Neuromuscular Ultrasound in Cervical Nerve Root Avulsion

A 22-year-old man was injured in a high-speed motor vehicle collision, sustaining multiple limb fractures and pneumothoraxes. Immediately following the accident, he had difficulty moving his right upper limb. A brachial plexus injury was suspected. He was referred for electrodiagnostic studies (EDX) 3 months later, without imaging studies available for review. At the time of EDX, he described minimal strength improvements since the accident. The examination revealed atrophy of the right deltoid and rotator cuff muscles, which had 0 of 5 strengths, respectively, on the Medical Research Council (MRC) scale. Right biceps brachii was atrophic with MRC 2 of 5 strengths. Sensation was reduced around the right upper shoulder and the right lateral forearm. EDX results suggested a severe nerve injury involving both the upper trunk of the brachial plexus and the nerve roots on the right. Neuromuscular ultrasound (NMUS) was performed using a 4–12 MHz linear transducer. Ultrasound findings were most concerning for a C6 nerve root avulsion (Fig 1). This finding dramatically impacts treatment as reinnervation cannot occur in a nerve root avulsion. Ultrasound additionally demonstrated less marked right upper trunk enlargement. MRI imaging was obtained, confirming a pseudomeningocele at C6, the key finding of a traumatic nerve root avulsion. MRI also demonstrated enhancement of the upper trunk. The patient underwent multiple nerve transfer surgeries attempting to restore innervation to the right deltoid, biceps brachii, and supraspinatus muscles. NMUS provides rapid and valuable information complementary to EDX in brachial plexus injuries. Previous case reports suggest the ultrasound finding of a large hypoechoic structure, adjacent to the nerve root at the neural foramen may indicate nerve root avulsion.1 The ultrasonographic beam cannot penetrate bone to image into the neural foramen, an advantage of MRI imaging, the gold standard in nerve root avulsion.1 In our case, the pseudomeningocele did not extend past the neural foramen on MRI (Fig 1). The ultrasound images obtained reflect the significant nerve root injury but likely also demonstrate additional pathology such as edema and inflammation in the nerve root. These ultrasound images demonstrate the ability of NMUS to add to patient care in cases of traumatic brachial plexus injuries. Panel (A) T2 STIR coronal MRI image demonstrating C6 nerve root enhancement and illustrating ultrasound transducer placement for long axis (panel B) and short axis (panel D) NMUS images. Panel (B) Long axis ultrasound image of the markedly enlarged C6 nerve root. Proximally, the root is diffusely hypoechoic. Distally, there is mixed hyper- and hypoechoic contents with nerve fascicles visualized. Panel (C) T2 axial MRI image of pseudomeningocele at the right C5-C6 neural foramen. Panel (D) Short axis ultrasound image of the C6 nerve root. This level is confirmed using bony anatomy; at this level, the transverse process has a large anterior tubercle (arrow).2 There is a large hypoechoic structure with a hyperechoic border (arrowhead) and increased Doppler flow suggesting increased vascularity (not shown). Internally, there is a region of hyperechogenicity which may represent neural elements. The cross-sectional area measuring inside the hyperechoic border is 63 mm2 (normal 5–11 mm2).3 None. N.M., J.M., J.C., and M.C. contributed to the conception and design of the study; N.M. and J.C. contributed to the acquisition and analysis of the data; N.M., J.M., and M.C. contributed to drafting the text and preparing the figures. Nothing to report.