From the Guidelines

Cubital tunnel syndrome diagnosis primarily involves clinical assessment and electrophysiologic studies.

Clinical assessment: This is the first step in diagnosing cubital tunnel syndrome, involving a thorough medical history and physical examination to identify symptoms and signs such as numbness, tingling, and weakness in the hand and arm.
Electrophysiologic studies: These include nerve conduction studies (NCS) and electromyography (EMG), which are used to assess the function of the ulnar nerve and the muscles it supplies 1.

Ultrasound (US): Although the provided evidence primarily discusses the use of US in diagnosing carpal tunnel syndrome, it can also be used to evaluate the ulnar nerve in cubital tunnel syndrome, helping to identify space-occupying lesions, anatomic variants, and other abnormalities. It's essential to note that the evidence provided focuses on carpal tunnel syndrome rather than cubital tunnel syndrome, but the diagnostic principles can be applied, with adjustments for the specific nerve and location involved. In real-life clinical practice, a combination of clinical assessment, electrophysiologic studies, and possibly US, is used to diagnose cubital tunnel syndrome, with the choice of tests depending on the individual patient's presentation and the clinical suspicion of the diagnosis.

From the Research

The following tests are used to diagnose cubital tunnel syndrome:

Tinel's sign: a test that involves tapping the ulnar nerve to elicit a tingling sensation 2
Elbow flexion test: a test that involves flexing the elbow to provoke symptoms of cubital tunnel syndrome 2, 3, 4
Pressure provocation test: a test that involves applying pressure to the ulnar nerve to provoke symptoms of cubital tunnel syndrome 2
Combined elbow flexion and pressure provocation test: a test that involves combining elbow flexion and pressure provocation to provoke symptoms of cubital tunnel syndrome 2
Shoulder internal rotation elbow flexion test: a test that involves combining shoulder internal rotation and elbow flexion to provoke symptoms of cubital tunnel syndrome 3
Electrodiagnostic studies: including motor conduction velocity and electromyography tests to assess the function of the ulnar nerve 5, 6
Imaging studies: including radiographs and MRI to evaluate the anatomy of the cubital tunnel and the ulnar nerve 5

The sensitivity and specificity of the tests for cubital tunnel syndrome are:

Tinel's sign: sensitivity 0.70 2
Elbow flexion test: sensitivity 0.32 2, 25% 3
Pressure provocation test: sensitivity 0.55 2
Combined elbow flexion and pressure provocation test: sensitivity 0.91 2
Shoulder internal rotation elbow flexion test: sensitivity 87% 3
Electrodiagnostic studies: can detect abnormalities in motor conduction velocity and electromyography in patients with cubital tunnel syndrome 6