Mediastinum Flashcards
mediastinal compartments
anterior: prevascular and precardiac anterior mediastinum (sternum/pericardium, ascending aorta)
middle: (heart and posterior tracheal wall)
posterior: (posterior trachea and posterior pericardium)
contents of anterior mediastinum
thymus, lymph nodes, thyroid gland if it extends inferiorly
middle mediastinum contents
heart, ascending aorta/arch, great vessels, trachea/bronchi, LN, phrenic/vagus/recurrent laryngeal nerves (pass through AP window)
posterior mediastinum
esophagus, descending thoracic aorta, azygos/hemiazygos, thoracic duct, vagus nerve, LN
define: line, stripe, interface on CXR
line: interface of tissue with air on both sides
stripe: air and adjacent soft tissues
interface: contact of two soft tissue structures of different densities
anterior junction line
4 layers of pleura between R/L lung, anterior junction
projects over superior 2/3 of sternum
abnormality suggests anterior mediastinal mas
posterior junction line
4 layers of pleura between R/L lung, anterior junction
projects through trachea; above clavicles
abnormality: posterior mediastinal mass/aortic aneurysm
paratracheal stripes
pleura where medial aspect of lung abuts trachea
abnormal R paratracheal stripe: pleural thickening, or paratracheal mass/thyroid
abnormal L paratracheal stripe: as above + mediastinal hematoma
posterior tracheal stripe
posterior wall of trachea and pleura of medial R lung
seen only on lateral radiograph
paraspinal lines
interfaces that appear as lines abutting posterior mediastinum
abnormal: posterior mediastinal mass–hematoma, neurogenic tumor, aortic aneurysm, extramedullary hematopoiesis, esophageal mass, osteophyte
azygoesophageal recess
posteromedial RLL and retrocardiac mediastinum
abnormal: esophageal mass, hiatal hernia, left atrial enlargement, LN
AP window
bound by aortic arch and top of pulmonary artery as well as esophagus/trachea/left mainstem bronchus
abnormal bulging of AP window ddx
LN, left phrenic nerve, recurrent laryngeal nerve, left vagus nerve, ligamentum arteriosum, left bronchial arteriosum, thoracic aortic aneurysm
retrosternal space
lateral radiograph, anterior mediastinum
obliteration: mass, RV dilation, pulmonary artery enlargement
increased: emphysema
aortic nipple
left superior intercostal vein
small round shadow to the left of the aortic knob on AP
may dilate in SVC obstruction
hilum overlay sign
hilar vessels visualized through mass
mass must be in anterior/posterior mediastinum, NOT middle
localizing mass to anterior mediastinum on XR
hilum overlay sign
obliteration of retrosternal clear space
localizing middle mediastinal mass
distortion of paratracheal stripes
convexity of AP window
localizing posterior mediastinal mass on XR
distortion of azygoesophageal recess, posterior junction line, displacement of paraspinal lines
anterior mediastinal mass
thymoma/thymic epithelial neoplasm, teratoma/germ cell tumor, thyroid, terrible lymphoma
thymoma
45-60yo, associated with myasthenia gravis
also associated with red cell aplasia, hypogammaglobulinemia, paraneoplastic syndrome, malignancy
considerations for thymoma
intact capsule, invasion
invasion into airways, chest wall, great vessels, phrenic nerve
check for elevation of hemidiaphragm
drop mets to pleural/pericardial surfaces
thymic carcinoma
poor prognosis, aggressive and mets to lungs, liver, brain, bone
thymic carcinoid
neural crest origin; hormonally active and can secrete ACTH (cushings)
associated with MEN I/II
scan with In-111 octreotide
thymic cyst
secondary to radiation therapy (Hodgkin), AIDS (multilocular), or congenital (thymopharyngeal duct)
thymolipoma
fat lesion interspersed with soft tissue
germ cell tumor (anterior mediastinum)
teratoma and seminoma
most are benign although malignant GCT usually in males
most common anterior mediastinal germ cell tumor
teratoma
teratoma imaging features (anterior mediastinum)
encapsulated, cystic with fat/calcifications; may be malignant if large and irregularly shaped
seminoma
most common malignant mediastinal germ cell tumor
exclusively in men
thyroid lesions
goiter, thyroid neoplasm, thyroiditis
mediastinal mass: lymphoma
HL and NHL
superior mediastinal nodes involved: prevascular, AP, paratracheal
non-lymphomatous adenopathy
silicosis, coal workers pneumoconiosis, sarcoidosis, active TB, fungal infection, Castleman disease, vascular mets (RCC, thyroid, lung sarcoma, melanoma)
Castleman disease
angiofollicular lymph node hyperplasia; vascular thoracic lymph node enlargement
children/young adults OR older patients/AIDS
systemic disease: fevers/anemia/lymphoma
treat: surgical resection and chemotherapy for systemic dx
epicardial fat pad
silhouettes cardiac border on frontal radiograph; may look like cardiomegaly
pericardial cyst
benign cystic lesion at right CP angle
morgagni hernia
diaphragmatic hernia through foramen of Morgagni containing omental fat/bowel; right side
middle mediastinal masses
lymphadenopathy, ascending aortic arch/aneurysm, enlarged PA, foregut duplication cyst
hilum convergence sign
peripheral pulmonary arteries converge into a “mass”
foregut duplication cysts
bronchogenic cysts, esophageal duplication cyst, neurenteric cyst
posterior mediastinal mass
neurogenic tumor, hiatal hernia, descending TAA, extramedullary hematopoiesis, lateral meningocele , esophageal neoplasm, foregut duplication cyst, paraspinal abscess
neurogenic tumors: PNS and SNS
peripheral nerve tumors (adults): schwannoma, neurofibroma, malignant peripheral nerve sheath tumor
sympathetic ganglion tumor (peds): ganglioneuroma, neuroblastoma, ganglioblastoma
posterior mediastinal mass: hiatal hernia XR
air fluid level above diaphragm
posterior mediastinal mass: extramedullary hematopoeisis
soft tissue paravertebral mass in pts with severe hereditary anemia or thalassemia/sickle cell
may represent herniation of vertebral marrow or elements of reticuloendothelial system
bilateral and inferior to T6
posterior mediastinal mass: lateral meningocele
herniation of spinal meninges through intervertebral foramen or vertebral body defect; associated with NF
