Hiccups

Also called hiccoughs.

 

Physiology

A hiccup is a very a common and harmless phenomenon. 

It is a reflex arc from the diaphragm, up the phrenic nerve to the brainstem, then down the vagus nerve to the muscle fibers. It causes involuntary contraction of the diaphragm. The characteristic "hic" or "hup" sounds are caused by an involuntary closure of the glottis as air is drawn past them by the contracting diaphragm. The process usually repeats and may last for minutes or even days. 

The causes and treatments of hiccups are so numerous, that there is no consensus on how exactly the process is coordinated in the brain. The initiation and termination of hiccups are likely mediated by various neurotransmitters.

There is a phylogenetic hypothesis that hiccups are a remnant from the evolutionary history of humans. It may be an earlier pathway of respiration which was used by amphibious ancestors. 

 

Pathology

Even a prolonged bout of hiccups is usually not a sign of underlying disease. 

Hiccups can be triggered by: 

• Excessive air swallowing
• Eating too rapidly
• Intense emotions
• Laughter
• Certain beverages and foods

However, in some cases, it is a useful diagnostic clue. 

• Abdominal pathologies. E.g. subphrenic abscess. In cases with an abdominal infection, the diaphragm can become irritated, stimulating the phrenic nerve. 
• Metabolic disorders. E.g. uraemia. Uraemia may stimulate the initiation of hiccuping in the medulla. 
• Lesions of the central nervous system. E.g. brainstem tumours. 
• Lesions of the vagus nerve. 
• Psychogenic disorders. 
• Drug use. E.g. opioids.  

 

Management

Simple hiccups can often be resolved by simple stimulation of the involved nerves. For example, holding your breath, swallowing water, and other maneuvers may stimulate the glottis.