Mediastinum and Diaphragm

Unilateral Paralysis of the Diaphragm:

·         Causes

o        Trauma à sneezing, motor vehicle accident, post-open heart surgery

o        Lesions adjacent to or involving the phrenic nerve à pneumonia, substernal thyroid, aortic aneurysm, vasculitis (diabetes), neoplasm

·         Symptoms à dyspnea on exertion (variable intensity)

·         Physical examination à dullness to percussion, decreased breath sounds, decreased respiratory excursion on the involved side

·         Diagnostic studies

o        Chest X-ray à elevation of hemidiaphragm (most are picked up this way)

o        Sniff test à paradoxical movement of the diaphragm (fluoroscopy or ultrasound) with sniffing – this is a confirmatory test

o        Other studies à based in the likely diagnoses (ex: bronchoscopy if neoplasm seems to be likely)

·         Prognosis à usually good – gradual return in function over 6 months to 1 year 

Bilateral Diaphragmatic Paralysis:

·         Similar to unilateral paralysis however symptoms are worse & diagnosis may be more difficult (asymmetry of unilateral paralysis aids in diagnosis)

o        If both sides of the diaphragm are elevated its harder to determine that it’s abnormal
 

Mediastinum:

·         Mass à usually picked up on routine chest X-ray

o        Often asymptomatic

o        Usually benign

o        Clues to diagnosis are based on location (anterior, middle, or posterior)

o        Investigation à CT scanning or tissue diagnosis (needle mediastinoscopy)

·         Pneumomediastinum à air secondary to mechanical ventilation (barotrauma) or asthma

·         Acute mediastinitis à due to infection and can be treated with antibiotics & surgical drainage

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