss of some sensation in the wrist, hand, and fingers. Group three were normal, healthy adults matched by age and sex.

Measurements of perception and discrimination thresholds for vibration were done before and after a five-minute typing stress test. Threshold vibration was tested over the soft tissues of the forearm, palm, and back of the hand.

The authors found no difference in blood flow or volume among the three groups. There was no difference in vibration thresholds before and after the keyboard use. The major finding was that vibratory sense was changed in both arms and hands for ULPD and CTS on both sides. This was true even when only one limb was affected by the condition.

The authors suggest the changes occur in the central nervous system (spinal cord to brain pathway), rather than in the peripheral nervous system (spinal nerve to spinal cord) pathway.

It appears that widespread elevation of vibratory threshold occurs with chronic pain because of changes in the central processing of pain messages. There may not be any real changes in the nerves to the arms and hands. The problem is global, not local.
A. T. Tucker, et al. Comparison of Vibration Perception Thresholds in Individuals with Diffuse Upper Limb Pain and Carpal Tunnel Syndrome. In Pain. February 2007. Vol. 127. No. 3. Pp. 263-269.