Kiloh-Nevin syndrome / anterior interosseous nerve syndrome
The patient presented clinically with a Kiloh-Nevin or anterior interosseus nerve syndrome. MRI confirmed the clinical findings, revealing denervation-induced edema of the flexor pollicis longus (FPL) , flexor digitorum profundus (FDP) and pronator quadratus (PQ) muscles; typically, only the radial aspect of the FDP was affected.
The median nerve is prone to entrapment syndromes, the best-known of which is carpal tunnel syndrome. Two other distinct entities are pronator teres syndrome and anterior interosseous nerve, or Kiloh-Nevin syndrome.
Etiologically, direct trauma, muscle entrapment or entrapment by fibrous bands, aberrant vessels or adjacent pathology ( e.g. callus, soft tissue masses), and idiopathic are the most common causes; primary nerves tumor are a further, rarer consideration. Differential diagnoses are other entrapment syndromes (often with distinct clinical and neurophysiological findings) and brachial neuroplexitis / Parsonage-Turner syndrome.