There, the motor fibers supplying the facial musculature beneath the brows cross the midline to reach the contralateral motor nucleus in the reticular formation of the lower pons (anterior to the fourth ventricle). These fibers travel in the posterior limb of the internal capsule inferiorly to the caudal pons. As the mastoid tip develops, the extratemporal facial nerve is positioned in a more inferior and medial position.įacial motor fibers originate from cell bodies located in the precentral and postcentral gyri of the frontal motor cortex. The only difference between the anatomy of the facial nerve in infants compared with adults is in the region of the stylomastoid foramen. 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 ganglion) in the floor of the middle cranial fossa.
By the 16th week, the neural connections are completely developed. Complete separation of the facial and acoustic nerves and development of the nervus intermedius (or nerve of Wrisberg) occurs by 6 weeks of gestation. The facial nerve is composed of motor, sensory, and parasympathetic fibers. Development and Anatomy of the Facial Nerve 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.Ģ. In all cases, choice of the imaging modality utilized should be determined by specifics of the patient's symptoms and the differential diagnosis. This technique has been shown to be potentially useful in the identification displacement of cranial nerve fibers by vestibular schwannomas. Diffusion tensor (DT) tractography, which uses MRI to make three-dimensional (3D) reconstructions of the facial nerve, has recently been developed. Facial nerve ultrasound has been used in a recent study to predict functional outcomes in Bell's palsy. Magnetic resonance imaging (MRI) is useful for identifying soft tissue abnormalities around the facial nerve, as seen in inflammatory disorders, neoplasms, and hemifacial spasm. Computed tomography is useful for identifying bony abnormalities of the intratemporal facial nerve, which can occur with congenital malformations, trauma, and cholesteatoma. The facial nerve has a complex anatomical course, and dysfunction can be due to congenital, inflammatory, infectious, traumatic, and neoplastic etiologies. Imaging plays an important role in the evaluation of facial nerve disorders.
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