A desk worker complains of aching pain over the volar proximal forearm aggravated by repetitive pronation, with paraesthesia over the lateral three and a half digits and weakness of thumb abduction. On examination, resisted pronation of the forearm reproduces the symptoms and there is weakness of flexor carpi radialis. Which structure is most likely compressing the nerve?
- A Thickened edge of the lacertus fibrosus at the bicipital aponeurosis ✓
- B Transverse carpal ligament
- C Arcade of Struthers
- D Gantzer muscle accessory head of flexor pollicis longus
Correct answer: A. Thickened edge of the lacertus fibrosus at the bicipital aponeurosis
Explanation
Pronator teres syndrome involves median nerve compression between the two heads of pronator teres, under the lacertus fibrosus or the arch of flexor digitorum superficialis. Unlike carpal tunnel syndrome, it features aching proximal forearm pain, reproduction on resisted pronation and involvement of proximal median muscles such as flexor carpi radialis and pronator teres. The arcade of Struthers relates to the ulnar nerve at the distal arm.
Reference: Snell's Clinical Anatomy by Regions, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.