Long-term efficacy of triple semicircular canal plugging in the treatment of patients with ipsilateral delayed endolymphatic hydrops.

This study aims to explore the long-term efficacy of triple semicircular canal plugging (TSCP) in the treatment of intractable ipsilateral delayed endolymphatic hydrops (DEH), so as to provide an alternative therapy for this disease. Forty-eight patients diagnosed with ipsilateral DEH referred to vertigo clinic of our hospital between Dec. 2010 and Dec. 2017, were included in this study for retrospective analysis. All patients were followed up for 2 years. Vertigo control and auditory functions were measured and analyzed. Pure tone audiometry, caloric test, and vestibular evoked myogenic potential (VEMP) were performed in two-year follow-up. Forty-five patients who accepted intratympanic gentamicin (26.7 mg/mL) twice given one week apart were selected as a control group. The total control rate of vertigo in TSCP group was 97.9% (47/48) in the two-year follow-up, with complete control rate of 83.3% (40/48) and substantial control rate of 14.6% (7/48). The rate of hearing loss was 22.9% (11/48). The total control rate of vertigo in intratympanic gentamicin group was 80.0% (36/45), with complete control rate of 57.8% (26/45) and substantial control rate of 22.2% (10/45), and the rate of hearing loss was 20.0% (9/45). The vertigo control rate of TSCP was significantly higher than that of intratympanic gentamicin (χ2 = 6.01, p < 0.05). There was no significant difference of hearing loss rate between two groups. (χ2 = 0.12, p > 0.05). TSCP, which can reduce vertiginous symptoms in patients with intractable ipsilateral DEH, represents an effective therapy for this disorder.

Gene therapy via canalostomy approach preserves auditory and vestibular functions in a mouse model of Jervell and Lange-Nielsen syndrome type 2.

Mutations in voltage-gated potassium channel KCNE1 cause Jervell and Lange-Nielsen syndrome type 2 (JLNS2), resulting in congenital deafness and vestibular dysfunction. We conducted gene therapy by injecting viral vectors using the canalostomy approach in Kcne1-/- mice to treat both the hearing and vestibular symptoms. Results showed early treatment prevented collapse of the Reissner's membrane and vestibular wall, retained the normal size of the semicircular canals, and prevented the degeneration of inner ear cells. In a dose-dependent manner, the treatment preserved auditory (16 out of 20 mice) and vestibular (20/20) functions in mice treated with the high-dosage for at least five months. In the low-dosage group, a subgroup of mice (13/20) showed improvements only in the vestibular functions. Results supported that highly efficient transduction is one of the key factors for achieving the efficacy and maintaining the long-term therapeutic effect. Secondary outcomes of treatment included improved birth and litter survival rates. Our results demonstrated that gene therapy via the canalostomy approach, which has been considered to be one of the more feasible delivery methods for human inner ear gene therapy, preserved auditory and vestibular functions in a dose-dependent manner in a mouse model of JLNS2.

The Predictability Precision of Superior Semicircular Canal Through Radiological Assessment and Microanatomical Dissection.

OBJECTIVE: There is still ongoing research on the relationship of arcuate eminence (AE) and superior semicircular canal (SSC). We aimed to evaluate the precision of predictability of SSC through the morphology of AE via radiological means. MATERIALS AND METHODS: This investigation is performed on 12 dry skulls belonging to Mersin University Medical Faculty department of anatomy. Computed tomography (CT) assessment is performed with 0.5-mm-thin sections temporal bone algorithm on dry skulls which were marked with fixated copper wire by scotch tapes on the most prominent part of the middle fossa floor assuming the location of AE. The data are reformatted on the workstation with vitrea 2.0. The distances of the determined three points including lateral (A), apical (B), and medial (C) of the SSC and the copper wire are measured radiologically. Also, the height between the most apical part of the SSC to the floor of the skullbase (H) is measured. The angles between the placed copper wires and the SSC (E) are calculated. The angle between SSC and the midpoint of the IAC (F) and SSC to the sulcus of the greater GSPN (G) were measured. The nearest distance was measured between the most posterior part of the SSC and the point marked by the perpendicular line drawn from the medial border of the petrous bone to the most posterior part of the internal auditory canal (IAC) (D). RESULTS: The right and left A, B, and C distances are 2.54+/- 2.75, 3.67+/-3.16, 5.85+/-3.77; 2.92+/-2.24, 3.68+/-2.93, 6.09+/-3.40, respectively. We could not find any statistical significance when the right A, B, and C distances were compared with the left values. Examination of the values revealed that C distance is greater than the A distance of the same side both for right (p=0.040) and left (p=0.022) measurements. The calculated left and right E angles are 30.313+/-12.838, and 35.558+/-18.437 degrees, respectively. Statistical significance was not found between the right and left angles. The right and left F, G angles were 53.17, 47.25; 93.58, 100.92 degrees; and D distances are 8.01, 8.13 millimeters, respectively. Statistical significance was not found when right and left E, F, G angles and D distances were compared. Among 12 left and 12 right sides, the copper wire was found to be nearly overlapping to SSC in two in the right and only one in the left. CONCLUSION: This study reveals that there is a great variability predicting the exact location of SSC through the prominence of AE. Complementary studies are needed with greater number of dry skulls and cadavers. Comparison of different hypothesis including the effect of temporal lobe sulcus is to be discussed to better enlighten the exact relationship of the aforementioned anatomical structures.

The Gopen-Yang Superior Semicircular Canal Dehiscence Questionnaire: development and validation of a clinical questionnaire to assess subjective symptoms in patients undergoing surgical repair of superior semicircular canal dehiscence.

OBJECTIVE: To characterise subjective symptoms in patients undergoing surgical repair of superior semicircular canal dehiscence. METHODS: Questionnaires assessing symptom severity and impact on function and quality of life were administered to patients before superior semicircular canal dehiscence surgery, between June 2011 and March 2016. Questionnaire sections included general quality of life, internal amplified sounds, dizziness and tinnitus, with scores of 0-100 points. RESULTS: Twenty-three patients completed the questionnaire before surgery. Section scores (mean±standard deviation) were: 38.2 ± 25.2 for general quality of life, 52.5 ± 23.9 for internal amplified sounds, 35.1 ± 28.8 for dizziness, 33.3 ± 30.7 for tinnitus, and 39.8 ± 22.2 for the composite score. Cronbach's α statistic averaged 0.93 (range, 0.84-0.97) across section scores, and 0.83 for the composite score. CONCLUSION: The Gopen-Yang Superior Semicircular Canal Dehiscence Questionnaire provides a holistic, patient-centred characterisation of superior semicircular canal dehiscence symptoms. Internal consistency analysis validated the questionnaire and provided a quantitative framework for further optimisation in the clinical setting.

Revisión sobre los conocimientos actuales de dehiscencia del canal semicircular posterior / Review of current knowledge of the dehiscence in the semicircular posterior canal

La dehiscencia del canal semicircular posterior es una patología rara y con baja incidencia, por ello hemos realizado una revisión de los conocimientos actuales de esta entidad. Se ha realizado una búsqueda bibliográfica desde 1998 hasta diciembre de 2016 de toda la literatura publicada sobre la misma en las bases de datos Allied and Complementary Medicine Database and the Embase, Health Management Information Consortium, Scopus, Consortium, Medline, PsycINFO y Scielo. Se han encontrado y revisado 53 trabajos relacionados con el tema. La dehiscencia del canal semicircular posterior presenta una prevalencia variable; 0,3%-4,5% en adultos y 1,2%-20% en niños. Su localización puede ser hacia el golfo de la yugular o fosa cerebral posterior. Los pacientes pueden ser asintomáticos o presentar clínica auditiva y/o vestibular. La tomografía computarizada y la prueba de potenciales vestibulares miogénicos evocados permiten establecer el diagnóstico de certeza. En el tratamiento quirúrgico la vía de abordaje de elección es la transmastoidea y las técnicas del cierre del canal son el "plugging" y el "resurfacing".

The posterior semicircular canal dehiscence is a rare pathology and it has a low incidence. We have realized a review about the current knowledge of this entity. We have performed a bibliographic research from 1998 to 2016 December about the literature published in this subject, in the data basis Allied and Complementary Medicine Database and the Embase, Health Management Information Consortium, Scopus, Consortium, Medline, PsycINFO y Scielo. I thas been found and reviewed 53 papers about the topic. The posterior semicircular canal dehiscence has a variable prevalence: 0,3%-4-5% in adults and 1,2%-20% in children. The location can be in the jugular bulb or in the posterior brain fossa. Some patients can be asymptomatic, whereas others can have auditory and/or vestibular signs and symptoms. Computed tomography and test of vestibular evoked myogenic potentials allow the diagnosis of certainty. In the surgical treatment the approach of choice is transmastoid and techniques to close the canal are plugging and resurfacing.

Upbeat nystagmus after bilateral superior canal plugging: A peripheral cause of vertical nystagmus.

Vertical nystagmus without a torsional component is generally considered a finding indicative of central nervous system pathology. We report two cases of purely upbeat nystagmus elicited with mastoid vibration after bilateral superior canal plugging, to highlight the vestibular pathophysiology involved in this unusual peripheral cause for upbeat nystagmus. Laryngoscope, 127:1698-1700, 2017.

Recent advances in superior semicircular canal dehiscence syndrome.

OBJECTIVE: This study aimed to review the current advances in superior semicircular canal dehiscence syndrome and to ascertain its aetiology, whether dehiscence size correlates with symptoms, signs and investigation results, the best investigations, and its surgical management. METHODS: A literature search using the key words 'superior semicircular canal dehiscence' was performed using the Allied and Complementary Medicine Database and the Embase, Health Management Information Consortium, Medline, PsycINFO, British Nursing Index, Cinahl and Health Business Elite databases for the period January 2009 to May 2014. Systematic reviews, meta-analyses, randomised controlled trials, prospective and retrospective case series, case reports, and observational studies were included. RESULTS: Of the 205 papers identified, 35 were considered relevant. CONCLUSION: The aetiology of superior semicircular canal dehiscence syndrome is unclear. Dehiscence size significantly affects the air-bone gap and ocular vestibular evoked myogenic potential thresholds. Computed tomography evaluation has a high false positive rate. The middle cranial fossa approach is the surgical standard for treating this syndrome; however, the transmastoid approach is gaining popularity.

A superior semicircular canal dehiscence-induced air-bone gap in chinchilla.

An SCD is a pathologic hole (or dehiscence) in the bone separating the superior semicircular canal from the cranial cavity that has been associated with a conductive hearing loss in patients with SCD syndrome. The conductive loss is defined by an audiometrically determined air-bone gap that results from the combination of a decrease in sensitivity to air-conducted sound and an increase in sensitivity to bone-conducted sound. Our goal is to demonstrate, through physiological measurements in an animal model, that mechanically altering the superior semicircular canal (SC) by introducing a hole (dehiscence) is sufficient to cause such an air-bone gap. We surgically introduced holes into the SC of chinchilla ears and evaluated auditory sensitivity (cochlear potential) in response to both air- and bone-conducted stimuli. The introduction of the SC hole led to a low-frequency (<2000 Hz) decrease in sensitivity to air-conducted stimuli and a low-frequency (<1000 Hz) increase in sensitivity to bone-conducted stimuli resulting in an air-bone gap. This result was consistent and reversible. The air-bone gaps in the animal results are qualitatively consistent with findings in patients with SCD syndrome.

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.

Mitigation of hearing loss from semi-circular canal transection in pseudomonas otitis media with ciprofloxacin-dexamethasone irrigation.

HYPOTHESIS: Irrigation of the mastoid with a quinolone antibiotic-steroid solution may mitigate hearing loss caused by iatrogenic semicircular canal injury in the presence of Pseudomonas aeruginosa (PA) otitis media (OM). BACKGROUND: Studies have shown the cochlea to be more vulnerable to semicircular canal transection (SCT)-related hearing loss in the presence of PA OM. Prophylactic systemic antibiotics and steroids may decrease this hearing loss, but SCT is usually not planned. The aim of this study was to determine if irrigation with ciprofloxacin-dexamethasone (cipro-dex) could improve hearing outcomes following SCT in PA OM. METHODS: PA OM was induced in 28 animals. After three to five days, unilateral SCT was performed in each animal, with sham SCT on the contralateral ear. At surgery, half of the animals (n = 14) underwent irrigation of the both mastoid bullae with cipro-dex; the second group of animals (n = 14) underwent irrigation of the bullae with sterile saline. Auditory thresholds were obtained immediately prior to SCT and 7-10 days after SCT. RESULTS: SCT ears treated with cipro-dex showed a mean click threshold improvement of 4.6 dB from pre-transection to 7-10 days post-transection, whereas thresholds in the SCT ears treated with saline worsened by 7.5 dB (p = 0.15). CONCLUSION: Irrigation of the guinea pig bulla with cipro-dex following SCT in the setting of PA OM appears safe and may yield beneficial effects on hearing.

Cochlear activation at low sound intensities by a fluid pathway.

In order to assess the mechanisms responsible for cochlear activation at low sound intensities, a semi-circular canal was fenestrated in fat sand rats, and in other experiments a hole was made in the bone over the scala vestibuli of the first turn of the guinea-pig cochlea. Such holes, which expose the cochlear fluids to air, provide a sound pathway out of the cochlea which is of lower impedance than that through the round window. This should attenuate the pressure difference across the cochlear partition and thereby reduce the driving force for the base-to-apex traveling wave along the basilar membrane. The thresholds of the auditory nerve brainstem evoked responses (ABR) and of the cochlear microphonic potentials were not affected in the fenestration experiments. In addition, holes in the scala vestibuli of the first turn did not cause ABR threshold elevations. These results contribute further evidence that at low sound intensities the outer hair cells are probably not activated by a base-to-apex traveling wave along the basilar membrane. Instead it is possible that they are excited directly by the alternating condensation/rarefaction fluid pressures induced by the vibrations of the stapes footplate. The activated outer hair cells would then cause the localized basilar membrane movement.

Superior canal dehiscence syndrome.

OBJECTIVE: To present the symptoms, signs, and findings on diagnostic tests of patients with the superior canal dehiscence syndrome and to describe the surgical procedures used to treat the dehiscence in five patients. DESIGN AND SETTING: Prospective study of a series of patients identified as having this syndrome at a tertiary care referral center. PATIENTS AND RESULTS: Seventeen patients with vertigo, oscillopsia, or both evoked by intense sounds or stimuli that caused changes in middle ear and/or intracranial pressure were identified over a 4-year period. The evoked eye movements had vertical and torsional components, with the direction corresponding to the effect of the stimuli in causing excitation (Valsalva against pinched nostrils, tragal compression, sounds) or inhibition (Valsalva against a closed glottis or jugular venous compression) of the affected superior semicircular canal. Thirteen (76%) of these patients also experienced chronic dysequilibrium that was often the most debilitating symptom. Dehiscence of bone overlying the superior semicircular canal on the affected side was confirmed with computed tomographic scans in each case. Surgical procedures through the middle fossa approach to plug or resurface the superior canal were performed in five patients (canal plugging in three cases and resurfacing of the dehiscence without plugging in two). The debilitating symptoms resolved or improved after the procedures. Signs of vestibular hypofunction, without loss of hearing, were noted in one patient after plugging of the superior canal and in one other patient after resurfacing of the canal. CONCLUSIONS: The superior canal dehiscence syndrome is identified based on characteristic symptoms, signs, and computed tomographic findings. The clinical presentation and findings can be understood in terms of the effect of the dehiscence on the physiology of the labyrinth. The syndrome is a treatable cause of vestibular disturbance.

Carbon dioxide laser occlusion of the guinea pig posterior semicircular canal.

Preservation of hearing is possible with selective ablation of the vestibular system and mechanical occlusion of the semicircular canals. Complete ablation of all three canals would improve exposure of the internal auditory canal fundus (e.g., for acoustic tumor exposure), but mechanical packing of the vestibule would disrupt normal sound transduction. This study was designed to assess the feasibility of preserving hearing with CO2 laser occlusion, without mechanical packing of the posterior semicircular canal membranous labyrinth. Twenty adult Hartley guinea pigs underwent occlusion of the right posterior semicircular canal with one of three techniques: mechanical packing, laser coagulation, or laser coagulation with mechanical packing. Electrocochleographic thresholds to clicks and 1-kHz and 8-kHz tone bursts did not change significantly 6 weeks after posterior semicircular canal occlusion with any of these techniques. Histopathologic examination revealed complete canal occlusion with all methods. These findings suggest that mechanical occlusion and CO2 laser occlusion of the posterior semicircular canal do not significantly affect cochlear function in the guinea pig. CO2 laser occlusion of the membranous labyrinth may prove useful for more extensive selective vestibular ablation by obviating the need for mechanical packing of the labyrinth.

Effect on cochlear potentials of lateral semicircular canal destruction.

Recording of the cochlear potentials was successfully performed during experimental labyrinthectomy in the guinea pig and in three patients with acoustic neuromas during translabyrinthine removal of the tumors. In the guinea pig, complete interruption of the duct of the lateral semicircular canal including the endolymphatic canal caused little change in the endocochlear DC potential of the first cochlear turn and input-output function curve of the N1 component of the compound action potential elicited by 8-kHz tone bursts. Further drilling of the vestibular labyrinth in the guinea pig caused decline of these potentials when the vestibular was opened. In patients with acoustic neuromas, the interruption of the duct of the lateral semicircular canal hardly altered the N1 input-output function curve and N1 input-latency function curve during the 1-hour observation period. Consistent preservation of cochlear function even after interruption of lateral semicircular canals suggests the possibility of partial surgical labryrinthectomy with preservation of hearing for lesions involving semicircular canals.

Fenestration of the horizontal semicircular canal in congenital conductive deafness.

Fenestration of the horizontal semicircular canal enables the otologic surgeon to restore hearing in those patients with congenital conductive deafness who are not candidates for stapedectomy, ossicular reconstruction, or tympanoplasty. Since the development of stapedectomy, much of the finesse technique of fenestration surgery has been lost, and many otologic surgeons today are unfamiliar with the fenestration operation. The surgical technique for creating a permanently patent fenestra in the horizontal semicircular canal is described. The causes of failure in fenestration surgery are reviewed. Thirty-three patients who have undergone fenestration for congenital conductive deafness over a 30-year period, and 100 patients who underwent fenestration for otosclerosis in 1950, are reviewed to demonstrate patient selection and the efficacy of this operation in establishing long-term hearing improvement.