Diaphragm Eventration

The diaphragm begins to develop between the fourth and twelfth weeks of embryogenesis. During this period, the central tendon is formed from the anterior septum transversum, which then merges with the pleuroperitoneal folds on the sides and the dorsal mesentery of the esophagus in the center, creating the initial structure of the diaphragm. Additionally, the muscular portions of the diaphragm arise from the peripheral cervical somites at levels C3 to C5. Upon its formation, the diaphragm is a dome-shaped structure measuring approximately 2 to 4 mm in thickness and is located at the lower boundary of the thoracic cavity. The central tendon, positioned beneath the heart, is fused with the parietal pericardium. At the same time, the surrounding muscle fibers attach to the sternal xiphoid process, the lower ribs, and the upper lumbar vertebrae. The crura, which anchors the diaphragm to the lumbar vertebrae, consists of the right crus attaching to vertebrae L1 to L3 and the left crus attaching to L2 to L3 (see Normal Diaphragm Anatomy).  The diaphragm is vital in the inspiratory phase of respiration and acts as a barrier between the thoracic and abdominal cavities. The left and right phrenic nerves provide the motor function to each hemidiaphragm, respectively, and impaired development or injury to this nerve can lead to diaphragmatic paralysis and diminished lung expansion. Diaphragmatic eventration is the abnormal elevation of a portion or entire hemidiaphragm due to a lack of muscle or nerve function while maintaining anatomical attachments. The abnormality can be congenital or acquired, thus presenting in pediatric and adult populations.  In both congenital and acquired eventration, a portion of the diaphragm is weakened and thin, causing reduced function. Patients may be asymptomatic or present with respiratory symptoms depending on the severity. Diagnosis is confirmed by radiographic imaging, and treatment usually consists of supportive care and, in some cases, surgical plication.