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The word hiccup (hiccough or singultus) appears, from its date, to be a variation of the earlier hickock, or hicket. Hiccough, a later spelling, appearing under the erroneous impression that the second syllable was cough; it ought to be abandoned as a mere error (OED).
The English hicket corresponds in formation to the French, and is the earliest form that evolved in series through, hickot, hickock, hickop, to hiccup. For example, T Phaer in Regim Lyfe (1553) remarked,
“It is good to cast colde water in the face of him that hath the hicket.”
Many other 16th century writers suggested imaginative domestic remedies. Burton’s famous Anatomy of melancholy (1651) notes the effect of shock as a cure:
“By some false accusation, as they do to such as have the hick/hop, to make them forget it.”
And in the 1727 Bradley’s family dictionary you find:
“You must in the very instant that the hickup seizes the party pull his ring-finger, and it will go off.”
The South African hiccup-nut is a fruit of an ornamental shrub, Combretum bracteosum (Poivrea), that presumably affects the hiccups. 20th century medical texts afford little detail. It does not feature in the index of Gowers’ first edition but is briefly mentioned on p 295 of the second edition:
“connected with affections of the pneumogastric nerve as they certainly are with the respiratory centre”.
SAK Wilson, in Neurology (London, Edward Arnold, 1940; 2nd vol: 1652), provides a brief account without his usual historical notes. He describes a common clonic type and a tonic type seen in tetanus and tonic fits.
Hiccups occur in late fetal life and often in neonates. A hiccup is an intense synchronous contraction of the diaphragmatic and inspiratory intercostal muscles lasting about 500 ms, followed 30 ms after its onset by glottal closure, which causes the characteristic inspiratory sound and discomfort. It can continue in sleep, and may cease in response to emotional shock. They usually occur with a frequency of 15–30/min. Increasing PaCO2 and breath holding reduce hiccup frequency (and may eliminate it); but a low PaCO2 increases the amplitude but not frequency.1 It seems to be served by a supraspinal mechanism largely distinct from the automatic respiratory system. The characteristics suggest a gastrointestinal nature; its function (if any) is unknown.
Diseases of the medulla in the region of nucleus of tractus solitarius may cause symptomatic hiccup. Common causes are brainstem infarction, tumour, and encephalitis. Uraemia and diverse cardiothoracic, and abdominal pathologies, related to the vagus nerves are well recognised. Many attacks cease spontaneously or respond to pharyngeal stimuli such as drinking iced water. When caused by brainstem or metabolic disease, most methods fail to sustain relief. Raising the PaCO2 by rebreathing from a paper bag is an old but generally effective remedy.
Nasal mucosal stimulation sufficient to provoke sneezing may also abort hiccup, as first reported by Plato in The Symposium, in 416 BC— an observation seldom credited by modern authors.
A related curiosity is high frequency diaphragmatic flutter. Symptoms are of chronic oesophageal belching, hiccups, and, sometimes, dyspnoea, chest pain, and visible epigastric pulsations. EMG and spirometry show 9–15 Hz frequency contractions in the diaphragm, scalene, and parasternal intercostal muscles. Antony van Leeuwenhoek described this condition in himself.2 It may respond to carbamazepine.3