Diaphragmatic paralysis

Diaphragmatic paralysis can be unilateral or bilateral.

Clinical features are highly variable according to underlying aetiological factor:

  • unilateral paralysis: asymptomatic in most of the patients as the other lung compensates
    • may have dyspnoea, headaches, fatigue, insomnia and overall breathing difficulty
  • bilateral diaphragmatic palsy can be a medical emergency; they present with severe dyspnoea, even with mild exertion

Normally the right dome of the diaphragm is higher in position as compared to the left dome, if the left dome of the diaphragm is elevated (>2 cm) diaphragmatic palsy should be suspected.

Fluoroscopic examination of the diaphragm ("sniff test") very useful in diagnosing a diaphragmatic paralysis. In normal individuals, both hemidiaphragm will descend with inspiration. In cases of unilateral diaphragmatic paralysis, the affected side demonstrates a paradoxical upward movement.

An alternative to fluoroscopy in diagnosing this condition, particularly useful in the paediatric population. Real-time ultrasound is ideal for evaluation of spontaneous respiratory diaphragmatic motion (may require temporary disconnection of the ventilator). This can be performed in the axial plane to compare the two hemidiaphragm simultaneously. Additional coronal or sagittal M-mode can help quantify the degree of movement of each individual hemidiaphragm. Diagnostic criteria include paradoxical movement, excursion of less than 4 mm, and a difference >50% between the excursion of one hemidiaphragm compared to the other.

Patients with unilateral diaphragmatic paralysis do not require treatment. There may be an option for phrenic nerve stimulation in some cases.

On a chest radiograph consider:

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Article information

rID: 25469
Section: Gamuts
Tag: cases
Synonyms or Alternate Spellings:
  • Paralysis of diaphragm
  • Paralysis of the diaphragm

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Cases and figures

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    Figure 1: normal sniff test
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    Case 1
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    Figure 2: abnormal sniff test
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    Case 2
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    Case 3
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    Case 4
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