Meidastinum OSCE

Middle mediastinum ●​ Pericardium and heart ●​ Root of great vessels ○​ Intrapericardial parts ○​ Ascending aorta ○​ Pulmonary trunk ○​ SVC ■​ Terminal part ○​ IVC ■​ Terminal part ○​ Pulmonary bronchi ●​ Main bronchi ○​ Proximal portion ●​ Phrenic nerves + pericardiacophrenic vessels ○​ Runs on fibrous pericardium Important!! ●​ Phrenic nerve ○​ Anterior to root of lung ●​ Vagus nerve ○​ Posterior to root of lung Pericardium layer ●​ Fibrous pericardium ○​ Tough bag on outer side ○​ Dense CT ○​ Anchors ■​ Central tendon of diaphragm ●​ Inferior ■​ Sternum ●​ Sternopericardial ligament ●​ Anterior ○​ Limit acute over distension of heart ●​ Serous pericardium ○​ Inner part ○​ Slippery sac ○​ Parietal layer ■​ Lining of inner fibrous pericardium ○​ Visceral layer ■​ Epicardium ■​ Heart surface ○​ Between Parietal layer and visceral layer… ■​ Pericardial cavity ■​ Thin film of fluid ■​ Low friction Pericardial Sinus (most likely to be on exam!!) ●​ Made by reflection of serous pericardium around great vessels ○​ Transverse pericardial sinus ■​ Posterior of… ●​ Ascending aorta ●​ Pulmonary trunk ■​ Anterior to… ●​ SVC ■​ Cx ●​ Able to pass clamp and ligature through it ●​ Control arterial outflow ○​ Aorta and pulmonary trunk ○​ Oblique pericardial sinus ■​ Bind recess posterior to left atrium ■​ Reflection around pulmonary veins ■​ IVC ■​ Able to collect fluid on supine ●​ Back of LA region Meidastinum OSCE ●​ Anterior mediastinum ○​ Thymus and remnant ■​ Fat ■​ Nodes ■​ Masses 4Ts ●​ Thymoma ●​ Teratoma ●​ Thyroid ●​ Lymphoma (terrible) ●​ Middle mediastinum ○​ Heart ○​ Pericardium ○​ Great vessel roots ○​ Phrenic ■​ Pericardial effusion/tamponade ■​ Caridomegaly ■​ Lymph nodes ●​ Posterior mediastinum ○​ Aorta ○​ Esophagus ○​ Thoracic duct ○​ Azygos ○​ Symp ○​ Splanchinics ■​ Neurogenic tumors ■​ Esophageal disease ■​ Aortic aneurysm Smx recognition ●​ Facial neck swelling ○​ Distended chest veins and worse bending forward ■​ SVC syndrome ■​ SVC and brachiocephalic veins ■​ Superior mediastinum ●​ Anterior-ish ■​ Lung cancer ■​ Lymphoma ■​ Thrombosis ■​ Mediastinal mass ●​ Hoarseness and cough ○​ Hoarseness new ○​ Recurrent laryngeal nerve involvement ■​ Left RLN ●​ Loops under aortic arch ●​ Left main bronchus ●​ Diaphragm ●​ Dysphagia or food sticking ○​ Progressive ○​ Esophageal compression and intrinsic lesion ○​ Esophagus ○​ Posterior to mediastinum ○​ Constriction sites ■​ Arch of aorta ■​ Left main bronchus ■​ Diaphragm ●​ Stridor ○​ Cough from central obstruction ■​ Tracheal compression ■​ Trachea ●​ Carina region ■​ Superior mediastinum ●​ Trachea is central ●​ Shoulder-tip pain ○​ Especially with pericarditis/diaphragmatic pleura irritation ■​ Phrenic nerve C3-C5 referred pain ■​ Fibrous pericardium ■​ Central diaphragmatic pleura ■​ Peritoneum ■​ Middle mediastinum ●​ Prenic runs on pericardium ●​ Pleural effusion after surgery or trauma ○​ Milky ○​ Chylothorax ○​ Injury of thoracic duct ○​ Posterior mediastinum ■​ Duct ascends ■​ Crosses on left on upper thorax ●​ Hypotension ○​ Increased JVP ○​ Heart sound muffled ○​ Cardiac tamponade ○​ Pericardial cavity pressure ○​ Middle mediastinum Posterior mediastinum ●​ Behind pericardium ●​ Anterior of T5-T12 vertebral bodies ●​ Tube+vessel+nerve corridor along the diaphragm ●​ Aortic arch → runs down on left side of vertebral bodies ●​ Passes along abdomen through aortic hiatus ○​ T12 ○​ Abdominal aorta ●​ Major branches ○​ Posterior intercostal arteries ■​ 2-11 ■​ Supplying intercostal spaces ○​ Subcostal artery ■​ Inferior to rib 12 ○​ Bronchial arteries ■​ To bronchial tree ■​ Small ■​ High-yield ○​ Esophageal branches ■​ Towards esophagus ○​ Mediastinal branches ■​ Small ○​ Superior phrenic arteries ■​ Superior surface of diaphragm Cx ●​ Aneurysm ●​ Dissection ●​ Compress nearby esophagus ○​ Dysphagia ○​ Irritate pain pathway Esophagus in posterior mediastinum ●​ Posterior to trachea on superior position ○​ Continues down towards anterior to vertebral column ○​ Slightly left as it descends ○​ Shifts near diaphragm ●​ Physiologic constriction ○​ Upper esophageal sphincter ■​ Cricopharyngeus ■​ Crossed by aortic arch ■​ Crossed by left main bronchus ■​ Esophageal hiatus in diaphragm ●​ T10 Cx ●​ Common places for foreign bodies lodges ●​ Stricture forms ●​ Reflux and hiatal hernia ties into T10 regions Azygos venous system ●​ Drainage of thoracic wall ●​ Drains posterior thoracic wall ●​ Providing of collateral pathway ○​ Between IVC and SVC system ●​ Azygos vein ○​ Ascends on right side of vertebral bodies ⇒ arches over right lung root ⇒ joins SVC ■​ Close to T4 and T5 plane area ●​ Hemiazygos vein ○​ Ascends on left lower side ○​ Crosse midline to join azygos ●​ Accessory hemiazygos vein ○​ Draining left upper posterior intercostals ○​ Crosses to azygos Cx ●​ SVC obstruction ●​ Azygos system can enlarge = bypass route Superior mediastinum ●​ Mediastinum ○​ Central compartment of thorax ○​ Between pleural cavities ●​ Superior mediastinum ○​ Above transverse thoracic plane ○​ Sternal angle ■​ T4 and T5 disc ●​ Boundaries ○​ Anterior ■​ Manubrium ○​ Posterior ■​ Bodies of T1 and T4 ○​ Superior ■​ Thoracic inlet ○​ Inferior ■​ Plane of sternal angle ●​ T4 and T5 ○​ Lateral ■​ Mediastinal pleura ●​ Cx significant ○​ Traffic junction ■​ Great vessels ■​ Airway ■​ Esophagus ■​ Big nerves Front ⇒ back contents ●​ Thymus ○​ Fatty tissues in adults ●​ Veins ○​ Brachiocephalic veins → SVC ●​ Arteries ○​ Arch of aorta ○​ Branches ■​ Brachiocephalic trunk ■​ Left common carotid ■​ Left subclavian ○​ Trachea ○​ Esophagus ○​ Thoracic duct ■​ One of the most posterior of the major tube Useful for exams!!! Key vessels ●​ Brachiocephalic veins + SVC ○​ Right + left brachiocephalic veins ⇒ SVC ■​ Upper right mediastinum ○​ Left brachiocephalic vein tends to be longer ■​ Run obliquely on midline ■​ Behind manubrium ■​ Left-sided venous blood tends to reach right-sided SVC ●​ Arch of aorta ○​ Curving over left main bronchus region ○​ Become descending aorta ○​ BCT ⇒ LCC ⇒ LS Inferior mediastinum ●​ Mediastinum inferior to the transverse thoracic plane ●​ Sternal angle → T4/5 ●​ Superior to the diaphragm ●​ Subdivisions ○​ Front→back ■​ Anterior mediastinum ●​ Smallest ●​ Anterior ○​ Sternum ○​ Transversus thoracis ●​ Posterior ○​ Fibrous pericardium ●​ Superior ○​ Continuous with superior mediastinum ●​ Inferior ○​ Diaphragm ●​ Lateral ○​ Mediastinal pleura ●​ Mostly empty ○​ Fat and loose CT ○​ Lymph nodes and vessels ○​ Inferior parts of thymus ■​ Mainly present in child\ ■​ Remnant in adults ○​ Small branches of internal thoracic vessels ●​ Cx ○​ Anterior mediastinal mass differential ■​ Thymoma ■​ (Terrible) lymphoma ■​ Thyroid ●​ Ectopic ●​ Retrosternal ■​ Teratoma ■​ Middle mediastinum ●​ Heart compartment ●​ Pericardium + heart ●​ Roots of great vessels ○​ Ascending aorta ○​ Pulmonary trunk ○​ SVC ■​ Intrapericardial part ○​ IVC ■​ Terminal part ○​ Pulmonary veins ●​ Main bronchi ○​ Proximal parts ●​ Phrenic nerves ○​ Pericardiacophrenic vessels ■​ On fibrous pericardium Phrenic N. is anterior to lung root since vagus is posterior to lung root ■​ Posterior mediastinum ●​ Tube ●​ Anterior ○​ Pericardium ●​ ●​ ●​ ●​ ●​ ●​ ●​ ●​ ●​ ●​ ●​ ○​ Diaphragm ■​ Central tendon region Posterior ○​ T5-T12 vertebral bodies Inferior ○​ Diaphragm Superior ○​ Continuous with superior mediastinum Lateral ○​ Mediastinal pleura Descending thoracic aorta Esophagus ○​ Esophageal plexus Thoracic duct Azygos system ○​ Azygos ○​ Hemiazygos ○​ Accessory hemiazygos Sympathetic trunks Splanchnic nerves ○​ Greater ○​ Lesser ○​ Least Cx ○​ Posterior mediastinal masses are often neurogenic ■​ Sympathetic chain ■​ Schwannoma types ○​ Esophageal disease ⇒ present with mediastinal symptoms ■​ Aorta pathology ⇒ compress adjacent structures