The addition of a spatial auditory cue improves spatial updating in a virtual reality navigation task.

Auditory cues are integrated with vision and body-based self-motion cues for motion perception, balance, and gait, though limited research has evaluated their effectiveness for navigation. Here, we tested whether an auditory cue co-localized with a visual target could improve spatial updating in a virtual reality homing task. Participants navigated a triangular homing task with and without an easily localizable spatial audio signal co-located with the home location. The main outcome was unsigned angular error, defined as the absolute value of the difference between the participant's turning response and the correct response towards the home location. Angular error was significantly reduced in the presence of spatial sound compared to a head-fixed identical auditory signal. Participants' angular error was 22.79° in the presence of spatial audio and 30.09° in its absence. Those with the worst performance in the absence of spatial sound demonstrated the greatest improvement with the added sound cue. These results suggest that auditory cues may benefit navigation, particularly for those who demonstrated the highest level of spatial updating error in the absence of spatial sound.

Age-Related Changes in Temporal Binding Involving Auditory and Vestibular Inputs.

Maintaining balance involves the combination of sensory signals from the visual, vestibular, proprioceptive, and auditory systems. However, physical and biological constraints ensure that these signals are perceived slightly asynchronously. The brain only recognizes them as simultaneous when they occur within a period of time called the temporal binding window (TBW). Aging can prolong the TBW, leading to temporal uncertainty during multisensory integration. This effect might contribute to imbalance in the elderly but has not been examined with respect to vestibular inputs. Here, we compared the vestibular-related TBW in 13 younger and 12 older subjects undergoing 0.5 Hz sinusoidal rotations about the earth-vertical axis. An alternating dichotic auditory stimulus was presented at the same frequency but with the phase varied to determine the temporal range over which the two stimuli were perceived as simultaneous at least 75% of the time, defined as the TBW. The mean TBW among younger subjects was 286 ms (SEM ± 56 ms) and among older subjects was 560 ms (SEM ± 52 ms). TBW was related to vestibular sensitivity among younger but not older subjects, suggesting that a prolonged TBW could be a mechanism for imbalance in the elderly person independent of changes in peripheral vestibular function.

Prevalence and Risk Factors of Self-reported Dizziness in Post-9/11 Service Members and Veterans.

INTRODUCTION: Dizziness is prevalent in the general population, but little is known about its prevalence in the U.S. military population. Dizziness is commonly associated with blast exposure and traumatic brain injury (TBI), but the potential independent contributions of blast and TBI have yet to be evaluated. This study's goal was to estimate the prevalence of dizziness among post-9/11 service members and Veterans and to examine independent and joint associations between military TBI history, blast exposure, and self-reported dizziness. MATERIALS AND METHODS: The study sample consisted of service members (n = 424) and recently separated (< ∼2.5 years) Veterans (n = 492) enrolled in the Noise Outcomes in Service members Epidemiology (NOISE) Study. We examined associations between self-reported history of probable TBI and blast exposure and recent dizziness using logistic regression. Models were stratified by service member versus Veteran status and adjusted to account for potentially confounding demographic and military characteristics. RESULTS: Overall, 22% of service members and 31% of Veterans self-reported dizziness. Compared to those with neither TBI nor blast exposure history, both service members and Veterans with TBI (with or without blast) were three to four times more likely to self-report dizziness. Those with blast exposure but no TBI history were not more likely to self-report dizziness. There was no evidence of an interaction effect between blast exposure and a history of TBI on the occurrence of dizziness. CONCLUSION: Self-reported dizziness was prevalent in this sample of service members and Veterans. Probable TBI history, with or without blast exposure, was associated with dizziness, but blast exposure without TBI history was not. This suggests that treatment guidelines for TBI-related dizziness may not need to be tailored to the injury mechanism. However, future efforts should be directed toward the understanding of the pathophysiology of TBI on self-reported dizziness, which is fundamental to the design of treatment strategies.

Influence of Hearing Rehabilitation With Active Middle Ear and Bone Conduction Implants on Postural Control.

Background: As audition also seems to contribute to balance control, additionally to visual, proprioceptive, and vestibular information, we hypothesize that hearing rehabilitation with active middle ear and bone conduction implants can influence postural control. Methods: In a prospective explorative study, the impact of hearing rehabilitation with active middle ear [Vibrant Soundbrige (VSB), MED-EL, Innsbruck, Austria] and bone conduction implants [Bonebridge (BB), MED-EL, Innsbruck, Austria] on postural control in adults was examined in three experiments. Vestibulospinal control was measured by cranio-corpography (CCG), trunk sway velocity (°/s) by the Standard Balance Deficit Test (SBDT), and postural stability with a force plate system, each time in best aided (BA) and unaided (UA) condition with frontal-noise presentation (Fastl noise, 65 dB SPL), followed by subjective evaluation, respectively. Results: In 26 subjects [age 55.0 ± 12.8 years; unilateral VSB/BB: n = 15; bilateral VSB/BB: n = 3, bimodal (VSB/BB + hearing aid): n = 8], CCG-analysis showed no difference between BA and UA conditions for the means of distance, angle of displacement, and angle of rotation, respectively. Trunk sway measurements revealed a relevant increase of sway in standing on foam (p = 0.01, r = 0.51) and a relevant sway reduction in walking (p = 0.026, r = 0.44, roll plane) in BA condition. Selective postural subsystem analysis revealed a relevant increase of the vestibular component in BA condition (p = 0.017, r = 0.47). As measured with the Interactive Balance System (IBS), 42% of the subjects improved stability (ST) in BA condition, 31% showed no difference, and 27% deteriorated, while no difference was seen in comparison of means. Subjectively, 4-7% of participants felt that noise improved their balance, 73-85% felt no difference, and 7-23% reported deterioration by noise. Furthermore, 46-50% reported a better task performance in BA condition; 35-46% felt no difference and 4-15% found the UA situation more helpful. Conclusions: Subjectively, approximately half of the participants reported a benefit in task performance in BA condition. Objectively, this could only be shown in one mobile SBDT-task. Subsystem analysis of trunk sway provided insights in multisensory reweighting mechanisms.

Influence of predictability on saccade timing in a head impulse VOR suppression task.

Gaze stabilization performance has been shown to be influenced differently when the head is either passively or actively moved in normal healthy participants. However, for a visual fixation suppression task, it remains unknown if the pattern of coordinated head and eye movement is influenced differently by passive or active head movements. We used a suppression head impulse paradigm (SHIMP), where the subject's goal was to maintain gaze stabilized on a visual target that moved with the head during rapid impulsive head movements, to evaluate gaze fixation performance in three conditions: (1) passive-unpredictable where the examiner applied impulsive head yaw rotations with random timing and direction, (2) passive-predictable where the direction of head rotation was announced and then the examiner repeatedly applied impulses in the same direction, and (3) active where the test subject self-generated their head movements. Thirteen young healthy adults performed all three conditions to assess the percentage of early saccades that initiated the gaze shift toward the final visual target position and the latency of first saccades. Early saccades were defined as those occurring within the duration of the head impulse. Results showed that active head impulses generated the greatest percentage of early saccades, followed by predictable and unpredictable. Among the two passive conditions, predictability shortened the first saccade onset latencies. Active condition onset latencies were shorter than in either of the passive conditions, showing a consistent head-leads-eye pattern defining a specific behavioral pattern that could vary across patient groups leading to insights into central neural mechanisms that control eye-head coordination.

Clinical Considerations for Routine Auditory and Vestibular Monitoring in Patients With Cystic Fibrosis.

Purpose Specific classes of antibiotics, such as aminoglycosides, have well-established adverse events producing permanent hearing loss, tinnitus, and balance and/or vestibular problems (i.e., ototoxicity). Although these antibiotics are frequently used to treat pseudomonas and other bacterial infections in patients with cystic fibrosis (CF), there are no formalized recommendations describing approaches to implementation of guideline adherent ototoxicity monitoring as part of CF clinical care. Method This consensus statement was developed by the International Ototoxicity Management Working Group (IOMG) Ad Hoc Committee on Aminoglycoside Antibiotics to address the clinical need for ototoxicity management in CF patients treated with known ototoxic medications. These clinical protocol considerations were created using consensus opinion from a community of international experts and available evidence specific to patients with CF, as well as published national and international guidelines on ototoxicity monitoring. Results The IOMG advocates four clinical recommendations for implementing routine and guideline adherent ototoxicity management in patients with CF. These are (a) including questions about hearing, tinnitus, and balance/vestibular problems as part of the routine CF case history for all patients; (b) utilizing timely point-of-care measures; (c) establishing a baseline and conducting posttreatment evaluations for each course of intravenous ototoxic drug treatment; and (d) repeating annual hearing and vestibular evaluations for all patients with a history of ototoxic antibiotic exposure. Conclusion Increased efforts for implementation of an ototoxicity management program in the CF care team model will improve identification of ototoxicity signs and symptoms, allow for timely therapeutic follow-up, and provide the clinician and patient an opportunity to make an informed decision about potential treatment modifications to minimize adverse events. Supplemental Material https://doi.org/10.23641/asha.16624366.

Exploring persistent complaints of imbalance after mTBI: Oculomotor, peripheral vestibular and central sensory integration function.

BACKGROUND: Little is known on the peripheral and central sensory contributions to persistent dizziness and imbalance following mild traumatic brain injury (mTBI). OBJECTIVE: To identify peripheral vestibular, central integrative, and oculomotor causes for chronic symptoms following mTBI. METHODS: Individuals with chronic mTBI symptoms and healthy controls (HC) completed a battery of oculomotor, peripheral vestibular and instrumented posturography evaluations and rated subjective symptoms on validated questionnaires. We defined abnormal oculomotor, peripheral vestibular, and central sensory integration for balance measures among mTBI participants as falling outside a 10-percentile cutoff determined from HC data. A X-squared test associated the proportion of normal and abnormal responses in each group. Partial Spearman's rank correlations evaluated the relationships between chronic symptoms and measures of oculomotor, peripheral vestibular, and central function for balance control. RESULTS: The mTBI group (n = 58) had more abnormal measures of central sensory integration for balance than the HC (n = 61) group (mTBI: 41% -61%; HC: 10%, p's < 0.001), but no differences on oculomotor and peripheral vestibular function (p > 0.113). Symptom severities were negatively correlated with central sensory integration for balance scores (p's < 0.048). CONCLUSIONS: Ongoing balance complaints in people with chronic mTBI are explained more by central sensory integration dysfunction rather than peripheral vestibular or oculomotor dysfunction.

Superior semicircular canal dehiscence syndrome: Diagnostic criteria consensus document of the committee for the classification of vestibular disorders of the Bárány Society.

This paper describes the diagnostic criteria for superior semicircular canal dehiscence syndrome (SCDS) as put forth by the classification committee of the Bárány Society. In addition to the presence of a dehiscence of the superior semicircular canal on high resolution imaging, patients diagnosed with SCDS must also have symptoms and physiological tests that are both consistent with the pathophysiology of a 'third mobile window' syndrome and not better accounted for by another vestibular disease or disorder. The diagnosis of SCDS therefore requires a combination of A) at least one symptom consistent with SCDS and attributable to 'third mobile window' pathophysiology including 1) hyperacusis to bone conducted sound, 2) sound-induced vertigo and/or oscillopsia time-locked to the stimulus, 3) pressure-induced vertigo and/or oscillopsia time-locked to the stimulus, or 4) pulsatile tinnitus; B) at least 1 physiologic test or sign indicating that a 'third mobile window' is transmitting pressure including 1) eye movements in the plane of the affected superior semicircular canal when sound or pressure is applied to the affected ear, 2) low-frequency negative bone conduction thresholds on pure tone audiometry, or 3) enhanced vestibular-evoked myogenic potential (VEMP) responses (low cervical VEMP thresholds or elevated ocular VEMP amplitudes); and C) high resolution computed tomography (CT) scan with multiplanar reconstruction in the plane of the superior semicircular canal consistent with a dehiscence. Thus, patients who meet at least one criterion in each of the three major diagnostic categories (symptoms, physiologic tests, and imaging) are considered to have SCDS.

Reliability of Vestibular Perceptual Threshold Testing About the Yaw Axis.

OBJECTIVES: Vestibular reflexes have traditionally formed the cornerstone of vestibular evaluation, but perceptual tests have recently gained attention for use in research studies and potential clinical applications. However, the unknown reliability of perceptual thresholds limits their current importance. This is addressed here by establishing the test-retest reliability of vestibular perceptual testing. DESIGN: Perceptual detection thresholds to earth-vertical, yaw-axis rotations were collected in 15 young healthy people. Participants were tested at two time intervals (baseline, 5 to 14 days later) using an adaptive psychophysical procedure. RESULTS: Thresholds to 1 Hz rotations ranged from 0.69 to 2.99°/s (mean: 1.49°/s; SD: 0.63). They demonstrated an excellent intraclass correlation (0.92; 95% confidence interval: 0.77 to 0.97) with a minimum detectable difference of 0.45°/s. CONCLUSIONS: The excellent test-retest reliability of perceptual vestibular testing supports its use as a research tool and motivates further exploration for its use as a novel clinical technique.

Stapes Surgery Outcomes in Patients With Concurrent Otosclerosis and Superior Semicircular Canal Dehiscence.

OBJECTIVE: To review outcomes of stapes surgery in patients with concurrent otosclerosis and superior semicircular canal dehiscence. STUDY DESIGN: Retrospective case series. SETTING: Tertiary referral center. PATIENTS: Patients with concurrent otosclerosis and superior canal dehiscence, confirmed by computed tomography (CT) imaging. INTERVENTION(S): Stapes surgery for conductive hearing loss. MAIN OUTCOME MEASURE(S): Postoperative air-bone gap (ABG), as well as the number of patients in whom surgery was deemed successful (postoperative ABG <10 dB HL). RESULTS: Five patients with superior canal dehiscence and concomitant otosclerosis who underwent surgical repair were identified. Mean preoperative ABG was 29.0 ±â€Š6.4 dB HL. Mean postoperative ABG was 13.0 ±â€Š13 dB HL. Three patients (60%) had a successful outcome, defined as postoperative ABG less than 10. One patient experienced unmasking of superior canal dehiscence vestibular symptoms. CONCLUSIONS: Patients with concurrent otosclerosis and superior canal dehiscence appear to have a lower likelihood of successful hearing restoration following stapes surgery. Patients should be counseled accordingly. Routine preoperative CT imaging before stapes surgery may be helpful to identify patients at risk for poor outcomes.

Frequency-dependent integration of auditory and vestibular cues for self-motion perception.

Recent evidence has shown that auditory information may be used to improve postural stability, spatial orientation, navigation, and gait, suggesting an auditory component of self-motion perception. To determine how auditory and other sensory cues integrate for self-motion perception, we measured motion perception during yaw rotations of the body and the auditory environment. Psychophysical thresholds in humans were measured over a range of frequencies (0.1-1.0 Hz) during self-rotation without spatial auditory stimuli, rotation of a sound source around a stationary listener, and self-rotation in the presence of an earth-fixed sound source. Unisensory perceptual thresholds and the combined multisensory thresholds were found to be frequency dependent. Auditory thresholds were better at lower frequencies, and vestibular thresholds were better at higher frequencies. Expressed in terms of peak angular velocity, multisensory vestibular and auditory thresholds ranged from 0.39°/s at 0.1 Hz to 0.95°/s at 1.0 Hz and were significantly better over low frequencies than either the auditory-only (0.54°/s to 2.42°/s at 0.1 and 1.0 Hz, respectively) or vestibular-only (2.00°/s to 0.75°/s at 0.1 and 1.0 Hz, respectively) unisensory conditions. Monaurally presented auditory cues were less effective than binaural cues in lowering multisensory thresholds. Frequency-independent thresholds were derived, assuming that vestibular thresholds depended on a weighted combination of velocity and acceleration cues, whereas auditory thresholds depended on displacement and velocity cues. These results elucidate fundamental mechanisms for the contribution of audition to balance and help explain previous findings, indicating its significance in tasks requiring self-orientation.NEW & NOTEWORTHY Auditory information can be integrated with visual, proprioceptive, and vestibular signals to improve balance, orientation, and gait, but this process is poorly understood. Here, we show that auditory cues significantly improve sensitivity to self-motion perception below 0.5 Hz, whereas vestibular cues contribute more at higher frequencies. Motion thresholds are determined by a weighted combination of displacement, velocity, and acceleration information. These findings may help understand and treat imbalance, particularly in people with sensory deficits.

Comparison of balance outcomes according to treatment modality of vestibular schwannoma.

OBJECTIVES: We sought to compare balance outcomes according to treatment modality of vestibular schwannoma (VS) via a meta-analysis that divided measuring tools of balance outcomes into three categories based on type. METHODS: A comprehensive review of the literature from January 1966 to September 2017 was performed, looking for studies about long-term balance outcomes after microsurgery (MS), radiotherapy (RT), or observation for VS. A comprehensive meta-analysis was used to analyze effect sizes, explore possible causes of heterogeneity, and check publication bias with a funnel plot and Egger's regression. RESULTS: Among 633 references, 34 were included in the meta-analysis. Perceived dizziness improvement rate was significantly higher in the MS group than in the RT group (odds ratio [OR]: 1.61; 95% confidence interval [CI]: 1.08 to 2.40; P < .05, I2 = 4.18], but no significant difference was observed between the two groups with regard to validated dizziness questionnaire score (standardized mean difference: 0.04; 95% CI: -0.36 to 0.44; P = .84, I2 = 69.61) or dizziness or disequilibrium-related symptom incidence rate (OR: 0.91; 95% CI: 0.50 to 1.68; P = .77, I2 = 0). In a subanalysis conducted within the groups after intervention, the MS group demonstrated a lower vertigo incidence rate (P < .001), and the RT group experienced a significant reduction in validated dizziness questionnaire score (P < .05). CONCLUSIONS: Our results indicate that MS should be considered at least equal to RT in regard to resolving long-term dizziness and improving balance outcomes. Furthermore, well-designed studies are necessary to predict balance outcomes after VS treatment and to choose from among possible treatment options. LEVEL OF EVIDENCE: 2a Laryngoscope, 130:178-189, 2020.

Geographic Disparities in US Veterans' Access to Cochlear Implant Care Within the Veterans Health Administration System.

IMPORTANCE: Veterans are at high risk for developing sensorineural hearing loss leading to cochlear implant (CI) candidacy; however, the ability to care for these patients is limited by the number and location of Veterans Health Administration (VHA) facilities that provide specialized CI services. OBJECTIVE: To investigate geographic disparities in access to CI care within the VHA system for US veterans. DESIGN, SETTING, AND PARTICIPANTS: An analysis of census tract-level data including US veterans was conducted using the nationwide American Community Survey data collected by the US Census Bureau from January to December 2016, which were accessed in 2017. MAIN OUTCOMES AND MEASURES: Maps showing the geographic variability in need for specialized CI services, estimated as a function of the number of veterans and the distance to the nearest established VHA-based CI surgical or audiologic facilities. RESULTS: A total of 19.9 million veterans within the continental United States resided at a median distance of 80 miles (interquartile range [IQR], 30.1-140.9 miles; mean [SD], 1002 [465.8] miles) from the nearest VHA facility offering CI care; of these, 3.98 million (20.0%) resided more than 160.7 miles from the nearest VHA facility. When considering only comprehensive facilities offering both surgical and audiologic care, the median distance was 101.3 miles (IQR, 39.4-178.7 miles; mean [SD], 126.0 [448.4] miles), but 20.0% of veterans had to travel more than 201.0 miles to a VHA facility. Veterans residing in urban areas (74.0%) lived a median distance of 61.2 miles (IQR, 23.7-121.3 miles; mean [SD], 83.8 [477.1] miles) from the nearest VHA facility, with 2.9 million (20.0%) living the farthest at 140.7 miles. Veterans residing in rural areas (26.0%) lived a median distance of 119.8 miles (IQR, 79.0-182.4 miles; mean [SD], 146.9 [431.0] miles) from their nearest VHA facility, with 1.04 million (20.0%) living more than 206.2 miles from the nearest VHA facility. CONCLUSIONS AND RELEVANCE: This study's findings suggest that large disparities exist in the distance to the nearest VHA-based CI facilities. Veterans face considerable geographic barriers to obtaining VHA-based CI care in many parts of the country, including some large metropolitan areas. Those requiring only audiologic services face similar geographic barriers as those requiring surgery. Thoughtful placement of new facilities, along with upcoming advances in remote programming of implants, may help ensure appropriate care for this high-risk population.

Surgical Parameters for Minimally Invasive Trans-Eustachian Tube CSF Leak Repair: A Cadaveric Study and Literature Review.

BACKGROUND: Cerebrospinal fluid rhinorrhea from a lateral skull base defect refractory to spontaneous healing and/or conservative management is most commonly managed via open surgery. Approach for repair is dictated by location of the defect, which may require surgical exploration. The final common pathway is the eustachian tube (ET). Endoscopic ET obliteration via endonasal and lateral approaches is under development. Whereas ET anatomy has been studied, surgical landmarks have not been previously described or quantified. We aimed to define surgical parameters of specific utility to endoscopic ET obliteration. METHODS: A literature review was performed of known ET anatomic parameters. Next, using a combination of endoscopic and open techniques in cadavers, we cannulated the intact ET and dissected its posterior component to define the major curvature position of the ET, defined as the genu, and quantified the relative distances through the ET lumen. The genu was targeted as a major obstacle encountered when cannulating the ET from the nasopharynx. RESULTS: Among 10 ETs, we found an average distance of 23 ± 5 mm from the nasopharynx to the ET genu, distance of 24 ± 3 mm from the genu to the anterior aspect of the tympanic membrane and total ET length of 47 ± 4 mm. CONCLUSIONS: Although membranous and petrous components of the ET are important to its function, the genu may be a more useful surgical landmark. Basic surgical parameters for endoscopic ET obliteration are defined.

Relationship between vestibular sensitivity and multisensory temporal integration.

A single event can generate asynchronous sensory cues due to variable encoding, transmission, and processing delays. To be interpreted as being associated in time, these cues must occur within a limited time window, referred to as a "temporal binding window" (TBW). We investigated the hypothesis that vestibular deficits could disrupt temporal visual-vestibular integration by determining the relationships between vestibular threshold and TBW in participants with normal vestibular function and with vestibular hypofunction. Vestibular perceptual thresholds to yaw rotation were characterized and compared with the TBWs obtained from participants who judged whether a suprathreshold rotation occurred before or after a brief visual stimulus. Vestibular thresholds ranged from 0.7 to 16.5 deg/s and TBWs ranged from 13.8 to 395 ms. Among all participants, TBW and vestibular thresholds were well correlated ( R2 = 0.674, P < 0.001), with vestibular-deficient patients having higher thresholds and wider TBWs. Participants reported that the rotation onset needed to lead the light flash by an average of 80 ms for the visual and vestibular cues to be perceived as occurring simultaneously. The wide TBWs in vestibular-deficient participants compared with normal functioning participants indicate that peripheral sensory loss can lead to abnormal multisensory integration. A reduced ability to temporally combine sensory cues appropriately may provide a novel explanation for some symptoms reported by patients with vestibular deficits. Even among normal functioning participants, a high correlation between TBW and vestibular thresholds was observed, suggesting that these perceptual measurements are sensitive to small differences in vestibular function. NEW & NOTEWORTHY While spatial visual-vestibular integration has been well characterized, the temporal integration of these cues is not well understood. The relationship between sensitivity to whole body rotation and duration of the temporal window of visual-vestibular integration was examined using psychophysical techniques. These parameters were highly correlated for those with normal vestibular function and for patients with vestibular hypofunction. Reduced temporal integration performance in patients with vestibular hypofunction may explain some symptoms associated with vestibular loss.

Minimally invasive endoscopic repair of refractory lateral skull base cerebrospinal fluid rhinorrhea: case report and review of the literature.

Cerebrospinal fluid (CSF) leaks occur in approximately 10% of patients undergoing a translabyrinthine, retrosigmoid, or middle fossa approach for vestibular schwannoma resection. Cerebrospinal fluid rhinorrhea also results from trauma, neoplasms, and congenital defects. A high degree of difficulty in repair sometimes requires repetitive microsurgical revisions-a rate of 10% of cases is often cited. This can not only lead to morbidity but is also costly and burdensome to the health care system. In this case-based theoretical analysis, the authors summarize the literature regarding endoscopic endonasal techniques to obliterate the eustachian tube (ET) as well as compare endoscopic endonasal versus open approaches for repair. Given the results of their analysis, they recommend endoscopic endonasal ET obliteration (EEETO) as a first- or second-line technique for the repair of CSF rhinorrhea from a lateral skull base source refractory to spontaneous healing and CSF diversion. They present a case in which EEETO resolved refractory CSF rhinorrhea over a 10-month follow-up after CSF diversions, wound reexploration, revised packing of the ET via a lateral microscopic translabyrinthine approach, and the use of a vascularized flap had failed. They further summarize the literature regarding studies that describe various iterations of EEETO. By its minimally invasive nature, EEETO imposes less morbidity as well as less risk to the patient. It can be readily implemented into algorithms once CSF diversion (for example, lumbar drain) has failed, prior to considering open surgery for repair. Additional studies are warranted to further demonstrate the outcome and cost-saving benefits of EEETO as the data until now have been largely empirical yet very hopeful. The summaries and technical notes described in this paper may serve as a resource for those skull base teams faced with similar challenging and otherwise refractory CSF leaks from a lateral skull base source.

The effect of spatial auditory landmarks on ambulation.

The maintenance of balance and posture is a result of the collaborative efforts of vestibular, proprioceptive, and visual sensory inputs, but a fourth neural input, audition, may also improve balance. Here, we tested the hypothesis that auditory inputs function as environmental spatial landmarks whose effectiveness depends on sound localization ability during ambulation. Eight blindfolded normal young subjects performed the Fukuda-Unterberger test in three auditory conditions: silence, white noise played through headphones (head-referenced condition), and white noise played through a loudspeaker placed directly in front at 135 centimeters away from the ear at ear height (earth-referenced condition). For the earth-referenced condition, an additional experiment was performed where the effect of moving the speaker azimuthal position to 45, 90, 135, and 180° was tested. Subjects performed significantly better in the earth-referenced condition than in the head-referenced or silent conditions. Performance progressively decreased over the range from 0° to 135° but all subjects then improved slightly at the 180° compared to the 135° condition. These results suggest that presence of sound dramatically improves the ability to ambulate when vision is limited, but that sound sources must be located in the external environment in order to improve balance. This supports the hypothesis that they act by providing spatial landmarks against which head and body movement and orientation may be compared and corrected. Balance improvement in the azimuthal plane mirrors sensitivity to sound movement at similar positions, indicating that similar auditory mechanisms may underlie both processes. These results may help optimize the use of auditory cues to improve balance in particular patient populations.