Introduction This is a retrospective review of 135 consecutive patients (M:F=71:64, mean age 52.6 years; 141 arms) referred to our institution with ulnar neuropathy over a two year period. We analysed electrodiagnostic and ultrasound findings in relation to clinical severity.

Methods All patients underwent electrodiagnostic (AAN) and ultrasound examination of the symptomatic ulnar nerve(s). Clinical severity was graded on a 4 point scale from ‘very mild’ (symptoms only) to ‘severe’ (sensory loss plus marked atrophy of ulnar-innervated hand muscles).

Results In ‘very mild’ neuropathies, the number of abnormal electrodiagnostic and ultrasound studies was 2 and 11 respectively, out of 54; in ‘mild’ neuropathies 19 and 25 out of 40; in ‘moderate’, 23 and 24 out of 24; and in ‘severe’, 23 and 23 out of 23. In 25 arms, (18 of which were clinically ‘severe’ or ‘moderate’), electrophysiology was abnormal but non-localising. Ultrasound showed abnormally large cross-sectional area at the elbow in 22 and diffuse nerve enlargement in three. Ultrasound identified nerve subluxation in 24 (17%) neuropathies, 58% of which were ‘very mild’, 25% ‘mild’ and 17% ‘moderate’ or ‘severe’.

Conclusion In patients with symptoms but no clinical signs, electrophysiological evidence of ulnar neuropathy was present in 3.7%, whereas abnormal nerve ultrasound, often associated with subluxation, was demonstrated in 20%. Ultrasound increased the diagnostic yield of electrophysiology in the ‘very mild’ and, to a lesser extent, the ‘mild’ neuropathies by a combined 11%, and localised the lesion in all ulnar neuropathies with abnormal but non-localising electrophysiology. Nerve subluxation was disproportionately represented amongst the clinically ‘very mild’ neuropathies with abnormal ultrasound.