313.1 🎓 醫孞生版

313.1.0.1 📌 䞀頁重點

313.1.0.1.1 Mediastinum Anatomy
313.1.0.1.1.1 Compartments
  • Anterior mediastinum: anterior to pericardium
  • Middle mediastinum: pericardium + heart + major vessels
  • Posterior mediastinum: posterior to pericardium
313.1.0.1.1.2 Anterior Mediastinum Masses — “4 Ts”
  1. Thymoma + Thymic Carcinoma
    • Thymoma: epithelial tumor; 30-40% have myasthenia gravis association
    • Thymic carcinoma: more aggressive
    • Diagnosis: CT + percutaneous biopsy
    • Treatment: surgical resection; chemoradiation for invasive
    • WHO classification A-B3
  2. Teratoma / Germ Cell Tumors
    • Most common in young adults
    • Mature teratoma (benign)
    • Seminoma + non-seminomatous germ cell tumors (NSGCT)
    • β-hCG, AFP tumor markers
    • NSGCT: chemotherapy (cisplatin-based)
    • Seminoma: chemo + RT
  3. Thyroid (Substernal Goiter)
    • Extension of cervical goiter
    • Compression symptoms (dysphagia, dyspnea, hoarseness)
    • I-131 imaging for radioiodine uptake
    • Surgery (thyroidectomy) for symptomatic
  4. Terrible Lymphoma
    • Hodgkin lymphoma (esp nodular sclerosing)
    • Non-Hodgkin lymphoma (DLBCL, primary mediastinal B-cell lymphoma)
    • Mediastinal LAD prominent
    • Biopsy + immunohistochemistry
    • Chemotherapy + RT
    • Excellent prognosis with modern therapy
313.1.0.1.1.3 Middle Mediastinum Masses
  • Lymphadenopathy:
    • Infection (TB, histoplasmosis, sarcoidosis)
    • Malignancy (lung cancer, lymphoma, metastases)
  • Bronchogenic cyst (cystic, often subcarinal)
  • Aortic aneurysm
  • Pericardial cyst (springwater cyst, right cardiophrenic)
  • Vascular anomalies
  • Enteric cysts
313.1.0.1.1.4 Posterior Mediastinum Masses
  • Neurogenic tumors (~ 75% of posterior masses):
    • Schwannoma (most common, adults)
    • Neurofibroma (NF1-associated)
    • Ganglioneuroma, ganglioneuroblastoma, neuroblastoma (children)
    • Paragangliomas
  • Lateral meningoceles
  • Esophageal duplication cyst
  • Vertebral abnormalities
313.1.0.1.2 Mediastinal Mass Workup
313.1.0.1.2.1 Imaging
  • CT chest with contrast (cornerstone)
  • MRI for neurogenic tumors, posterior masses
  • PET-CT for staging, malignancy assessment
  • β-hCG + AFP + LDH (germ cell)
313.1.0.1.2.2 Biopsy
  • Image-guided (CT-guided)
  • Mediastinoscopy (middle mediastinum)
  • VATS / open biopsy (anterior, posterior)
  • EBUS-TBNA for middle mediastinal LN
313.1.0.1.3 Mediastinitis
313.1.0.1.3.1 Acute Mediastinitis

Causes: - Post-cardiac surgery (sternal wound infection extending; deep sternal infection) - Esophageal rupture (Boerhaave) — high mortality - Iatrogenic (endoscopy, surgery) - Penetrating trauma

Clinical: - Fever, chest pain, dysphagia, dyspnea - Subcutaneous emphysema (esophageal) - Hamman sign (mediastinal crunch with heartbeat) - Sepsis, shock

Diagnosis: - CT with oral contrast (esophageal leak — gold standard) - Esophagogram

Treatment: - Emergent surgical exploration + repair - IV broad-spectrum antibiotics - NPO, IV nutrition - Source control critical

313.1.0.1.3.2 Chronic (Fibrosing) Mediastinitis

Causes: - Histoplasmosis (most common in US endemic areas) - Tuberculosis - Sarcoidosis - IgG4-related disease - Idiopathic - Drug-induced (methysergide, others)

Clinical: - Compressive symptoms: superior vena cava syndrome, dysphagia, dyspnea - Pulmonary venous obstruction - Bronchial / esophageal compression

Treatment: - Address underlying disease - Steroids for IgG4 - Antifungal for active histo (debated for fibrotic) - Surgical decompression rarely - Vascular stenting for SVC syndrome

313.1.0.1.4 Pneumomediastinum
313.1.0.1.4.1 Definition
  • Air in mediastinum
  • Spontaneous (idiopathic) or secondary
313.1.0.1.4.2 Causes (Macklin Effect)
  • Spontaneous: young + healthy; alveolar rupture due to ↑ pressure (cough, vomiting, Valsalva, drug inhalation)
  • Asthma exacerbation
  • Mechanical ventilation (high pressure)
  • Vomiting / Boerhaave (esophageal rupture — distinguish)
  • Trauma / iatrogenic
  • Childbirth
  • Tracheobronchial injury
313.1.0.1.4.3 Clinical
  • Chest pain (sharp, sudden)
  • Subcutaneous emphysema (neck, chest wall)
  • Hamman sign (mediastinal crunch)
  • Hoarseness
313.1.0.1.4.4 Diagnosis
  • CXR: air outlining mediastinal structures, continuous diaphragm sign
  • CT: definitive
  • Esophagogram or endoscopy if Boerhaave suspected
313.1.0.1.4.5 Treatment
  • Self-limited usually
  • Oxygen (high-flow promotes resorption)
  • Pain management
  • Treat underlying (asthma, etc.)
  • Surgical if Boerhaave or tracheobronchial
313.1.0.1.5 Diaphragm Disorders
313.1.0.1.5.1 Diaphragm Paralysis

Unilateral: - Phrenic nerve injury (cardiac surgery, trauma, tumor) - Idiopathic (Parsonage-Turner / brachial neuritis) - Often asymptomatic in healthy - Exertional dyspnea - CXR: elevated hemidiaphragm - Sniff test (fluoroscopy): paradoxical movement - Treatment: usually conservative; diaphragm plication if symptomatic

Bilateral: - Severe respiratory failure - Orthopnea (worse supine — abdominal contents push diaphragm up) - Causes: trauma, ALS, GBS, polyneuropathy, SLE, paraneoplastic - Treatment: NIV, mechanical ventilation, diaphragm pacemaker for select

313.1.0.1.5.2 Diaphragmatic Hernias
  • Bochdalek hernia: posterolateral; left > right; congenital
  • Morgagni hernia: anterior; less common; congenital
  • Hiatal hernia: through esophageal hiatus
  • Traumatic
313.1.0.1.5.3 Eventration
  • Abnormal elevation due to muscular thinning
  • Usually asymptomatic
  • Surgical plication if symptomatic
313.1.0.1.5.4 Hiccups (Singultus)
  • Phrenic / vagal stimulation
  • Persistent (> 48h) or intractable (> 1 month) warrants workup
  • Causes: GERD, esophagitis, CNS lesions, metabolic, medications
  • Treatment: chlorpromazine, baclofen, gabapentin, metoclopramide
313.1.0.1.6 Chest Wall Disorders
313.1.0.1.6.1 Pectus Excavatum
  • Sunken sternum
  • Often pectus carinatum (protruding sternum) in others
  • May cause cardiopulmonary symptoms
  • Haller index > 3.25 = severe
  • Nuss procedure (minimally invasive bar) — definitive correction in adolescents/young adults
  • Symptomatic improvement post-op
313.1.0.1.6.2 Pectus Carinatum
  • Protruding sternum
  • Pulmonary effects modest
  • Bracing in young; surgery rarely
313.1.0.1.6.3 Kyphoscoliosis
  • Severe curvature
  • Restrictive lung disease
  • Hypoventilation possible
  • NIV for severe
  • Spine surgery for select
313.1.0.1.6.4 Ankylosing Spondylitis
  • Restrictive pattern (thoracic immobility)
  • Upper lobe fibrosis can occur
  • Treatment: TNF inhibitor
313.1.0.1.6.5 Neuromuscular Weakness Affecting Respiration
  • Amyotrophic Lateral Sclerosis (ALS):
    • Progressive respiratory failure
    • NIV improves survival + QOL
    • Riluzole, edaravone, AMX0035
  • Guillain-Barré (GBS):
    • Ascending paralysis
    • Acute respiratory failure
    • IVIG, plasmapheresis, ventilation
  • Myasthenia Gravis (MG):
    • Myasthenic crisis = respiratory failure
    • Plasmapheresis, IVIG, IS
  • Muscular Dystrophy (Duchenne, Becker, myotonic):
    • Progressive
    • NIV, ventilation
    • Cardiomyopathy associations
  • Spinal Cord Injury (high cervical):
    • Diaphragmatic dysfunction
    • Ventilator dependence
    • Diaphragm pacing option
313.1.0.1.7 Ventilatory Control Disorders
313.1.0.1.7.1 Obesity Hypoventilation Syndrome (OHS)

Definition: - BMI ≥ 30 + chronic alveolar hypoventilation (PaCO2 > 45 awake) - Often OSA + OHS overlap

Pathophysiology: - Reduced ventilatory drive - Increased work of breathing (obesity) - OSA contribution - Leptin resistance

Clinical: - Hypersomnolence - Edema, polycythemia, pulmonary HTN (advanced) - Cor pulmonale

Treatment: - Weight loss (bariatric surgery very effective) - CPAP / BiPAP (NIV) - Supplemental O2 - Treat OSA

313.1.0.1.7.2 Congenital Central Hypoventilation Syndrome (CCHS / Ondine’s Curse)
  • PHOX2B mutation
  • Loss of automatic breathing during sleep
  • Diagnosis usually pediatric
  • Treatment: lifelong nocturnal ventilation; diaphragmatic pacing
313.1.0.1.7.3 Cheyne-Stokes Respiration
  • Crescendo-decrescendo breathing pattern
  • HF (most common), brainstem lesion, high altitude
  • Treatment: address underlying
313.1.0.1.8 Sleep-Disordered Breathing (Brief — See Ch313)
  • OSA (obstructive sleep apnea)
  • Central sleep apnea (CSA)
  • Cheyne-Stokes
  • Hypoventilation syndromes
  • See Ch313 for details

313.1.0.2 🩺 床邊速查

  • Anterior mediastinum “4 Ts”: thymoma, teratoma, thyroid, lymphoma
  • Middle mediastinum: lymphadenopathy (sarcoid, infection, malignancy), bronchogenic cyst, aortic aneurysm
  • Posterior mediastinum: neurogenic tumors (schwannoma, neuroblastoma)
  • Acute mediastinitis (Boerhaave / post-cardiac surgery): emergency surgical + antibiotics
  • Chronic fibrosing mediastinitis: histoplasmosis, IgG4, sarcoid
  • Pneumomediastinum: usually self-limited; rule out Boerhaave + airway injury
  • Diaphragm paralysis: unilateral often asymptomatic; bilateral severe respiratory failure
  • Pectus excavatum: Nuss procedure
  • OHS: BMI ≥ 30 + PaCO2 > 45 awake; NIV + weight loss