Sonography, CT, CT sialography, MRI and MRI sialography in investigation of the facial nerve and the differentiation between deep and superficial parotid lesions.

Our aim was to explore the possibility of delineation of the facial nerve within the parotid gland and to differentiate between superficial and deep parotid lesions in relationship to it, using ultrasound, CT, MRI, MRI sialography (MRIS) and CT sialography (CTS). We examined 47 patients with clinically suspected parotid tumours by US, 31 of them also by CT, MRI and CTS, and 13 by MRIS as well. Low-intensity curvilinear structures seen on T1-weighted MRI were delineated better after intraductal gadolinium injection and proved to represent parotid ducts on CTS. Using the main parotid duct as a landmark, we distinguished parotid lesions as deep or superficial to the facial nerve by T1-weighted MRI images in 69% and by MRIS in all cases. The facial nerve itself was indistinguishable from the parotid gland in all our imaging methods.