What are the main characteristics of anterior interosseous syndrome?

The main characteristics of anterior interosseous syndrome primarily revolve around weakness in the muscles innervated by the anterior interosseous nerve (AIN), which is a branch of the median nerve. This syndrome is characterized by weakness in the flexor pollicis longus, the lateral half of the flexor digitorum profundus, and the pronator quadratus. Patients may present with difficulty in pinching, gripping, or performing tasks that require thumb and index finger function because of this weakness.

The anterior interosseous nerve does not carry sensory fibers, which means that sensory loss in the hand is not a typical feature of this syndrome. Instead, patients experience motor deficits without associated sensory disturbances. The syndrome is also not characterized by pain localized to the shoulder region, as it is strictly a condition presenting with specific muscle weakness and not broad musculoskeletal pain. Additionally, wrist extensors are innervated by the radial nerve, and their weakness would not be a symptom of anterior interosseous syndrome, which focuses on the muscles served by the AIN. Thus, the correct identification of weakness in the muscles innervated by the AIN effectively encapsulates the essence of anterior interosseous syndrome.