PMC8062872_01
Imaging findings for Patient 1. (A,B) Computed tomography (CT) angiography performed with 180  shoulder abduction. (C-E) Brachial plexus magnetic resonance imaging (MRI). (A) Coronal image showing the tip of the left cervical rib arising from the C7 vertebra (arrow) abutting the left subclavian artery (arrowhead). (B) Sagittal image showing the tip (arrow) compressing the subclavian artery (arrowhead) in the anterior direction, causing stenosis. (C) Coronal maximum intensity projection (MIP) image showing stenosis of the left subclavian artery (arrowhead). (D) Coronal T2-weighted fat suppression MIP image showing upward angulation of the lower trunk (arrow), presumably caused by the anterior tip of the cervical rib, although not shown in this image. Swelling or abnormal signal intensity of the brachial plexus was not definite. (E) Oblique sagittal T2-weighted fat suppression image showing the spatial associations of the anterior tip of the cervical rib (arrow), brachial plexus (U, upper trunk; M, middle trunk; L, lower trunk), and subclavian artery (arrowhead).
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F1
Computed tomography (CT) angiography of her upper extremities performed in 180  shoulder abduction showed the left cervical rib arising from the C7 vertebra and mild stenosis of the left subclavian artery near the lateral tip of the cervical rib, suggesting arterial thoracic outlet syndrome (A-TOS) (Figures 1A-C). Brachial plexus magnetic resonance imaging (MRI) revealed upward and anterior angulation and displacement of the left lower trunk or C8/T1 extraforaminal nerve roots of the brachial plexus, presumably caused by the anterior tip of the cervical rib (Figures 1D,E).
PMC8062872_02
Imaging findings for Patient 2. (B-D) Computed tomography (CT) angiography performed with 180  shoulder abduction. (E,F) Brachial plexus magnetic resonance imaging (MRI). (A) Plain radiograph of the cervical spine showing upwardly convex curvature and an anomaly of the right first rib (arrow). (B) When viewed from the front, a reconstruction image using volume rendering shows stenosis (arrow) and post-stenotic dilatation (arrowhead) of the right subclavian artery. (C) Axial image showing the spatial relationships of the anomalous right first rib (arrow) articulating with the second rib, narrowed subclavian artery (arrowhead), and clavicle (voided arrow). (D) Maximum intensity projection (MIP) image showing thromboembolic occlusion of the right brachial artery at the elbow level (circle). (E) Coronal T2-weighted fat suppression MIP image showing a high-riding right T1 extraforaminal root and lower trunk (arrow) compared to those on the opposite side. Abnormal signal intensity of the brachial plexus was not definite. (F) Axial T2-weighted fat suppression MIP image showing anterior angulation of the right lower trunk (arrow) by the anomalous right first rib (arrowhead).
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F2
The patient's right first rib was anomalous (upwardly convex and anterior tip fused with the second rib) in cervical spine plain radiograph (Figure 2A). Segmental thromboembolic stenosis of the right brachial artery was also observed (Figures 2B-D). Brachial plexus MRI revealed high-riding T1 extraforaminal nerve root or lower trunk compared with that of the left side and anterior angulation of the right lower trunk by the anomalous right first rib (Figures 2E,F).