Diaphragm paralysis is a condition where the diaphragm, the primary muscle responsible for breathing, loses its ability to function properly. This significantly reduces the lungs’ capacity to take in air, making it difficult to inhale and exhale effectively. The condition can range in severity, impacting one side of the diaphragm or both, leading to various respiratory challenges.
The Diaphragm’s Essential Role
The diaphragm is a large, dome-shaped muscle located at the base of the chest cavity, separating it from the abdomen. During inhalation, the phrenic nerve, which originates from cervical spinal nerves C3 through C5, sends signals to the diaphragm, causing it to contract and flatten. This contraction increases the volume within the chest cavity, allowing the lungs to expand and draw in air.
Conversely, during exhalation, the diaphragm relaxes and returns to its dome shape, reducing the chest cavity volume and passively expelling air from the lungs. The diaphragm accounts for approximately 70-80% of the effort required for normal breathing.
Understanding the Causes
Diaphragm paralysis often results from damage or disruption to the phrenic nerve, which controls the diaphragm’s movement. Common causes include surgical trauma, particularly after cardiothoracic or cervical procedures, and birth trauma in infants. Blunt or penetrating trauma to the neck or chest can also disrupt nerve function.
Neurological conditions are another significant category of causes. Diseases such as Amyotrophic Lateral Sclerosis (ALS), muscular dystrophy, multiple sclerosis, and Guillain-Barré syndrome can progressively weaken or paralyze the diaphragm. Spinal cord disorders, especially injuries to the cervical spine (C3-C5), can interrupt signals to the diaphragm. Infections like polio, herpes zoster, and Lyme disease have also been linked to phrenic nerve damage. In some cases, tumors in the lung or lymph nodes can compress the phrenic nerve. Despite investigation, the cause remains unknown for 20-50% of cases, classified as idiopathic.
Identifying the Symptoms
Symptoms vary depending on whether one side (unilateral) or both sides (bilateral) of the diaphragm are affected, and any underlying lung or heart conditions. Shortness of breath (dyspnea) is the most common symptom, often worsening during physical activity or when lying flat. This difficulty breathing when supine is known as orthopnea.
Individuals with unilateral diaphragm paralysis may experience no symptoms at rest, or only mild shortness of breath during exertion. However, if they have pre-existing heart or lung conditions, symptoms can become more evident. Bilateral diaphragm paralysis leads to more severe symptoms, including shortness of breath even at rest. Patients may also experience sleep disturbances, such as sleep apnea, hypersomnia, or morning headaches, due to reduced oxygen levels during sleep. Other indicators include fatigue, reduced exercise tolerance, and increased susceptibility to recurrent respiratory infections like pneumonia, as the weakened diaphragm struggles to clear lung secretions. A physical sign often observed in bilateral cases is paradoxical abdominal motion, where the abdomen moves inward during inhalation instead of outward.
Diagnosis and Treatment Approaches
Diagnosing diaphragm paralysis typically begins with a physical examination, where a healthcare provider may observe paradoxical abdominal movement during breathing. Imaging techniques are crucial for confirmation. A chest X-ray can reveal an elevated hemidiaphragm, often the first indication. Fluoroscopy, combined with a “sniff test,” allows real-time visualization of diaphragm motion, showing absent or paradoxical movement. Ultrasound can assess diaphragm movement, while MRI may identify underlying conditions affecting the spinal column or nerve roots. Lung function tests, such as spirometry, help evaluate respiratory capacity, often showing reduced vital capacity that further decreases when lying down. Electromyography (EMG) and nerve conduction studies assess the electrical activity of the diaphragm muscle and phrenic nerve function.
Treatment depends on the underlying cause, symptom severity, and whether the condition is unilateral or bilateral. For mild or unilateral paralysis, watchful waiting may be recommended, as spontaneous recovery can occur. Non-invasive ventilation (NIV), such as CPAP or BiPAP, is a common supportive treatment, especially for nocturnal breathing difficulties. For individuals with intact phrenic nerves, phrenic nerve pacing is a surgical option where a device is implanted to send electrical impulses to the diaphragm, stimulating it to contract and assist breathing. This can help reduce dependence on mechanical ventilation. Diaphragmatic plication, another surgical intervention, involves suturing the diaphragm to flatten and stabilize it, improving lung expansion, particularly in unilateral cases. When an identifiable cause exists, such as nerve compression by a tumor, surgical nerve decompression may be the most effective treatment.