Diaphragm Anatomy and Differential Diagnosis

Original Editor - Carin Hunter based on the course by Rina Pandya
Top Contributors - Carin Hunter, Jess Bell, Kim Jackson, Wanda van Niekerk, Merinda Rodseth, Lucinda hampton, Ewa Jaraczewska and Tarina van der Stockt

Anatomy of the diaphragm

• Fibromuscular dome shaped muscle of inspiration that separates thorax from the abdomen.
• Forms the floor of thorax and roof of abdomen
• Left side lower than the right due to presence of the liver on the right.
• The left side may also be partially inferiorly located because of the push by the heart.

3 Major openings in the Diaphragm:

1. Caval hiatus: at the level of the T8 vertebra in the central tendon. It allows passage of Inferior vena cava and some branches of the right phrenic nerve.
2. The esophageal hiatus: at the level of the T10. It allows passage of esophagus, the right and left vagus trunks, the esophageal branches of the left gastric vessels, and the lymph vessels.
3. The aortic hiatus: anterior to the body of the T12 vertebra between the crura. It allows passage of aorta, thoracic duct, and azygos vein.

Nerve Supply

The diaphragm is supplied by the Phrenic Nerve: C3, C4,C5 and sometimes C6

• Motor nerve supply:

1. left hemidiaphragm with left phrenic nerve
2. Right hemidiaphragm with right phrenic nerve.

• Sensory nerve supply:
  1. The phrenic nerve innervates the parietal pleura and peritoneum covering the central surfaces of the diaphragm. The lower 6 intercostal nerves supply the periphery of the diaphragm.
  2. Large diameter myelinated Phrenic nerve afferents fire with diaphragm contraction. The small diameter continues to fire through out the respiratory cycle
     • Activation of phrenic nerve modulates the sympathetic motor outflow.
     • Phrenic afferents also contribute to somatosensation of the diaphragm and make one aware of the sensation of breathing while awake

Vascular Supply

Arterial supply:

• Inferior phrenic arteries from abdominal aorta
• The others are superior phrenic, pericardiophrenic, musculophrenic arteries.

Venous supply:

• Inferior phrenic vein

Fascial attachments:

1. Vertebrae

• The medial lumbocostal arch is a tendinous arch in fascia covering psoas major. Medially, it attaches to the side of the body of vertebra L1. Laterally, it connects to the front of the transverse process of vertebra L1.
• The lateral lumbocostal arch is a tendinous arch in fascia covering the upper part of quadratus lumborum. Medially, attach to the front of the transverse process of vertebra L1. Laterally, it connects to the lower border of the 12th rib.

2. Muscles

• The QL attaches to the inferior portion of the 12th rib, while a portion of the diaphragm attaches to the superior portion of this rib. However, the fascia between these attachments is continuous.
• The psoas has a more direct pathway, covering the same basic territory as the QL-iliac muscle to blend with the fascia of the posterior portion of the diaphragm at its proximal end.

Etiology for Elevated Diaphragm

An elevated hemidiaphragm may result from direct and indirect causes. The causes can be grouped into 3 catagories due to the location of the cause. These can include:

1. Above the diaphragm
   • Decreased lung volume
   • Atelectasis/collapse
   • Prior lobectomy or pneumonectomy
   • Pulmonary hypoplasia

1. At the level of the diaphragm
   • Phrenic nerve palsy
   • Diaphragmatic eventration
   • Contralateral stroke: usually middle cerebral artery (MCA) distribution
2. Below the diaphragm
   • Abdominal tumor, e.g. liver metastases or primary malignancy
   • Subphrenic abscess
   • Distended stomach or colon, including Chilaiditi sign/syndrome

Differential Diagnosis for Elevated Diaphragm

Other situations which may mimic an elevated hemidiaphragm include:

• Subpulmonic effusion
• Diaphragmatic hernia
• Diaphragmatic rupture
• Tumor of the pleura or diaphragm

Etiology for Paralysis of the Diaphragm

Diaphragmatic paralysis is due to an interruption in its nervous supply. This can occur in the phrenic nerve, cervical spinal cord, or the brainstem. It is most often due to a lesion of the phrenic nerve:

1. Mechanical trauma: ligation or damage to the nerve during surgery.
2. Compression: due to a tumor within the chest cavity.
3. Myopathies: such as myasthenia gravis.
4. Neuropathies: such diabetic neuropathy.
5. Inflammatory: Many systemic diseases can lead to inflammation of the phrenic nerve or diaphragm leading to diaphragmatic palsy. Viral infections like HIV, West Nile virus and poliomyelitis virus, bacterial infections like Lyme disease, and noninfectious causes like sarcoidosis and amyloidosis have been linked to diaphragmatic weakness.
6. Myopathies: such as myasthenia gravis.
7. Neuropathies: such diabetic neuropathy, inclusion body myositis, dermatomyositis, multiple sclerosis, anterior horn cell disease, chronic demyelinating disease, and neuralgic myopathy.(Ricoy, 2019)
8. Idiopathic: In nearly 20% cases, no obvious cause if detected after extensive investigations and are referred as idiopathic

Differential Diagnosis for Paralysis of the Diaphragm

• 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

1. Unilateral weakness : Often asymptomatic and detected incidentally. They show limitation in exercise capacity, lower O2 Saturation levels.
   • ⅓ of the patients: exertional breathlessness
   • Dyspnea at rest with comorbidities such as cardiopulmonary conditions.
2. Bilateral weakness: dyspnea at mild exertion to dyspnea at rest.
   • Further compromise→ orthopnea.
   • Progressive hypoventilation → hypercapnia and right heart failure. Worse during sleep.

Paradoxical Breathing

Paralysis of the diaphragm produces a paradoxical movement. The affected side of the diaphragm moves upwards during inspiration, and downwards during expiration. A unilateral diaphragmatic paralysis is usually asymptomatic and is most often an incidental finding on x-ray. If both sides are paralysed, the patient may experience poor exercise tolerance, orthopnoea and fatigue. Lung function tests will show a restrictive deficit.

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References

1,2 : Oliver KA, Ashurst JV. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Dec 9, 2018. Anatomy, Thorax, Phrenic Nerves.

Bordoni B, Purgol S, Bizzarri A, Modica M, Morabito B. The Influence of Breathing on the Central Nervous System. Cureus. 2018 Jun 01;10(6):e2724

3. Fayssoil A, Behin A, Ogna A, Mompoint D, Amthor H, Clair B, Laforet P, Mansart A, Prigent H, Orlikowski D, Stojkovic T, Vinit S, Carlier R, Eymard B, Lofaso F, Annane D. Diaphragm: Pathophysiology and Ultrasound Imaging in Neuromuscular Disorders. J Neuromuscul Dis. 2018;5(1):1-10

4. The Diaphragm - Actions - Innervation - TeachMeAnatomy. Teachmeanatomy.info. https://teachmeanatomy.info/thorax/muscles/diaphragm/. Accessed July 30, 2020.