Ulnar nerve (UN) entrapment at the elbow is the second most frequent tunnel syndrome, following carpal tunnel syndrome.
Cubital tunnel syndrome (CuTS) is a common nerve entrapment syndrome of the upper extremity, caused by compression of the ulnar nerve at the cubital tunnel of the elbow.
The presentation of cubital tunnel syndrome varies, ranging from mild sensory symptoms to debilitating functional loss.
Typical CuTS symptoms include numbness, tingling, and dysesthesia in the ring, small finger and dorsum of the hand. As the disease progresses, atrophy of the hypothenar and first dorsal interosseous muscles occurs, which may interfere with daily activities. CuTS is likelier to be at an advanced stage at the time of intervention than carpal tunnel syndrome (CTS). Therefore, early diagnosis and treatment are important.
Also, due to anatomic variations, a broad spectrum of differential diagnosis, and miscellaneous clinical presentations, the clinical diagnosis is often far from straightforward. If not treated timely and adequately, CuTS can progress to persistent impairment of sensation, paresis, and joint contracture.
This condition is typically diagnosed using patient's history, physical examination, and electrodiagnostic studies. However, because CuTS has a variety of clinical characteristics, it is difficult to differentiate it from other diseases that can affect the elbow joint based on clinical presentation and an electrodiagnostic study.
Electroneuromyography (ENMG) is the gold standard examination in CuTS, but sheds no light on etiology.
Although an electrodiagnostic study is considered the most important diagnostic test for CuTS, it has some critical drawbacks. It is time-consuming, causing pain and injury to patients due to needle insertion and electrical stimulation, provides limited information regarding lesion localization and structural abnormalities, and carries a strong possibility of false negative results.
Thus, complementary imaging studies such as magnetic resonance or high resolution ultrasound (HRU) imaging are required for the diagnosis of various neuropathies. Ultrasound imaging in particular supports the diagnosis of neuropathy by providing superior spatial resolution of small peripheral nerves, allowing for dynamic evaluation and detailed information regarding lesion localization in addition to advantages of being fast, cheap, non invasive and painless procedure.
Moreover, as a recently-developed ultrasound imaging technology, shear-wave elastography (SWE) has the potential to provide quantitative values for the soft tissue stiffness of tissues, including the muscle, tendon, joint capsule, benign soft tissue mass, and nerves, and to improve the diagnostic performance of ultrasound imaging for various nerve neuropathies.
SWE is also an advanced quantitative ultrasound technique that can be used to evaluate soft tissue elasticity. In compressive neuropathy, a higher pressure within the canal could cause ischemia, edema, inflammation, and finally fibrosis in the intraneural space and the synovium. All of these changes to the compressed nerve may result in increased nerve stiffness. Therefore, SWE could be a valuable complement in the diagnosis of compressive neuropathy.
So, SWE seems to be a new, reliable, and simple quantitative diagnostic technique to aid in the precise diagnosis of ulnar neuropathy at the cubital tunnel, and HRU proved to be an effective diagnostic tool for CuTS and its etiologies
