Résumé
Lesions of the brachial plexus are most commonly caused by traumatic injuries. Other causes include infiltration by tumors, intrinsic or extrinsic compressions, damage from radiation therapy, or neuralgic amyotrophy (Parsonage-Turner syndrome). Less frequent causes of brachial plexus lesions include metabolic disease (e.g. diabetes), viral infections, immunological reactions to vaccination or infections, drugs, malignancies, paraneoplastic conditions, or hereditary disease (SEPT9 mutations, HNPP). The diagnosis of brachial plexus lesion is based upon history, clinical examination, and instrumental investigations, particularly, nerve conduction studies, electromyography, evoked potentials, magnetic stimulation, and the MRI. Treatment depends on the cause of the plexus lesion and includes prophylactic measures, physiotherapy, drugs, or surgery. Rarely applied measures include therapeutic magnetic stimulation or pulsed radiofrequency treatment. Outcome of plexus lesions depends on the underlying cause and the effectiveness of the treatment and ranges from favorable to deleterious. The outcome can be improved if diagnosis is made early and treatment is immediately applied after diagnosis.