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Musculoskeletal Imaging

E2939. Ultrasound Evaluation of Peripheral Nerves

Mehta S,  Huang J,  Khoury V. University of Pennsylvania Health System, Philadelphia, PA

Address correspondence to S. Mehta (samir.mehta2@uphs.upenn.edu)

Background Information: Ultrasound is a cost-effective method to evaluate peripheral nerves. It is less expensive than MRI and is much easier for the patient to tolerate. Other advantages over MRI include time-efficient assessment of long segments of peripheral nerves, ability to perform dynamic maneuvers, and lack of contraindications. Ultrasound can also be used to guide perineural injections and other interventions. We aim to show that ultrasound is an effective, convenient tool to image peripheral nerves at a high level.

Educational Goals/Teaching Points: We will review the wide variety of lesions that are associated with the peripheral nerves. We will describe in detail the unique ultrasound imaging findings seen in these lesions, which can aid radiologists in determining the correct diagnosis. We will also include a brief discussion of ultrasound technique and comparison with MRI.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: There are many lesions that involve the peripheral nerves. In the past, these have been evaluated predominantly with MRI. However, ultrasound examination offers a quick and convenient way to image the lesions. The normal appearance of a peripheral nerve on ultrasound is described as “honeycomb” in the transverse plane, with a fascicular pattern in the longitudinal plane, due to the presence of hyperechoic lines representing the perineurium. In chronic nerve degeneration, the normal fascicular architecture will be lost. In penetrating trauma, a transection of the nerve can be seen. In infective processes, there may be compression of the nerve by peripheral soft tissue and invasion of the infectious or inflammatory process into the epineurium. Schwannomas are eccentrically located along the nerve and appear as a fusiform mass; neurofibromas are spindle-shaped with loss of fascicles; Morton neuromas appear as a hypoechoic focus in the intermetatarsal space; carpal tunnel syndrome appears as enlargement and hypoechogenicity of the median nerve, with decreased mobility on dynamic maneuvers. Diagnosis of nerve entrapment can be aided with provocative ultrasound maneuvers during the examination.

Conclusion: Ultrasound is a cost-effective, efficient imaging method to evaluate peripheral nerves in high resolution in real-time. Ultrasound can be used to diagnose various peripheral nerve pathologic lesions of traumatic, inflammatory, mechanical, and neoplastic etiologies.