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.ΔΆ. 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. The decision should be based on the functional status of the cranial nerves, for which reliable electrophysiological monitoring is indispensable.Imaging plays an important role in the evaluation of facial nerve disorders. In view of the nonneoplastic characteristic of these lesions, a more conservative approach is justified. Intraoperative surgical findings of tumor infiltration of the faciocochlear cranial nerve complex may support simple observation. Accurate preoperative diagnosis by radiological means is not possible, but careful evaluation of the different signal intensities on magnetic resonance imaging studies may indicate this rare pathological condition. Symptoms and signs of internal auditory canal hamartomas are congruent with other typical pathological lesions of the internal auditory canal and cerebellopontine angle. Therefore, a radical tumor removal was performed that sacrificed the cochlear but preserved the facial nerve. In Patient 2, minimal tumor dissection resulted in complete loss of auditory brainstem response without reversibility. In Patient 1, after nerve decompression by subtotal tumor removal, preserved auditory brainstem responses and facial nerve electromyography indicated functional nerve preservation and facilitated the decision for partial resection. In view of the unclear intraoperative histology, surgical management was based on criteria of cranial nerve function. The lesions were exposed via a suboccipital transmeatal approach, and tumor infiltration of the cochlear and/or facial cranial nerves was identified. Two patients presented with clinical findings typical of vestibular schwannomas, i.e., tinnitus, hearing loss of 30 dB, and an intrameatal contrast-enhancing lesion on magnetic resonance imaging studies. To highlight the clinical, radiological, and surgical findings and therapeutic options for this rare entity, which may mimic a purely intrameatal vestibular schwannoma, and to define the particular aspects of preoperative differential diagnosis and surgical management.
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