A CLINICO-ANATOMIC STUDY OF THE AURICULAR BRANCH OF THE VAGUS NERVE AND ARNOLDS EAR-COUGH REFLEX

The results of a clinico-anatomic study of the auricular branch of the vagus nerve (ABVN) and Arnold's ear-cough reflex are presented. The f requency of the ear-cough reflex was found to be 2.3% (12 out of 514 p atients). It was bilateral in 3 cases (0.6%). The reflex was elicited by palpation of the posteroinferior wall of the external acoustic meat us (EAM) in 11 patients, and by palpation of the antero-inferior wall in one patient (0.2%). The reflex was frequently noticed to occur afte r a short latent period. The course of the ABVN inside the jugular for amen (JF), and distribution of the terminal branches of the ABVN in th e external acoustic meatus were determined in 8 male cadavers (16 side s). In addition, the length of the mastoid canaliculus (MC) and the re lationships of the ABVN with the facial nerve and stylomastoid foramen (SMF) were studied in both cadavers and 25 dry skulls (50 sides). Hig h-resolution computed tomography (HRCT) scanning was also performed in all cadavers prior to microdissections. The ABVN emerged from the sup erior ganglion of the vagus nerve in all the cadavers. It ran between the internal jugular vein (IJV) and the bony wall of the jugular foram en. The ABVN was encased in a partial bony canal during its course fro m the jugular foramen to mastoid canaliculus in 18% of all specimens. The average length of the mastoid canaliculus was 5.6 mm (4.2-6.5), an d it ran transversely towards the tympanomastoid suture 4.5 mm (4-5.1) above the stylomastoid foramen. The mastoid canaliculus was well demo nstrated in all the HRCT scans.