Anterior interosseous nerve

Anterior Interosseous Nerve

The anterior interosseous nerve (AIN) is a motor branch of the median nerve that is primarily responsible for the innervation of several muscles in the forearm. It originates in the upper forearm, just below the elbow, and extends down to the wrist. The AIN is crucial for the functionality of the forearm and hand, particularly in movements involving the flexion of the thumb and index finger.

Anatomy

The anterior interosseous nerve branches off from the median nerve approximately 5 to 8 cm distal to the lateral epicondyle of the humerus. It descends along the interosseous membrane of the forearm, lying between the flexor digitorum profundus and the flexor pollicis longus muscles, which it innervates. Additionally, it supplies the pronator quadratus muscle, a deep muscle of the forearm that plays a significant role in the pronation of the forearm.

Function

The primary function of the anterior interosseous nerve is to innervate the flexor pollicis longus, the radial half of the flexor digitorum profundus, and the pronator quadratus. These muscles are essential for the flexion of the thumb and index finger, as well as the pronation of the forearm. The AIN does not have any sensory fibers; therefore, it does not contribute to the sensation in the hand or forearm.

Clinical Significance

1. 1. 1. Anterior Interosseous Nerve Syndrome

Anterior interosseous nerve syndrome (AINS) is a condition characterized by weakness or paralysis of the muscles innervated by the AIN. Patients with AINS may have difficulty performing the "pinch" gesture, where the thumb and index finger are brought together. This condition can result from trauma, compression of the nerve, or idiopathic causes.

1. 1. 1. Diagnosis and Treatment

Diagnosis of AINS involves clinical examination and may be supported by electromyography (EMG) and nerve conduction studies. Treatment typically focuses on relieving the compression of the nerve, which may involve physical therapy, anti-inflammatory medications, or surgical intervention in severe cases.

See Also

• Median nerve
• Nerve compression syndrome
• Forearm anatomy
• Motor neuron