Hiccups occur when the diaphragm (the muscle separating the lung and abdominal cavities that plays an important role in breathing) starts to involuntarily contract, causing a rapid closing of the vocal cords. There are many relatively minor causes of short-term hiccups, but there are also some serious causes of persistent hiccups, including nerve damage and brain injury.
Common Causes
According to Scientific American, hiccups most commonly arise when the stomach expands and stomach acid moves into the esophagus. Other common causes of short-term hiccups include drinking carbonated beverages, consuming too much food, eating too quickly, consuming spicy food and drinking excessive amounts of alcohol. The Mayo Clinic also cites sudden changes in temperature and emotional stress or excitement as common causes of hiccups.
Nerve Irritation
According to the Mayo Clinic, the most common cause of hiccups that persist for more than 48 hours is irritation of the nerves of the diaphragm, specifically the vagus or phrenic nerves. These nerves can become irritated if a hair or other object inside of the ear touches the eardrum. They may also become irritated or damaged by illness or disease, including a tumor, cyst or goiter in the neck region. Gastroesophageal reflux disease (GERD), a chronic condition in which digestive juices or bile flows back into the esophagus, can irritate the nerves of the diaphragm. Pneumonia, sore throat or laryngitis (an inflammation of the voice box due to a virus, damage or overuse) can also damage the vagus or phrenic nerves and induce hiccups.
Disease Affecting the Brain
The National Institutes of Health notes that serious causes of hiccups include diseases that damage the "hiccup center" of the brain, the area responsible for regulating the hiccup reflex. Stroke, tumors, multiple sclerosis, traumatic brain injury and encephalitis (an acute inflammation of the brain commonly caused by a virus) can all cause chronic hiccups. Meningitis, a swelling of the membranes covering the brain and spinal cord caused by viruses, bacteria or fungi, can also damage the brain and lead to uncontrollable hiccups.
Other Causes
The Mayo Clinic advises that metabolic disorders such as diabetes that interfere with the body's ability to make and use energy may lead to hiccups. Kidney failure, electrolyte imbalances (too much or too little potassium, sodium or calcium in the bloodstream), along with certain drugs like steroids, alcohol, barbiturates, tranquilizers and anesthesia, may also induce hiccups. According to the National Institutes of Health, other potential causes of hiccups include abdominal surgery or noxious fumes. In some cases, there may be no apparent cause for hiccups.
