A New Perspective to Interpret How the Vestibular Efferent System Correlates the Complexity of Routine Balance Maintenance with Management of Emergency Fall Prevention Strategies.

Bipedalism is unique among mammals. Until modern times, a fall and resulting leg fracture could be fatal. Balance maintenance after a destabilizing event requires instantaneous decision making. The vestibular system plays an essential role in this process, initiating an emergency response. The afferent otolithic neural response is the first directionally oriented information to reach the cortex, and it can then be used to initiate an appropriate protective response. Some vestibular efferent axons feed directly into type I vestibular hair cells. This allows for rapid vestibular feedback via the striated organelle (STO), which has been largely ignored in most texts. We propose that this structure is essential in emergency fall prevention, and also that the system of sensory detection and resultant motor response works by having efferent movement information simultaneously transmitted to the maculae with the movement commands. This results in the otolithic membrane positioning itself precisely for the planned movement, and any error is due to an unexpected external cause. Error is fed back via the vestibular afferent system. The efferent system causes macular otolithic membrane movement through the STO, which occurs simultaneously with the initiating motor command. As a result, no vestibular afferent activity occurs unless an error must be dealt with.

Evolution of postural control assessment: From dynamic posturography to virtual reality.

During the early years of spaceflight it was documented that astronauts were impaired and incapacitated upon return to earth. Computerized Dynamic Posturography (CDP) was devised to investigate and quantify this deficit, and eventually progressed into a clinical assessment tool. The current sprouting of virtual reality (VR) technologies has allowed for the development of an alternative approach that could be more informative. Many low-cost VR systems (including desktop gaming programs designed for rehabilitation) are now available. Continued improvements in this technology indicate a high probability that VR will become an integral component of posturography by replacing present mechanical CDP techniques. We researched the relevant literature to evaluate the strengths and weaknesses of CDP using the Equitest (Neurocom International; Clackamas USA), and the added benefits of incorporating VR to help clinicians assess the complex task of balance maintenance. VR is capable of manipulating task and environmental demands in order to assess functional postural behavior. VR is also a useful tool for clinical testing of postural disorders resulting from sensory mismatch. Although posturography is still a useful clinical tool, VR provides an inherent conflict between the visual and vestibular senses and can elevate the effectiveness of CDP for both assessment and intervention. We conclude that, when initially developed, CDP was innovative and ahead of its time. However, with the advent of VR, we have a chance to modernize CDP and enhance its value as a clinical instrument.

Understanding and Managing Trauma-Induced Vestibular Deficits.

OBJECTIVES: Traumatic brain injury occurs frequently worldwide. Half of traumatic brain injuries are related to falls or motor vehicle accidents. The term "concussion" is often used to describe a minor form of traumatic brain injury. These often involve decelerative events to the head (e.g., flexion/extension injury) and can also cause damage to the vestibular system of the inner ear. MATERIALS AND METHODS: The European Society for Clinical Evaluation of Balance Disorders meets yearly and has proposed an investigation and analysis of the vestibular consequences of traumatic brain injury. This review paper outlines these discussions. RESULTS: The Society discussed all aspects of trauma-induced vestibular disorders along with diagnosis and management. They also assessed the diagnostic tests available to investigate these disorders. CONCLUSION: Trauma-induced vestibular disorders are difficult to manage, as our level of understanding of the pathology can be poor and anatomical localization can also be difficult. Accordingly, a definitive diagnosis cannot be pinpointed in many patients, but an extensive history taking is crucial to determine the nature and extent of vestibular involvement. Trauma can not only result in microtrauma to the central nervous system but can also significantly affect peripheral vestibular structures, particularly the otolith organs. The committee hopes that better understanding of trauma to the vestibular system, along with improvements in the field of radiology and vestibular assessments, will aid in more precise techniques of pinpointing pathology in order to develop an adapted treatment plan.

Migraine and vertigo: a marriage of convenience?

"Migraine associated vertigo" is emerging as a popular diagnosis for patients with recurrent vertigo. However, in view of our current understanding of both migraine and vertigo, "migraine associated vertigo," in contrast to basilar artery migraine, is neither clinically nor biologically plausible as a migraine variant.

Vestibular suppression of normal bodily sounds.

Background: Vestibular-evoked myogenic potentials (VEMPs) are present in almost everyone. The proximity of the cochlear and vestibular end organs strongly indicates an overlap of the stimuli to which they respond.Aims/objectives: To determine the loudness of shouting compared to the external auditory canal (EAC) and explore how hyperstimulation of the cochlea and vestibular structures might be prevented.Materials and methods: We compared the loudness and frequency response of sound during shouting, biting and chewing, as well as the measurement of the loudness and frequency of sound in the external auditory canal (EAC) when a calibrated minishaker is applied to the forehead and to the upper incisor teeth.Results: We showed that vibratory sounds produced by vocalizations and oral activities were attenuated when they reached the ear, so that these sounds would not act as vestibular stimulants.Conclusions and significance: Chewing is known to cause a stapedius reflex which suppresses internal sounds to optimize audition of external sounds, while at the same time suppressing vestibular stimulation, which serves to optimize the sensitivity of the vestibular system, in order that it may respond precisely to a threat.

Energy reflectance and tympanometry in normal and otosclerotic ears.

OBJECTIVE: The major goal of this study was to examine differences in the middle ear mechano-acoustical properties of normal ears and ears with surgically confirmed otosclerosis using conventional and multifrequency tympanometry (MFT) as well as energy reflectance (ER). Second, we sought to compare ER, standard tympanometry, and MFT in their ability to distinguish healthy and otosclerotic ears examining both overall test performance (sensitivity and specificity) and receiver- operating characteristic analyses. DESIGN: Sixty-two normal-hearing adults and 28 patients diagnosed with otosclerosis served as subjects. Tympanometric data were gathered on a clinical immittance machine, the Virtual 310 equipped with a high-frequency option. Two of the parameters, static admittance and tympanometric width, were measured automatically at a standard 226 Hz frequency. The remaining two parameters, resonant frequency and frequency corresponding to admittance phase angle of 45 degree (F45 degrees ), were derived from MFT, multicomponent tympanometry, using a mathematical approach similar to the method used in GSI Tympstar Version 2. ER data were gathered using Mimosa Acoustics (RMS-system v4.0.4.4) equipment. RESULTS: Analyses of receiver-operating characteristic plots confirmed the advantage of MFT measures of resonant frequency and F45 degrees over the standard low-frequency measures of static admittance and tympanometric width with respect to distinguishing otosclerotic ears from normal ears. The F45 degrees measure was also found to be the best single index for making this distinction among tympanometric parameters. ER less than 1 kHz was significantly higher in otosclerotic ears than normal ears. This indicates that most of the incident energy below 1 kHz is reflected back into the ear canal in otosclerotic ears. ER patterns exceeding the 90th percentile of the normal ears across all frequencies correctly identify 82% of the otosclerotic ears while maintaining a low false alarm rate (17.2%); thus, this measure outperforms the other individual tympanometric parameters. Combination of ER and F45 degrees were able to distinguish all otosclerotic ears. Correlations and the individual patterns of test performance revealed that information provided by ER is supplemental to the information provided by conventional and MFT with respect to distinguishing otosclerotic ears from normal ears. CONCLUSION: The present findings show that the overall changes of ER across frequencies can distinguish otosclerotic ears from normal ears and from other sources of conductive hearing loss. Incorporating ER in general practice will improve the identification of otosclerotic ears when conventional tympanometry and MFT may fail to do so. To further improve the false alarm rate, ER should be interpreted in conjunction with other audiologic test batteries because it is unlikely that signs of a conductive component, including abnormal middle ear muscle reflex and ER responses, would be observed in an ear with normal middle ear function.

Wideband energy reflectance patterns in preoperative and post-operative otosclerotic ears.

The purpose of this study was to examine patterns of energy of reflectance (ER) in preoperative and post-operative conditions in otosclerotic ears. It was also within the scope of this paper to investigate whether the changes in ER pattern post-operatively correlate to the improvement in hearing as measured by pure-tone audiometry. ER was measured in 15 surgically confirmed otosclerotic ears (mean age: 44 years) before and after the stapes surgery. The most prominent change in ER pattern following the surgery in majority of the subjects was a sharp and deep drop in ER value between 700-1000 Hz. There was also a secondary wider and smaller increase in ER value following the surgery between 2000-4000 Hz. Moreover, in most cases the drop in ER values following the surgery at low frequencies (

Computerized Dynamic Posturography does not detect measured CVEMP and OVEMP abnormalities.

BACKGROUND: Computerized Dynamic Posturography (CDP)was developed by the American space program to assess imbalance in astronauts, and eventually evolved into a clinical diagnostic tool. However it is not a specific measure of vestibular function. Vestibular Evoked Myogenic Potential testing (VEMPs) is a new clinical tool which is sensitive and specific for measuring otolithic pathology, especially in the atypical vestibular patient. RESEARCH QUESTION: As posturography measures ability to maintain balance, and VEMP testing measures the structures responsible for this, we wondered if CDP results would correlate with VEMP abnormalities in the clinical setting. METHODS: We analysed 180 patients sequentially referred to our unit for vestibular complaints. All patients had a full battery of vestibular assessments. We correlated VEMP results with CDP results to look for abnormality patterns and correlations. An occasional patient's only abnormality was on CDP RESULTS: There was a high rate of VEMP abnormalities seen, which correlates with the fact that our referral base consists of patients with chronic vestibular complaints. The rate of VEMP abnormalities was the same in patients with normal CDP and those with abnormal CDP. SIGNIFICANCE: Our results do not suggest that CDP is unnecessary, but we feel that they emphasize the idea that these tests are measuring two different aspects of balance control. In some patients, all assessments are abnormal, but in some patients only one assessment is abnormal, suggesting that these modalities measure different things and are all important in the diagnostic armamentarium. Hopefully in the near future, the use of virtual reality will reduce the cost of CDP to the point where it can be made widely accessible to patients and clinicians.

Optimum Number of Sweeps in Clinical OVEMP Recording; How Many Sweeps are Necessary?

OBJECTIVE: Ocular vestibular-evoked myogenic potentials (OVEMPs) in our hands provide us with reproducible and consistent results; however, it has been shown that the OVEMP amplitude decreases with increased stimulus duration. The exact number of stimuli for OVEMP recording is not consistent among the published papers describing this test. We aimed to determine the number of stimuli needed to produce a satisfactory OVEMP response and the consequences of a more prolonged stimulation to the OVEMP response. MATERIALS AND METHODS: We retrospectively analyzed 50 OVEMP patient recordings and found that the average number of sweeps carried out was 26. We carried out three different OVEMP recordings using our standard protocol of (1) a "standard" OVEMP protocol, in which we record until the OVEMP wave becomes obvious; (2) an OVEMP recording using our average of 26 sweeps; and (3) an OVEMP recording with twice as many sweeps. RESULTS: OVEMP latencies did not change when using different number of sweeps; however, the amplitudes showed a significant decrease with an increasing number of sweeps. CONCLUSION: OVEMPs can be completed in a satisfactory manner with a much lower number of stimuli than those usually carried out. Reducing the stimulus number reduces the time taken for the test, minimizes the cochlear insult while not reducing the valuable information obtained, and maximizes the amplitude of the stimulus, possibly increasing the accuracy of measuring interaural amplitudes and helping to measure asymmetry.

Barotrauma presenting as temporal lobe injury secondary to temporal bone rupture.

We present the case of a scuba diver who experienced acute ear pain during ascent from a dive. CT imaging was performed because of severe unrelenting headache. Blood and gas was identified within the epidural space of the middle fossa and over the petrous bone, as well as hemorrhage within the adjacent temporal lobe. To the best of our knowledge, this is the first case of CT-documented barotrauma affecting the brain as a result of middle-ear gas rupturing through the tegmen tympani.

Exostosis of the external auditory canal: a technical note.

OBJECTIVE: To describe the author's method of managing occlusive exostosis of the external auditory canal. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral ambulatory otology clinic. PATIENTS: A case series of patients treated sequentially by the author over 15 years, all of whom had occlusive external auditory canal exostoses that could not be treated by medical management. INTERVENTION: Permeatal surgical removal of the anterior exostosis only. MAIN OUTCOME MEASURE: Surgical relief of occlusive external auditory canal disease by restoration of hearing and absence of infection with persistence of an external auditory canal and no symptoms of recurrence. RESULTS: A total of 8 men were treated by anterior exostosis removal. Follow-up continued on these patients for a period of 5 to 15 years after the operation, and none showed any evidence of recurrence or tendency to narrowing of the deep ear canal. One patient incurred a tympanic membrane perforation at escostosis surgery that was repaired during the operation. CONCLUSION: Anterior exostosis removal by a permeatal route is a safe, rapid, and effective method of relieving patients of occlusive external auditory canal exostosis. By leaving the posterior exostosis intact, patients are not put at risk for injury to the facial nerve, chorda tympani nerve, or ossicles. When the deep ear canal is drilled blind, there are no landmarks to indicate the true path of the external canal.

Longitudinal analysis of hearing loss in a case of hemosiderosis of the central nervous system.

OBJECTIVE: To describe cochleovestibular aspects of superficial hemosiderosis of the central nervous system. BACKGROUND: Superficial hemosiderosis of the central nervous system is a rare disease in which cochleovestibular impairment, cerebellar ataxia, and myelopathy are the most frequent signs. Chronic recurrent subarachnoidal hemorrhage with bleeding into the cerebrospinal fluid is the cause of deposition of hemosiderin in leptomeningeal and subpial tissue, cranial nerves, and spinal cord. Removing the cause of bleeding can prevent irreversible damage to these structures. Because this is the only effective treatment, an early diagnosis is crucial. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENT: A 72-year-old woman with superficial hemosiderosis of the central nervous system that developed when she was age 39. METHODS: Neurologic and imaging diagnostic examinations and longitudinal evaluation of cochleovestibular features were performed. Neurosurgery was not performed. RESULTS: Progressive bilateral sensorineural hearing loss and severe vestibular hyporeflexia developed within 15 years, which can be attributed to lesions in the cochleovestibular system. Additional pathology of the central nervous system developed later. CONCLUSION: The patient demonstrated cochlear and vestibular findings that are typical of this pathologic condition. It is the first documented case with extensive serial audiometry used to precisely outline the degree of hearing deterioration during the course of the disease.

Clinical romberg testing does not detect vestibular disease.

OBJECTIVE: To evaluate the effectiveness of tandem Romberg and tandem walking testing at detecting vestibular disease and to increase the difficulty of these standard screening assessments in an attempt to try and make them more effective in the clinical office setting. STUDY DESIGN AND SETTING: A prospective study in a tertiary and quaternary care neuro-otology clinic comparing performance on tandem Romberg and tandem walking between patients with vestibular disease and controls matched for age and sex. RESULTS: Making the tandem Romberg test and tandem walking tests more difficult for patients was not helpful because it also made the tests more difficult to perform for controls with no symptoms of vestibular disease. When comparing a young and an old cohort, there was a significant difference in performance. CONCLUSION: Our techniques of sharpening and sensitizing tandem Romberg and tandem walking tests were not useful at delineating vestibular disease, and age itself may be a confound that mimics the effects of balance system disease. SIGNIFICANCE: The tandem Romberg and tandem walking tests, despite being in widespread clinical use as office screening tests, may not be effective at determining the presence of newly developed vestibular disease.

Increasing the usefulness of tandem walking evaluation.

OBJECTIVE: Tandem walking testing is a "standard" clinical technique for assessing balance and gait, but it is not a standardized test. We wished to develop a protocol by which we could measure sway during tandem walking at a patient's preferred cadence and at an altered cadence, which might be more challenging. DESIGN: Fifteen patients with vestibular complaints were evaluated with standard tandem walking testing while wearing the Swaystar belt-mounted accelerometer and were also assessed in the same way with tandem walking at two altered cadences. METHODS: We measured tandem walking sway amplitude and sway velocity with eyes open in both pitch and roll planes at a patient's preferred cadence, at 75% of their preferred cadence, and at 125% of their preferred cadence. MAIN OUTCOME MEASURES: We measured total sway amplitude and sway velocity in pitch and roll planes during tandem walking with eyes open while wearing Swaystar to see if there was any increase in sway at nonpreferred cadences. RESULTS: There was no correlation between preferred cadence and the age of the patient. However, there was a significant increase in both sway amplitude and sway velocity at both of the nonpreferred cadences. CONCLUSION: Disruption of a patient's preferred cadence may present an unnatural task, and this challenge to a patient's innate gait may help detect subtle vestibular disease.