Sympathetic pathology evidenced by hand thermal anomalies in carpal tunnel syndrome

To clarify sympathetic pathology in carpal tunnel syndrome and the usefulness of digital infrared thermography as a diagnostic aid.

38 clinically diagnosed carpal tunnel syndrome hands from 30 patients (confirmed by the standard nerve conduction studies) and 41 hands from 22 healthy volunteers (the hands having current finger inflammation were excluded) were studied. A series of hand infrared photos of each subject were taken and stored by using the technique of digital infrared thermography. We studied the infrared pictures and measured the temperatures of finger tips from digit 1 (D1) to digit 5 (D5), the center point of thenar (Th) and hypothenar eminences (Ht), then we calculated the temperature differences (absolute values) between each two of the 7 points, and median index (MI): (D1-D2)+(D2-D3)+(D1-D3). The means of D2 and Th (MD2+Th), D5 and Ht (MD5+Ht) were also calculated.

The results showed that the temperatures of median nerve distribution area in the hands were highly significantly different (Th-Ht, p < 0.001, MI, p < 0.001) between carpal tunnel syndrome (CTS) and the control group. The differences between the median and ulnar nerve distribution area were also highly significantly different in CTS hands (MD2+Th compared to MD5+Ht, p < 0.01). The sensitivity and specificity of digital infrared thermography were 84 and 91%, respectively.

Digital infrared thermography suggests sympathetic neural pathology in carpal tunnel syndrome. It may also be useful as an additional non-invasive tool in the diagnosis of CTS especially in the early stage.