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Vertigo
Published in Alexander R. Toftness, Incredible Consequences of Brain Injury, 2023
There are two main categories of vertigo: peripheral and central. Peripheral vertigo is a collection of vertigo types that are caused by problems in the inner ear, such as problems with the vestibular mechanisms that were mentioned above. The nerve that sends signals from your inner ear into your brain is called the vestibular nerve, and all kinds of peripheral vertigo warp the signals being sent through that nerve such that the signals end up being incorrect. Once the signals make it into your brain they don't make sense when compared to what your visual and proprioceptive systems are reporting, and this causes the sensation of spinning. Peripheral vertigo is usually temporary and may depend on the position that your body is in such as whether you are standing, lying down, or if your head is moving—if you have ever experienced temporary vertigo, it was probably caused by a peripheral change (Brandt et al., 2013). One potential cause of peripheral vertigo is that the otoconia crystals become misaligned in your semicircular canals and disrupt the movement of fluid. This results in a condition called benign paroxysmal positional vertigo, which usually shows up mysteriously but can sometimes be linked to anything from head trauma to viral infections, to the position that you sleep in at night, and many other factors (Yetiser, 2019). So yes, crystal misalignment can make you dizzy. That's just science.
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
The semicircular canals are orientated so that they provide complementary information about angular movement. Anti-clockwise head rotation (turning your head to the left) increases the nerve-fibre firing rate of the left lateral semicircular canal and decreases the firing rate of fibres from the right lateral semicircular canal. The perception of head rotation is the net result of differential firing rates between these complementary lateral semicircular canals (see Figure 2.4). The superior and posterior canals of opposing ears lie in the same plane. Therefore, with the head rotated 45° to right, head flexion results in an increased fibre firing rate of the right superior semicircular canal and decreased firing rate of the left posterior semicircular canal. With the head rotated 45° to right, head extension causes reversal in this pattern of activation, between the right superior and left posterior semicircular canals.
Developmental Diseases of the Nervous System
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
James H. Tonsgard, Nikolas Mata-Machado
Cochlear implantation has shown some benefit in NF-2 patients and may influence the surgical approach on vestibular tumors. Signing is an important skill for patients and families to develop because of inevitable hearing loss. Because hearing loss can be due to an inflammatory process in the semicircular canals in some patients, steroids and other anti-inflammatory agents may be helpful.
Hearing preservation/rehabilitation surgery for small vestibular schwannoma: preliminary experience with the presigmoid retrolabyrinthine approach
Published in Acta Oto-Laryngologica, 2021
Jie Wang, Yong Li, Xingmei Wei, Jingyuan Chen, Lifang Zhang, Xinping Hao, Yongxin Li
Partial labyrinthectomy (Figure 3) was performed in three patients. One achieved hearing preservation, a preservation rate similar to that of another study [9]. In that study, the authors conducted a systematic analysis of 84 patients with AN from seven studies and 55 patients with other lesions from three studies and found that the hearing preservation rate after partial labyrinthectomy was 31% for patients with AN. However, for patients with non-AN, the rate was 76%. A reason for hearing loss in patients with VS resection is that surgery may affect the cochlear nerve. Magliulo et al. [17] used postoperative CT and MRI in patients undergoing partial labyrinthectomy and they demonstrated that this approach does not cause any detectable ultrastructural injury. The semicircular occlusion did not result in hearing loss, which is a fundamental factor for hearing preservation in partial labyrinthectomy. Nevertheless, vestibular damage affects hearing, which reminds us that semicircular canal resection should be posterior to the vestibule and the SSC and PSC ampullae. This is also a fundamental factor in successful hearing preservation [17]. Moreover, when the semicircular canal is closed, the bone wax should be directed away from the ampulla, because it is vulnerable to ototoxicity.
Intraoperative auditory brainstem response monitoring during semicircular canal plugging surgery in treatment of Meniere’s disease
Published in Acta Oto-Laryngologica, 2021
Xiaofei Li, Yafeng Lv, Ruijie Wang, Xiuhua Chao, Zhaomin Fan, Haibo Wang, Daogong Zhang
Plugging surgery is based on the theory that occlusion of a semicircular canal can prevent the movement of liquid and, therefore, prevent cupular displacement in the canal. This eliminates stimulation of the receptor cells, thereby preventing attacks of vertigo. Semicircular canal plugging was first utilized to treat intractable benign paroxysmal positional vertigo [10]. Since then, semicircular canal plugging has been tested for its ability to treat intractable peripheral vertigo. Charpiot et al. reported that the control rate of vertigo was 75% in 28 patients with MD who underwent lateral canal plugging [11]. Yin et al. used triple semicircular canal occlusion to treat only three patients with MD who underwent unsuccessful ESD or mastoid shunt, finding that two cases had complete control of vertigo and the other had substantial control [12].
Video head impulse testing in patients with benign paroxysmal positional vertigo
Published in Acta Oto-Laryngologica, 2020
Semicircular canals are activated during rapid head movements and otolithic signal is created to provide information to central structures for the direction of motion and the orientation of the body [6]. Compensatory eye movement occurs, opposite in direction to the head movement and is generated to stabilize the image on the target in co-ordination of movement and balance. This is critical to maintain the retinal image for body stability during high velocity head motion. Reflex eye velocity delay occurs in patients with vestibular dysfunction which means significant retinal slip between the position of the target on the retina and the desired position on the fovea. Video head impulse test allows to study the vestibular function of the semicircular canal separately by recording head and eye velocity in the plane of head movement and provides earlier and much information than other tests [7]. It enables to analyze the VOR gain and gain asymmetry and also detects overt or covert saccades.