What causes spasms of the diaphragm?

Causes of Diaphragm Spasms

Diaphragm spasms result from pathological excitation of the diaphragm muscle due to neuromuscular dysfunction, metabolic disturbances, mechanical stress, or inflammatory conditions affecting the muscle or its innervation. 1

Neurological and Neuromuscular Causes

The diaphragm's function depends critically on intact phrenic nerve innervation and neuromuscular transmission, making it vulnerable to numerous neurological disorders:

Motor Neuron and Nerve Disorders

• Phrenic neuropathies (isolated unilateral or bilateral) can cause significant diaphragm weakness and abnormal contractile patterns 2
• Motor neuron diseases including amyotrophic lateral sclerosis, spinal muscular atrophy, and Kennedy syndrome affect diaphragmatic control 2
• Brachial plexitis can extend to involve phrenic nerve function 2
• Peripheral neuropathies such as Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy (CIDP), and critical illness neuropathy commonly affect respiratory muscle function 2

Neuromuscular Junction Disorders

• Myasthenia gravis, Lambert-Eaton syndrome, and botulism frequently affect diaphragmatic function through impaired neuromuscular transmission 2
• These conditions can cause fluctuating diaphragm weakness and abnormal contractile patterns 2

Muscle-Based Causes

Primary Muscle Diseases

• Muscular dystrophies, polymyositis/dermatomyositis, and congenital myopathies directly affect diaphragm contractility 2
• Mitochondrial encephalomyopathies and acid maltase deficiency impair muscle energy metabolism, predisposing to abnormal contractions 2
• Hereditary channel disorders can cause episodic muscle dysfunction including spasms 2

Diaphragm Fatigue and Injury

• Respiratory muscle fatigue is central to pathological diaphragm excitation, particularly in infants where it can trigger spasms, flutter, or cramp 1
• Malnutrition causes respiratory muscle weakness and susceptibility to diaphragmatic fatigue, increasing risk of abnormal contractions 3
• Diaphragm injury from hypoxemia, hyperthermia, or viral myositis can lead to disrupted myofibers and abnormal excitation patterns 1

Mechanical and Structural Causes

Trauma and Structural Damage

• Traumatic diaphragmatic injury from blunt or penetrating trauma creates defects that can alter normal contractile patterns 3
• Diaphragm contusion (AAST Grade I injury) can cause localized dysfunction 3
• Lacerations of varying severity (Grades II-V) disrupt normal muscle architecture and function 3

Increased Workload

• Abnormal lung mechanics increase pleural pressure swings to which the diaphragm is exposed, potentially triggering abnormal contractions 3
• A workload surge from position changes or REM-sleep inactivation of accessory muscles can trigger pathological diaphragm excitation 1

Gastrointestinal and Inflammatory Causes

• Gastroesophageal reflux and aspiration cause pulmonary inflammation and bronchospasm, which can secondarily affect diaphragmatic function 3
• Viral infections contribute to diaphragm fatigue and can cause viral myositis affecting the muscle directly 1
• Esophageal spasms can be confused with diaphragmatic dysfunction when measuring pressures 3

Metabolic and Systemic Factors

Fluid and Electrolyte Imbalances

• Decreased renal excretion of water causes increased lung water and altered respiratory mechanics that stress the diaphragm 3
• Cardiac dysfunction leading to increased lung water can increase airway resistance and diaphragmatic workload 3

Environmental and Toxic Factors

• Nicotine exposure, overheating, and rebreathing all contribute to diaphragm fatigue and abnormal excitation 1
• These factors are particularly relevant in vulnerable populations like infants 1

Clinical Pitfalls

A critical caveat: Diaphragm spasms detected during pressure measurements may actually represent esophageal spasms rather than true diaphragmatic dysfunction, emphasizing the need for careful technique and interpretation 3. Additionally, diaphragm dysfunction often remains underdiagnosed because patients may not be aware of non-respiratory symptoms, and clinicians may not immediately recognize manifestations beyond dyspnea 4, 5.

In preterm infants, electromyography studies demonstrate that diaphragm fatigue causes temporary failure through transient spasms, inducing apneas and hypoxemic episodes 1. This represents a particularly dangerous scenario where prolonged spasm could theoretically cause sustained apnea and cardiac arrest 1.