SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
This paper discusses the applicability of a previously developed model of endolymph movement in the semicircular canals of the vestibular apparatus for an adequate interpretation of experimental data concerning the effect of microgravity on thermal responses of the semicircular canal.
Cochlear- and vestibular function were investigated in 72 patients, aged between 4 and 7 years who had neonatal hyperbilirubinaemia. Markedly more and more serious damage was found in the group of patients, who as neonates had serum bilirubin levels above 25 mg-%. The frequency of loss of cochlear and vestibular function was significantly higher in patients with hyperbilirubinaemia for more than 4 days. Contrary to data published until now, it can be concluded that the vestibular apparatus is the most sensitive part of the nervous system to bilirubin.
A guinea pig model of viral labyrinthitis was established by inoculating guinea pig cytomegalovirus into the inner ear and then determine its effect on vestibular function. Neither spontaneous nor positional nystagmus could be detected postoperatively. Nine out of 18 (50%) animals had caloric hyperfunction in the virus-inoculated ear at 1 to 3 weeks postoperatively. Five of these 9 animals also had caloric hyperfunction in the control ear. A morphological study in animals with caloric hyperfunction showed no change in the peripheral vestibular apparatus by light microscopy. It is thus assumed that caloric hyperfunction in experimental viral labyrinthitis is transient and functional.
Acute hemilabyrinthectomized tadpoles of the Southern Clawed Toad (Xenopus laevis), younger than stage 47 (about 6 days old), perform no static vestibulo-ocular reflex (Fig. 1). Older acute lesioned animals respond with compensatory movements of both eyes during static roll. Their threshold roll angle, however, depends on the developmental stage. For lesioned stages 60 to 64, it is 75 degrees while stage 52 to 56 tadpoles respond even during a lateral roll of 15 degrees (Figs. 1 and 2). Selective destruction of single macula and crista organs revealed that the static vestibulo-ocular reflex is evoked by excitation of the macula utriculi (Figs. 3 and 4) even in young tadpoles. The results demonstrate that bilateral projections of the vestibular apparatus must have developed at the time of occurrence of the static VOR, that during the first week of life the excitation of a single labyrinth is subthreshold (Fig. 1). We discuss the possibility whether the loss of the static VOR during the prometamorphic period of life (Fig. 2) is caused by increasing formation of multimodal connections in the vestibular pathway.
The effect of radiation on the vestibular apparatus of animals and man have not been widely investigate. Referred symptoms are disequilibrium and spontaneous nystagmus in animals while histological features are intralabyrinthic haemorrhage, edema of the endolymphatic spaces and alterations of sensory hair cells. A group of 20 patients with head and neck cancer located in different sites (nasal cavity, oropharynx, oral cavity, parotid gland) underwent to vestibular investigations before and 3-6 months after radiation therapy. Ten patients (50%) showed an alteration of the vestibular function of peripheral origin after radiation treatment. Complications appeared from a few weeks up to several months following termination of radiotherapy. The slow development of the lesion permitted central compensation. Few patients had symptoms and vestibular symptomatology was always of secondary importance with respect to the initial pathology.
The two vestibular receptors, right and left, hidden in the petrous part of the temporal bone with the cochlear receptors, receive information from angular and linear movements of the head and transform them into a nerve message sent to the nuclei of the brainstem, which are connected directly on the one hand to the oculomotor nuclei, at the origin of the oculovestibular reflex (induction of nystagmus), and on the other hand, to the spinal motor neurons, at the origin of the vestibulospinal reflex. These reflexes are associated with responses to visual and somaesthetic information for maintenance or return to the standing position, which characterises the function of equilibrium. Vertigo and disorders of balance reflect a conflict of information between these two labyrinths, or between the vestibular apparatus and the messages issued by other captors, and sometimes also dysfunction of central nervous system treatment of information or a lesion of the effector motor systems.
Spaceflight aboard the "Cosmos-605" artificial satellite during 22 d does not have a substantial effect upon the activity of enzymes involved in energy metabolism--lactate dehydrogenase and creatine kinase--in cytoplasm of the giant neurons of the dorsocaudal part of the Deiters' nucleus and cortex layers of the cerebellar nodulus in rats. At the same time, on the second postflight day, in the molecular layer of cerebellar nodulus in rats flown for 22 d in space, some increase in lipid content was noted, probably connected with quantitative or qualitative changes in afferent impulses from the vestibular apparatus to the nodulus. On the 27th postflight day, lipid content in the molecular layer returned to the level observed in rats during ground-based experiments.
CONCLUSION: Cochlear implantation (CI) may induce vestibular impairment soon after surgery as well as after implant activation. This impairment seems to be independent from the cause of deafness and can be considered a possible complication from the intra-operative trauma and, to minor degree, from the ongoing electric stimulation. It would also seem that vestibular damage occurs independently from the likelihood of post-operative hearing deterioration. In unilateral selected CI cases, vestibular examination can be proposed as additional pre-operative exam for selection of the ear to be implanted. OBJECTIVES: This study has been planned in order to get evidence of eventual impairment of the vestibular apparatus after cochlear implantation as well as to verify whether the impairment could be related to different variables, such as cause of deafness, concomitant hearing deterioration, surgical trauma and duration of electrical stimulation. METHOD: Charts from two different populations of implantees have been reviewed, 21 from a prospective, 72 from a retrospective study, respectively. All the patients were implanted with Clarion(R) devices of different generation. Vestibular testing was based on rotatory, caloric (when possible) and stabilometric measurements, which were carried out pre-operatively and at the following different times: 5 weeks after CI surgery, and 30, 60 and 90 days after CI activation. Hearing thresholds were also assessed in those patients who showed signs of vestibular impairment as well as in a group of patients without vestibular disorders (control). Patients belonging to the retrospective group were all asked to fill a questionnaire regarding their balance condition. Results. In 14.3% of the prospective study group, a grade I and II spontaneous nystagmus was evidenced pre-operatively and remained unchanged during the whole assessment period. A grade II spontaneous nystagmus was present in 3 patients (21.4%) of the same group after surgery. In the immediate post-operative period, vestibular impairment was displayed as true rotational vertigo in 21.4% and unsteadiness in 42.8% of the study group. Severe unsteadiness was present during the first 2 days after activation in 14.3% of the subjects. In 21.4% of the patients a VPPB episode occured. In the retrospective study group, 26.4% of the subjects referred pre-operative dizziness and 25 patients (34.7%) referred immediate post-operative vertigo episodes, which remained in a milder form after CI activation in 12% of them. The hearing threshold showed to deteriorate in both vestibular-impaired and control CI population without significant difference.
There is controversy as to whether the vestibulosympathetic reflexes demonstrated in experimental animals actually exist in human subjects. While head-down neck flexion and off-vertical axis rotation can increase muscle sympathetic nerve activity (MSNA) in awake subjects, we recently showed that bipolar galvanic vestibular stimulation (GVS) does not. However, it is possible that our stimuli (2 mA, 1 s)-although capable of causing strong postural and occulomotor responses-were too brief. To address this issue we activated vestibular afferents using continuous sinusoidal (0.5-0.8 Hz, 60-100 cycles, +/-2 mA) bipolar binaural GVS in 11 seated subjects. Sinusoidal GVS evoked robust vestibular illusions of "rocking in a boat" or "swinging from side to side." Cross-correlation analysis revealed a cyclic modulation of MSNA ranging from 31 to 86% across subjects (mean +/- SE 58 +/- 5%), with total MSNA increasing by 156 +/- 19% (P = 0.001). Furthermore, we documented de novo synthesis of sympathetic bursts that were coupled to the sinusoidal input, such that two bursts-rather than the obligatory single burst-could be generated within a cardiac interval. This demonstrates that the human vestibular apparatus exerts a potent facilitatory influence on MSNA that potentially operates independently of the baroreceptor system.
HYPOTHESIS: Adeno-associated virus (AAV) is a suitable viral vector for transgene expression within the mammalian vestibular organs. BACKGROUND: In vivo introduction and expression of a foreign gene within the cochlear tissues have been established using a variety of viral vectors and guinea pig as the animal model. However, the vestibular neuroepithelia of the mammalian inner ear as a potential target for transgene expression remain to be investigated. METHODS: Transgene expression was assessed within the vestibular neuroepithelia of guinea pigs after intracochlear infusion of the recombinant AAV vector with the aid of an osmotic minipump. Evaluation of the transgene within the vestibular apparatus focused on its duration of expression from 2-24 weeks after intracochlear AAV infusion using immunohistochemistry. RESULTS: In the AAV-beta-galactosidase (beta-gal)-infused animals, the sensory hair cells as well as the supporting epithelial cells of cristae and maculae were positive for the transgene expression. The relative level of beta-gal expression was noted to decrease progressively over time. Transduction of the vestibular neuroepithelia also was observed in the contralateral ear, a finding that has been documented previously in AAV-integrated transgene expression in the cochlea. CONCLUSION: This study reports the first demonstration of introduction and long-term transgene expression within the vestibular neuroepithelia. The ability to express a foreign gene with the vestibular system allows the possibility of experimental and therapeutic application of gene therapy technology to address vestibular function and dysfunction.
Rotation and caloric methods of vestibular stimulation proposed and adopted during the last decades have been reviewed in terms of their efficacy in differential and topic diagnosis, clinical practicability. Systemic and bio-cybernetics approaches to vestibular apparatus and function have been analyzed. The need of using neurophysiological and cybernetics methods for further progress in relevant research and most promising trends in advancing clinical vestibulometry have been determined.
We reviewed the clinical histories, examinations and results of quantitative vestibular testing in 91 patients with migraine-associated dizziness. Nausea and vomiting, hypersensitivity to motion and postural instability accompanied the dizziness. In the majority of patients, the temporal profile of the dizziness was more typical of the headache phase of migraine than of the aura phase. Nineteen patients (20.9%) had unilateral hypoexcitability to caloric stimulation, which represents a modestly increased risk of damage to the peripheral vestibular apparatus. We propose two separate pathophysiologic mechanisms for the production of dizziness with migraine: Short-duration vertiginous attacks lasting minutes to 2 hours and temporally associated with headache are due to the same mechanism as other aura phenomena (spreading wave of depression and/or transient vasospasm). Longer-duration attacks of vertigo and motion sickness lasting days, with or without headache, result from the release of neuroactive peptides into peripheral and central vestibular structures, causing an increased baseline firing of primary afferent neurons and increased sensitivity to motion.
1. The effects of galvanic stimulation of the vestibular apparatus (with electrodes on the mastoid processes) have been studied in standing human subjects. With the head turned to one side, subjects swayed towards the anode. 2. Forwards sway was preceded by electromyographic (EMG) activity in quadriceps and tibialis anterior muscles. Backwards sway was preceded by EMG activity in soleus and hamstring muscles. 3. Using the method of H reflex conditioning, forward sway was found to be preceded by inhibition of soleus motoneurones. 4. Interaction between the vestibular-evoked inhibition of soleus motoneurones preceding forwards sway and peripheral reflex inhibition was examined by a spatial facilitation method. 5. Interaction was found between vestibular-evoked inhibition and Ia reciprocal, group I non-reciprocal and group Ia-Ia presynaptic inhibitory pathways. It is concluded that vestibular signals converge on spinal interneurones subserving these inhibitory actions. 6. A 'decoupling' of soleus motoneurons and soleus-coupled Renshaw cells was found in the period of soleus activation preceding backwards sway.
Aging of the vestibular apparatus is shown to consist of processes similar to those occurring in other parts of the nervous system. The recognition of these findings is a first step in the clinical differentiation of presbyastasis from symptoms related to specific disease processes. Authors had reviewed results of otoneurological investigations in the material of 8328 patients and realised that 1034 of them (12.4%) were over-60-year-old. These patients suffered from pathology of peripheral as well as central part of vestibular system.
The vestibular apparatus provides information about the position and movements of the head. Craniocervical muscles position the head with respect to the upper part of the neck. Motoneurons innervating these muscles are located in the supraspinal nucleus and ventral horn of the rostral cervical cord. Premotor neurons of craniocervical muscles have been found in the medial two-thirds of the medullary reticular formation: the ventromedial part of the parvocellular reticular formation and the gigantocellular reticular formation. In the present study, projections from vestibular nuclei upon craniocervical premotor neurons were investigated using anterograde and retrograde tracers. Vestibulospinal fibers run bilaterally in the medial vestibulospinal tract and ipsilaterally in the lateral vestibulospinal tract. Vestibuloreticular projections are mainly ipsilateral, and originate from the n. vestibularis lateralis pars ventralis and pars dorsalis, and from the n. vestibularis descendens. Terminal labeling is found in the border zone between the parvocellular and gigantocellular reticular formation. These projections show that in addition to direct bilateral vestibulo-craniocervical projections an indirect vestibular pathway to craniocervical motor nuclei exists. The direct pathway probably is the neural substrate for the vestibulocollic reflex, whereas the vestibular projection upon the reticular formation might influence head orientation during various kinds of activities, such as pecking, preening and so on.
Aging in the peripheral vestibular apparatus is shown to consist of processes similar to those occurring in other parts of the nervous system. Sensory epithelium and primary efferents degenerate and are not replaced. Type I hair cells and elements of the pars inferior are most susceptible. Remaining cells show a build-up of lipofuscin and microstructural changes suggesting compromised metabolism. Rupture of the saccular membrane and microfractures of the otic capsule are frequently seen. Otoconia undergo degeneration, and the tissue between the endolymphatic duct and bony vestibular aqueduct becomes fibrotic. The recognition of these findings is a first step in the clinical delineation of the "dysequilibrium of aging" from symptoms related to specific disease processes. Further clinical correlation will remain difficult until changes in the central vestibular pathways and their connections with the optic and locomotor systems are better understood.
The effect of enkephalins, morphine and some neurotransmitters on spontaneous and evoked activity of neurons of the medial vestibular nucleus was investigated. The evoked activity was produced by an adequate stimulation of the vestibular apparatus. It was shown that neurons of this nucleus were highly sensitive to enkephalins, morphine, acetyl choline, GABA and L-glutamate (approximately 80% of the nerve cells were inhibited or excited in response to the micro-iontophoretic application of these substances). It was found that activation and depression effects of opioid peptides and morphine occurred due to the stimulation of mu- and delta-opiate receptors. It can be concluded that enkephalins modulate cholinergic and glutamatergic synaptic transfer in the medial vestibular nucleus. Together with opiate receptors, they participate in the perception and processing of vestibular information at the level of neurons of this nucleus.
OBJECTIVE: The purpose of this study was to determine whether vestibular evoked myogenic potentials from the sternocleidomastoid muscle in response to bone-conducted clicks and short tone-bursts can be used to assess vestibular apparatus function in patients with conductive hearing problems, particularly bilateral external auditory canal atresia. DESIGN: Evoked-potential responses to bone-conducted auditory stimuli were recorded from the sternocleidomastoid muscle of 15 patients (11 male and four female, aged 4--20 years) with congenital bilateral atresia of the external auditory canal, with or without the middle ear anomalies. SETTING: This study was conducted in the outpatient clinic of the Tokyo University Hospital, Department of Otolaryngology, University of Tokyo. INTERVENTION: Diagnostic. OUTCOME MEASURES: Bone-conducted vestibular evoked myogenic potentials in response to clicks and short tone-bursts were recorded with surface electrodes over both sternocleidomastoids in each patient. RESULTS: In all patients, bone-conducted clicks and short tone-bursts evoked larger biphasic responses from the sternocleidomastoid ipsilateral to the stimulated ear. Short tone-bursts evoked vestibular evoked myogenic potentials with higher amplitude and better waveform morphology than clicks at the same subjective intensity. CONCLUSION: Loud auditory stimuli delivered by bone conduction can evoke myogenic potentials from the sternocleidomastoid. This method is a noninvasive, rapid, and convenient test for investigating the vestibular system function in patients with bilateral external auditory canal atresia, with or without the middle ear anomalies.