CT OF THE MEDIASTINUM

DR SAKHER-ALKHADERICONSULTANT RADIOLOGIST AMC

Teaching Point : Each compartment of the mediastinum could have

Pericardial (mesothelial) cysts result from aberrations in the formation of coelomic (somatic) cavities. The cyst walls are composed of connective tissue and a single layer of mesothelial cells (Fig 6), and they usually contain clear fluid. Pericardial cysts are invariably connected to the pericardium,

Bronchogenic cysts are congenital malformations of the bronchial tree (type of bronchopulmonary foregut malformation). They can present as a mediastinal mass that may enlarge and cause local compression. It is also considered the commonest of foregut duplication cysts.

INTRAPULMONARY BROCHOGENIC CYST

DistributionCan be broadly classified as mediastinal and intrapulmonary types. The most common location is the middle mediastinum (65-90%). The distribution of locations can be quite varied :mediastinal (~70%) 5

usually does not communicate with the tracheo-bronchial treesubcarinal, right paratracheal and hilar locations most common approximate incidence includes

carinal area: ~50%paratracheal area: ~20%oropharangeal wall: ~15%retrocardiac area: ~10% 

parenchymal (intrapulmonary)typically perihilarpredilection for lower lobes 1

other uncommon locationsneckcutaneous 2

pericardium 5

extending across the diaphragm and appearing dumb-bell shaped 1

retroperitoneal 3

Esophageal duplication cysts are developmental in origin and are classified as foregut cysts that are either bronchogenic or neurenteric (15). Esophageal duplication cysts are uncommon. Many are asymptomatic, but they may cause dysphagia, pain, or other symptoms owing to compression of adjacent structures (16). The majority are detected in infants or children (16), usually adjacent to or within the esophageal wall. Ectopic gastric mucosa in the cyst may cause hemorrhage or perforation of the cyst, or infection

Thymic CystThymic cysts are uncommon and represent 1% of all mediastinal masses (25). They can be congenital or acquired.   Acquired thymic cysts may occur in patients after radiation therapy for Hodgkin disease (27), in association with thymic tumors (28), and after thoracotomy (29). They may be unilocular or multilocular (26). 

HEMANGIOMA

Extramedullary haematopoiesis (EMH) is a response to erythropoiesis failure in bone marrow. EMH occurs in haemoglobinopathies, myeloproliferative disorders, or bone marrow infiltration. EMH occurs most often in the spleen and liver and occasionally in the lymph nodes. Less common organs include the pleura, lungs, posterior mediastinum , gastrointestinal tract, breast, skin, brain, kidneys, and adrenal glands.

Lateral thoracic meningiocele

MeningoceleAn intrathoracic meningocele is an anomalous herniation of the leptomeninges through an intervertebral foramen or a defect in the vertebral body. This abnormality is frequently associated with neurofibromatosis. Most meningoceles are detected in adults (23). On conventional radiographs, they appear as sharply defined round, smooth, or lobulated paraspinal masses. However, they demonstrate no specific features that distinguish them from neurogenic neoplasms. At CT, they appear as well-defined, homogeneous, low-attenuation paravertebral masses (Fig 7). Other findings may include enlargement of intervertebral foramina and associated vertebral and rib anomalies or scoliosis (5). CT or myelography performed after intraspinal injection of contrast material shows filling of the meningocele and helps confirm the diagnosis (Fig 7) (2

More than one compartment

LymphangiomaLymphangiomas are rare, benign congenital malformations consisting of focal proliferations of well-differentiated lymphatic tissue that are present in a multicystic or spongelike accumulation (41). They represent 0.7%–4.5% of all mediastinal tumors (42). The majority of lymphangiomas are discovered during the first 2 years of life.

 Lymphangioma in a 35-year-old man with a history of multiple resections of cystic hygroma since infancy. (a) Chest radiograph shows a large mediastinal mass. (b) Contrast-enhanced CT scan shows a low-attenuation mass (arrow) that extends to all mediastinal compartments. (c) Coronal T2-weighted MR image shows a high-signal-intensity cystic mass with multiple septa (arrows).

THE END