John P. Carey

Disorders of Balance and Vestibular Function in US Adults: Data From the National Health and Nutrition Examination Survey, 2001-2004

BACKGROUND Balance dysfunction can be debilitating and can lead to catastrophic outcomes such as falls. The inner ear vestibular system is an important contributor to balance control. However, to our knowledge, the prevalence of vestibular dysfunction in the United States and the magnitude of the increased risk of falling associated with vestibular dysfunction have never been estimated. The objective of this study was to determine the prevalence of vestibular dysfunction among US adults, evaluate differences by sociodemographic characteristics, and estimate the association between vestibular dysfunction and risk of falls. METHODS We included data from the 2001-2004 National Health and Nutrition Examination Surveys, which were cross-sectional surveys of US adults aged 40 years and older (n = 5086). The main outcome measure was vestibular function as measured by the modified Romberg Test of Standing Balance on Firm and Compliant Support Surfaces. RESULTS From 2001 through 2004, 35.4% of US adults aged 40 years and older (69 million Americans) had vestibular dysfunction. Odds of vestibular dysfunction increased significantly with age, were 40.3% lower in individuals with more than a high school education, and were 70.0% higher among people with diabetes mellitus. Participants with vestibular dysfunction who were clinically symptomatic (ie, reported dizziness) had a 12-fold increase in the odds of falling. CONCLUSIONS Vestibular dysfunction, as measured by a simple postural metric, is common among US adults. Vestibular dysfunction significantly increases the likelihood of falls, which are among the most morbid and costly health conditions affecting older individuals. These data suggest the importance of diagnosing, treating, and potentially screening for vestibular deficits to reduce the burden of fall-related injuries and deaths in the United States.

Dehiscence of bone overlying the superior canal as a cause of apparent conductive hearing loss.

Objective To identify patients with superior semicircular canal dehiscence and apparent conductive hearing loss and to define the cause of the air-bone gap. Study Design Prospective study of patients with superior canal dehiscence. Setting Tertiary referral center. Patients Vestibular and/or auditory findings indicative of canal dehiscence and demonstration of superior canal dehiscence on computed tomography of the temporal bone. Intervention Vestibular-evoked myogenic potentials, three-dimensional eye movement recordings, and surgical resurfacing of the superior canal. Outcome Measure Association of superior canal dehiscence with an air-bone gap on audiometry. Results Four patients with dehiscence of bone overlying the superior canal were found to have air-bone gaps in the affected ears that were greatest at lower frequencies and averaged 24 ± 7 dB over the frequency range of 250 to 4,000 Hz. Three of these patients had undergone stapedectomy before the identification of superior canal dehiscence. The air-bone gap was unchanged postoperatively. Each patient had an intact vestibular-evoked myogenic potential (VEMP) response from the affected ear, a finding that would not have been expected based on a middle ear cause of conductive hearing loss. One patient underwent resurfacing of the superior canal through a middle fossa approach. Postoperatively, his vestibular symptoms were relieved, and his air conduction thresholds were improved by 20 dB. Conclusions Superior canal dehiscence can result in apparent conductive hearing loss. The third mobile window created by the dehiscent superior canal results in dissipation of acoustic energy and is a cause of inner ear conductive hearing loss.

Meniere's disease

PURPOSE OF REVIEW Ménières disease is characterized by spontaneous attacks of vertigo, fluctuating sensorineural hearing loss, aural fullness, and tinnitus. The pathologic process involves distortion of the membranous labyrinth with the formation of endolymphatic hydrops. This review describes the pathogenesis and etiology as well as the diagnosis and treatment of Ménières disease. RECENT FINDINGS Initial management of Ménières disease can involve a low-salt diet and a diuretic. Treatment with intratympanic injection of gentamicin can be beneficial when vertigo persists despite optimal medical management. Recent studies have shown that gentamicin reduces vestibular function in the treated ear, although complete ablation of this vestibular function is not typically required in order to achieve control of vertigo. SUMMARY Vertigo is often the most debilitating symptom associated with Ménières disease. Many treatment options exist for the management of vertigo. Intratympanic injection of gentamicin (low dose) can be used in patients for whom vertigo has not been controlled by medical measures. Ongoing research is providing a greater understanding of the effects of gentamicin on vestibular function and of the mechanisms through which gentamicin leads to control of vertigo.

Eye movements in patients with superior canal dehiscence syndrome align with the abnormal canal

Background: The superior canal dehiscence (SCD) syndrome consists of sound- or pressure-induced nystagmus and vertigo caused by a defect in bone overlying the superior semicircular canal. The SCD syndrome is diagnosed based upon characteristic symptoms, signs, and findings on CT imaging of the temoral bones. However, SCD syndrome is often misdiagnosed as perilymphatic fistula (PLF), and the symptoms of sound- and pressure-induced vertigo are more commonly attributed to the vestibular utricle, rather than to the superior semicircular canal. This study explored the role of the superior canal and the utricle in the pathophysiology of SCD syndrome. Methods: Three-dimensional scleral search coils were used to record eye movements in 11 patients with SCD syndrome. Results: Ten patients developed nystagmus with upward torsional slow phases characteristic of superior canal activation when loud tones were presented to the affected ear or when the patients performed a Valsalva maneuver. Visual fixation led to a suppression of the nystagmus and the appearance of a sustained torsional deviation of the eyes. Two patients also had sound-evoked head movements in the same direction as the ocular slow phases. The response of the affected superior canal to rapid head rotations was tested in nine patients. The response was diminished in those with large (≥5 mm) defects in the bone overlying the superior canal. Conclusions: The evoked eye movements in patients with SCD syndrome arise from the superior canal, not the utricle. The syndrome is recognized by the characteristic nystagmus evoked by tones or maneuvers that change middle ear or intracranial pressure. Examination for this nystagmus should be performed under conditions that prevent visual fixation.

Vestibular-evoked myogenic potential thresholds normalize on plugging superior canal dehiscence

Background: Diagnosis of the superior canal dehiscence syndrome (SCDS) relies on symptoms such as sound- or pressure-induced vertigo or oscillopsia, demonstration of sound or pressure-evoked vertical/torsional eye movements, and the presence of a defect in the bony roof overlying the superior semicircular canal. Lowered thresholds for eliciting vestibular-evoked myogenic potentials (VEMPs) provide additional conformation. Objective: To examine VEMP characteristics before and after canal plugging for SCDS. Methods: VEMPs evoked by air- and bone-conducted tones were measured from the sternocleidomastoid muscles (cVEMP) and periocular sites (oVEMP) of 20 normal volunteers, 10 newly diagnosed subjects with SCDS, and 12 subjects who underwent successful superior canal plugging. Results: In all SCDS ears, thresholds for evoking VEMP using air-conducted tones were pathologically lowered, with average values of 83.85 ± 1.40 dB sound pressure level (SPL) for cVEMP and 85.38 ± 1.32 dB SPL for oVEMP, 20 to 30 dB below those of controls. Successful canal plugging resulted in normal reflex thresholds. For bone vibration, average thresholds in SCDS ears were 114.62 ± 1.54 dB FL (force level) for cVEMP and 116.0 ± 1.52 dB FL for oVEMP, 10 to 20 dB below controls, yet three SCDS ears had normal thresholds. Conclusions: Ocular and cervical vestibular-evoked myogenic potentials evoked by air-conducted sound are equally useful in the diagnosis and follow-up of superior canal dehiscence syndrome. Stimulus thresholds are consistently lowered upon presentation and normalize after corrective surgery. Thresholds for bone vibration, in contrast, have a lower diagnostic yield.

Symptoms and signs in superior canal dehiscence syndrome.

Abstract: Patients with superior canal dehiscence (SCD) syndrome experience vertigo and oscillopsia in response to loud sounds and to stimuli that result in changes in middle ear or intracranial pressure. They may also experience hyperacusis to bone‐conducted sounds. The evoked eye movements in this syndrome align with the plane of the dehiscent superior canal. The symptoms and signs can be understood in terms of the effect of the dehiscence in creation of a third mobile window into the inner ear. The SCD syndrome has been diagnosed in 28 patients who were examined in the neuro‐otology clinics at the Johns Hopkins Medical Institutions from May 1995 through January 2001. The diagnosis is best established based upon the symptoms that are characteristic for the syndrome, the vertical‐torsional eye movements evoked by sound or pressure stimuli noted on examination performed with Frenzel goggles, the lowered thresholds for responses to vestibular‐evoked myogenic potentials, and CT imaging of the temporal bones.

Vestibular-Evoked Myogenic Potentials in the Diagnosis of Superior Canal Dehiscence Syndrome

Patients with superior canal dehiscence (SCD) syndrome have vertigo and oscillopsia induced by loud noises and by stimuli that result in changes in middle ear or intracranial pressure. We recorded vestibular-evoked myogenic potentials (VEMP responses) in 10 patients with SCD syndrome. The diagnosis had been confirmed in each case by evoked eye movements and by high-resolution CT scans of the temporal bones that showed a dehiscence overlying the affected superior canal. For the 8 patients without prior middle ear disease, the VEMP threshold from the dehiscent ears measured 72 - 8 dB NHL (normal hearing level) whereas the threshold from normal control subjects was 96 - 5 dB NHL ( p < 0.0001). The VEMP threshold measured from the contralateral ear in patients with unilateral dehiscence was 98 - 4 dB NHL ( p > 0.9 with respect to normal controls). Two patients with apparent conductive hearing loss from middle ear disease, and SCD, had VEMP responses from the affected ears. In the absence of dehiscence, VEMP responses would not have been expected in the setting of conductive hearing loss. These findings confirm earlier studies demonstrating that patients with SCD syndrome have lowered VEMP thresholds. Conditions other than SCD syndrome may also lead to lowered VEMP thresholds. Rather than being based upon a single test, the diagnosis of SCD syndrome is best established when the characteristic symptoms, signs, VEMP response, and CT imaging all indicate SCD.Patients with superior canal dehiscence (SCD) syndrome have vertigo and oscillopsia induced by loud noises and by stimuli that result in changes in middle ear or intracranial pressure. We recorded vestibular-evoked myogenic potentials (VEMP responses) in 10 patients with SCD syndrome. The diagnosis had been confirmed in each case by evoked eye movements and by high-resolution CT scans of the temporal bones that showed a dehiscence overlying the affected superior canal. For the 8 patients without prior middle ear disease, the VEMP threshold from the dehiscent ears measured 72 +/- 8 dB NHL (normal hearing level) whereas the threshold from normal control subjects was 96 +/- 5 dB NHL (p < 0.0001). The VEMP threshold measured from the contralateral ear in patients with unilateral dehiscence was 98 +/- 4 dB NHL (p > 0.9 with respect to normal controls). Two patients with apparent conductive hearing loss from middle ear disease, and SCD, had VEMP responses from the affected ears. In the absence of dehiscence, VEMP responses would not have been expected in the setting of conductive hearing loss. These findings confirm earlier studies demonstrating that patients with SCD syndrome have lowered VEMP thresholds. Conditions other than SCD syndrome may also lead to lowered VEMP thresholds. Rather than being based upon a single test, the diagnosis of SCD syndrome is best established when the characteristic symptoms, signs, VEMP response, and CT imaging all indicate SCD.

Test-retest reliability and age-related characteristics of the ocular and cervical vestibular evoked myogenic potential tests.

Objective: To determine the test-retest reliability and age-related trends of the cervical and ocular vestibular evoked myogenic potential (cVEMP and oVEMP, respectively) responses to air-conducted sound and bone-conducted vibration stimulation. Study Design: Prospective study. Setting: Tertiary referral center. Patients: Fifty-three healthy adults with no hearing or vestibular deficits. Intervention(s): All subjects underwent cVEMP and oVEMP testing in response to sounds (0.1-ms clicks and 500-Hz tone bursts) and vibration (midline forehead taps at the hairline, Fz, with a reflex hammer and a Brüel & Kjær Mini-Shaker Type 4810). Twelve subjects underwent an additional testing session that was conducted at a mean of 10 weeks after the first one. Main Outcome Measure(s): Test-retest reliability for VEMP response parameters (latency, peak-to-peak amplitude, and asymmetry ratio) were assessed using the intraclass correlation coefficient (ICC). Results: oVEMP amplitudes had excellent test-retest reliability (ICC > 0.75) for all 4 stimuli; cVEMP amplitudes had excellent reliability for hammer taps and fair-to-good reliability for other stimuli. oVEMP asymmetry ratios had excellent reliability for clicks and fair-to-good reliability (ICC = 0.4-0.75) for other stimuli; cVEMP asymmetry ratios had fair-to-good reliability for clicks and hammer taps. Older subjects (>50 years old) were found to have significantly decreased cVEMP amplitudes in response to clicks, tones, and taps with a Mini-Shaker and significantly decreased oVEMP amplitudes in response to clicks, tones, and taps with a reflex hammer. No age-related changes were found for latencies or asymmetry ratios. Conclusion: Overall, oVEMP response parameters demonstrated better test-retest reliability than cVEMP response parameters, but oVEMPs and cVEMPs had similar age-related changes.

Auditory function in patients with surgically treated superior semicircular canal dehiscence.

Objective: To characterize preoperative and postoperative audiologic findings in patients with superior semicircular canal dehiscence syndrome. Study Design: Retrospective case review. Setting: Tertiary referral center. Patients: Patients with documented superior semicircular canal dehiscence syndrome (according to history, vestibular testing, and high-resolution computed tomography imaging) who underwent surgical repair of their dehiscence. Intervention: Middle fossa craniotomy for superior semicircular canal plugging and/or resurfacing. Main Outcome Measures: Audiologic testing both before and after surgery with pure-tone threshold measurements of air and bone conduction. Results: Twenty-nine subjects underwent surgical repair of superior semicircular canal dehiscence. Overall, there were no statistically significant differences by paired t test in hearing before or after surgery, in either air-conduction or bone-conduction thresholds, for 19 patients that had no previous surgical history. At least partial closure of air-bone gap was achieved in five patients. One patient with previous stapes surgery had significantly worse hearing both before and after canal repair compared with those without previous surgery. Two patients who had undergone previous middle fossa surgery with incomplete resolution of symptoms developed sensorineural hearing loss after revision surgery. Previous middle-ear exploration and tympanostomy tube placement did not seem to affect audiologic outcomes. Surgical hearing results did not differ according to method of canal repair (plugging versus resurfacing). Conclusion: Primary middle fossa repair of superior semicircular canal dehiscence is not associated with sensorineural hearing loss and, in some cases, can lead to normalization of conductive hearing loss. Revision middle fossa repair or previous stapes surgery may be associated with postoperative sensorineural hearing loss.

Semicircular canal function before and after surgery for superior canal dehiscence.

Objective: To characterize semicircular canal function before and after surgery for superior semicircular canal dehiscence (SCD) syndrome. Study Design: Prospective unblinded study of physiologic effect of intervention. Setting: Tertiary referral center. Patients: Patients with SCD syndrome documented by history, sound- or pressure-evoked eye movements, vestibular-evoked myogenic potential testing, and high-resolution multiplanar computed tomographic scans. Intervention: Nineteen subjects with SCD had quantitative measurements of their angular vestibulo-ocular reflexes (AVOR) in response to rapid rotary head thrusts measured by magnetic search coil technique before and after middle fossa approach and repair of the dehiscence. In 18 subjects, the dehiscence was plugged; and in 1, it was resurfaced. Main Outcome Measures: The AVOR gains (eye velocity/head velocity) for excitation of each of the semicircular canals. Results: Vertigo resulting from pressure or loud sounds resolved in each case. Before surgery, mean AVOR gains were normal for the ipsilateral horizontal (0.94 ± 0.07) and posterior (0.84 ± 0.09) canals. For the superior canal to be operated on, AVOR gain was 0.75 ± 0.13; but this was not significantly lower than the gain for the contralateral superior canal (0.82 ± 0.11, p = 0.08). Mean AVOR gain decreased by 44% for the operated superior canals (to 0.42 ± 0.11, p < 0.0001). There was a 13% decrease in gain for the ipsilateral posterior canal (p = 0.02), perhaps because plugging affected the common crus in some cases. There was a 10% decrease in gain for excitation of the contralateral posterior canal (p < 0.0001), which likely reflects the loss of the inhibitory contribution of the plugged superior canal during head thrusts exciting the contralateral posterior canal. Mean AVOR gain did not change for any of the other canals, but two subjects did develop hypofunction of all three ipsilateral canals postoperatively. Conclusion: Middle fossa craniotomy and repair of SCD reduce the function of the operated superior canal but typically preserve the function of the other ipsilateral semicircular canals.