When an audiologist cleans out an ear canal, the patient often coughs. Since it is a normal part of the process in cerumen management or other procedures, clinicians expect and prepare for these reflexive coughs. But what causes this cough reflex, and where does it come from?
The story begins with Philipp Friedrich Arnold (1803-1890), who was born in Edenkoben at Landau, Germany, in the middle of wine country. He and his older brother Johann Wilhelm Arnold (1801-1873) grew up together playing in the vineyards of Edenkoben in the shadow of a Royal Bavarian Castle, “Villa Ludwigshoehe“. The Royal Bavarian Castle was where King Ludwig of Bavaria would summer.
While roughly 50 miles may have seemed like quite a distance in the 1820s, Friedrich and Johann stayed rather close to home for their university education at the University of Heidelberg. Friedrich studied medicine as did Johann, who later became a homeopathic physician and physiologist at the University of Heidelberg. Friedrich’s teachers included Fredrich Tidemann (1781-1861) and Vincenz Fohmann (1794-1837). Tiedemann was a famous anatomist and also one the first people to present a scientific challenge of racism. In his article entitled “On the Brain of the Negro, compared with that of the European and the Orang-outang” (1836) he argued, based on craniometric and brain measures taken by him from Europeans and black men from different parts of the world, that the then-common European belief that Negroes have smaller brains and are thus intellectually inferior was scientifically unfounded and based merely on the prejudice of travelers and explorers.
In 1826, Friedrich visited the institutions of natural sciences and medicine in Paris with his brother, before being called back to Heidelberg to become a professor at the anatomical institution. In 1834, Friedrich Arnold was appointed extraordinary professor at the faculty of medicine in Heidelberg, and in 1835 accepted an invitation to become professor at and director of the institute of anatomy at the University of Zurich, where he stayed for five years. After stints at the University of Freiburg, and the University of Tübingen, he returned in 1852 to the University of Heidelberg, and in 1873 he completed his career where it had begun.
Arnold was a popular teacher who felt a deep concern for the welfare of his students. His early work in anatomy and physiology focused on the microanatomy of the nervous system beginning, but his long list of publications include a variety of themes. Of special importance is his textbook Lehrbuch der Physiologie der menschen (Textbook of Human Physiology), published in 1839 with his brother Johann. He published the Handbuch der Anatomie des Menschen (Handbook of Human Anatomy) in three volumes between 1843 and 1851. This work is of particular importance because it is the basis for Rudolf Arndt’s (1835-1900) theories on the build and development of the histological element of the animal body. His illustrated works, starting with Icones Nervorum Capitis published in 1834, are unique in German medical literature for their artistic merits. This was the first time art used as a teaching tool in medicine. He died in Heidelberg in 1890 at the age of 87.
Back to our original question……The cough reflex was outlined by Friedrich Arnold in his dissections and his writings, hence the names “Arnold’s Cough Reflex” and “Arnolds nerve.” Arnold dissected numerous human brains; his primary area of research was the “vagus nerve” (the 10th cranial nerve). He was the first to describe the auricular branch of the vagus (a nerve, which innervates the skin around the ear). Since then the following nomenclature is used in countries where English is spoken: “Arnold’s canal,” “Arnold’s ganglion,” “Arnold’s nerve” and “Arnold’s nerve cough.” In a small portion of individuals, the auricular nerve is the afferent limb of the Ear-Cough or Arnold Reflex. Physical stimulation of the external acoustic meatus, particularly the inferior and anterior areas innervated by the auricular nerve, elicits a cough, much like the other cough reflexes associated with the vagus nerve. References indicate that rarely, on the introduction of a speculum into the external ear, patients experience syncope (or fainting) due to the stimulation of the auricular branch of the vagus nerve. In reality, clinical experience indicates that preparation for a cough reflex must be made during cerumen management and when working deep in the canal as when taking impressions for CIC or ITC hearing instruments and inserting or removing extended wear hearing instruments such as Lyric. …..And we owe it all to Fred…..