A hiccup or hiccough (pronounced /ˈhɪkʌp/ HICK-up) is an esophageal contraction of the diaphragm that repeats several times per minute. In humans, the abrupt rush of air into the lungs causes the epiglottis to close, creating a "hic" sound.
In medicine it is known as synchronous diaphragmatic flutter (SDF), or singultus, from the Latin singult, "the act of catching one's breath while sobbing". The hiccup is an involuntary action involving a reflex arc.
A bout of hiccups, in general, resolves itself without intervention, although many home remedies claim to shorten the duration, and medical treatment is occasionally necessary in cases of chronic hiccups.
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Hiccups are caused by many central and peripheral nervous system disorders, all from injury or irritation to the phrenic and vagus nerves, as well as toxic or metabolic disorders affecting the aforementioned systems. Hiccups often occur after drinking carbonated beverages or alcohol. Prolonged laughter is also known to cause hiccups. Eating too fast can also cause the hiccups. Persistent or intractable hiccups may be caused by any condition which irritates or damages the relevant nerves. Chemotherapy—which can include a huge amount of different drugs—has been implicated in hiccups (some data states 30 percent of patients), while other studies have not proven such a relationship. Many times chemotherapy is applied to tumors sitting at places that are by themselves prone to cause hiccups, if irritated.
Christian Straus and co-workers at the Respiratory Research Group, University of Calgary, Canada, propose that the hiccup is an evolutionary remnant of earlier amphibian respiration; amphibians such as frogs gulp air and water via a rather simple motor reflex akin to mammalian hiccuping. In support of this idea, they observe that the motor pathways that enable hiccuping form early during fetal development, before the motor pathways that enable normal lung ventilation to form; thus according to recapitulation theory the hiccup is evolutionarily antecedent to modern lung respiration. Additionally, they point out that hiccups and amphibian gulping are inhibited by elevated CO2 and can be completely stopped by the drug Baclofen (a GABAB receptor agonist), illustrating a shared physiology and evolutionary heritage. These proposals explain why premature infants spend 2.5% of their time hiccuping, indeed they are gulping just like amphibians, as their lungs are not yet fully formed.
Ordinary hiccups are cured easily without medical intervention; in most cases they can be stopped simply by forgetting about them. However, there are a number of anecdotal treatments for casual cases of hiccups. Some of the more common home remedies include giving the afflicted a fright or shock, eating peanut butter, taking a teaspoon of vinegar, drinking water (sometimes in an unorthodox manner), holding one's breath and altering one's breathing patterns. A solution involving sugar placed on or under the tongue was cited in the December 23, 1971 issue of the New England Journal of Medicine.
Hiccups are treated medically only in severe and persistent (termed "intractable") cases, such as in the case of a 15-year-old girl who, in 2007, hiccuped continuously for five weeks. Haloperidol (Haldol, an anti-psychotic and sedative), metoclopramide (Reglan, a gastrointestinal stimulant), and chlorpromazine (Thorazine, an anti-psychotic with strong sedative effects) are used in cases of intractable hiccups. In severe or resistant cases, baclofen, an anti-spasmodic, is sometimes required to suppress hiccups. Effective treatment with sedatives often requires a dose that renders the person either unconscious or highly lethargic. Hence, medicating singultus is done short-term, as the affected individual cannot continue with normal life activities while taking the medication.
Persistent and intractable hiccups due to electrolyte imbalance (hypokalemia, hyponatremia) may benefit from drinking a carbonated beverage containing salt to normalize the potassium-sodium balance in the nervous system. The carbonation promotes quicker absorption. Carbonated beverages by themselves may have a tendency to provoke hiccups in some people.
The administration of intranasal vinegar was found to ease the chronic and severe hiccups of a three-year old Japanese girl. Vinegar may stimulate the dorsal wall of the nasopharynx, where the pharyngeal branch of the glossopharyngeal nerve (the afferent of the hiccup reflex arc) is located.
Dr. Bryan R. Payne, a neurosurgeon at the Louisiana State University Health Sciences Center in New Orleans, has had some success with an experimental procedure in which a vagus nerve stimulator is implanted in the upper chest of patients with an intractable case of hiccups. "It sends rhythmic bursts of electricity to the brain by way of the vagus nerve, which passes through the neck. The Food and Drug Administration approved the vagus nerve stimulator in 1997 as a way to control seizures in some patients with epilepsy. In 2005, the agency endorsed the use of the stimulator as a treatment of last resort for people with severe depression".
While numerous home remedies are offered, they mostly fall into two broad categories: purely psychosomatic cures centered on relaxation and distraction and cures involving swallowing and eating (with the general rationale that this would remove irritants or reset mechanisms in the affected region).
In 2007, a teenager from Washington State in the United States named Cheyenne Motland hiccuped around 50 times a minute for more than five weeks. After her hiccups returned, her neurologist suggested that she may have Tourette syndrome, and the hiccups may be a "tic" caused by Tourette's.
Christopher Sands from the UK had hiccups for a period of almost three years which was eventually discovered to be due to a tumor located on the part of the brain that controls vascular activities, once 2/3 of the tumor was removed the hiccups appeared to settle and Sands no longer suffers from his condition.