Causes of Diaphragmatic Spasms
Diaphragmatic spasms result from a combination of traumatic injury, metabolic derangements, neurological dysfunction, and gastrointestinal disorders, with trauma and malnutrition being the most common structural and systemic causes respectively. 1
Traumatic and Structural Causes
- Blunt or penetrating trauma creates diaphragmatic defects that fundamentally alter normal contractile patterns, representing a primary mechanical cause of abnormal diaphragmatic movement 2, 1
- Diaphragm contusion (AAST Grade I injury) produces localized dysfunction that can manifest as spasmodic activity 2, 1
- Lacerations ranging from Grade II through Grade V progressively disrupt muscle architecture and coordinated function 2, 1
Metabolic and Systemic Factors
- Malnutrition weakens respiratory muscles and increases susceptibility to diaphragmatic fatigue, predisposing to abnormal contractile patterns and spasms 2, 1
- Decreased renal function causes water retention that increases lung water content, altering respiratory mechanics and stressing the diaphragm 2, 1
- Cardiac dysfunction similarly increases lung water, raising airway resistance and diaphragmatic workload, which can trigger spasmodic activity 2, 1
Neurological Causes
- Central nervous system dyscoordination contributes to diaphragmatic flutter, particularly in patients with developmental delay or underlying neurological conditions 2
- Lower motor neuron involvement from spinal cord injury affects diaphragmatic function, demonstrable on needle electromyography 2
- Phrenic neuropathy represents a common neurological pathway, with causes including iatrogenic injury during thoracic surgery, amyotrophic lateral sclerosis, neuralgic amyotrophy, neuroborreliosis, multifocal motor neuropathy, chronic inflammatory demyelinating neuropathy, post-polio syndrome, cervical spondylosis affecting C4/5 nerve roots, and diabetes mellitus 3
- Demyelinating conditions such as multiple sclerosis can cause diaphragmatic paralysis through brainstem lesions affecting fibers descending to the phrenic nucleus 4
Gastrointestinal and Inflammatory Causes
- Gastroesophageal reflux and aspiration cause pulmonary inflammation and bronchospasm that secondarily affect diaphragmatic function 2, 1
- Esophageal spasms can be confused with diaphragmatic dysfunction during pressure measurements and may coexist with true diaphragmatic spasms 2, 1
High-Frequency Flutter Variant
- A distinct entity of high-frequency diaphragmatic flutter (9-15 Hz) presents with esophageal belching, hiccups, and retching rather than classic respiratory symptoms 5
- This variant responds to carbamazepine 200-400 mg three times daily, suggesting a neurogenic origin 5
Clinical Pitfall
The key diagnostic challenge is that symptoms vary dramatically based on whether involvement is unilateral or bilateral—unilateral cases may be completely asymptomatic while bilateral involvement can cause disabling dyspnea and ventilatory failure requiring mechanical ventilation 6, 7. Maintain high clinical suspicion in patients with unexplained dyspnea that worsens in supine position, as this postural change is typical of diaphragmatic dysfunction 6, 7.