A
hiccup (
// HIK-əp; also spelled
hiccough) is an involuntary contraction (myoclonic jerk) of the
diaphragm that may repeat several times per minute. In
medicine, it is known as
synchronous diaphragmatic flutter (SDF), or
singultus, Latin for the act of catching one's breath while sobbing.
[1] The hiccup is an
involuntary action involving a
reflex arc.
[1]
Once triggered, the reflex causes a strong contraction of the diaphragm
followed about 0.25 seconds later by closure of the vocal cords, which
results in the classic "hic" sound. At the same time, the normal
peristalsis of the
esophagus is suppressed.
[citation needed]
Hiccups may occur individually, or they may occur in bouts. The
rhythm of the hiccup, or the time between hiccups, tends to be
relatively constant.
A bout of hiccups, in general, resolves itself without intervention, although many
home remedies are often used to attempt to shorten the duration.
[2] Medical treatment is occasionally necessary in cases of chronic hiccups.
Phylogenetic hypothesis
An international respiratory research group composed of members from
Canada, France and Japan proposed that the hiccup is an evolutionary
remnant of earlier
amphibian respiration.
[3] Amphibians such as
tadpoles gulp air and water across their gills via a rather simple motor reflex akin to
mammalian hiccuping. The motor pathways that enable hiccuping form early during
fetal development, before the motor pathways that enable normal
lung ventilation form. Thus, according to
recapitulation theory the hiccup is
evolutionarily antecedent to modern
lung respiration.
Additionally, this group (C. Stauss et al.) points out that hiccups and
amphibian gulping are inhibited by elevated
CO2 and may be stopped by
GABAB receptor agonists, illustrating a possible shared physiology and
evolutionary heritage. These proposals may explain why
premature infants spend 2.5% of their time hiccuping, possibly gulping like
amphibians, as their
lungs are not yet fully formed.
[4]
Fetal intrauterine hiccups are of two types. The physiological type
occurs prior to twenty-eight weeks after conception and tend to last
five to ten minutes. These hiccups are part of fetal development and are
associated with the myelination of the
phrenic nerve, which primarily controls the
thoracic diaphragm.
The
phylogeny hypothesis explains how the hiccup reflex might have
evolved, and if there is not an explanation it may explain hiccups as an evolutionary remnant, held-over from our amphibious ancestors.
[5]
This hypothesis has been questioned because of the existence of the
afferent loop of the reflex, the fact that it does not explain the
reason for glottic closure, and because the very short
contraction of the hiccup is unlikely to have a significant strengthening effect on the slow-
twitch muscles of
respiration.
Clearance of air from stomach
A more recent explanation by Howes in 2012 suggests that hiccups may
have evolved along with other reflexes developed in mammals that allow
them to coordinate suckling milk and breathing.
[6]
Hiccups are only found in mammals, and are most common in infants,
becoming rarer as mammals age. This may suggest that they evolved to
allow air trapped in the stomach of suckling infants to escape, allowing
more milk to be ingested. The hypothesis suggests that the air bubble
in the stomach stimulates the sensory limb of the reflex at receptors in
the stomach, esophagus and along the diaphragm. This triggers the
hiccup, which creates suction in the chest, pulling air from the stomach
up and out through the mouth, effectively burping the animal. This
theory is supported by the strong tendency for infants to get hiccups,
the component of the reflex that suppresses peristalsis in the
esophagus, and the existence of hiccups only in milk-drinking mammals.
Signs and symptoms
- A single or a series of breathing diaphragm spasms, of variable spacing and duration.
- A brief (less than one half second), unexpected, shoulder, abdomen, throat, or full body tremor.
- Hiccups may present as an audible chirp, squeak, "hupp", or if controlled, a quick inhaling gasp, sigh, or sniff.
- Hiccups may present as brief but distracting or painful, frequent or
occasional interruptions in normal breathing, with sudden momentary
pain of the throat, chest, and/or abdomen.
Causes
- Coughing
- Rapid eating[6]
- Intense emotions such as fear, anxiety, excitement, joy, or euphoria
- Carbonated beverages, alcohol, dry breads, and some spicy foods[7]
- Laughing[8]
Pathologic causes for hiccups
Hiccups may be triggered by a number of common human conditions. Rarely, they can be a sign of serious medical problems.
Pre-phrenic nucleus irritation of medulla
Clinical case reports mention that lesions of the
medulla that involve the area slightly ventral and lateral to nucleus and
tractus solitarius cause hiccups. One (of several) explanations for this finding is that such a lesion “irritates” descending information from
nucleus solitarius to the
phrenic nucleus. The phrenic nucleus consists of a functionally related group of cell bodies in the
ventral horn from C3-C5. Axons arising from the phrenic nucleus comprise the
phrenic nerve,
which innervates the diaphragm. The hiccups result from spasmodic
lowering of the diaphragm that causes a short, sharp inspiratory cough.
Brain stem lesions involving the area ventral and lateral to nucleus and tractus solitarius result in hiccup.
[9]
Infections
CNS disorders
Nerve damage/irritation
Treatment
Hiccups are normally treated at home through self-care. Hiccups are
treated medically only in severe and persistent (termed "intractable")
cases.
Numerous medical remedies exist but no particular treatment is known to be especially effective.
[13] Many drugs have been used, such as
baclofen,
chlorpromazine,
metoclopramide,
gabapentin, and various
proton-pump inhibitors. Hiccups that are secondary to some other cause like
gastroesophageal reflux disease or
esophageal webs are dealt with by treating the underlying disorder. The
phrenic nerve can be
blocked temporarily with injection of 0.5%
procaine,
or permanently with bilateral phrenicotomy or other forms of surgical
destruction. Even this rather drastic treatment does not cure some
cases, however.
An anecdotal medical approach is to install
lidocaine
liniment 3% or gel 2% into the ear canal. Somehow this creates a vagus
nerve-triggering reflex through its extensions to the external ear and
tympanus (ear drum). The effect can be immediate, and also have lasting
effect after the lidocaine effect expires after about two hours.
[14]
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. Effective treatment with sedatives often
requires a dose that renders the person either unconscious or highly
lethargic. Hence, medicating with sedatives is only appropriate
short-term, as the affected individual cannot continue with normal life
activities while under their effect.
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.
[citation needed] The carbonation promotes quicker absorption.
Carbonated beverages, including beer, by themselves may provoke hiccups in some people.
[citation needed]
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.
[15]
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."
[16]
Lockhart stated that hiccups can sometimes be cured by pinching the skin that covers the surface of the
deltoid muscles, thus pinching the phrenic nerve branch located there.
[17]
Self-care and folk remedies
There are many superstitious and folk remedies for hiccups, including
headstanding,
drinking a glass of water upside-down, being frightened by someone,
breathing into a bag, and eating a large spoonful of peanut butter.
Placing sugar on or under the tongue has also been used.
[18][19]
A simple treatment involves increasing the
partial pressure of
CO2 and inhibiting diaphragm activity by holding one’s breath or rebreathing into a
paper bag.
Vagus nerve stimulation can improve hiccups, done at home by irritating the
pharynx through swallowing dry bread or crushed ice, or by applying
traction to the tongue, or by stimulating the
gag reflex.
In
Plato's
Symposium,
Aristophanes has a case of the hiccups and is advised by Eryximachus, a physician, to cure them by holding his breath, or, failing that, by
gargling or provoking
sneezing. This ancient recommendation can be compared with the vagus nerve stimulation techniques mentioned previously.
Society and culture
American
Charles Osborne had hiccups for 68 years, from 1922 to February 1990,
[20] and was entered in the
Guinness World Records as the man with the longest attack of hiccups, an estimated 430 million hiccups.
[21] In 2007,
Florida teenager Jennifer Mee gained media fame for hiccuping around 50 times per minute for more than five weeks.
[22][23]
Christopher Sands, a Briton, hiccupped an estimated 10 million times in
a 27-month period from February 2007, to May 2009. His condition, which
meant that he could hardly eat or sleep, was eventually discovered to
be caused by a tumor on his brain stem pushing on nerves causing him to
hiccup every two seconds, 12 hours a day. His hiccups stopped in 2009
following surgery.
[24]
In Slavic, Baltic and Hungarian folklore, it is said that hiccups
occur when the person experiencing them is being talked about by someone
not present. In Indian, Nepalese, and Arabic folklore, they are
similarly said to occur when the person experiencing them is being
thought of by somebody close.