Ultrasound Imaging of Disorders of Small Nerves of the Extremities: Less Recognized Locations

Abstract

Ultrasound is a well‐proven imaging modality for showing peripheral nerve disorders and guiding perineural injections. The aim of this review is to focus on small peripheral nerve abnormalities, which are usually not recognized by sonologists. In fact, most of these small nerves have a tiny diameter (<2 mm), and their anatomy is less familiar. We describe the most common causes of small peripheral nerve disorders, providing an accurate description of their anatomic locations and relationships with adjacent structures; we also focus on technical hints that may help in their evaluation.

Ultrasound Imaging of the Deep Peroneal Nerve

“…Ultrasound can delineate the normal fascicular nerve appearance, composed of hypoechoic nerve fascicles and surrounded by hyperechoic connective tissue. This honeycomb structure can be well depicted on short‐axis sonograms 1,4,29 …”

“…Higher‐frequency transducers, up to 17 to 18 MHz, are useful for scanning the nerve at the ankle and distally; they may also be used to evaluate the proximal course of the nerve at the fibular tunnel, particularly in slender patients. Hockey stick transducers, thanks to their small footprint, also allow accurate compression of the pathologic DPN to confirm pain radiating distally (the so‐called US Tinel sign) 29 …”

“…We suggest following the DPN in the short‐axis view, from proximal to distal (using the so‐called elevator technique) to promptly evaluate long segments of the nerve, thus showing its relationship with surrounding structures 1,29 . We usually do not acquire longitudinal sonograms of a normal DPN.…”

Compression of the lateral antebrachial cutaneous nerve by a traumatic arteriovenous fistula

“…Therefore, US has been expected to overcome the limitations of NCS in the diagnosis of cutaneous nerve disorders. Recently, with efforts made by clinicians and researchers, new knowledge has accumulated on methods for tracking several cutaneous nerves using US [1,3]. Additionally, the development of high-resolution US allows clinicians to evaluate cutaneous nerve pathologies in greater detail.…”

Ultrasound Findings in Less Frequent Causes of Carpal Tunnel Syndrome

“…[2][3][4][5] Carpal tunnel syndrome due to secondary causes most commonly presents with unilateral involvement, and its suspicion should prompt imaging of the CT to define the etiology of the MN compression. Ultrasound (US) is a cost-effective, dynamic, noninvasive, and patientfriendly imaging modality that allows an accurate assessment of peripheral nerves, 6,7 including the MN within the CT. [8][9][10] The purpose of this pictorial essay is to present the US appearance of less common causes of secondary CTS as well as several lookalike conditions mimicking CTS.…”