The anatomy of the facial nerve in relation to CT/sialography of the parotid gland.

The technique of computed tomography with simultaneous parotid sialography allows for accurate localisation of tumours within the parotid gland. The relationship of these tumours to the facial nerve, which divides within the gland, is of surgical significance. A study of the course of the facial nerve through the parotid gland in the cadaver was therefore undertaken in order to identify relevant landmarks for the CT prediction of its relationship to those tumours. The heads of five cadavers were sectioned in the Frankfurt plane into 1 cm slices which were then X-rayed. Individual slices were examined and the course of the facial nerve was plotted on the X-ray plate of the same slice. It was found that the nerve could be represented on a CT scan by an arc of radius 8.5 mm, the centre of which is the most posterior point of the ramus of the mandible. The arc extends from directly lateral to directly posterior to that point. Pre-operative visualisation of parotid tumours by simultaneous CT scan and sialography in conjunction with an appreciation of the course of the facial nerve through the parotid gland may allow for more precise presurgical planning.