313.3 🏥 內科專科考前版

313.3.1 Mechanistic Deep Dive

313.3.1.1 Phrenic Nerve Anatomy

  • C3-C5 origin
  • Innervates diaphragm
  • Vulnerable in cardiac surgery (mediastinal cooling)
  • Brachial plexus inflammation (Parsonage-Turner)

313.3.1.2 Mediastinal Anatomy + Compartments

  • Anterior: thymus, lymph nodes
  • Middle: pericardium, heart, great vessels, trachea, lymph nodes
  • Posterior: descending aorta, esophagus, thoracic duct, sympathetic chain

313.3.2 Recent Trials & Updates

313.3.2.1 Thymoma Treatment

  • WHO classification A-B3
  • Surgical resection if resectable
  • Chemo (cisplatin-based) for unresectable / invasive
  • Pembrolizumab for refractory (immune-related: paraneoplastic flares)

313.3.2.2 Primary Mediastinal B-Cell Lymphoma (PMBCL)

  • Young adults (often female)
  • DA-R-EPOCH regimen (NCI)
  • ~ 90% cure rate
  • Less radiation needed

313.3.2.3 Histoplasmosis Fibrosing Mediastinitis

  • Endemic to Ohio/Mississippi River
  • Vascular compression
  • Treatment limited; supportive

313.3.3 High-Yield Specialist Points

313.3.3.1 MG + Thymoma

  • Anti-AChR or anti-MuSK antibodies
  • Thymectomy can improve MG even without thymoma
  • AntiMGTX trial (2016): thymectomy benefits non-thymomatous MG
  • Pre-op pyridostigmine, steroids, IVIG, plasmapheresis

313.3.3.2 Mediastinitis Post-Cardiac Surgery

  • 1-3% of CABG / valve surgery
  • S. aureus (50%), CoNS, GNR
  • Risk factors: diabetes, obesity, IDU
  • Treatment: surgical debridement + omental / pectoralis flap + long IV antibiotics
  • Mortality 10-30%

313.3.3.3 Boerhaave Syndrome

  • Spontaneous esophageal rupture (post-vomiting)
  • Left posterior wall typically
  • High amylase in pleural fluid + acidic pH
  • Surgical emergency (within 12-24 h optimal)
  • Mortality < 10% with early diagnosis, > 50% delayed

313.3.3.4 Diaphragmatic Plication

  • Indications: symptomatic unilateral paralysis
  • Improves spirometry + dyspnea
  • VATS approach increasing

313.3.3.5 Diaphragmatic Pacing

  • For bilateral paralysis (with intact phrenic nerves) or high cervical spinal cord injury
  • Phrenic nerve stimulation
  • Improves QOL + freedom from ventilator

313.3.3.6 Nuss Procedure

  • Minimally invasive pectus excavatum repair
  • Substernal bar
  • Adolescents to young adults
  • Removed after 2-3 years
  • Excellent cosmetic + functional outcome

313.3.3.7 OHS Treatment Algorithm

  • CPAP if predominantly OSA + 70-90% mild OHS
  • BiPAP for severe + lack of response to CPAP
  • Weight loss (bariatric surgery > diet alone)
  • Treat hypothyroidism if present
  • Avoid sedatives

313.3.3.8 Cheyne-Stokes Respiration

  • Common in HF (especially advanced)
  • ASV (adaptive servo-ventilation): caution in HFrEF (SERVE-HF — ↑ mortality)
  • CPAP for OSA component
  • Heart failure optimization

313.3.3.9 Anti-MDA5 Pulmonary Involvement

  • See Ch295, 309
  • Rapidly progressive ILD
  • Mediastinal LAD possible

313.3.3.10 Pancoast Tumor

  • Superior sulcus lung cancer
  • Mediastinal extension
  • Horner syndrome (cervical sympathetic)
  • Brachial plexus involvement
  • Treatment: neoadjuvant chemoradiation + surgery

313.3.4 Pearls

  • Anterior mediastinum “4 Ts”: thymoma, teratoma, thyroid, lymphoma
  • Thymoma + MG: 30-40% association
  • Posterior: neurogenic tumors
  • Acute mediastinitis: Boerhaave + post-cardiac; high mortality; surgical emergency
  • Chronic fibrosing: histoplasmosis, IgG4, idiopathic
  • Pneumomediastinum: usually self-limited; rule out Boerhaave + airway injury
  • Diaphragm paralysis: unilateral often asymptomatic; bilateral severe failure
  • Pectus excavatum: Nuss procedure for severe
  • OHS: BMI ≥ 30 + PaCO2 > 45; NIV + weight loss
  • CCHS: PHOX2B mutation; lifelong ventilation