DOI: https://doi.org/10.36347/sjmcr.2026.v14i05.078

Pages: 1194-1196

Posterior interosseous nerve syndrome is an uncommon compressive neuropathy of the deep motor branch of the radial nerve, typically presenting with motor deficit without sensory impairment. Among its causes, synovial ganglion cysts arising from the proximal radioulnar joint represent a rare but important etiology. We report a case of progressive finger extension weakness related to posterior interosseous nerve compression by a synovial ganglion cyst. MRI demonstrated a well-defined cystic lesion arising from the proximal radioulnar joint extending into the radial tunnel and compressing the posterior interosseous nerve with associated denervation muscle edema. Early imaging diagnosis is essential for appropriate surgical management and favorable functional recovery [1].