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Anatomy and Physiology of Balance
Published in R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne, Scott-Brown's Essential Otorhinolaryngology, 2022
Nishchay Mehta, Andrew Forge, Jonathan Gale
Sensory afferents of the saccule and the posterior semicircular canal are formed into the inferior vestibular nerve and those of the utricle; lateral and superior semicircular canals are formed into the superior vestibular nerve. The vestibular nerves travel medially in the internal auditory canal to the vestibular nuclei at the medullary-pontine junction. There is cross communication of nuclei on each side. In addition, each nucleus sends fibres to the nuclei of the ipsilateral and contralateral abducens, trochlear and oculomotor nerves, cerebellum, and descending fibres to the vestibulo-spinal tracts.
Facial anatomy
Published in Michael Parker, Charlie James, Fundamentals for Cosmetic Practice, 2022
The facial nerve exits the pons at the level of the pontomedullary junction and projects through the cerebellopontine angle via the cerebellopontine cistern towards the internal auditory meatus within the petrous temporal bone. The internal auditory canal runs laterally through this bone for approximately 1 cm whilst it gradually narrows until it creates a fundus at its lateral boundary. The facial nerve enters the internal auditory canal via the anterosuperior quadrant and runs along this canal to the fundus, where it enters the facial canal. The facial canal is approximately 3 cm long and “Z”-shaped. Despite being small, it is divided into three sections, the labrynthine, tympanic and mastoidal segments. The facial nerve traverses the facial canal, giving off branches as it does so, such as the chorda tympani and the nerve to stapedius.
Ear, Nose, and Paranasal Sinus
Published in Swati Goyal, Neuroradiology, 2020
The external auditory canal (EAC), with lateral one-third cartilaginous and medial two-thirds bony composition, extends from the auricle to the tympanic membrane. The middle ear cavity is within the petrous portion of the temporal bone and consists of the tympanic cavity (containing the ossicles, namely the malleus, incus, and stapes) and the antrum. The mastoid antrum communicates with the epitympanum via aditus ad antrum. The middle ear also contains muscles (tensor tympani and stapedius), the round and oval windows, and the chorda tympani nerve. The inner ear consists of the osseous labyrinth (cochlea, vestibule, and the three semicircular canals, namely the superior, posterior, and lateral canals) and the membranous labyrinth (the cochlear duct, utricle, saccule, semicircular ducts, endolymphatic duct, and endolymphatic sac). The membranous labyrinth contains endolymph, surrounded by perilymph, and is enclosed within the bony labyrinth. The internal auditory canal (IAC) is located in the petrous bone and transmits facial and vestibulocochlear nerves along with the labyrinthine artery. The pars flaccida is the upper delicate part that is associated with Eustachian tube dysfunction and cholesteatoma. The pars tensa is larger and more robust, and associated with perforations.
Long-term tumor growth and hearing after conservative management of vestibular schwannomas
Published in Acta Oto-Laryngologica, 2023
Kazutake Yagi, Ryoukichi Ikeda, Jun Suzuki, Hiroki Sunose, Tetsuaki Kawase, Yukio Katori
The incidence of diagnosed VS has increased due to improved accessibility of magnetic resonance imaging (MRI) [3]. In addition, an increasing number of incidental tumors are being found in patients who have had MRIs for other reasons such as post-trauma, headaches, vertigo, etc. The increasingly high image resolution of MRI allows the diagnosis of still smaller tumors confined to the internal auditory canal. Therefore, it is expected that the number of cases requiring long-term follow-up will increase [4]. A large national cohort study of 3637 cases of VS in Denmark revealed that most patients received active treatment within 5 years. The latest active treatment was performed after 22 years of observation, and in total, three patients (0.1%) were treated after 10 years of observation [5].
ABI-auditory brainstem implant
Published in Acta Oto-Laryngologica, 2021
Anandhan Dhanasingh, Ingeborg Hochmair
In some instances, candidates show no response or a questionable response to sound whilst diagnostic imaging tests suggest normal or abnormal anatomy. This may occur in patients with a narrow internal auditory canal or patients with either malformed or patent cochlea. For such cases, the preoperative Promontory Stimulation System was developed. Its benefits were evidenced in initial studies with a success rate of 80–90% in CI implanted children. The system intends the transtympanic electrode to be placed on the round window niche, and biphasic electric pulses are delivered to the transtympanic electrodes. At the time of stimuli, the MAX interface triggers the evoked potential device, and the eABR response is obtained from the surface electrodes, as shown in Figure 26. If the eABR shows a positive response, the implant team may decide to proceed with cochlear implantation. If no responses are obtained, the candidate may be considered for an ABI, or further tests may be required.
Recovery of ocular and cervical vestibular evoked myogenic potentials after treatment of inner ear diseases
Published in International Journal of Neuroscience, 2019
Juan Hu, Hua Wang, Zichen Chen, Yuzhong Zhang, Wei Wang, Maoli Duan, Min Xu, Qing Zhang
The facial nerve is most frequently involved in RHS resulting in facial palsy. In some cases, however, the lesion site might be associated with the eighth cranial nerve (vestibulocochlear nerve), causing inner ear symptoms such as hearing loss and vertigo. Such inner ear symptoms indicate the involvement of nerve trunks within the internal auditory canal revealed by pathologic and radiographic studies. Based on cVEMP and caloric tests, the inflammatory lesion of RHS was located in both superior and inferior branches of the vestibular nerve and contributed to vertigo attacks [21,22]. To date, VEMP recovery in patients with RHS has not been reported. In this study, three RHS patients showed normal oVEMP response but no cVEMP response prior to treatment and then complete cVEMP recovery after treatment. Therefore, we hypothesize that the inflammation from viral infection in these patients was likely located in the saccule and/or inferior vestibular nerve and recovered after therapy.