Case 70
Simon Lloyd, Manohar Bance, Jayesh Doshi in ENT Medicine and Surgery, 2018
Otological manifestation Serous otitis media is the most common presentation (40%–70%) secondary to Eustachian tube obstruction. This can lead to secondary bacterial infection with intervening acute otitis media and mastoiditis.Sensorineural hearing loss and vertigo can be due to inflammation of the blood vessels supplying the cochlear, labyrinth or vestibulo-cochlear nerve.Similarly vasculitis and granulomas can affect the facial nerve causing facial palsy. Large inflammatory masses in the petrous apex and skull base can also affect cranial nerves VI, IX, XII.
Paediatric Implantation Otology
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
Pre-operative imaging therefore plays a very important role. An MRI not only is important in confirming the presence of a cochlear nerve in the presence of pre-lingual deafness, but will also show the turns of the cochlea and the anatomy of the vestibule. Furthermore, in cases where a CT scan may identify a narrow internal auditory canal, an MRI is also important to confirm that the nerve is present and not hypoplastic, especially when associated with certain syndromes such as CHARGE (coloboma, heart defects, atresia choanae, retardation of growth, genital anomalies and ear abnormalities). An absent cochlear nerve is a contraindication for CI. A finding of a hypoplastic cochlear nerve needs to be assessed individually, which may involve further imaging or an electrically evoked ABR.
Electrophysiology and Monitoring
John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie in Basic Sciences Endocrine Surgery Rhinology, 2018
The aim of monitoring the status of the auditory pathway during cerebellopontine angle (CPA) surgery is the prevention of avoidable post-operative hearing deficit. The achievement of this laudable aim is fraught with difficulty and hearing preservation rates in comparison with facial nerve outcomes remain poor.35 The cochlear nerve is sensitive to mechanical manipulation and easily damaged, as the intra-cranial section of the nerve is sheathed in central myelin and has no perineurium.36 Additionally, the cochlear nerve is intimately involved with pathologies, such as vestibular schwannoma, and hence at very considerable risk during the surgical removal of such lesions, even when every care is taken to preserve the nerve anatomically. The basic principle of intra-operative monitoring is that changes in recordable neuroelectric potentials occur whilst the injury is still reversible and before permanent deficits result.37 Recent research38 has demonstrated that this principle holds for changes in auditory brainstem responses (ABR) wave V amplitude (and to a lesser extent latency) in rat auditory nerves manipulated in a fashion analogous to that undergone in humans during vestibular schwannoma removal. It is therefore theoretically feasible that monitoring auditory function may inform the surgeon of reversible injury to the cochlear nerve.
Vestibular nerve deficiency and vestibular function in children with unilateral hearing loss caused by cochlear nerve deficiency
Published in Acta Oto-Laryngologica, 2021
Keita Tsukada, Shin-ichi Usami
Recently, advances in diagnostic imaging technology have made it possible to diagnose CND, which has been recognized as a cause of SNHL[1,2]. It is proposed that CND results from developmental disorders in the embryonic stage and/or inner ear neuropathy in the early post-natal period [2]. The inner ear nerves consist of the cochlear nerve, and the upper and lower vestibular nerves. Based on the possibility of a developmental disorder, not only CND but also VND is expected. However, there have been few reports to date focusing on VND. McClay reported that hypoplasia or an absence of the vestibular nerve was observed in 12 of 49 ears (24%) with CND [3], and Adunka also reported that a loss of vestibular nerve was observed in 11 of 20 (55%) ears in CND cases [7]. In the present study, 36.8% of patients showed a vestibular nerve that was absent or smaller than that on the contralateral side (Figure 2(a)), suggesting that majority of the cases had only cochlear nerve deficiencies without VND.
Sound localisation of low- and high-frequency sounds in cochlear implant users with single-sided deafness
Published in International Journal of Audiology, 2023
J. Seebacher, A. Franke-Trieger, V. Weichbold, O. Galvan, J. Schmutzhard, P. Zorowka, K. Stephan
The reason for the improvement in sound localisation when patients with SSD are given a CI in their deaf ear is not yet fully understood. The acoustic information is delivered to the auditory system via two distinctly different pathways: in one ear via normal (acoustic) hearing and on the other side via direct electrical stimulation of the cochlear nerve. Two different inputs (acoustic and electric signals) have to be combined along the auditory pathway in order to evaluate ITDs and ILDs of incident sound. Coding of these cues relevant for localisation of sounds is not primarily considered in today’s CI coding strategies. Originally, the primary focus of development was to improve speech perception, followed by the sound quality. Typically, signal processing in CI is optimised to encode the envelope of the acoustic signal. Fundamental observations were made by Shannon and colleagues, who found that envelope coding of a few tonotopically arrayed frequency bands was already sufficient for speech recognition in patients with CI (Dillon et al. 2016). Current processing strategies further attempt to encode the low-frequency acoustic fine structure information of sound, which could also be used for localisation issues.
Chameleons, red herrings, and false localizing signs in neurocritical care
Published in British Journal of Neurosurgery, 2022
Boyi Li, Tolga Sursal, Christian Bowers, Chad Cole, Chirag Gandhi, Meic Schmidt, Stephan Mayer, Fawaz Al-Mufti
Damage to the vestibulo-cochlear nerve can cause auditory neuropathy, as the propagation of auditory information downstream of the mechanical and electrical conduction is disrupted.36 Notably, this damage leading to hearing loss can be caused by temporal bone fracture, trauma even in the absence of fracture, transient demyelination, and infarction due to stroke.37–39 As a FLS, hearing loss, in addition to the other otologic symptoms of pulsatile tinnitus and aural fullness, has been reported as a complication of IIH.3,40 The hearing loss is low-frequency and may also present with vertigo.40 About 1/3 of patients with IIH demonstrate prolonged interpeak latencies in auditory brainstem-evoked response, suggesting that the pathophysiology of this hearing loss is the ICP causing stretching and/or compression of the vestibulocochlear nerve and brainstem.40 Detection of this type of low-frequency sensorineural hearing loss may be especially helpful in diagnosing IIH, as it can be detected even when other symptoms are absent.41 Thus, audiological evaluations play an important role in the diagnosis of IIH, which should always be suspected in the presence of neurotological symptoms such as tinnitus, vertigo, aural fullness, and hearing disturbances.41
Related Knowledge Centers
- Axon
- Bipolar Neuron
- Cochlea
- Inner Ear
- Semicircular Canals
- Vestibular Nerve
- Vestibulocochlear Nerve
- Brain
- Cranial Nerves
- Unipolar Neuron