From the Guidelines
To test for ulnar nerve radiculopathy, a comprehensive neurological examination focusing on the C8-T1 nerve roots should be performed, followed by electrodiagnostic studies like EMG and nerve conduction studies to confirm the diagnosis and determine the level of pathology. This approach is crucial in differentiating between ulnar nerve entrapment at the elbow and true radiculopathy originating from the spine. The examination should include sensory testing of the medial forearm, little finger, and half of the ring finger using light touch and pinprick, as well as assessing motor function by testing the intrinsic hand muscles, particularly the interossei and hypothenar muscles 1.
Key components of the examination include:
- Sensory testing of specific areas
- Motor function assessment, especially of the intrinsic hand muscles
- Testing for deep tendon reflexes at the triceps (C7-C8)
- Special tests such as Froment's sign, Wartenberg's sign, and the elbow flexion test
- Tinel's test at the elbow to identify ulnar nerve irritation
- A thorough cervical spine examination, as radiculopathy originates from nerve root compression
It's also important to note that while MRI can provide accurate diagnosis of disc disease and nerve root compression, as seen in the context of low back pain and radiculopathy 1, the primary approach to diagnosing ulnar nerve radiculopathy involves clinical examination and electrodiagnostic studies. MRI of the cervical spine may be considered if there's diagnostic uncertainty or if the patient is a candidate for surgery or intervention, based on guidelines for low back pain which may extrapolate to other forms of radiculopathy 1.
From the Research
Testing for Ulnar Nerve Radiculopathy
To test for ulnar nerve (UN) radiculopathy, several methods can be employed, including:
- Needle electromyography (EMG) to diagnose radiculopathy, with nerve conduction studies used to exclude alternative diagnoses 2
- Electromyographic motor Tinel's sign, which has a sensitivity of 78% and a specificity of 79% for suspected ulnar mononeuropathies at the elbow 3
- Nerve conduction studies (NCS), including short-segment incremental studies, which can help differentiate lesions at different locations 4, 5
- Ultrasonography (US), which can be used to localize ulnar neuropathies at the elbow, although its sensitivity is lower than that of NCS 4
Diagnostic Approaches
The diagnostic approach may involve:
- Combining needle EMG with NCS to exclude entrapment neuropathies and polyneuropathy, which can mimic radicular symptoms 6
- Using receiver operating characteristic curves to determine optimal cut-offs for electromyographically confirmed radiculopathy, such as ulnar motor amplitudes of 10.2 mV for C8 radiculopathy 2
- Considering the clinical severity of ulnar neuropathies at the elbow, as the sensitivity of different diagnostic tests may vary depending on the severity of the condition 4
Test Sensitivities and Specificities
The sensitivities and specificities of different tests for ulnar nerve radiculopathy are:
- Electromyographic motor Tinel's sign: 78% sensitivity, 79% specificity 3
- Nerve conduction studies: varying sensitivities depending on the specific test and clinical severity, but generally higher than ultrasonography 4
- Ultrasonography: lower sensitivity than NCS, but can be useful for localizing ulnar neuropathies at the elbow 4