Pictorial Review of the Congenital Abnormalities of the Facial Nerve, on CT and MRI

The frequency and importance of the imaging evaluation of the temporal bone and middle ear have increased significantly over the past 30 years, especially prior to ear surgery. Nowadays, conventional computed tomography (CT) of the temporal bone and in fewer cases magnetic resonance imaging (MRI) of the middle ear allow a detailed evaluation of the small and complex structures of the ear and the surrounding nerves. Familiarity with the spectrum of congenital anomalies of the facial nerve and knowledge of normal facial nerve anatomy lead to simple well-defined diagnostic imaging criteria. The purpose of this article is to discuss the different imaging features of the congenital anomalies of the facial nerve, including agenesia, hypoplasia, anomalies of the course, size, and nerve duplications, compared with normal anatomical images at the same level of section for a better understanding, as the facial nerve must always be analyzed on temporal bone imaging, and any modification of its size or course has to be reported prior to any surgical procedure.