US of the Peripheral Nerves of the Upper Extremity: A Landmark Approach

Abstract

Ultrasonography (US) has become a first-line modality for the evaluation of the peripheral nerves of the upper extremity. The benefits of US over magnetic resonance (MR) imaging include higher soft-tissue resolution, cost effectiveness, portability, real-time and dynamic imaging, and the ability to scan an entire extremity quickly and efficiently. US can be performed on patients who are not eligible for MR imaging. Metallic implant artifacts are usually not problematic. US has been shown to have equal specificity and greater sensitivity than MR imaging in the evaluation of peripheral nerves. Any abnormal findings can be easily compared with the contralateral side. The published literature has shown that US has demonstrated clinical utility in patients with suspected peripheral nerve disease by guiding diagnostic and therapeutic decisions as well as by confirming electrodiagnostic findings. Common indications for upper extremity peripheral nerve US are the evaluation for injury due to penetrating trauma, entrapment by scar tissue, and tumor. US of the upper extremity is most commonly performed to evaluate carpal and cubital tunnel syndrome. It is important for the radiologist or sonographer to have a detailed knowledge of anatomy and specific anatomic landmarks for each nerve to efficiently and accurately perform an examination. The goal of this article is to introduce readers to the basics of US of the peripheral nerves of the upper extremity with a focus on the median, ulnar, and radial nerves. Common sites of disease and the location of important anatomic landmarks will be reviewed.

Ultrasonography of Hands and Wrists in the Diagnosis of Complications of Chikungunya Fever

“…Median nerve ultrasound measurements have a sensitivity of 89% and a specificity of 83% for a CTS diagnosis, which makes this method an important tool for the rapid diagnosis of this complication and for monitoring its progression and perhaps as a criterion of severity that should be evaluated in prospective CHIKF studies . As occurs in other conditions, such as mucopolysaccharidosis, in which ultrasound demonstrates good sensitivity and specificity, and hypothyroidism, in which the method is quite specific, CTS can be detected in CHIKF in association with clinical data and may prove to be as accurate as electroneuromyography …”

Sonography of the Pronator Teres: Normal and Pathologic Appearances

“…An anatomic variation of the brachial artery may also occur. In this case, its proximal division, with its presence at the elbow of the ulnar and radial arteries, is well depicted on Doppler sonography (Figure ) …”

“…Sonograms at this level allow depiction of the median nerve located between the two pronator teres heads (below the humeral head and superficial to the ulnar head). The ulnar artery can be seen immediately below the ulnar head, which is then located between the median nerve and ulnar head . A dynamic sonographic examination performed at this level is necessary to assess potential compression of the median nerve by the pronator teres.…”

“…Anteroposterior and lateral radiographs are the reference standards for an inexpensive evaluation of this anatomic variant (Figure ). Clinically, a reduction or suppression of radial artery pulsations during supination‐extension of the forearm, due to compression of the brachial artery which accompanies the median nerve under this ligament, can be noted . The lacertus fibrosus, an aponeurotic band located between the bicipital tendon and pronator teres fascia, may also compress the median nerve and brachial artery (Figure ) .…”

Optimal Radial Motor Nerve Conduction Study Using Ultrasound in Healthy Adults

“…First, we hypothesized that the lateral edge of the spiral groove was the optimal stimulation site for radial motor NCS. In the forearm, the radial nerve is located in the deep layer with nearby radial-innervated muscles, and the diameter of the radial nerve is much smaller than at the spiral groove (4.61±0.88 mm 2 vs. 1.99±0.43 mm 2 ) [192021]. For these reasons, there may be several significant technical errors when stimulation is conducted at the forearm compared with the spiral groove, such as exaggerated CMAP response via volume-conducted potentials from nearby radial-innervated muscles, initial positive deflection with unclear onset latency, or lower CMAP amplitude caused by insufficient stimulation.…”