Proximal Median Mononeuropathy

1. What is the Ligament of Struthers and how does the median nerve become entrapped in this region? What is the presentation?
2. What is the bicipital aponeurosis and how does the median nerve become entrapped in this region? What is the presentation?
3. What is pronator teres syndrome and how does it present?
4. What is anterior interosseous syndrome?


Answers:
1. The ligament of Struthers is a ligament that connects the medial epicondyle to a bone spur 3-6cm proximal to the medial epicondyle in 1% of the population. The brachial artery and median nerve pass under this ligament and may become entrapped. There is weakness of all median innervated nerves (pronation, wrist flexion, finger flexion) and there may be decreased brachial pulse. SNAP and CMAP are abnormal.
2. The bicipital aponeurosis is a thickening of the antebrachial fascia attaching the biceps to the ulna, overlying the median nerve in the proximal forearm. It can be injured by entrapment or hematoma (from blood draw). It presents similarly to entrapment in the ligament of Struthers.
3. PT syndrome is when the median nerve becomes entrapped during its course between the two heads of the PT or by the bridging fascial band of the FDS. It presents with dull ache in proximal forearm exaggerated by pronation or finger flexion. The PT is usually spared. SNAP and CMAP are abnormal.
4. AIS is a motor syndrome, although the AI also provides sensation to the wrist joint. The FPL is usually affected first. It is injured by fractures of the forearm, lacerations, or compression. Patient may have positive OK sign (difficult to make OK sign due to FPL, FDP weakness). SNAP is normal, CMAP may be abnormal to pronator quadratus.