Median to ulnar nerve comparison on diagnosis of carpal tunnel syndrome in patients with diabetic polyneuropathy - A neurophysiological study.

<p style="text-align: justify;"><strong>Background and purpose </strong>&ndash; To analyze the utility of median nerve (MN) to ulnar nerve (UN) comparative parameters on the diagnosis of carpal tunnel syndrome (CTS) in diabetic patients with distal symmetrical sensorimotor polyneuropathy (DSMPNP). <br><br><strong>Methods</strong> &ndash; Patients who were referred to our electroneuromyography laboratory within the last two years were included. We compared the diagnostic accuracy values of traditional MN conduction parameters, and the MN-to-UN comparative tests on electrodiagnosis of CTS between the patients with DSMPNP involving the nerves of upper and lower extremities (UEI-positive group), and the ones without the involvement of upper extremities (UEI-negative group). <br><br><strong>Results</strong> &ndash; There were 64 upper extremities in the UEI-positive group and 70 patients in the UEI-negative group. The most accurate traditional parameter was MN distal motor latency (DML) with a diagnostic accuracy of 70.2% whereas the most accurate comparative technique was the second lumbricalinterosseous DML difference (2L-INT DMLD) with an accuracy of 81.3%. (p=0.03). In addition, when compared diagnostic accuracy values of MN parameters with their corresponding comparative parameters in the UEI-positive group which carries the major diagnostic challenges for detecting co-morbid CTS, MN to UN minimum F wave latency (mFWL) difference, SNAP amplitude ratio on the ring finger (RF), and 2L-INT DMLD had higher accuracy values than MN mFWL, MN SNAP amplitude on RF, and MN DML on lumbrical muscle, respectively (p&lt;0.05 for all comparisons). <br><br><strong>Conclusion</strong> &ndash; MN to UN comparative studies have high accuracy values in electrodiagnosis of CTS in DSMPNP. In particular, 2L-INT DMLD could be helpful to overcome the diagnostic difficulty in the presence of UEI as an additional conduction technique.</p>.