According to the WHO classification, they are tumors belonging to the group of parasympathetic (non-chromaffin) branchiomeric
paragangliomas, known as chemodectomas (1).
The phylogeny of the muscles of facial expression and the facial nerve is somewhat less easily understood than that of other muscles of branchiomeric
These segmentally and symmetrically distributed paraganglia may be classified according to their anatomic distribution as branchiomeric
, intravagal, aorticosympathetic, and visceral autonomic.
Paragangliomas are made up of cells that originate in the branchiomeric
paraganglionic system and that develop in close relationship to the laryngeal arteries.