Diagnosis of a typical idiopathic cubital tunnel syndrome (CuTS) is straight forward but the work-up of mild forms is clinically challenging. The diagnostic value of high-resolution ultrasound (HRUS) relying solely on nerve measurements is doubtful. Additional textural analysis of the nerve may possibly overcome this drawback. Thirty-eight prospectively enrolled patients with idiopathic CuTS and 23 healthy volunteers underwent standardized HRUS. A cubital-to-humeral nerve area ratio (CHR) was calculated and the texture of the most swollen nerve segment assessed. CHR was significantly different among patients and volunteers (p<0.001) but with a marked overlap. Combination of at least partial inner fascicular masking plus a CHR>1.4 showed a positive linear coherence with idiopathic CuTS at a specificity>95% and a PPV>90%. Thus, the combined textural analysis and CHR calculation seems a powerful tool for the sonographic diagnosis of idiopathic CuTS.