What causes hiccups?

What Causes Hiccups

Hiccups result from involuntary myoclonic contractions of the diaphragm and intercostal muscles followed by sudden glottic closure, triggered by irritation anywhere along a reflex arc involving the phrenic nerve, vagus nerve, and sympathetic pathways with central modulation in the brainstem. 1, 2

Mechanism of Hiccup Generation

The hiccup reflex arc consists of three components that, when stimulated, produce the characteristic "hic" sound 2:

• Afferent pathways: Phrenic nerve, vagus nerve, and sympathetic nerve fibers (T6-T12) 2
• Central processing: Midbrain modulation center in the brainstem 2
• Efferent pathways: Phrenic nerve to diaphragm, causing sudden contraction followed immediately by laryngeal closure 1, 2

Common Causes by Category

Gastrointestinal Causes (Most Common)

Gastric distention and gastroesophageal reflux are the most frequent triggers of hiccups in clinical practice. 1, 3

• Gastric distention from overeating or carbonated beverages 1
• Gastroesophageal reflux disease (GERD) and esophagitis 1, 3, 2
• Gastric and duodenal ulcers, gastritis 1
• Inflammatory bowel diseases and celiac disease 4

Cardiovascular Causes

• Myocardial infarction 1, 2
• Pericarditis and pericardial effusion (via phrenic nerve compression) 5, 4

Central Nervous System Causes

• Brain tumors and space-occupying lesions 1, 2
• Stroke 2
• CNS injury 2

Medication-Induced Hiccups

• Aripiprazole (acts as dopamine agonist at low doses <7.5 mg/day, stimulating D2/D3 receptors in the brainstem hiccup center) 6
• Mycophenolate mofetil, propofol, and beta-blockers 4
• Anti-parkinsonism drugs, anesthetic agents, steroids, and chemotherapy 2

Other Peripheral Causes

• Mediastinal lesions and tumors 4, 2
• Post-surgical complications and abdominal surgery 4, 1
• Herpes infection 2
• Ear, nose, and throat conditions affecting the vagus nerve 4, 2
• Renal failure 1
• Prostate cancer 1

Transient Triggers

• Alcohol intake 1
• Sudden temperature changes 2

Clinical Significance by Duration

Short hiccup bouts (<48 hours) are typically benign and associated with gastric distention or alcohol, resolving spontaneously without medical intervention. 1

• Persistent hiccups (>48 hours): Warrant medical evaluation 2
• Intractable hiccups (>2 months): Indicate serious underlying pathology requiring comprehensive workup including upper GI endoscopy, pH monitoring, chest/brain CT imaging, and abdominal ultrasound 1, 2

Key Clinical Pitfall

Upper gastrointestinal pathology (GERD, ulcers, gastritis, esophagitis) is commonly overlooked but frequently responsible for chronic hiccups—upper GI investigations including endoscopy should be performed systematically in all persistent cases. 1 This is critical because gastroesophageal reflux may be substantially underestimated as a hiccup etiology, and treating the underlying reflux can lead to complete resolution even when other antisingultus medications have failed 3.