Diaphragm Anatomy and Differential Diagnosis
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Anatomy of the Diaphragm[edit | edit source]
The diaphragm is a major muscle of respiration.
- It is a dome-shaped, "fibromuscular sheet" that separates the thorax from the abdomen
- It forms the floor of the thorax and the roof of the abdomen
- The left side is lower than the right due to presence of the liver on the right
- The left side may also be located partially inferiorly due to the "push" by the heart
- The peripheral portion of the diaphragm is muscular and is composed of three distinct muscle groups:
- The central portion of the diaphragm is made up of very strong aponeurotic tendinous ligaments without any bony attachment.
Major Openings in the Diaphragm[edit | edit source]
- Caval hiatus: at the level of the T8 vertebra in the central tendon. Allows passage of the inferior vena cava and some right phrenic nerve branches.
- Oesophageal hiatus: at the level of the T10. It allows the oesophagus, the right and left vagus trunks, the oesophageal branches of the left gastric vessels, and the lymph vessels to pass through.
- Aortic hiatus: anterior to the T12 vertebral body between the crura. Allows the aorta, thoracic duct, and azygos vein to pass through.
Nerve Supply[edit | edit source]
- Motor nerve supply:
- Left hemidiaphragm is supplied by the left phrenic nerve
- Right hemidiaphragm is supplied by the right phrenic nerve
- Sensory nerve supply:
- The phrenic nerve innervates the parietal pleura and the peritoneum which covers the diaphragm's central surfaces. The periphery of the diaphragm is innervated by the bottom six intercostal nerves.
- The phrenic nerve is made up of large-diameter myelinated, small-diameter myelinated, and unmyelinated fibres. The large diameter fibres fire when the diaphragm contracts while the small diameter fibers fire throughout respiration.
Vascular Supply[edit | edit source]
- Inferior phrenic artery from abdominal aorta 
- Superior phrenic artery
- Pericardiophrenic, musculophrenic arteries
- Inferior phrenic vein
Fascial Attachments[edit | edit source]
1. Vertebrae[edit | edit source]
- Medial lumbocostal arch
- Lateral lumbocostal arch
- A tendinous arch in the fascia which covers the upper portion of quadratus lumborum
- Medially, it attaches to the front of the L1 transverse process
- Laterally, it attaches to the lower border of rib 12
2. Muscles[edit | edit source]
- Quadratus lumborum (QL) attaches to the inferior portion of the 12th rib. A part of the diaphragm attaches to this rib's superior portion. The fascia is continuous between these attachments.
- The psoas muscle is in a similar area as the QL. It blends with the fascia at the proximal end of the posterior portion of the diaphragm.
Aetiology of an Elevated Diaphragm[edit | edit source]
An elevated hemidiaphragm may be due to both direct and indirect causes.
- Above the diaphragm
- At the level of the diaphragm
- Phrenic nerve palsy
- Diaphragmatic eventration (an abnormal placement of the diaphragm, located too high in the body, either due to issues with the nerves that supply the muscle, or the muscle itself. In more severe cases, this can compress the lungs and interfere with breathing).
- Contralateral stroke: usually middle cerebral artery (MCA) distribution
- Below the diaphragm
- Abdominal tumour, e.g. liver metastases or primary malignancy
- Subphrenic abscess
- Distended stomach or colon, including Chilaiditi sign/syndrome
Differential Diagnosis for Elevated Diaphragm[edit | edit source]
Other situations which may mimic an elevated hemidiaphragm include:
Aetiology for Paralysis of the Diaphragm[edit | edit source]
Diaphragmatic paralysis occurs when the nerve supply is interrupted. This interruption might occur in the phrenic nerve itself, at the cervical spinal cord, or in the brainstem. However, it is most commonly caused by a phrenic nerve lesion:
- Mechanical trauma: such as nerve damage / ligation during surgery
- Compression: due to a chest cavity tumour
- Myopathies: including myasthenia gravis
- Neuropathic: including conditions such as diabetic neuropathy, inclusion body myositis, dermatomyositis, multiple sclerosis, anterior horn cell disease, chronic demyelinating disease, and neuralgic myopathy
- Inflammation: a number of systemic diseases can cause inflammation in the phrenic nerve / diaphragm, which results in diaphragmatic palsy. Examples include:
- Idiopathic: around 20 percent of cases have no obvious cause
Differential Diagnosis for Paralysis of the Diaphragm[edit | edit source]
- Alveolar hypoventilation
- Anterior horn cell or neuromuscular junction disease
- Cerebral haemorrhage
- Cervical fracture
- Decreased pulmonary compliance
- Guillain-Barre syndrome
- Myasthenia gravis
- Peripheral neuropathies
- Pleural adhesions
Symptoms of Diaphragmatic Weakness[edit | edit source]
- Unilateral weakness: Often asymptomatic and detected incidentally. Patients show limitations in exercise capacity, lower oxygen saturation levels:
- A third of patients complain of exertional breathlessness
- Dyspnoea at rest with co-morbidities such as cardiopulmonary conditions
- Bilateral weakness: dyspnoea at mild exertion to dyspnoea at rest:
- Further compromise→ orthopnoea
- Progressive hypoventilation → hypercapnia and right heart failure. Worse during sleep.
Paradoxical Breathing[edit | edit source]
Paralysis of the diaphragm results in a "paradoxical movement". The affected side moves up during inspiration and down during expiration.
- Unilateral diaphragmatic paralysis is frequently asymptomatic and is often found incidentally on x-ray.
- Bilateral paralysis can result in poor exercise tolerance, orthopnoea and fatigue. There will also be a restrictive deficit on lung function tests.
References[edit | edit source]
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- Columbia Surgery Diaphragm Eventration Available:https://columbiasurgery.org/conditions-and-treatments/diaphragm-eventration (accessed 9.5.2022)
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