Kenneth H. Brookler

Surface Tension Lowering Substance of the Canine Eustachian Tube

The presence of a surface tension lowering substance (surfactant) in the surface lining of lung alveoli has become an established fact.2 This has led some to suggest that the same substance might exist in the auditory tube mucosa to facilitate in opening the auditory tube3 Brookler suggested that blocked tuba1 lymphatics may cause lymphangiectasis with resultant serous otitis4 This lymphangiectasis may result in a decrease in surface tension lowering substance of the auditory tube, thus requiring a greater force to open it.

Sensorineural hearing loss associated with takayasu's disease†‡

This is a case report of sensorineural hearing loss associated with Takayasus disease. Also known as ‘pulseless disease’ and ‘aortic arch syndrome,’ Takayasus disease involves narrowing of the aortic arch and its branches. Although the etiology is unknown, it is suspected to be an autoimmune disorder. In the case presented, steroid therapy resulted in an improvement of hearing. On one relapse the hearing loss worsened before the sedimentation rate increased. We speculate that the hearing loss is due to an autoimmune process or an ischemia involving the inner ear. We further speculate that hearing loss may indicate subsequent worsening of the disease.

Underrated neurotologic symptoms.

Patients present themselves with neurotologic symptoms which may be early and subtle indicators of active vestibular pathology. The frequently slighted complaints of light‐headedness, imbalance and a floating sensation are as important as “true rotatory vertigo.” Ear fullness, the most underinvestigated of neurotologic complaints may be a cardinal symptom. Occipital headaches are a frequent complaint of the dizzy patient. Blurred vision, and, in some severe peripheral disorders, diplopia are symptoms referrable to oculovestibular interaction. Visual stimulation intensifies vestibular symptoms. Stress may precipitate or increase dizziness in patients who have partially compensated for a vestibular deficit. Anxiety, fatigue and systemic illness are exemplary. Patient histories are presented to emphasize clinical relevance and therapeutic modalities.

Oculo-vestibular recoupling using galvanic vestibular stimulation to mitigate simulator sickness.

INTRODUCTION Despite improvement in the computational capabilities of visual displays in flight simulators, intersensory visual-vestibular conflict remains the leading cause of simulator sickness (SS). By using galvanic vestibular stimulation (GVS), the vestibular system can be synchronized with a moving visual field in order to lessen the mismatch of sensory inputs thought to result in SS. METHODS A multisite electrode array was used to deliver combinations of GVS in 21 normal subjects. Optimal electrode combinations were identified and used to establish GVS dose-response predictions for the perception of roll, pitch, and yaw. Based on these data, an algorithm was then implemented in flight simulator hardware in order to synchronize visual and GVS-induced vestibular sensations (oculo-vestibular-recoupled or OVR simulation). Subjects were then randomly exposed to flight simulation either with or without OVR simulation. A self-report SS checklist was administered to all subjects after each session. An overall SS score was calculated for each category of symptoms for both groups. RESULTS The analysis of GVS stimulation data yielded six unique combinations of electrode positions inducing motion perceptions in the three rotational axes. This provided the algorithm used for OVR simulation. The overall SS scores for gastrointestinal, central, and peripheral categories were 17%, 22.4%, and 20% for the Control group and 6.3%, 20%, and 8% for the OVR group, respectively. CONCLUSIONS When virtual head signals produced by GVS are synchronized to the speed and direction of a moving visual field, manifestations of induced SS in a cockpit flight simulator are significantly reduced.

Radiologic Diagnosis of Labyrinthitis Ossificans

Labyrinthitis ossificans is the pathological ossification of the membranous labyrinthine spaces in response to processes which are destructive of the membranous labyrinth or the endosteum of the otic capsule. It has been primarily a histopathologic diagnosis. Complex motion tomography however, allows a detailed view of the osseous labyrinth and permits the diagnosis in the living state. Radiologic documentation of labyrinthitis ossificans is objective evidence of a process destructive of the membranous labyrinth. It supports the likelihood of an absence of cochlear and vestibular function. It alerts the surgeon to the possible obliteration of key inner ear anatomical landmarks.

The accuracy of the simultaneous binaural bithermal test in the diagnosis of acoustic neuroma.

Forty-three patients with a surgically confirmed unilateral acoustic neuroma were studied preoperatively with both alternate and simultaneous binaural bithermal caloric tests using horizontal lead electronystagmography. Twenty-four patients had a significant reduced vestibular response on the side of the tumor utilizing the alternate binaural bithermal calorization of Fitzgerald-Hallpike. The addition of the simultaneous binaural bithermal stimulus improved the diagnostic accuracy of caloric testing from 56% to 86%. The simultaneous test was of particular accuracy in diagnosing the inferior vestibular nerve neuroma. The simultaneous stimulus, which adds only six and one-half minutes to overall testing time, is felt to be a valuable adjunct to the alternate test of Fitzgerald-Hallpike.

SYMPOSIUM: OTOLOGIC SURGERY REASSESSMENT AFTER 25 YEARS. OTOSCLEROSIS SURGERY

Today, surgical correction is the treatment of choice for the hearing loss associated with footplate otosclerosis. Experience with stapes surgery reveals this to be functionally and economically superior to the long‐term use of hearing aids. There is, however, a predictable rate of surgical complications. Sensorineural hearing loss, dizziness and/or facial nerve palsy have an immense social and economic impact upon the patient, the family and the surgeon.

The effect of galvanic vestibular stimulation on distortion product otoacoustic emissions

Galvanic stimulation has long been used as a nonmechanical means of activating the vestibular apparatus through direct action on the vestibular nerve endings. This stimulation has been reported to be safe, but no studies have examined the potential changes in the corresponding cochlear receptors. The aim of the present study was to evaluate the effect of galvanic vestibular stimulation (GVS) on distortion product otoacoustic emissions (DPOAEs). Fourteen subjects underwent DPOAEs during several conditions of GVS. The DPOAEs ranged from ∼ 1 kHz to ∼ 8 kHz at 65/55 dB for f1/f2 and with an f2/f1 ratio of 1.2. The subjects were evaluated at 10 stimulation conditions that ranged from -2.0 mA to +2.0 mA for each frequency. Statistical analysis showed no significant differences in DPOAE amplitudes for all conditions with and without GVS. Results also showed no significant differences between DPOAE amplitudes before and after GVS. Multivariate analysis found subject variability in DPOAE amplitude, which was not thought to be GVS related. Results indicated that GVS produced neither temporary nor permanent changes in DPOAEs.

Can insulin response patterns predict metabolic disease risk in individuals with normal glucose tolerance

To the Editor: We commend the authors of the recent publication in Diabetologia entitled ‘Glucose patterns during an oral glucose tolerance test and associations with future diabetes, cardiovascular disease and all-cause mortality rate’ [1] and would encourage them to repeat their investigation using insulin response patterns in people with normal glucose tolerance. Hyperinsulinaemia is becoming well-established in the aetiology of many metabolic diseases [2], yet many people will be unaware that they are at risk. Insulin levels are posited to be elevated for many years, possibly even decades, before changes in blood glucose are noted [3, 4]. Although fasting insulin is used inmany studies as a disease riskmarker, it has a high coefficient of variation leading to concerns about repeatability [5]. There has been little emphasis on the use of insulin response patterns to assess the risk of metabolic disease, yet the patterns observed when tracking blood insulin levels following an OGTT may provide an earlier opportunity to assess disease risk compared with changes in blood glucose levels. Hayashi and colleagues noted that cumulative incidence of type 2 diabetes in Japanese-American men over 10 years of follow-up was between 38% and 48% in those who reached a peak insulin level at 120 min following a 75 g OGTT, which was higher than those whose insulin levels peaked at 30 or 60 min (cumulative incidence, <16%) [6]. However, these response patterns were based on relative insulin serum levels in a cohort that included a high proportion of participants with pre-existing impaired fasting glucose and/or impaired glucose tolerance [5]. Between 1970 and 1990, Dr J. R. Kraft collated a large database holding data from multiple-sampled OGTTs with insulin assays. Further analysis of this database suggests that up to 75% of people with normal glucose tolerance may have hyperinsulinaemia [7], but there are no longitudinal outcomes to support risk calculations. There is a distinct paucity of data on insulin response patterns and subsequent risk of cardiovascular disease and we believe the authors would advance the field with further data analysis.

Basis for Understanding Otic Capsule Bony Dyscrasias

To the editor: In the past several months, three seminal papers have been published relating to the capsule of the bone surrounding the inner ear and the potential effect of bony dyscrasias on the hair cells enclosed. Although these papers may appear to be disparate, they are strongly linked. It is to their substance and relationship I would like to comment. Two of these papers appeared in Laryngoscope in the past 6 months1,2: Zehnder AF, Kristiansen AG, Adams JC, et al. Osteoprotegerin in the inner ear may inhibit bone remodeling in the otic capsule. Laryngoscope 2005;115: 172–177. Karosi T, Konya J, Szabo LZ, et al. Codetection of measles virus and tumor necrosis factor-alpha mRNA in otosclerotic stapes footplates. Laryngoscope 2005;115: 1291–1297. These two papers contain new information about the regulation of otic capsule bone. These basic science papers may explain the clinical findings seen with bony dyscrasias of the otic capsule such as otosclerosis, Paget’s disease, and osteopetrosis affecting the temporal bone. The first paper entitled “Osteoprotegerin in the Inner Ear may Inhibit Bone Remodeling in the Otic Capsule”1 is a highly original, potentially influential paper in the understanding of the otic capsule bone in normal individuals. It reveals that in addition to acting as a sensor for auditory and vestibular stimuli, the inner ear produces its own osteoprotegerin (OPG)! Although it is produced in a number of other organs in the body, the inner ear is the only organ totally surrounded by bone. As the authors indicate, this finding accounts for the slow turnover of otic capsule bone and for maintenance of one of the most dense bones in the body. This finding also accounts for nonhealing of fractures of the otic capsule. Osteoclastogenesis is the science that explains the maintenance of bone including the role of OPG in normal and pathologic conditions of bone such as osteoporosis,3 Paget’s disease,4 otosclerosis,5 fibrous dysplasia,6,7 osteopetrosis,7 labyrinthitis ossificans, and the erosion of temporal bone in association with cholesteatoma.8 Although not a criticism, the process whereby osteoclasts are formed was not clearly emphasized. The osteoclasts come from the macrophage line and are transformed into osteoclasts by a combination of macrophage colony stimulating factor and the effect of receptor activator of nuclear factor kappa b ligand (RANKL) on the RANK receptor on the macrophage. OPG is a “decoy” of the same receptor structure as RANK and competes for RANKL, thus preventing activation of the macrophage to an active osteoclast.9 The second and very important finding of this paper confirms the previous investigations and the clinical finding of “bony canaliculi were spreading out into the otic capsule from the spiral ligament” without an apparent membrane separating them. This accounts for the OPG in perilymph diffusing out into the otic capsule. Thus, OPG produced by the inner ear in the normal otic capsule results in the low turnover of otic capsule bone. Factors that affect the balance of OPG and RANKL may explain the scientific basis of the pathologic otic capsule bone disorders that affect inner ear function. These findings also explain why in temporal bones with otosclerosis, the osteoclasts are found in the otic capsule bone far removed from the membranous labyrinth (Linthicum F, House Ear Institute, Los Angeles, CA, personal communication, 2004). These canaliculi may also explain how lesions in the otic capsule may affect the function of the inner ear, as observed in the past.10 This finding also clarifies the debate of years past in regard to the presence of inner ear disorders without close proximity to the endosteal membrane.11 The second paper “Codetection of Measles Virus and Tumor Necrosis Factor-alpha m-RNA in Otosclerotic Stapes Footplates” confirms the suspicion that measles virus may be one of the factors playing a role in the activation of an otosclerotic process. More importantly, the presence of the cytokine tumor necrosis factor (TNF)-alpha also identified lends credence to the possibility that other inflammatory conditions entering the inner ear could release cytokines and activate a similar process to that seen clinically with some evidence of measles infection. The authors may be incorrect in identifying osteocytes as the precursor for the osteoclasts because the osteoclasts emerge from the bone marrow precursors. The authors suggest that a secondary autoimmune reaction could occur as a result of this process. Another avenue for the clinical findings may be related to the science of “osteoclastogenesis.” This process of osteoclastogenesis, although activated by cytokines, also produces cytokines as a byproduct of the activity of the osteoclasts.12 These cytokines may diffuse into the perilymph by the bony canaliculi and could be toxic to the hair cells, and thus producing the clinical findings seen in these patients. From this combination of findings, comes a clinical question regarding the use of the glucocorticoid corticosteroids. The glucocorticoid corticosteroids have an effect of reducing OPG.13-15 If a hearing loss (HL) or ves-