Diaphragmatic Paralysis

Updated: Jun 22, 2017
  • Author: Justina Gamache, MD; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
  • Print


The diaphragm, the most important muscle of ventilation, develops negative intrathoracic pressure to initiate ventilation. Innervated by cervical motor neurons C3-C5 via the phrenic nerves, these two nerves provide both sensory and motor function to the diaphragm. [1, 2] With contraction, the cone-shaped muscle of the diaphragm decreases intrapleural pressure during inspiration and thereby facilitates movement of air into the lungs. Diaphragmatic paralysis is an uncommon, yet underdiagnosed cause of dyspnea. [3]



Diaphragmatic paralyses encompass a spectrum of diseases involving a single leaflet, known as unilateral diaphragmatic paralysis (UDP), and that involving both leaflets, known as bilateral diaphragmatic paralysis (BDP).

Although the diaphragm performs most of the work, normal ventilation also requires the simultaneous contraction of respiration accessory muscles (ie, scalene, parasternal portion of the internal and external intercostal muscles, sternocleidomastoid, trapezius). In bilateral diaphragmatic paralysis, accessory muscles assume some or all of the work of breathing by contracting more intensely. An increased effort in the struggle to breathe may fatigue the accessory muscles and lead to ventilatory failure.




Incidence is unknown.


Like diaphragm eventration, diaphragm paralysis is more common among males. [4]



Unilateral diaphragmatic paralysis

Depending on the etiology of the diaphragmatic paralysis, the prognosis of unilateral disease usually is excellent unless the patient has significant underlying pulmonary disease. Patients develop compensatory mechanisms, and patients with phrenic injuries may recover fully or partially. [5] At times, patients may spontaneously recover from idiopathic disease. Patients who do not recover from unilateral diaphragmatic dysfunction generally lead relatively normal lives. In this group, dyspnea may develop with exertion, leading to increased ventilatory demands.

Bilateral diaphragmatic paralysis  [6]

The prognosis depends on the nature of the underlying disease. Patient diaphragm function may recover if nerve injury is not permanent, while other patients may require long-term treatment as elaborated before. If recovery occurs, it usually takes considerable time, in excess of one year.


Unilateral diaphragmatic paralysis

The morbidity of the unilateral paralysis is mainly based on the underlying pulmonary functional status and the etiology of the paralysis. Because most cases of unilateral diaphragmatic paralysis are found incidentally during imaging studies, many patients have no symptoms. Diaphragmatic paralysis is more likely to affect the left hemidiaphragm. [4] The patients with unilateral diaphrmatic paralysis that do have symptoms and decreased quality of life are those who have concurrent underlying lung diseases.

Bilateral diaphragmatic paralysis

Patients with bilateral diaphragmatic paralysis are usually symptomatic and, when symptoms are severe or in the presence of underlying lung pathology, may develop ventilatory failure without medical intervention.