Diaphragmatic paralysis overview

# Overview
Diaphragmatic paralysis was first suggested by Steurtz, in 1911 during a simple phrenicotomy for treatment of lung disease. Diaphragmatic paralysis may be classified according to involvement of leaflets into unilateral or bilateral. It is thought that diaphragmatic paralysis is the result of paralysis of cervical nerve roots( C3-C5). Common causes of unilateral diphragmatic paralysis include idiopathic, phrenic nerve injury in cardiac surgery and viral infection. Common causes of bilateral diphragmatic paralysis include idiopathic, cervical spinal cord disease and motor neuron disease. Unilateral diaphragmatic paralysis must be differentiated from eventration of the diaphragm. Eventration of the diaphragm is an abnormal elevation of the hemidiaphragm. Bilateral diaphragmatic paralysis must be differentiated from other diseases that cause elevation of the diaphragm such as pleural adhesions, subpulmonic effusions, obesity, ascites, abdominal organomegaly and ileus. Other differential diagnosis are dermatomyositis, polymyositis, rib fracture, pleural effusions, amyotrophic lateral sclerosis.The incidence of diaphragmatic paralysis is unknown, but incidence of diaphragmatic paralysis after cardiac surgery is approximately 30,000 to 75,000 per 100,000 individuals. Prevalence of diaphragmatic paralysis after cardiac surgery is 1,600 per 100,000 in children. The most potent risk factor in the development of diaphragmatic paralysis is cooling or stretching in cardiac surgery. Common complication of diaphragmatic paralysis includes severe pulmonary dysfunction in bilateral diaphragmatic paralysis. Studies of choice for unilateral diaphragmatic paralysis include upright chest radiograph and fluoroscopic sniff test. Studies of choice for bilateral diaphragmatic paralysis include measurement of transdiaphragmatic pressure (Pdi). The majority of patients with unilateral diaphragmatic paralysis are asymptomatic.  Dyspnea in supine position and orthopnea are common symptoms of bilateral diphragmatic paralysis. Laboratory findings consistent with the diagnosis of diaphragmatic paralysis include reduced oxygen saturation in the supine position in unilateral and bilateral diaphragmatic paralysis and elevated arterial partial pressure of carbon dioxide (PaCO2) in bilateral diaphragmatic paralysis. An x-ray and ultrasound are helpful in the diagnosis of diaphragmatic paralysis. No treatment is required for unilateral diaphragmatic paralysis because most patients are asymptomatic. In bilateral diaphragmatic paralysis treatment options are ventilatory support and diaphragmatic pacing. Surgery is usually reserved for patients with either dyspnea in strenous physical activity and patients with underlying severe pulmonary disease. Surgical plication of the involved hemidiaphragm can be considered for unilateral diaphragmatic paralysis. surgery in bilateral diaphragmatic paralysis can be done via neurolysis and nerve grafting.

# Historical Perspective
Diaphragmatic paralysis was first suggested by Steurtz, in 1911 during simple phrenicotomy for treatment of lung disease. In 1946, a case of poliomyelitiswith respiratory paralysis was explained in Romania.

# Classification
Diaphragmatic paralysis may be classified according to involvement of leaflets into unilateral or bilateral. Bilateral diaphragmatic paralysis is a medical emergency. Unilateral diaphragmatic paralysis is often discovered incidentally on chest x-ray for other reasons.

# 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. left untreated, patients with unilateral diaphragmatic paralysis may recover fully or partially.

# Causes
Common causes of unilateral diphragmatic paralysis include idiopathic, phrenic nerve injury in cardiac surgery and viral infection and less common causes include cervical spondylosis, cervical compressive tumors and blunt neck trauma. Common causes of bilateral diphragmatic paralysis include idiopathic, cervical spinal cord disease and motor neuron disease. Less common causes of bilateral diphragmatic paralysis include parsonage turner syndrome and malnutrition.

# Differentiating Diaphragmatic Paralysis from Other Diseases
Unilateral diaphragmatic paralysis must be differentiated from eventration of the diaphragm. Eventration of the diaphragm is an abnormal elevation of the hemidiaphragm. Bilateral diaphragmatic paralysis must be differentiated from other diseases that cause elevation of the diaphragm such as pleural adhesions, subpulmonic effusions, obesity, ascites, abdominal organomegaly and ileus. Diaphragmatic paralysis must be differentiated from other disease that cause dyspnea such as dermatomyositis, polymyositis, rib fracture, pleural effusions, and amyotrophic lateral sclerosis.

# Epidemiology and Demographics
The incidence of diaphragmatic paralysis is unknown, but incidence of diaphragmatic paralysis after cardiac surgery is approximately 30,000 to 75,000 per 100,000 individuals. Prevalence of diaphragmatic paralysis after cardiac surgery is 1,600 per 100,000 in children.The morbidity and mortality of the unilateral diaphragmatic paralysis is related to underlying pulmonary function and etiology. Most of the bilateral diaphragmatic paralysis are symptomatic and may develop ventilatory failure. Patients of all age groups may develop diaphragmatic paralysis. There is no racial predilection to diaphragmatic paralysis. Men are more commonly affected.

# Risk Factors
The most potent risk factor in the development of diaphragmatic paralysis is cooling or streching in cardiac surgery. Other risk factors include viruses, spinal cord transection and malnutrition.

# Screening
There is insufficient evidence to recommend routine screening for diaphragmatic paralysis.

# Natural History, Complications, and Prognosis
If left untreated, patients with unilateral diaphragmatic paralysis may recover fully or partially. Common complications of diaphragmatic paralysis includes severe pulmonary dysfunction in bilateral diaphragmatic paralysis. Prognosis is generally excellent in unilateral diaphragmatic paralysis. Bilateral diaphragmatic paralysis is a medical emergency.

# Diagnosis

## Diagnostic Study of Choice
Studies of choice for unilateral diaphragmatic paralysis include upright chest radiograph and fluoroscopic sniff test. Studies of choice for bilateral diaphragmatic paralysis include measurement of transdiaphragmatic pressure (Pdi).

## History and Symptoms
The majority of patients with unilateral diaphragmatic paralysis are asymptomatic. Exertional dyspnea and decreased exercise performance are common symtoms of unilateral diaphragmati paralysis. Less common symtoms of unilateral diaphragmatic paralysis include dyspnea at rest and orthopnea. Dyspnea in supine position and orthopnea are common symtoms of bilateral diphragmatic paralysis. Less common symtoms of bilateral diaphragmatic paralysis include daytime fatigue and confusion.

## Physical Examination
Patients with unilateral diphragmatic paralysis usually appear normal. Patients with bilateral diaphragmatic paralysis usually are in respiratory distress. The severe forms of bilateral diaphragmatic paralysis would lead to pulmonary hypertension.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of diaphragmatic paralysis include reduced oxygen saturation in the supine position in unilateral and bilateral diaphragmatic paralysis and elevated the arterial partial pressure of carbon dioxide (PaCO2) in bilateral diaphragmatic paralysis. Hypoxemia may be seen in arterial blood gas in bilateral diaphragmatic paralysis.

## Electrocardiogram
There are no ECG findings associated with diaphragmatic paralysis.

## X-ray
An x-ray is helpful in the diagnosis of diaphragmatic paralysis. Findings on an x-ray suggestive of unilateral diaphragmatic paralysis include elevated hemidiaphragm on the paralysed side and small lung volumes. Findings on an x-ray suggestive of bilateral diaphragmatic paralysis include smooth elevation of the hemidiaphragms and atelectasis at the lung base.

## Echocardiography and Ultrasound
Ultrasound may be helpful in the diagnosis of diaphragmatic paralysis. Findings on an ultrasound suggestive of diaphragmatic paralysis include abnormal paradoxical movement during inspiration and Less than 20% thickening of the diaphragm.

## CT scan
Chest CT scan may be helpful in the diagnosis of tumors as causes of diaphragmatic paralysis. Findings on CT scan suggestive of diaphragmatic paralysis include patchy areas of atelectasis and elevation of one or both hemidiaphragm.

## MRI
Cervical spine MRI may be helpful in the diagnosis of diaphragmatic paralysis. Findings on MRI suggestive of diaphragmatic paralysis include spinal column or nerve roots pathologic conditions as causes of diaphragmatic paralysis.

## Other Imaging Findings
Fluoroscopic sniff test may be helpful in the diagnosis of diaphragmatic paralysis. Findings on sniff test suggestive of diaphragmatic paralysis include paradoxical elevation of the paralyzed hemidiaphragm during inspiration.

## Other Diagnostic Studies
Other diagnostic studies for diphragmatic paralysis include pulmonary function test which demonstrates decrease in vital capacity in diaphragmatic paralysis. Maximal inspiratory pressure (MIP) can be decreaed. Electromyography and polysomnography are other diagnostic studies.

# Treatment

## Medical Therapy
No treatment is required for unilateral diaphragmatic paralysis because most patients are asymptomatic. In bilateral diaphragmatic paralysis treatment options are ventilatory support and diaphragmatic pacing.

## Surgery
Surgery is not the first-line treatment option for patients with unilateral diaphragmatic paralysis. Surgery is usually reserved for patients with either dyspnea in strenous physical activity and patients with underlying severe pulmonary disease. Surgical plication of the involved hemidiaphragm can be considered for unilateral diaphragmatic paralysis. surgery in bilateral diaphragmatic paralysis can be done via neurolysis and nerve grafting.

## Primary Prevention
There are no established measures for the primary prevention of diaphragmatic paralysis. However, the incidence of diaphragmatic paralysis is less in off-pump coronary artery bypass grafting (OPCAB) compared to conventional CABG.

## Secondary Prevention
Effective measures for the secondary prevention of diaphragmatic paralysis include chest physiotherapy following post cardiac surgery diaphragmatic paralysis.