MRI characteristics of ulnar nerve and muscles in cubital tunnel syndrome

Abstract

Objective To investigate the MR characteristics of ulnar nerve and muscles in cubital tunnel syndrome.Methods Twenty eight patients with cubital tunnel syndrome and 28 asymptomatic volunteers underwent MR imaging,MR neurography was performed by using an isotropic three dimensions T2 sampling perfection with application optimized contrasts using different flip angle evolutions (3D T2 SPACE)on 15 patients with cubital tunnel syndrome.To evaluate changes in T2 signal intensity of the ulnar nerve,regions of interest were placed in the center of the location of the highest apparent ulnar nerve signal intensity on the axial FS T2WI images and in normal muscle within the same image slice,and the ratio of signal intensity was calculated.The sensitivity of 3D T2 SPACE sequence in detecting cubital tunnel syndrome was determined.The standard t tests were used to assess whether ulnar nerve size and relative signal intensity in symptomatic patients were statistically different from normal volunteers.Results The cross-sectional area of ulnar nerve in 24 patients and 2 volunteers was enlarged,the signal intensity of ulnar nerve in 26 patients and 16 volunteers was increased.Increased signal and muscle atrophy adjacent to the ulnar nerve were detected in 4 patients.Cubital tunnel syndrome was detected in 14 patientson 3D T2 SPACE sequence.The mean ulnar nerve sizes in the symptomatic and normal group were (0.15±0.06)and (0.06±0.01)cm2 respectively,the mean relative signal intensities in the symptomatic and normal groups were (2.86± 1.45) and 1.57±0.39 respectively (t values were 2.220 and 4.546,P＜0.05).Conclusions Ulnar nerve size and T2 signal intensity were increased,in patients with cubital tunnel syndrome.In addition,muscles innervated by the ulnar nerve showed atrophy with increased T2 signal intensity. Key words: Magnetic resonance imaging; Ulnar nerve; Cubital tunnel syndrome