Dysfunction of the Diaphragm

Imaging as a Diagnostic Tool

Nadir Kharma

Disclosures

Curr Opin Pulm Med. 2013;19(4):394-398. 

In This Article

Dysfunction of the Diaphragm

When interpreting radiographs and other imaging studies, it is important to bear in mind that in normal individuals, the right hemidiaphragm is somewhat higher than the left hemidiaphragm. Furthermore, the anterior and medial portions of the diaphragm are normally higher than the posterior and lateral portions.[6]

Diaphragmatic dysfunction can be viewed as paralysis or weakness. Diaphragmatic elevation at chest radiography will often be the first clue of dysfunction. Usually, the entire hemidiaphragm will be elevated in paralysis or weakness. With eventration, only a portion of a hemidiaphragm is elevated. Muscle atrophy and diaphragmatic thinning can be seen in some cases of dysfunction.

Another way of classifying diaphragmatic dysfunction is according to the involvement of one or both hemidiaphragms. Dysfunction can be unilateral or, less commonly, bilateral. Unilateral impairment is often asymptomatic and discovered incidentally on radiographic imaging. However, patients can be symptomatic and complain of dyspnoea on exertion. Patients with underlying lung disease are usually more symptomatic. Shortness of breath in the supine position or orthopnoea in particular can be present because of pressure from abdominal contents on the undersurface of the diaphragm.[7] Pulmonary function tests show a restrictive pattern, which manifests as a reduction in total lung capacity and in vital capacity.[8]

As opposed to unilateral diaphragmatic dysfunction, bilateral diaphragmatic dysfunction is usually symptomatic, often leading to respiratory failure.[7] Hypoventilation that may result in hypercapnic respiratory failure with elevated arterial carbon dioxide tension (paCO 2) is the hallmark of this condition. At this point, the accessory muscles of respiration will take over the role of the dysfunctional diaphragm.

Diaphragmatic Weakness and Paralysis

This can be classified according to the anatomic region of abnormality. Some diseases, however, may affect more than one region.[9,10] Diaphragmatic paralysis and weakness may be unilateral or bilateral, temporary or permanent, depending on the cause.

The brain may be affected by several diseases, including multiple sclerosis, stroke and Arnold–Chiari malformation, all of which can present with weakness or paralysis of the diaphragm.

At the level of the spinal cord, quadriplegia, amyotrophic lateral sclerosis, poliomyelitis, spinal muscular atrophy, syringomyelia or West Nile virus infection may be important causes of weakness or paralysis.[11–13]

Guillain–Barré syndrome, tumour compression, neuralgic neuropathy, critical illness polyneuropathy, chronic inflammatory demyelinating polyneuropathy and Charcot–Marie–Tooth disease can all affect the phrenic nerve and the function of diaphragm. Cold cardioplegia used in cardiac surgery is another common cause of phrenic nerve injury.[14,15] In addition, radiation therapy can affect the phrenic nerve resulting in diaphragmatic dysfunction.[16]

The weakness of the diaphragm may occur at the level of the neuromuscular junction, caused by such as myasthenia gravis, botulism, organophosphates and Lambert–Eaton syndrome.[17]

Obstructive airway diseases that affect the lungs, such as chronic obstructive pulmonary disease (COPD) and asthma, can result in significant hyperinflation resulting in diaphragmatic disadvantage and weakness.

Several disease processes can also affect the diaphragm as a muscle. Examples include muscular dystrophies, myositis, glucocorticoids and disuse atrophy.[18]

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