Epidemiology

• xx

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Etiology

• Cervical Osteoarthritis (with bilateral C3-C5 compression)
• Cervical Spine Manipulation/Mass Lesion (with bilateral C3-C5 compression)
• Herpes Zoster (bilaterally involving C3-C5)
• Neuralgic Amyotrophy (bilaterally involving C3-C5): usually affects brachial plexus
• Multiple sclerosis (bilaterally involving C3-C5)

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Physiology

• Pulmonary hypertension due to neuromuscular disease (bilateral diaphragmatic paresis or paralysis)
  • Hypoventilation leads to hypoxia/ acidosis (with resultant pulmonary vasoconstriction)

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Pathology

• xxx

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Diagnosis

• ABG: hypoxemia/hypercapnia
• PFT’s: restriction
  • Decreased FEV1 (about 50% predicted)
  • Decreased VC (about 45% predicted/ due to muscle weakness, decreased lung and chest wall compliance): supine VC <75% of upright VC
  • Decreased TLC,RV,FRC
  • Decreased MVV
  • Decreased MIP
  • Decreased lung compliance (due to chronically low lung volumes: microatelectasis/ reduced surface tension/ altered interstitial elastic fibers)
• CXR: low volumes/elevated diaphragms
• Sniff test: paradoxic motion of diaphragms (normal in some cases due to expiratory abdominal muscle contraction with upward diaphragm motion, passive inspiratory downward motion)
• Phrenic nerve stimulation (percutaneous/ needle electrodes): observe diaphragm
• Transdiaphragmatic pressure (more specific for diaphragm than MIP:) using NG balloon (Pga-Pes)/normal change >25 cm H2O (to TLC), usually 2-20 cm H2O in bilateral paralysis
• EMG/NCV: normal (?)

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Clinical

• Bilateral Diaphragmatic Paralysis (severe symptoms):
  • Severe exert dyspnea
  • Orthopnea (due to vis-ceral pressure on dia-phragm)
  • Dullness/ decreased BS at bases
  • Tachypnea
  • Prominent scalene/ SCM contractions
  • Paradoxic inspiratory inward movement of abdomen (classic sign)
  • Respiratory failure/ atelectasis/ aspiration pneumonia/ sleep-disordered breathing/ pulmonary HTN/cor pulmonale
  • Acute/Chronic Hypoventilation (see Acute Hypoventilation, [[Acute Hypoventilation]] and Chronic Hypoventilation, [[Chronic Hypoventilation]])

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Treatment

• Treat underlying disease
• Spontaneous recovery (takes up to 2 years in some cases): may occur if a progressive generalized neuropathy is not present
• Ventilation: rocking bed/ CPAP/ ventilator
• Phrenic nerve pacing: not useful (due to injured phrenic nerve/ pacing beyond site of injury is usually not possible due to atrophy of nerve)
  • Direct pacing of muscle requires high thresholds

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