PMC4891580_01
39-year-old woman with right radial neuropathy on electrodiagnostic testing.. A. Longitudinal sonogram of the right posterior interosseous nerve demonstrates fusiform swelling (arrowheads) of the nerve immediately before it pierces the supinator muscle (S). Within the muscle the nerve is almost imperceptible (arrow).. B. Longitudinal sonogram of the left posterior interosseous nerve performed for comparison demonstrates normal caliber of the nerve both proximal to (arrowheads) and within (arrow) the supinator muscle (S).. C. Short axis sonogram of the right posterior interosseous nerve (arrow) just proximal to the supinator muscle (S) demonstrates swelling, with short axis dimension 2mm. R = radius.. D. Short axis sonogram of the left posterior interosseous nerve (arrow) just proximal to the supinator muscle (S) performed for comparison demonstrates normal caliber of the nerve, with short axis dimension 1mm. R = radius. [Powerpoint Slide]
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Findings showed that the radial nerve and proximal posterior interosseous nerve (PIN) were normal, but just proximal to the supinator, the PIN swelled to 2 mm compared with 1 mm on the asymptomatic left side (Fig. 1 A-D). Although follow up US demonstrated persistent swelling of the PIN proximal to the supinator muscle, compared to the preoperative US the nerve was of higher caliber within the supinator itself, consistent with successful radial tunnel release (Fig. 1E).