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Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The vestibular receptors are found in the vestibular labyrinth of the inner ear and comprise two otolith organs – the utricle and saccule – and three semicircular canals. The otolith organs provide information on the static position of the head relative to the gravitational axis and respond to linear accelerations, whereas the semicircular canals respond to the angular acceleration of the head arising from self-induced rotations or from external forces. Both the linear and angular accelerations can be in any direction. These vestibular receptor organs project, through approximately 20,000 nerve fibers on each side, via cranial nerve VIII, to the vestibular nuclei and also directly to the cerebellum.
Vestibular Respiratory Regulation
Published in Alan D. Miller, Armand L. Bianchi, Beverly P. Bishop, Neural Control of the Respiratory Muscles, 2019
Vertical linear acceleration (up and down movements), which should affect one of the otolith organs (the sacculus) but not the semicircular canals, can produce increases in the depth and frequency of respiration that are markedly reduced by transection of the vestibular nerve in animals.35 It has also been reported that the activity of hypoglossal neurons is modulated by static ear-down (roll) tilts, which activate the utriculus, and by thermal (caloric) stimulation of the vestibular labyrinth.20 The study using tilt is questionable, however, since proper controls were not done to assure that the responses were due to activation of labyrinthine receptors (as opposed to nontarget receptors, such as those in the upper airway and thorax).
Evaluation of Balance
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
Loud sounds can activate the vestibular labyrinth. If these sounds are brief in duration (clicks), the total amount of energy delivered to the ear is small and the procedure harmless. Using averaging techniques similar to those in brainstem auditory evoked potentials, an electromyographic (EMG) potential can be identified from neck muscles.148,149 The response is a sound-evoked vestibulocollic (or vestibulospinal) reflex and this is often called the cervical vestibular-evoked myogenic potential (cVEMP). The technique can be easily set up in any clinical neurophysiology or audiology department with access to calibrated sound generators, averaging equipment and surface recording electrodes and several devices are available commercially.
White Matter Hyperintensities (WMH) and clinical outcome after vestibular neuritis
Published in Neurological Research, 2022
Huimin Fan, Jing Feng, Melissa Wills, Liying Wang, Xiaomeng Chen, Xiaokun Geng, Yuchuan Ding
In our study, we found that only 8 (18.6%) patients have a history of preceding or accompanying viral infection. Therefore, the cause of VN is not completely understood at the present, as viral infection is evidently not responsible for all cases. The leading hypothesis involves reactivation of a latent neurotropic virus[16]. The hypothesis is based on the findings of HSV type 1 DNA in human vestibular and other cranial nerve ganglia on autopsy[17] and the finding of Herpes simplex virus type 1 in the saliva of the patients with Vestibular Neuronitis[18]. Interestingly, there is no intrinsic difference in HSV-1 infection or virion production between superior and inferior VN. In our study, the superior VN subtype was identified in 31 of 43 patients (72.1%). Only 1 of 43 patients (2.3%) demonstrated exclusively inferior VN affecting saccule function, implying that other factors such as length and width of the bony canal containing the ganglia and nerves may account for the greater involvement of the superior vestibular ganglion. Other possible mechanisms include autoimmune[19] and microvascular ischemic insults to the vestibular labyrinth[20]. These patients had not been tested for the detailed etiology of neuritis in our study, which is a retrospective study. Future investigations of VN should include exploration of these etiologies.
Effect of advancing age on inter-frequency amplitude ratio of ocular vestibular evoked myogenic potentials
Published in International Journal of Audiology, 2021
Niraj Kumar Singh, Husna Firdose, Animesh Barman
In the present study, we found that the IFARs increased steadily with age; however, a significant increase in the IFAR was evident only after the age of 50 years. This could be attributed to the degeneration occurring in different parts of the vestibular labyrinth and the neural network beginning in the labyrinth. Degenerative changes due to ageing have been reported at various levels in the vestibular system, including the vestibular neuroepithelia after 40 years, although more marked changes increase with advancing age in the 50 s, 60 s, and 70 s age groups (Rosenhall 1973). These degenerative changes cause a reduction of macular mass. Since resonance frequency is inversely proportional to the square root of mass (Vanhuyse, Creten, and Van Camp 1975), it would cause an upward shift in the best frequency towards 1000 Hz in older individuals from 500 Hz in younger ones (Singh and Barman 2016; Singh and Firdose 2018). This shift in the frequency dynamics between 500 Hz and 1000 Hz, therefore tilts more and more towards 1000 Hz (dominance) as age increases. Since IFAR is the ratio of peak-to-peak amplitude between oVEMP obtained in response to 1000 Hz and 500 Hz tone-bursts (Kim-Lee et al. 2009; Jerin et al. 2014; Singh and Barman 2016), the increased dominance of the 1000 Hz response with age could increase the ratio between the two, as shown by an increased IFAR in older adults.
Vestibular evoked myogenic potentials in chronic renal disease
Published in Acta Oto-Laryngologica, 2021
Shibi Varghese, Kaushlendra Kumar, Mohan Kumar Kalaiah, Usha Shastri, Anupriya Ebenezer, Mayoor Vasant Prabhu
Findings of the present study showed a significant reduction in the peak-to-peak amplitude of VEMP among individuals with CRD compared to individuals with no CRD. Similarly, reduced amplitude of cVEMP has been reported in two groups of patients with CRD undergoing conservative treatment and hemodylasis [7]. The reduction in the amplitude of VEMP may be due to ionic imbalance in perilymph and endolymph, leading to poor coupling of energy from the saccule and utricle to the hair cells. The CRD patient may have disturbance in the blood level of sodium and potassium, which is also present in endolymph and perilymph [7,8]. A large number of individuals with CRD are reported to have hyperexcitable vestibular labyrinth [11]. In addition, the abnormal VEMP in individuals with CRD could be due to electrolyte imbalance in the inner ear, intake of ototoxic drugs, and hemodialysis. The electrolyte imbalance in the vestibular labyrinth is due to the pressure variation in the inner ear endolymphatic or perilymphatic fluids. This variation in the inner ear endolymphatic or perilymphatic fluids can be due to the osmotic fluid shift, imbibition to mucopolysaccharides or influence of hormones acting on the cellular permeability, receptor sensitivity, or mucopolysaccharides metabolism. Ototoxic drugs such as aminoglycosides and gentamicin are commonly provided to individuals with CRD individuals along with hemodialysis procedure [11]. CRD individuals who are under medication of drugs that contain aminoglycosides have vestibular toxicity. They also revealed there is a delay in the onset in the functioning of the vestibular system [12].