Imaging plays a critical role in the evaluation of a number of facial nerve disorders. The facial nerve has a complex anatomical course; thus, a thorough understanding of the course of the facial nerve is essential to localize the sites of pathology. Facial nerve dysfunction can occur from a variety of causes, which can often be identified on imaging. Computed tomography and magnetic resonance imaging are helpful for identifying bony facial canal and soft tissue abnormalities, respectively. Ultrasound of the facial nerve has been used to predict functional outcomes in patients with Bell’s palsy. More recently, diffusion tensor tractography has appeared as a new modality which allows three-dimensional display of facial nerve fibers. 1. Introduction Imaging plays an important role in the evaluation of facial nerve disorders. The facial nerve has a complex anatomical course, and dysfunction can be due to congenital, inflammatory, infectious, traumatic, and neoplastic etiologies. Computed tomography is useful for identifying bony abnormalities of the intratemporal facial nerve, which can occur with congenital malformations, trauma, and cholesteatoma. Magnetic resonance imaging (MRI) is useful for identifying soft tissue abnormalities around the facial nerve, as seen in inflammatory disorders, neoplasms, and hemifacial spasm. Facial nerve ultrasound has been used in a recent study to predict functional outcomes in Bell’s palsy [1]. Diffusion tensor (DT) tractography, which uses MRI to make three-dimensional (3D) reconstructions of the facial nerve, has recently been developed. This technique has been shown to be potentially useful in the identification displacement of cranial nerve fibers by vestibular schwannomas [2]. In all cases, choice of the imaging modality utilized should be determined by specifics of the patient’s symptoms and the differential diagnosis. In this paper we describe the development and anatomy of the facial nerve, then radiographic techniques used in facial nerve evaluation, and finally the pathologic entities that affect the facial nerve. 2. Development and Anatomy of the Facial Nerve The facial nerve is composed of motor, sensory, and parasympathetic fibers. Complete separation of the facial and acoustic nerves and development of the nervus intermedius (or nerve of Wrisberg) occurs by 6 weeks of gestation. By the 16th week, the neural connections are completely developed. The bony facial canal develops until birth, enclosing the facial nerve in bone throughout its course except at the facial hiatus (the site of the geniculate
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