Ultrasonography in ulnar neuropathy at the elbow: relationships to clinical and electrophysiological findings

INTRODUCTION: Though ultrasonography (US) is commonly used in the diagnosis of carpal tunnel syndrome (CTS), there are only few studies on the utility of US in ulnar neuropathy at the elbow (UNE). The aims of this study were to measure the cross-sectional area (CSA) of the ulnar nerve at the elbow and to correlate CSA values with clinical and electrophysiological findings. PATIENTS AND METHODS: Thirty-three UNE patients (mean age 50.1 years) were consecutively enrolled. Diagnosis was based on clinical findings and slowing of the motor conduction velocity (MCV) of the ulnar nerve across the elbow. CSAs of the ulnar nerve were measured within the cubital tunnel at the level of the medial epicondyle (CSA-M) and approximately 2cm proximal to this point (CSA-I). Correlations between CSA and demographic, clinical (ordinal severity scale and self-administered symptom questionnaire), and electrophysiological findings (neurographic results and ordinal electrophysiological severity scale) were calculated using Spearman's correlation coefficient. RESULTS: The mean CSA-M and CSA-I were 9.6+/-8.5 and 9.3+/-5.6mm2, respectively. Fifteen (45.5%) and eight (24.5%) cases showed abnormal CSA-M and CSA-I values, respectively (mean+2S.D. compared to a control group of the same age). All cases with abnormal CSA-I had abnormal CSA-M except one. Significant relationships were only found between CSA-M and CSA-I with across elbow MCV, sensory action potential amplitude, and the electrophysiological severity scale score. DISCUSSION: Our study showed anomalous CSA values in less than 50% of the UNE cases. This is less than the reported percentages in the few literature reports. This difference may be due to our enrolment criteria or to the electrophysiological and US techniques. It is likely that the CSAs measured by axial scan at a fixed level of the cubital tunnel may have lower diagnostic sensitivity than the same technique used in CTS.