Diaphragmatic Paralysis - Causes, Clinical Features, and Treatment

Introduction:

The diaphragm is one of the most important muscles involved in the breathing process, other than the scalene, sternocleidomastoid, and intercostal muscles. The function of the diaphragm is more significant for the functioning of the lungs and adequate ventilation. It separates the chest and the abdominal cavities. Different phrenic nerves activate the diaphragm on the left and right sides. It develops negative intrathoracic pressure making space for lung expansion and allowing airflow into the lungs by contracting downwards.

What Are the Causes of Diaphragmatic Paralysis?

Various causes are encountered in causing the paralysis of the diaphragm. These include:

Trauma:

• Injury or trauma is one of the familiar causes of diaphragm weakness.

• Either blunt trauma or direct injury during the surgical procedure may cause phrenic nerve injury resulting in the weakness or paralysis of diaphragm muscles.

• Due to the cooling necessity in the case of cardiac bypass surgical procedures, it possesses the highest risk of temporary diaphragm weakness.

• Injury to diaphragm muscles is also reported in the cases of esophageal, lung, and mediastinal surgeries and also in the cases of laparoscopic cholecystectomy.

Neuropathic Causes:

• Diseases involved in causing nerve damage or demyelination may result in weakness or paralysis of the diaphragm muscles.

• In diabetic neuropathy cases, the phrenic nerve gets affected if the glucose level is not in control.

• In the case of multiple sclerosis, it may affect the functions of the phrenic nerve based on the location of the lesions, resulting in the weakness of the diaphragm muscles.

• In addition, neuralgic amyotrophy cases were also reported with damage to the phrenic nerve.

Iatrogenic Causes:

• In the cases of patients receiving nerve blocks during or post-surgical procedures, the effect of anesthesia can cause the blockage of impulses from the phrenic nerve to the diaphragm and may cause paralysis of the diaphragm.

• These cases are most commonly associated with the thoracic paravertebral, brachial plexus nerve blocks, and inter scalene nerve blocks.

Inflammatory Causes:

• Viral infections caused by Zika, Poliovirus, and Herpes zoster are related to unilateral diaphragmatic paralysis.

• Certain bacterial infections, such as Lyme disease, also show the involvement of phrenic nerves.

• In neuromyelitis conditions, the phrenic nerve gets affected and causes diaphragm paralysis.

Idiopathic Causes:

• Around 20 percent of cases are related to unilateral or bilateral paralysis of diaphragm muscles of unknown origin.

• The exact cause of diaphragmatic paralysis is not sure or unknown; therefore, it is mentioned as idiopathic.

What Are the Clinical Features of Diaphragmatic Paralysis?

• In some cases, associated unilateral paralysis is found to be asymptomatic.

• Depending on the underlying condition, especially related to cardiopulmonary disease, dyspnea is a typical feature representing diaphragmatic weakness.

• Exertional dyspnea can be seen in patients in around one-third of cases, whereas the remaining cases present with complaints of dyspnea.

• Patients may manifest with the hypoventilation condition, leading to hypercapnia, which worsens during sleep and finally results in daytime fatigue.

• Immediately after unilateral diaphragmatic paralysis, symptoms may get worse due to the shortage of time for which the body needs to compensate.

• The physical examination reveals non-specific findings for unilateral diaphragmatic paralysis.

• Rarely, the findings may show dullness to percussion, and diminished breath sounds at the base of the lungs, particularly on the affected side.

• The paradoxical thoracoabdominal movement can be observed, along with the findings of orthopnea in the supine position during sleep. The symptoms of orthopnea can be relieved with lateral positioning with the healthy lung down.

• The sleep-related disorders are also associated with diaphragmatic paralysis, specifically with REM sleep.

What Are the Investigatory Approaches to Diaphragmatic Paralysis?

• When evaluating a patient with suspected diaphragmatic paralysis, it is necessary to consider the underlying cause.

• For example, if a patient undergoes cardiac surgery, around 20% of patients have weakness due to the cooling of the phrenic nerves, which can be resolved with time.

• Extensive treatment is not mandatory with urgent care in these patients.

• Certain factors should be considered while ruling out the diagnosis, including: Patient’s history, imaging, other tests, and physical examination.

Chest Radiographs:

• Many cases left undiagnosed due to asymptomatic conditions are found incidentally with the findings of chest radiographs.

• In the case of unilateral diaphragmatic paralysis, around 90% of the diagnosis cases are confirmed through the findings of chest radiography.

• The findings reveal that the right hemidiaphragm is usually more elevated than the left side.

• If the elevations are furthermore with the acute costophrenic angle, it indicates the presence of right diaphragm paralysis.

• If the left and right side hemidiaphragm are equal, it indicates the left hemidiaphragm paralysis.

Pulmonary Tests:

• During the inspiration process, the diaphragm activity supports about 80 percent of the breathing process by contracting inwards.

• In the case of unilateral diaphragmatic paralysis, around 50% of declination is observed in the forced vital capacity.

• Due to muscle weakness, the value is decreased by up to 25% in the supine position and cranially directed pressure from the abdominal cavity.

• In unilateral paralysis, other values of pulmonary volumes are unaltered and remain the same.

• In bilateral paralysis, the patient may experience about 70 to 80% of declination in the lung capacity.

Sniff Test:

• The radiologists observe the diaphragm with the help of fluoroscopy when the patient sniffs.

• In a healthy individual, the normal lungs may move down, and the lung expands.

• In the case of paralysis, the affected lung moves up and gets compressed.

Phrenic Nerve Stimulation Testing:

• In the paralysis of diaphragm muscles, this test confirms the abnormality in the functionality of the phrenic nerves.

Magnetic Resonance Imaging:

This test determines the presence of any underlying conditions with the involvement of the spinal column.

Computed Tomography:

Computed tomography (CT) scans of the thorax reveals the highly positioned diaphragm and also confirms the absence of a tumor on the phrenic nerve.

What Are the Treatment Approaches for Diaphragmatic Paralysis?

Diaphragmatic Plication:

• It refers to the surgical procedure that positions the diaphragm down so that it does not compress the lungs.

• If the patient presents with mild symptoms, is asymptomatic, or is in good condition, no specific treatment is required other than temporary ventilator support.

Diaphragmatic Pacemakers:

• It is performed in patients with no incidence of phrenic injury.

• But this treatment approach is not indicated in patients with muscular atrophy.

• In most cases of bilateral muscle paralysis, the patient is placed under ventilatory support with a portable ventilator.

• Tracheostomy is a surgical procedure that helps form an opening in the trachea.

Conclusion:

Diaphragmatic paralysis involving unilateral and bilateral muscle weakness is serious if left untreated. A surgical approach to transfer phrenic nerves is considered. Many patients showed improvements in exercise tolerance with non-invasive positive pressure ventilation.