Comparison of Ultrasonography and Short-Segment Nerve Conduction Study in Ulnar Neuropathy at the Elbow

To assess the correlation between ultrasonographic and electrodiagnostic findings to determine the localization of the ulnar trapping at the elbow.

Cross-sectional and noninterventional trial.

Physical medicine and rehabilitation department of a teaching hospital.

Patients (N=14) diagnosed with ulnar nerve entrapment using short-segment nerve conduction study.

The elbow area was divided into 4 segments with 2-cm intervals. All patients underwent ultrasonographic and electrodiagnostic examinations.

The nerve conduction velocity (NCV) of each segment was measured. The cross-sectional area (CSA) of the ulnar nerve was measured at 5 levels. The proximal CSA/distal CSA ratio (PDR) was calculated by proportioning the CSA values for each segment. The highest PDR was accepted as a trapping segment, whereas the segment with the lowest NCV was accepted electrophysiologically (provided it was <50m/s).

A total of 80 PDR and NCV measurements were taken from 20 elbows. A statistically significant negative correlation (r=-.554; P<.001) was found between general PDR and NCV values. When we assumed that the NCV value <50m/s as the criterion standard for diagnosis, the cutoff value for the PDR was found to be 1.08, with a sensitivity of 70% and a specificity of 92.5%. The minimum NCV value and the maximum PDR value were mostly seen in the third segment compatible with the cubital tunnel.

Ultrasonography seems to be advantageous because it is more comfortable for the patient and requires shorter time than does electroneuromyography. To our knowledge, this is the first study to detect ulnar nerve entrapment by using not only CSA but also PDR as a ratio method with ultrasound.