Anterior interosseus syndrome

Anterior interosseous syndrome (AIS) is a neurological condition characterized by dysfunction or compression of the anterior interosseous nerve (AIN), which is a branch of the median nerve. The anterior interosseous nerve provides motor innervation to specific muscles in the forearm, and its compression can lead to weakness and impairment of certain hand and finger movements.

Key features of Anterior Interosseous Syndrome include:

  1. Etiology:
  • AIS is often caused by compression or injury to the anterior interosseous nerve, which is a branch of the median nerve. Common causes include trauma, nerve entrapment, and less frequently, inflammatory or neoplastic conditions affecting the nerve.
  1. Clinical Presentation:
  • Weakness in specific muscles of the forearm, particularly the flexor pollicis longus (responsible for flexing the thumb), the flexor digitorum profundus to the index finger, and, in some cases, the pronator quadratus.
  • Weakness may result in difficulty making an “O” shape with the thumb and index finger (OK sign) due to the impaired flexion of the thumb.
  • Sensory function is generally preserved, as the anterior interosseous nerve primarily carries motor fibers.
  1. Diagnosis:
  • Clinical examination and history are crucial in the diagnosis of AIS. Physicians may assess muscle strength, coordination, and the ability to perform specific hand movements.
  • Electrodiagnostic studies, such as nerve conduction studies and electromyography (EMG), may be used to confirm the diagnosis and determine the extent of nerve involvement.
  1. Treatment:
  • Conservative management is often the first approach and may include rest, activity modification, and physical therapy to maintain range of motion and strength.
  • In cases of persistent symptoms or severe nerve compression, surgical intervention to release the nerve may be considered.
  1. Prognosis:
  • The prognosis for AIS varies based on the underlying cause and the degree of nerve involvement. With appropriate treatment, many individuals experience improvement in symptoms over time.

It’s important for individuals experiencing symptoms suggestive of anterior interosseous syndrome to seek medical evaluation. A healthcare professional, typically a neurologist or orthopedic specialist, can perform a thorough examination and diagnostic tests to determine the underlying cause and develop an appropriate treatment plan.