Diaphragmatic paralysis pathophysiology

It is thought that diaphragmatic paralysis is the result of paralysis of cervical nerve roots( C3-C5 ). Diaphragmatic paralyses can be unilateral or bilateral according to involvemnet of one or two leaflets of diaphragm. In the case of unilateral diaphragm paralysis, it is compensated by other hemidiaphragm or accessory muscles of respiration. In bilateral diaphragmatic paralysis, accessory muscles do all of the work of breathing and finally it may lead to ventilatory failure. Early diaphragmatic paralysis may be one of the manifestations of genetic neuromuscular disorders such as spinal muscular atrophy (Werdnig-Hoffmann disease) and acid maltase deficiency. On gross and microscopic pathology, there are no characteristic findings of diaphragmatic paralysis.

The main muscles of inspiration include:

• Diaphragm (most important)

• Scalenes
• External intercostals
• Sternomastoids

The muscles of expiration:

• Internal intercostals
• Muscles of the abdominal wall
  • Rectus abdominus
  • Internal and external obliques
  • Transversus abdominus

• The diaphragm is the musculo-fibrous membrane. It has two parts: non-contractile central fibrous  and peripheral muscular components. ^[1][2][3]
• Peripheral muscular section has two fibers:
  • Type 1: slow and fatigue resistant fibers: play roles in low intensity, continual cycle of breathing
  • Type 2: fast fibers: play roles in rapid and intense situations such as:
    • Talking
    • Singing,
    • Sneezing,
    • Defecation
    • Acute hyperventilation

The diaphragm create negative intrathoracic pressure and facilitates movement of air into the lungs. It is innervated by cervical nerve roots ( C3-C5 ) via the phrenic nerves.^[4][5]

Diaphragmatic paralysis can be unilateral or bilateral according to involvemnet of one or two leaflets of diaphragm.

Diaphragmatic paralysis is an uncommon cause of dyspnea.

It is understood that diaphragmatic paralysis is the result of paralysis of cervical nerve roots (C3-C5 ).

In the case of unilateral diaphragm paralysis, it is compensated by other hemidiaphragm or accessory muscles of respiration.

In bilateral diaphragmatic paralysis, accessory muscles do all of the work of breathing and finally it may lead to ventilatory failure.

Bilateral diaphragmatic paralysis is usually seen with generalized muscle weakness. In some cases, the diaphragm is the only muscle involved. 

Early diaphragmatic paralysis may be one of the manifestations of genetic neuromuscular disorders such as spinal muscular atrophy (Werdnig-Hoffmann disease) and acid maltase deficiency.^[6]

• On gross pathology, there are no characteristic findings of diaphragmatic paralysis.

• On microscopic histopathological analysis, there are no characteristic findings of diaphragmatic paralysis.

Template:WH Template:WS