Superior Canal Dehiscence Similarly Affects Cochlear Pressures in Temporal Bones and Audiograms in Patients

OBJECTIVES

The diagnosis of superior canal dehiscence (SCD) is challenging and audiograms play an important role in raising clinical suspicion of SCD. The typical audiometric finding in SCD is the combination of increased air conduction (AC) thresholds and decreased bone conduction thresholds at low frequencies. However, this pattern is not always apparent in audiograms of patients with SCD, and some have hearing thresholds that are within the normal reference range despite subjective reports of hearing impairment. In this study, we used a human temporal bone model to measure the differential pressure across the cochlear partition (PDiff) before and after introduction of an SCD. PDiff estimates the cochlear input drive and provides a mechanical audiogram of the temporal bone. We measured PDiff across a wider frequency range than in previous studies and investigated whether the changes in PDiff in the temporal bone model and changes of audiometric thresholds in patients with SCD were similar, as both are thought to reflect the same physical phenomenon.

DESIGN

We measured PDiff across the cochlear partition in fresh human cadaveric temporal bones before and after creating an SCD. Measurements were made for a wide frequency range (20 Hz to 10 kHz), which extends down to lower frequencies than in previous studies and audiograms. PDiff = PSV- PST is calculated from pressures measured simultaneously at the base of the cochlea in scala vestibuli (PSV) and scala tympani (PST) during sound stimulation. The change in PDiff after an SCD is created quantifies the effect of SCD on hearing. We further included an important experimental control-by patching the SCD, to confirm that PDiff was reversed back to the initial state. To provide a comparison of temporal bone data to clinical data, we analyzed AC audiograms (250 Hz to 8kHz) of patients with symptomatic unilateral SCD (radiographically confirmed). To achieve this, we used the unaffected ear to estimate the baseline hearing function for each patient, and determined the influence of SCD by referencing AC hearing thresholds of the SCD-affected ear with the unaffected contralateral ear.

RESULTS

PDiff measured in temporal bones (n = 6) and AC thresholds in patients (n = 53) exhibited a similar pattern of SCD-related change. With decreasing frequency, SCD caused a progressive decrease in PDiff at low frequencies for all temporal bones and a progressive increase in AC thresholds at low frequencies. SCD decreases the cochlear input drive by approximately 6 dB per octave at frequencies below ~1 kHz for both PDiff and AC thresholds. Individual data varied in frequency and magnitude of this SCD effect, where some temporal-bone ears had noticeable effects only below 250 Hz.

CONCLUSIONS

We found that with decrease in frequency the progressive decrease in low-frequency PDiff in our temporal bone experiments mirrors the progressive elevation in AC hearing thresholds observed in patients. This hypothesis remains to be tested in the clinical setting, but our findings suggest that that measuring AC thresholds at frequencies below 250 Hz would detect a larger change, thus improving audiograms as a diagnostic tool for SCD.

Spectrum of Third Window Abnormalities: Semicircular Canal Dehiscence and Beyond

Third window abnormalities are defects in the integrity of the bony structure of the inner ear, classically producing sound-/pressure-induced vertigo (Tullio and Hennebert signs) and/or a low-frequency air-bone gap by audiometry. Specific anatomic defects include semicircular canal dehiscence, perilabyrinthine fistula, enlarged vestibular aqueduct, dehiscence of the scala vestibuli side of the cochlea, X-linked stapes gusher, and bone dyscrasias. We discuss these various entities and provide key examples from our institutional teaching file with a discussion of symptomatology, temporal bone CT, audiometry, and vestibular-evoked myogenic potentials.

Using LDV and ECR Measurements in the Differential Diagnosis of Partial and Complete Ossicular Discontinuity

Objectives:

Evaluate the reability of laser doppler vibrometry (LDV) of the tympanic membrane (TM) and ear canal reflectance (ECR) measurements in the differential diagnosis of partial and complete ossicular discontinuity (OD).

Methods:

Patients, with surgically confirmed partial or complete OD and an intact TM, were recruited from the Otology clinic. Pre-operative possible diagnosis were made by otoscopic examination, audiometry, LDV and ECR. Audiometry, LDV and ECR data in each of the two OD subgroups were evaluated in order to determine their use in differential diagnosis.

Results:

44 patients with surgically confirmed OD with intact TM (27 complete, 17 partial) were included in this study. Audiometry was performed in all cases. There were statistically significant differences in air-bone gap (ABG) between the two subgroups below 1 kHz. LDV was performed in 29 (16 complete, 13 partial). An increase in LDV magnitude and a decrease in phase angle below 1 kHz were greater in the complete OD subgroup, but not significantly. ECR was performed in 11 (5 complete, 6 partial). ECR near 1 kHz was lower than the normal in both OD subgroups and the difference between the two subgroups was significant.

Conclusions:

A difference between the means of ECR measurements suggests a possible clinical utility. On the other hand, subgroup difference in LDV magnitude and phase angle were not significant. A combination of LDV, ECR and audiometry may help differentiate the two conditions. More patient data will enable better evaluation of the diagnostic significance of the observed differences.

Oral vs intratympanic corticosteroid therapy for idiopathic sudden sensorineural hearing loss: a randomized trial

CONTEXT

Idiopathic sudden sensorineural hearing loss has been treated with oral corticosteroids for more than 30 years. Recently, many patients' symptoms have been managed with intratympanic steroid therapy. No satisfactory comparative effectiveness study to support this practice exists.

OBJECTIVE

To compare the effectiveness of oral vs intratympanic steroid to treat sudden sensorineural hearing loss.

DESIGN, SETTING, AND PATIENTS

Prospective, randomized, noninferiority trial involving 250 patients with unilateral sensorineural hearing loss presenting within 14 days of onset of 50 dB or higher of pure tone average (PTA) hearing threshold. The study was conducted from December 2004 through October 2009 at 16 academic community-based otology practices. Participants were followed up for 6 months.

INTERVENTION

One hundred twenty-one patients received either 60 mg/d of oral prednisone for 14 days with a 5-day taper and 129 patients received 4 doses over 14 days of 40 mg/mL of methylprednisolone injected into the middle ear.

MAIN OUTCOME MEASURES

Primary end point was change in hearing at 2 months after treatment. Noninferiority was defined as less than a 10-dB difference in hearing outcome between treatments.

RESULTS

In the oral prednisone group, PTA improved by 30.7 dB compared with a 28.7-dB improvement in the intratympanic treatment group. Mean pure tone average at 2 months was 56.0 for the oral steroid treatment group and 57.6 dB for the intratympanic treatment group. Recovery of hearing on oral treatment at 2 months by intention-to-treat analysis was 2.0 dB greater than intratympanic treatment (95.21% upper confidence interval, 6.6 dB). Per-protocol analysis confirmed the intention-to-treat result. Thus, the hypothesis of inferiority of intratympanic methylprednisolone to oral prednisone for primary treatment of sudden sensorineural hearing loss was rejected.

CONCLUSION

Among patients with idiopathic sudden sensorineural hearing loss, hearing level 2 months after treatment showed that intratympanic treatment was not inferior to oral prednisone treatment.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00097448.

Tinnitus, diminished sound-level tolerance, and elevated auditory activity in humans with clinically normal hearing sensitivity

Phantom sensations and sensory hypersensitivity are disordered perceptions that characterize a variety of intractable conditions involving the somatosensory, visual, and auditory modalities. We report physiological correlates of two perceptual abnormalities in the auditory domain: tinnitus, the phantom perception of sound, and hyperacusis, a decreased tolerance of sound based on loudness. Here, subjects with and without tinnitus, all with clinically normal hearing thresholds, underwent 1) behavioral testing to assess sound-level tolerance and 2) functional MRI to measure sound-evoked activation of central auditory centers. Despite receiving identical sound stimulation levels, subjects with diminished sound-level tolerance (i.e., hyperacusis) showed elevated activation in the auditory midbrain, thalamus, and primary auditory cortex compared with subjects with normal tolerance. Primary auditory cortex, but not subcortical centers, showed elevated activation specifically related to tinnitus. The results directly link hyperacusis and tinnitus to hyperactivity within the central auditory system. We hypothesize that the tinnitus-related elevations in cortical activation may reflect undue attention drawn to the auditory domain, an interpretation consistent with the lack of tinnitus-related effects subcortically where activation is less potently modulated by attentional state. The data strengthen, at a mechanistic level, analogies drawn previously between tinnitus/hyperacusis and other, nonauditory disordered perceptions thought to arise from neural hyperactivity such as chronic neuropathic pain and photophobia.

Medical record documentation of patients' hearing loss by physicians

BACKGROUND

Anecdotal evidence suggests that hearing loss, even when sufficient to prevent full access to spoken communication, often is underreported by patients and not documented by physicians. No published studies have investigated this issue quantitatively.

OBJECTIVE

To assess the documentation of hearing loss in comprehensive physician notes in cases where the patients are known to have substantial binaural loss.

DESIGN

Electronic medical record (EMR) notes for 100 consecutive patients with substantial binaural hearing loss were reviewed retrospectively at a large academic medical center. All records reviewed were created within 2 years before the patient's audiometry. Comprehensive physician notes containing the headings "History" and "Physical Exam" were examined for documentation of hearing loss and scored as: no mention of loss; finding of loss; or hearing reported as normal.

PARTICIPANTS

Consecutive adult patients with substantial binaural hearing loss by audiometry who also had a comprehensive medical assessment in their electronic medical record created within 2 years before audiometry.

RESULTS

Thirty-six percent of EMRs had no mention of hearing loss, 28% reported some loss, and 36% percent indicated that hearing was normal.

CONCLUSIONS

Substantial hearing loss, sufficient to prevent effective communication in the medical setting, often is underdocumented in medical records.

Evaluation of a behavioral audiometry simulator for teaching visual reinforcement audiometry

Eight audiology students with little or no visual reinforcement audiometry (VRA) experience each performed a VRA test on an infant. Four of the students received approximately 5 hours of behavioral audiometry simulator (BAS) training, and 1 week later, after the first VRA test, all eight students tested a second infant. Student performance was rated by three audiologists who were experienced in performing VRA with infants. The performance of the group that received BAS training improved significantly while the performance of the control group did not. Among the students who received BAS training, those who improved the most during stimulated testing also showed the greatest improvement in VRA with real infants.

Infant auditory temporal acuity: gap detection

The development of auditory temporal acuity during infancy was examined in 3-, 6-, and 12-month-old infants and in adults using the gap detection paradigm. Listeners detected a series of gaps, or silent intervals, or variable duration in a broadband noise. In order to vary the acoustic frequencies available to the listener, a high-pass noise was used to mask frequencies above specified cutoffs. High-pass maskers with cutoffs of 500, 2,000, and 8,000 Hz were used. The minimum detectable gap was determined using the Observer-based Psychoacoustic Procedure. The thresholds of 3- and 6-month-olds were considerably poorer than those of the adults, although the effect of masker condition was about the same for these 3 groups. The thresholds of 12-month-olds were significantly worse than the adults when the stimulus was unmasked or when the masker cutoff frequency was 2,000 or 8,000 Hz. When the masker cutoff frequency was 500 Hz, 12-month-olds fell into 2 groups: some had gap thresholds that were about the same as 3- and 6-month-olds, while some had gap thresholds that approached those of adults. In a second experiment, a larger group of 12-month-olds were tested with a 500-Hz masker cutoff. Average performance of 12-month-olds was about the same as that of 3- and 6-month-olds in Experiment 1. Some infants attained thresholds close to those of adults. Thus, gap detection thresholds are quite poor in infants, although the similarity of the effect of frequency on performance in infants and adults suggests that the mechanisms governing temporal resolution in infants operate qualitatively like those in adults.

Promontory electrical stimulation in labyrinthectomized ears

Bilateral deafness can occur in patients with Menière's disease who have undergone a labyrinthectomy in one ear. To investigate the feasibility of a cochlear implant in the labyrinthectomized ear, promontory electrical testing by transtympanic needle was performed in six patients who had undergone a unilateral transmastoid labyrinthectomy 6 weeks to 5 years previously. All patients had a behavioral response to the stimulus, and each described a different pitch percept with the four frequencies used. Five of the patients demonstrated an electrically evoked middle latency response. These data are comparable with behavioral and electrophysiologic responses from ears deafened by other causes and now successfully implanted. The results suggest that peripheral neural elements and central auditory pathways remain at least partially functional many years after a labyrinthectomy. Thus, a labyrinthectomy should not be withheld as a surgical option if otherwise indicated.