Anterior interosseous nerve syndrome: unusual etiologies.

The anterior interosseous nerve is a pure motor nerve supplying the flexor pollicis longus, flexor digitorum profundus to the index and middle finger, and the pronator quadratus. A relatively uncommon neuropathy of this nerve, called the anterior interosseous syndrome (AIS), sometimes occurs. This paper reports 2 cases of AIS which developed from unusual etiologies. The first patient developed AIS after some difficulty drawing blood from the cubital vein, while the second patient developed symptoms following bypass surgery involving intravenous injection in the cubital vein. Although the diagnosis of AIS can be made clinically by noting muscle weakness in the absence of sensory deficits, electrodiagnosis is helpful for confirming diagnosis and predicting prognosis.