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Nonconventional Clinical Applications of Otoacoustic Emissions: From Middle Ear Transfer to Cochlear Homeostasis to Access to Cerebrospinal Fluid Pressure
Published in Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm, Advances in Audiology and Hearing Science, 2020
Blandine Lourenço, Fabrice Giraudet, Thierry Mom, Paul Avan
The first issue is that ICP monitoring through the ear rests on the hypothetical presence of connections between intralabyrinthine fluids and CSF. Several anatomical pathways have been identified that possibly transmit pressure between these two spaces: The cochlear aqueduct, the endolymphatic duct and sac, and the venous system (Fig. 8.2). The cochlear aqueduct seems to provide a straightforward pressure communication with the cochlea; however, its very small diameter and the fact that normally when the cochlea is opened during surgery no gusher is observed suggest that a normal cochlear aqueduct is not patent to CSF flow. Anatomical data suggesting that the cochlear aqueduct gets gradually blocked with increasing age (Wlodyka, 1978) have been later challenged (Gopen et al., 1997). It has been shown that normal variations in ICP such as those induced by heartbeats and breathing are filtered by the pathways connecting CSF and cochlea in humans (Traboulsi and Avan, 2007), such that transmission of pressure waves from the skull to labyrinth undergoes a delay of the order of 10 seconds. Anyway, all that the in-ear monitoring of ICP requires is that there exist canal(s) between CSF and endocochlear fluid spaces that are patent to hydrostatic pressure even if they are not patent to fluid flow.
Anatomy and Embryology of the External and Middle Ear
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
The mesenchyme enclosing the otocyst becomes chondrified to form the otic capsule. As the membranous labyrinth expands, the otic capsule remodels and in places undergoes dedifferentiation to form fluid-filled spaces that eventually become the perilymphatic spaces. This dedifferentiation does not occur where nerves enter the sensory cell regions. Elsewhere, the perilymphatic spaces become continuous and a communication with the cerebrospinal fluid is formed by the development of the cochlear aqueduct, which runs to the posterior cranial fossa from the scala tympani in the base of the cochlea.
Anatomy
Published in Stanley A. Gelfand, Hearing, 2017
The cochlear aqueduct leads from the vicinity of the round window in the scala tympani to the subarachnoid space medial to the dura of the cranium. Although the aqueduct leads from the perilymph-filled scala to the cerebrospinal fluid-filled subarachnoid space, it is not patent in many humans. Thus, it is doubtful that there is any real interchange between these two fluid systems. The endolymphatic duct leads from the membranous labyrinth within the vestibule to the endolymphatic sac. The sac is located partially between the layers of the dura in the posterior cranial fossa and partly in a niche in the posterior aspect of the petrous portion of the temporal bone.
Non-iatrogenic spontaneous acute spinal subdural haematoma after transforaminal lumbar interbody fusion
Published in British Journal of Neurosurgery, 2023
Ahmed Aly, Daniel D’Aquino, Eman Khedr, Olakunle Badmus, Masood Shafafy
A durotomy that remained occult at the time of surgery is a possible explanation of our case. The initial post-operative was uncomplicated with headache, photophobia and tinnitus developing on the third which may have been secondary to cerebrospinal fluid (CSF) leakage as has been suggested.13 They reported a female case, who presented with left sciatica and underwent a standard L4/5 discectomy in which no dural tear or CSF leak was noted at the time of operation. Six days after operation, the patient developed headache, photophobia and hearing loss. An association between hearing symptoms and a CSF leak is well-established.14 The pathophysiology involves inner ear hydromechanics. The cochlear aqueduct communicates between the subarachnoid CSF and the cochlear perilymph, and bi-directional flow or diffusion within the duct allows equalisation of pressure in perilymph and CSF pressure. A CSF leak causes a reactive change in the endolymph volume and reversible hearing disturbance.
Effect of ossicular chain deformity on reverse stimulation considering the overflow characteristics of third windows
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Houguang Liu, Lin Xue, Jianhua Yang, Gang Cheng, Lei Zhou, Xinsheng Huang
The assumption that the fluid-filled cochlea is surrounded by bone with only two mobile windows, i.e., the oval window and the round window has been generally accepted under forward stimulation (Zhang and Gan 2013; Zhang et al. 2018). This assumption is supported by experimental studies (Kringlebotn 1995; Stenfelt et al. 2004), which found that the fluid volume displacement of the oval window and the round window are equal under forward stimulation. Whereas, the actual anatomy of the cochlea has other smaller-scale and longer sound pathways, mainly the vestibular aqueduct and cochlear aqueduct, which were named as third windows (Rosowski et al. 2018). By stimulating the round window with an actuator in human temporal bone experiment, Stieger et al. (2013) reported that there exists fluid flow through the third windows in the cochlea. Meanwhile, based on the measurement of intra-cochlear sound pressure and ossicular chain motion, Frear et al. (2018) also found that the third windows have volume velocities leakage during reverse stimulation. Moreover, our theoretical investigation found that the third windows have an important effect on the reverse stimulation at low frequencies (Xue et al. 2020). Therefore, incorporating the third windows is essential for investigating the influence of OCD during reverse stimulation.
Change of VOR gain and pure-tone threshold after single low-dose intratympanic gentamicin injection in Meniere’s disease
Published in Acta Oto-Laryngologica, 2020
The reason for failure of initial ITG is important because there could be several substantial factors which may influence on clear dose-response relationship. An Salt et al. reported that gentamicin may enter the inner ear more easily through the oval window than through the round window in guinea pigs study [13]. Also they demonstrated a slow flow of perilymph in the scala tympani towards the apex of the cochlear in previous study [14]. Another factor is anatomical difference around round window and permeability of round window membrane. In one study, 29 of the round windows were judged to be unobstructed, 7 were obstructed partially, and 5 were obstructed completely in 41 cases [15]. A. Walsted suggested that if the internal orifice of cochlear aqueduct is obliterated, drugs delivered into the middle ear concentrate in the inner ear fluids behind the round window membrane after absorption, resulting in a prolonged and damaging ototoxic effect in the cochlea [16]. In our study, 6 out of 16 patients needed further injection after initial ITG. We can expect that patients in multiple injections group might have anatomical obstruction through round window membrane or hindered cochlear aqueduct. In that cases, we can consider the method which can resolve impermeability or anatomical problems, such as exploratory tympanotomy and gentamicin application [17].