Clinical Manifestations of Superior Semicircular Canal Dehiscence

Infrasound transmission in the human ear: Implications for acoustic and vestibular responses of the normal and dehiscent inner ear

The transmission of infrasound within the human ear is not well understood. To investigate infrasound propagation through the middle and inner ear, velocities of the stapes and round window membrane were measured to very low frequencies (down to 0.9 Hz from 2000 Hz) in fresh cadaveric human specimens. Results from ear-canal sound stimulation responses show that below 200 Hz, the middle ear impedance is dominated by its stiffness term, limiting sound transmission to the inner ear. During air-conduction, normal ears have approximately equal volume velocities at the oval (stapes) and round windows, known as a two-window system. However, perturbing the impedance of the inner ear with a superior canal dehiscence (SCD), a pathological opening of the bone surrounding the semicircular canal, breaks down this simple two-window system. SCD changes the volume velocity flow in the inner ear, particularly at low frequencies. The experimental findings and model predictions in this study demonstrate that low-frequency auditory and vestibular sound transmission can be affected by a change in the inner-ear impedance due to a SCD.

Superior Canal Dehiscence: A Comparative Postmortem Multislice Computed Tomography Study

OBJECTIVE

Superior canal dehiscence is defined by missing bony coverage of the superior canal against the middle cranial fossa. The gold standard in diagnosis is high-resolution computed tomography (CT). A false-positive CT scan, identifying a dehiscence when one is not present, could lead to unnecessary surgical therapy. This study aims to compare postmortem CT scans with autopsy findings with regard to superior canal dehiscence.

STUDY DESIGN

Postmortem study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Twenty-two nontraumatic death cases within a 3-month period (January to March 2017) were included with 44 temporal bones. Each body underwent postmortem head CT prior to medicolegal autopsy. The middle fossa floor was exposed, and if present, the superior semicircular canal dehiscence was identified and measured. In each case, 3 comparable photographs were taken during the autopsy (left temporal bone, right temporal bone, overview).

RESULTS

Autopsy findings revealed bony dehiscences in 11% of the temporal bones, whereas CT scan revealed bony dehiscences in 16%. The length of the dehiscences were longer when measured by CT imaging.

CONCLUSION

The diagnosis of superior canal dehiscence syndrome requires high-resolution CT with clinical symptoms and physiologic evidence of a third mobile window. Our study underlines a mismatch between multislice CT imaging in the coronal plane and the presence of a dehiscence on autopsy.

Middle cranial fossa approach for the repair of superior semicircular canal dehiscence is associated with greater symptom resolution compared to transmastoid approach

BACKGROUND

Superior semicircular canal dehiscence (SSCD) is a disorder of the skull base that is gaining increasing recognition among neurosurgeons. Traditionally, the middle cranial fossa (MCF) approach has been used for the surgical repair of SSCD. However, the transmastoid (TM) approach is an alternative strategy that has demonstrated promising results.

METHODS

We performed independent searches of a popular database to identify studies that described outcomes following the surgical repair of SSCD through MCF and TM approaches. The primary outcome was symptom resolution.

RESULTS

Our analysis included 24 studies that described 230 patients that underwent either an MCF (n = 148, 64%) approach or a TM (n = 82, 36%) approach for primary surgical repair of SSCD. A greater percentage of patients in the MCF group experienced resolution of auditory symptoms (72% vs 59%, p = 0.012), aural fullness (83% vs 55%, p = 0.049), hearing loss (57% vs 31%, p = 0.026), and disequilibrium (75% vs 44%, p = 0.001) when compared to the TM group. The MCF approach was also associated with higher odds of symptom resolution for auditory symptoms (odds ratio [OR] 1.79, 95% confidence interval [CI] 1.14-2.82), aural fullness (OR 4.02, 95% CI 1.04-15.53), hearing loss (OR 2.91, 95% CI 1.14-7.42), and disequilibrium (OR 3.94, 95% CI 1.78-8.73). The mean follow-up was 9 months.

CONCLUSIONS

The literature suggests that the MCF approach for the repair of SSCD is associated with greater symptom resolution when compared to the TM approach. This information could help facilitate patient discussions.

Long-Term Patient-Reported Outcomes After Surgery for Superior Canal Dehiscence Syndrome

OBJECTIVE

Evaluate the long-term patient-reported outcomes of surgery for superior canal dehiscence syndrome (SCDS).

STUDY DESIGN

Cross-sectional survey.

SETTING

Tertiary referral center.

PATIENTS

Adults who have undergone surgery for SCDS with at least 1 year since surgery.

MAIN OUTCOME MEASURE(S)

Primary outcome: change in symptoms that led to surgery.

SECONDARY OUTCOMES

change in 11 SCDS-associated symptoms, change in psychosocial metrics, and willingness to recommend surgery to friends with SCDS.

RESULTS

Ninety-three (43%) respondents completed the survey with mean (SD) time since surgery of 5.3 (3.6) years. Ninety-five percent of respondents reported the symptoms that led them to have surgery were "somewhat better," "much better," or "completely cured." Those with unilateral symptoms were more likely to report improvement than those with bilateral symptoms. There was no difference between those with short (1-5 yr) versus long (5-20 yr) follow-up. Each of the SCDS-associated symptoms showed significant improvement. The largest improvements were for autophony, pulsatile tinnitus, audible bodily sounds, and sensitivity to loud sound. Headaches, imbalance, dizziness, and brain fog showed the least improvements. Most patients reported improvements in quality of life, mood, and ability to function at work and socially. Ninety-five percent of patients would recommend SCDS surgery.

CONCLUSIONS

Respondents demonstrated durable improvements in the symptoms that led them to have surgery. Auditory symptoms had the greatest improvements. Headaches, imbalance, dizziness, and brain fog showed the least improvements. Nearly, all patients would recommend SCDS surgery to others. These results can be used to counsel patients regarding the lasting benefits of surgery for SCDS.

Peripheral Vestibular Disorders in Children and Adolescents with Concussion

Objective To review peripheral vestibular disorders in pediatric patients with dizziness following concussion. Study Design Case series with chart review. Setting Pediatric vestibular clinic and pediatric multidisciplinary concussion clinic at a tertiary level pediatric hospital. Subjects and Methods We retrospectively reviewed 109 patients seen for dizziness following a concussion between September 2012 and July 2015. Patients were ≤20 years of age at the time of concussion. Incidences of specific peripheral vestibular disorders were assessed along with timing of diagnosis relative to the date of injury, diagnostic test findings, and treatment interventions associated with those diagnoses. Results Twenty-eight patients (25.7%) were diagnosed with peripheral vestibular disorders. None of these disorders were diagnosed prior to evaluation in our pediatric vestibular clinic or our multidisciplinary concussion clinic, which occurred a mean of 133 days (95% confidence interval, 89.2-177.3) after injury. Benign paroxysmal positioning vertigo was diagnosed in 19 patients, all of whom underwent successful canalith repositioning maneuvers. Other diagnoses included temporal bone fracture (n = 3), labyrinthine concussion (n = 2), perilymphatic fistula (n = 2), and superior semicircular canal dehiscence (n = 2). Both patients with perilymphatic fistula and 1 patient with superior semicircular canal dehiscence underwent successful surgical management, while 1 patient with superior semicircular canal dehiscence was managed nonsurgically. Conclusion Peripheral vestibular disorders may occur in pediatric patients with dizziness following concussion, but these disorders may not be recognized until symptoms have persisted for several weeks. An algorithm is proposed to guide the diagnosis and management of peripheral vestibular disorders in pediatric patients with concussion.

Mechanisms of Hearing Loss in a Guinea Pig Model of Superior Semicircular Canal Dehiscence

Defective acoustic transmission in the cochlea is closely related with various auditory and vestibular symptoms. Among them, semicircular canal dehiscence (SCD) with a defective semicircular bone is typical. Currently, the pathogenesis of SCD is usually explained by the third window hypothesis; however, this hypothesis fails to explain the variability in the symptoms and signs experienced by superior SCD (SSCD) patients. We evaluated the mechanism of hearing loss in a guinea pig model of bony dehiscence with various sizes and locations along the superior semicircular canal. Auditory brainstem responses (ABRs) and laser Doppler velocimetry were used to measure hearing loss and vibration changes before and after fenestration, as well as after restorative patching. ABR thresholds at low frequencies (e.g., 1000 Hz) increased after fenestration and decreased back to the normal range after we repaired the defect. Energy leakage from the surgically introduced third window was detected in the range of 300–1500 Hz, accompanied by increased vibration at the umbo, stapes head, and the dehiscence site, while decreased vibration was observed at the round window membrane in the same frequency range. After the patching procedure, the deviant vibrations were recovered. The degree of postfenestration energy leakage was proportional to the size of fenestration and the proximity of the fenestration site to the oval window. These results suggest that the bony fenestration of the superior semicircular canal mimics the hearing loss pattern of patients with SSCD. The decrease in perilymph wave impedance likely accounts for the auditory changes.

Recent surgical options for vestibular vertigo

Vertigo is not a well-defined disease but a symptom that can occur in heterogeneous entities diagnosed and treated mainly by otolaryngologists, neurologists, internal medicine, and primary care physicians. Most vertigo syndromes have a good prognosis and management is predominantly conservative, whereas the need for surgical therapy is rare, but for a subset of patients often the only remaining option. In this paper, we describe and discuss different surgical therapy options for hydropic inner ear diseases, Menière's disease, dehiscence syndromes, perilymph fistulas, and benign paroxysmal positional vertigo. At the end, we shortly introduce the most recent developments in regard to vestibular implants. Surgical therapy is still indicated for vestibular disease in selected patients nowadays when conservative options did not reduce symptoms and patients are still suffering. Success depends on the correct diagnosis and choosing among different procedures the ones going along with an adequate patient selection. With regard to the invasiveness and the possible risks due to surgery, in depth individual counseling is absolutely necessary. Ablative and destructive surgical procedures usually achieve a successful vertigo control, but are associated with a high risk for hearing loss. Therefore, residual hearing has to be included in the decision making process for surgical therapy.

Round window plugging in the treatment of superior semicircular canal dehiscence

OBJECTIVES/HYPOTHESIS

Objectives were to describe the use of round window plugging for superior semicircular canal dehiscence syndrome and review further recommendations regarding the procedure based on our experience and to compare results with recent literature on round window plugging.

STUDY DESIGN

Retrospective case series.

METHODS

Fourteen patients underwent round window plugging for superior semicircular canal dehiscence at our institution from 2012 to 2015. All patients underwent the same surgical procedure. Available pre- and postoperative data were reviewed.

RESULTS

Fourteen patient charts were reviewed. Symptoms of autophony improved in nine of 14 (64%) patients. Symptoms of pressure-induced vertigo improved in seven of 12 (58%) patients. Hennebert's sign that was positive preoperatively only improved in one of six (17%) patients. A positive preoperative vestibular evoked myogenic potential improved in only one of six (17%) patients. Six of 13 (46%) patients had increased air conduction thresholds postoperatively.

CONCLUSIONS

Round window plugging has been described as a less-invasive treatment for patients with superior semicircular canal dehiscence. Although the procedure did benefit some of our patients, successful outcomes were not predictable. Improvement in at least one objective finding was seen in only 21% of the patients studied. Hennebert's sign and vestibular evoked myogenic potentials that were positive preoperatively only improved in 17% of patients. At our institution, round window plugging is no longer considered a reasonable treatment option for most patients with superior semicircular canal dehiscence. We recommend that further study on this topic follow a standardized pre- and postoperative assessment.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:1445-1452, 2018.

An Easy and Reliable Method to Locate the Dehiscence During Middle Fossa Superior Canal Dehiscence Surgery: It is a (C)inch

OBJECTIVE

The middle fossa floor lacks reliable surface landmarks. In cases of superior semicircular canal dehiscence (SSCD), multiple skull base defects may be present, further confounding the location of the labyrinth. Misidentification of the SSCD during surgery may lead to treatment failure or sensorineural hearing loss. Anecdotally, the authors have observed the distance from the lateral edge of the craniotomy to the SSCD to be consistently 1 inch. Herein, we present radiologic evidence of this practical and clinically useful relationship.

PATIENTS

All patients at two tertiary care academic referral centers with high-resolution temporal bone computed tomography (CT) evidence of SSCD were retrospectively reviewed.

INTERVENTION(S)

Review of high-resolution temporal bone CT.

MAIN OUTCOME MEASURES

The horizontal distance from the outer cortex of the squama temporalis immediately superior to the bony external auditory canal (approximating lateral edge of craniotomy) to the SSCD was measured in the coronal plane by two independent reviewers.

RESULTS

A total of 151 adult ears with SSCD were analyzed. A Shapiro-Wilk goodness-of-fit test confirmed that measurements were normally distributed. Pearson inter-rater correlation was 0.95, confirming very strong agreement. The mean distance between the outer cortex of the squama temporalis and SSCD was 25.9 mm, or 1.02 inches. Sixty-eight percent of the SSCD population would fall between 0.92 and 1.12 inches and 95% would lie between 0.83 and 1.21 inches.

CONCLUSIONS

The horizontal distance from the outer cortex of the squama temporalis to the SSCD consistently approximates 1 inch. This easily remembered distance can aid surgeons in locating or confirming the SSCD during middle fossa surgery.

Audiologic, cVEMP, and Radiologic Progression in Superior Canal Dehiscence Syndrome

OBJECTIVE

To assess the change in hearing, vestibular function, and size of superior canal dehiscence (SCD) in patients with SCD syndrome over time.

PATIENTS

Adult patients with SCD in one or both ears with documented sign and symptom progression, as shown by the medical record, audiometry, cervical vestibular-evoked myogenic potentials (cVEMP), and computed tomography (CT).

INTERVENTION

Audiometry, cVEMPs, and temporal bone CT were performed on patients with high clinical suspicion of disease progression.

MAIN OUTCOME MEASURE

Audiometry (magnitude of the air-bone gap [ABG]), cVEMP (magnitude of the thresholds), and CT scans (size of the superior canal dehiscence) were analyzed. Symptoms were assessed at each clinical visit and before repeat testing.

RESULTS

Retrospective review of 250 patients with SCDS showed three patients with disease progression over time with follow-up testing as outlined above. All patients presented initially with mild symptoms, ABGs, low cVEMP thresholds, and small bony defects of the arcuate eminence. Four, 6, and 8 years later, progression of SCD signs and symptoms was observed in these three patients, respectively. Audiometry showed larger ABGs and lower cVEMP thresholds compared with previous testing. CT showed an increase in bony defect size.

CONCLUSION

Progression of SCD symptoms can be associated with a wider air-bone gap, lower cVEMP thresholds, and a larger bony defect. Prospective studies using validated measures of hearing loss and dizziness in patients who have not yet undergone surgery for SCD will determine the association between specific symptoms and objective test outcomes and how these change over time.

Vestibular rehabilitation following surgical repair for Superior Canal Dehiscence Syndrome: A complicated case report

Superior Canal Dehiscence Syndrome (SCDS) causes auditory and vestibular symptoms. Following surgical repair of the dehiscence, patients often experience dizziness and imbalance. This case report describes a postoperative vestibular exercise program, focusing on the principles of central compensation and habituation, and how it was modified for a patient with delayed progress secondary to strabismus and visual vertigo. A 63-year-old male with history of strabismus eye surgery, right hearing loss, aural fullness, and sensitivity to loud sounds was referred for vestibular rehabilitation (VR). He was seen for one preoperative and six postoperative PT visits over eight months. Outcome measures two weeks postoperative were as follows: Dizziness Handicap Inventory (DHI) 38/100; Timed Up & Go (TUG) 9.92 seconds; Dynamic Gait Index (DGI) 16/24; and a 3-line difference in Dynamic Visual Acuity (DVA). Improved outcomes at discharge included: DHI 18/100; TUG 6.87 seconds; DGI 23/24; and 1-line difference in DVA. He was able to return to work and previously enjoyed recreational activities. Postoperative vestibular rehabilitation programs are functionally and symptomatically beneficial following surgical repair for SCDS. Deviations from expected recovery should be addressed to achieve optimal outcomes as demonstrated in this complicated case report.

Cadaveric Study of an Endoscopic Keyhole Middle Fossa Craniotomy Approach to the Superior Semicircular Canal

OBJECTIVE

Demonstrate that an endoscopic keyhole approach to the middle cranial fossa is technically feasible for repair of semicircular canal dehiscence.

STUDY DESIGN

Cadaveric technical feasibility/methods development study.

SETTING

Tertiary care military medical center.

PATIENTS

Three fresh cadaveric heads (six sides).

INTERVENTION(S)

Endoscopic minimally invasive approach to the middle cranial fossa using the Medtronic Fusion Guidance system.

MAIN OUTCOME MEASURE(S)

Ability to identify the surgical landmarks of the middle cranial fossa and successfully identify and instrument the superior semicircular canal.

RESULTS

In every attempt, the arcuate eminence was successfully identified under endoscopic visualization and with the assistance of surgical navigation. The superior semicircular canal was unroofed, and its location confirmed visually and with the navigation system. The opened canal was then plugged with bone wax, bone pate, and covered with fascia. The 15-mm burr hole craniotomy provided ample room for one working instrument and a 4-mm 0-degree endoscope.

CONCLUSION

The endoscopic keyhole approach to superior semicircular canal dehiscence is technically feasible in a human cadaveric model. Further studies will determine 1) if this approach is possible and safe in vivo, 2) is associated with improved surgical outcomes, and 3) if surgical navigation aids in this approach.

Comorbidities confounding the outcomes of surgery for third window syndrome: Outlier analysis

Objective

Patients with third window syndrome and superior semicircular canal dehiscence (SSCD) symptoms whose surgical outcomes placed them as outliers were systematically studied to determine comorbidities that were responsible for their poor outcomes due to these confounding factors.

Study Design

Observational analytic case-control study in a tertiary referral center.

Methods

Twelve adult patients with clinical SSCD syndrome underwent surgical management and had outcomes that did not resolve all of their subjective symptoms. In addition to one of the neurotologists, 2 neurologists (one specializing in migraine and the other a neuro-ophthalmologist), and a psychologist clinician-investigator completed comprehensive evaluations. Neuropsychology test batteries included: the Millon Behavioral Medicine Diagnostic; Patient Health Questionnaire (PHQ-9) and Generalized Anxiety Disorder Screener (GAD-7); Adverse Childhood Experiences Scale; the Wide Range Assessment of Memory and Learning, including the 3 domains of verbal memory, visual memory, and attention/concentration; Wechsler Adult Intelligence Scale; and the Delis-Kaplan Executive Function System. The control cohort was comprised of 17 participants who previously underwent surgery for third window syndrome that resulted in the expected outcomes of resolution of their third window syndrome symptoms and cognitive dysfunction.

Results

There was a high rate of psychological comorbidity (n = 6) in the outlier cohort; multiple traumatic brain injuries were also a confounding element (n = 10). One patient had elevated cerebrospinal fluid (CSF) pressure requiring ventriculoperitoneal shunting to control the recurrence of dehiscence and one patient with a drug-induced Parkinson-like syndrome and idiopathic progressive neurological degenerative process.

Conclusions

Components of the Millon Behavioral Medicine Diagnostic, PHQ-9 and GAD-7 results suggest that these instruments would be useful as screening tools preoperatively to identify psychological comorbidities that could confound outcomes. The identification of these comorbid psychological as well as other neurological degenerative disease processes led to alternate clinical management pathways for these patients.

Level of Evidence

2b.

A Comparison of Surgical Treatments for Superior Semicircular Canal Dehiscence: A Systematic Review

OBJECTIVE

We investigate the postoperative subjective and objective outcomes of different surgical treatments for superior semicircular canal dehiscence (SSCD): vestibular signs, auditory signs, vestibular evoked myogenic potential test, pure tone audiogram, speech audiogram, or video-nystagmography.

DATA SOURCES

An electronic search performed in the PubMed, Cochrane Library, and EMBASE databases on 15th of September 2015. A systematic search was conducted. Articles were included if written in English, Dutch, German, or French language.

STUDY SELECTION

Original studies reporting on the pre and postoperative subjective and/or objective outcomes of surgical treatments for superior semicircular canal dehiscence were included.

DATA EXTRACTION

The methodological quality of the studies was independently assessed by two reviewers using a constructed critical appraisal, to assess the directness of evidence and the risk of bias. The results of the pre and postoperative subjective and/or objective outcomes were extracted.

DATA SYNTHESIS

Comparative study was conducted.

CONCLUSION

Surgical treatment for SSCD is particularly effective for vestibular symptoms and there is no evidence for improvement of hearing loss after surgical treatment. Since plugging using transmastoid approach had a lower complication rate, lower revision rate, and a shorter hospital stay, this treatment is recommended in high disabled SSCD patients.

Outcomes of Transmastoid Surgery for Superior Semicircular Canal Dehiscence Syndrome

OBJECTIVE

To present the management strategy and outcomes for our series of superior semicircular canal dehiscence syndrome (SSCDS) patients.

STUDY DESIGN

Retrospective cross-sectional study.

SETTING

Tertiary referral center.

PATIENTS

Thirty-seven consecutive patients referred from June 2011 to January 2015. Diagnosis of SSCDS based on presence of classical symptoms, computerized tomography, and concordant reduction in cervical vestibular evoked myogenic potentials.

INTERVENTIONS

Transmastoid resurfacing or plugging.

MAIN OUTCOME MEASURES

Pre- and postoperative pure tone audiometry. Nine item questionnaire grading pre- and postoperative symptom severity. Results of a short semi-structured telephone survey.

RESULTS

Twenty surgical patients: 13 women and 7 men. Mean age 52 years 6 months. Eighteen patients underwent transmastoid resurfacing and two underwent transmastoid plugging. Three of those who initially had resurfacing but had ongoing SSCD symptoms, subsequently had transmastoid plugging with complete resolution of third window symptoms. From the questionnaire there was improvement in mean scores for 8 of 9 of the SSCD symptoms, with statistically significant improvement in 6 of 9.

CONCLUSIONS

Management strategies and surgical techniques continue to evolve for SSCDS. We currently offer transmastoid resurfacing having informed patients of a 25% possibility of incomplete symptom resolution, and explain that plugging can be performed as a "second stage," if necessary. However, as we accrue more experience and there is more evidence from the literature we are considering whether to offer transmastoid plugging as our primary surgical procedure. In our experience, patients with multiple vestibular pathologies or atypical vestibular symptoms are the ones for whom SSCD surgery has not been curative, although they do report improvement in their SSCD symptoms.

Heterogeneity in Reported Outcome Measures after Surgery in Superior Canal Dehiscence Syndrome-A Systematic Literature Review

BACKGROUND

Superior canal dehiscence syndrome (SCDS) can be treated surgically in patients with incapacitating symptoms. However, the ideal treatment has not been determined.

OBJECTIVES

This systematic literature review aims to assess available evidence on the comparative effectiveness and risks of different surgical treatments regarding: (1) symptom improvement; (2) objectively measurable auditory and vestibular function; (3) adverse effects, and (4) length of hospitalization.

SEARCH METHOD AND DATA SOURCES

A systematic database search according to PRISMA statement was conducted on Pubmed, Embase, and Cochrane library. In addition, reference lists were searched. No correspondence with the authors was established. The last search was conducted on June 9, 2017.

STUDY ELIGIBILITY CRITERIA

Retrospective and prospective cohort studies were held applicable under the condition that they investigated the association between a surgical treatment method and the relief of vestibular and/or auditory symptoms. Only studies including quantitative assessment of the pre- to postoperative success rate of a surgical treatment method were included. Case reports, reviews, meta-analysis, and studies not published in English, Dutch, or German were excluded.

DATA COLLECTION AND ANALYSIS

The first author searched literature and extracted data; the first and last analyzed the data.

MAIN RESULTS

Seventeen studies (354 participants, 367 dehiscences) met the eligibility criteria and were grouped according to surgical approach. Seven combinations of surgical approaches and methods for addressing the dehiscence were identified: plugging, resurfacing, or a combination of both through the middle fossa (middle fossa approach); plugging, resurfacing, or a combination of both through the mastoid (transmastoid approach); round window reinforcement through the ear canal (transcanal approach). Several studies showed high internal validity, but quality was often downgraded due to study design (1). Outcome measures and timing of postsurgical assessment varied among studies, making it unfeasible to pool data to perform a meta-analysis.

CONCLUSION

A standardized protocol including outcome measures and timeframes is needed to compare the effectiveness and safety SCDS treatments. It should include symptom severity assessments and changes in vestibular and auditory function before and after treatment.

Surgical Complications from Superior Canal Dehiscence Syndrome Repair: Two Decades of Experience

Objective

To determine the incidence of surgical complications associated with superior canal dehiscence syndrome (SCDS) repair and identify the demographic, medical, and intraoperative risk factors that are associated with SCDS complications.

Study Design

Cases series with chart review, including patients who underwent SCDS repair between 1996 and 2015.

Setting

A tertiary care academic medical center.

Subjects and Methods

Data were collected from 220 patients, including demographic information, medical comorbidities, prior otologic surgical history, surgical approach, intraoperative findings, and postoperative complications. Relative risk analysis and multivariable logistic regression evaluated the associations between perioperative risk factors and SCDS complications.

Results

A total of 242 consecutive cases were performed: 95.5% middle fossa and 4.5% transmastoid approach (mean age: 47.8 ± 10.6 years; 54.5% female). Surgical complications were reported in 27 (11.2%) cases; 20 (8.3%) had Clavien-Dindo grade I complications, most commonly benign paroxysmal positional vertigo (n = 11, 4.5%) and profound sensorineural hearing loss (n = 6, 2.5%). Two cases (0.8%) had grade II; 4 cases (1.7%), grade III; and 1 case (0.4%), grade IV complications. In the analysis of comorbidities, only preoperative coagulopathy was significantly associated with increased risk of complications (relative risk = 6.4, P < .01). Following multivariate logistic regression adjusting for demographic covariates, coagulopathy was still associated with increased odds of complications (odds ratio = 15.7, P = .03). There were no significant associations between other risk factors and complications.

Conclusion

SCDS repair has low rates of adverse events. We observed an incidence of 11.2% complications, most commonly postoperative benign paroxysmal positional vertigo. The risk of nonotologic intracranial complications (1.7%) is low.

Outcomes of middle fossa craniotomy for the repair of superior semicircular canal dehiscence

Superior semicircular canal dehiscence (SSCD) is a rare defect of the arcuate eminence that causes an abnormal connection between the superior semicircular canal and middle cranial fossa. Patients often present with a variety of auditory and vestibular symptoms. Trigger avoidance is the initial strategy, but surgery may be necessary in debilitating cases. We retrospectively reviewed SSCD patients undergoing repair via a middle fossa craniotomy between March 2011 and September 2015. Forty-nine patients undergoing 58 surgeries were identified. Autophony was the most common symptom at presentation (n=44; 90%). Mean follow-up was 10.9months, with 100% of patients reporting resolution of at least one symptom. Aural fullness was the most commonly resolved symptom following surgical repair (n=19/22; 86%). Hearing loss (n=11/25; 44%) and tinnitus (n=11/38; 29%) were the most common symptoms to persist following surgery. The most common symptom to develop after surgery was disequilibrium (n=4/18; 22%). Upon comparing the overall pre-operative and post-operative groups, the number of patients with autophony (p<0.0001), aural fullness (p=0.0006), hearing loss (p=0.0119), disequilibrium (p=0.0002), sound- and pressure-induced vertigo (p<0.0001), and tinnitus (p<0.0001) were significantly different. Improved clinical outcomes were demonstrated in patients undergoing SSCD repair through a middle cranial fossa approach. The most common presenting symptom (autophony) was also most likely to resolve after surgery. Hearing loss is less amenable to surgical correction. Disequilibrium developed in a small number of patients after repair.

How I do it: underwater endoscopic ear surgery for plugging in superior canal dehiscence syndrome

Background:

Underwater endoscopic ear surgery does not require suction and so protects the inner ear from unexpected aeration that may damage its function in the treatment of labyrinthine fistula. A method of underwater endoscopic ear surgery is proposed for the treatment of superior canal dehiscence.

Methods:

Underwater endoscopic ear surgery was performed for plugging of the superior semicircular canal through the transmastoid approach. Saline solution was infused into the mastoid cavity through an Endo-Scrub Lens Cleaning Sheath. The tip of the inserted endoscope was filled completely with saline water.

Results:

Using this underwater endoscopic view, the canal was clearly dissected to expose the semicircular canal membranous labyrinth and dehiscence area. No particular complication occurred during the surgical procedure.

Conclusion:

The underwater endoscopic ear surgery technique for plugging in superior canal dehiscence secures an excellent visual field and protects the inner ear from unexpected aeration.

Superior petrosal sinus causing superior canal dehiscence syndrome

Objective:

To determine signs and symptoms for superior canal dehiscence syndrome caused by the superior petrosal sinus.

Methods:

A review of the English-language literature on PubMed and Embase databases was conducted, in addition to a multi-centre case series report.

Results:

The most common symptoms of 17 patients with superior petrosal sinus related superior canal dehiscence syndrome were: hearing loss (53 per cent), aural fullness (47 per cent), pulsatile tinnitus (41 per cent) and pressure-induced vertigo (41 per cent). The diagnosis was made by demonstration of the characteristic bony groove of the superior petrosal sinus and the ‘cookie bite’ out of the superior semicircular canal on computed tomography imaging.

Conclusion:

Pulsatile tinnitus, hearing loss, aural fullness and pressure-induced vertigo are the most common symptoms in superior petrosal sinus related superior canal dehiscence syndrome. Compared to superior canal dehiscence syndrome caused by the more common apical location of the dehiscence, pulsatile tinnitus and exercise-induced vertigo are more frequent, while sound-induced vertigo and autophony are less frequent. There is, however, considerable overlap between the two subtypes. The distinction cannot as yet be made on clinical signs and symptoms alone, and requires careful analysis of computed tomography imaging.

Superior Canal Dehiscence Syndrome: Lessons from the First 20 Years

Superior semicircular canal dehiscence syndrome was first reported by Lloyd Minor and colleagues in 1998. Patients with a dehiscence in the bone overlying the superior semicircular canal experience symptoms of pressure or sound-induced vertigo, bone conduction hyperacusis, and pulsatile tinnitus. The initial series of patients were diagnosed based on common symptoms, a physical examination finding of eye movements in the plane of the superior semicircular canal when ear canal pressure or loud tones were applied to the ear, and high-resolution computed tomography imaging demonstrating a dehiscence in the bone over the superior semicircular canal. Research productivity directed at understanding better methods for diagnosing and treating this condition has substantially increased over the last two decades. We now have a sound understanding of the pathophysiology of third mobile window syndromes, higher resolution imaging protocols, and several sensitive and specific diagnostic tests. Furthermore, we have a treatment (surgical occlusion of the superior semicircular canal) that has demonstrated efficacy. This review will highlight some of the fundamental insights gained in SCDS, propose diagnostic criteria, and discuss future research directions.

A Method of Locating the Dehiscence during Middle Fossa Approach for Superior Semicircular Canal Dehiscence Surgery

Objectives  Superior semicircular canal dehiscence (SSCD) results from a defect in the middle cranial fossa floor. One challenge during SSCD repair is the lack of a consistent landmark. This study proposes a reference point above the external auditory canal at the level of the zygoma as the inferior craniectomy edge during surgery. Design  This is a retrospective review of patients with SSCD. Setting/Participants  A total of 72 cases of SSCD in 60 patients were repaired via a middle fossa approach at a single institution. Main Outcome Measures  The distance from the proposed reference point to the dehiscence was statistically analyzed using Shapiro-Wilk's goodness-of-fit test and Student's t -test. Results  Average distance for all patients was 28.84 ± 2.22 mm (range: 22.96-33.43). Average distance for females was 29.08 mm (range: 24.56-33.43) versus 28.26 mm (range: 22.96-32.36) for males. There was no difference in distance by sex ( p  = 0.174). The distance measurements followed a normal distribution with 95% of the patients between 24.49 and 33.10 mm. Conclusion  This study analyzed a potential reference point during a middle fossa approach for SSCD surgery. The distance from this reference point to the SSCD was found to be consistent and may serve as a readily identifiable landmark in localizing the dehiscence.

Superior Semicircular Canal Dehiscence Syndrome - Diagnosis and Surgical Management

Introduction Superior semicircular canal dehiscence syndrome was described by Minor et al in 1998. It is a troublesome syndrome that results in vertigo and oscillopsia induced by loud sounds or changes in the pressure of the external auditory canal or middle ear. Patients may present with autophony, hyperacusis, pulsatile tinnitus and hearing loss. When symptoms are mild, they are usually managed conservatively, but surgical intervention may be needed for patients with debilitating symptoms.

Objective The aim of this manuscript is to review the different surgical techniques used to repair the superior semicircular canal dehiscence.

Data Sources PubMed and Ovid-SP databases.

Data Synthesis The different approaches are described and discussed, as well as their limitations. We also review the advantages and disadvantages of the plugging, capping and resurfacing techniques to repair the dehiscence.

Conclusions Each of the surgical approaches has advantages and disadvantages. The middle fossa approach gives a better view of the dehiscence, but comes with a higher morbidity than the transmastoid approach. Endoscopic assistance may be advantageous during the middle cranial fossa approach for better visualization. The plugging and capping techniques are associated with higher success rates than resurfacing, with no added risk of hearing loss.

Endoscopic-Assisted Repair of Superior Canal Dehiscence

Superior canal dehiscence (SCD) is a bony defect of the superior canal that can cause vestibular and/or auditory symptoms. Surgical repair of SCD provides effective relief from symptoms, and the middle fossa craniotomy approach with binocular microscopy offers direct visualization and surgical access to the arcuate eminence. However, for SCDs located along the downsloping tegmen medial to the peak of the arcuate eminence, a direct light of sight may be obscured, rendering visualization with traditional microscopy difficult. The endoscope is the ideal adjunct in middle fossa craniotomy approach SCD surgery and offers a safe, effective means to identify and repair arcuate eminence defects hidden from microscopic view.

Superior semicircular canal dehiscence syndrome: a new aetiology

Objective:

We report what we believe to be a unique aetiology of the superior semicircular canal dehiscence syndrome, a recently described condition in which vestibular imbalance and/or hearing loss results from the loss of continuity of the bone overlying the superior semicircular canals.

Case report:

A 58-year-old woman presented with autophony in the right ear and momentary imbalance when shouting (Tullio phenomenon). Temporal bone computed tomography revealed a defect of the right superior semicircular canal caused by an enlarged superior petrosal sinus receiving drainage from a large cerebellar developmental venous anomaly.

Conclusions:

We review superior semicircular canal dehiscence syndrome and its management, and we discuss common aetiologies, contrasting these with the unusual aetiology presented here. We conclude that superior semicircular canal dehiscence syndrome may present with a solely developmental aetiology, despite presenting late in life.

Síndrome da deiscência do canal semicircular superior: relato de dois casos

RESUMO A Síndrome da Deiscência do Canal Semicircular Superior (SDCSS) é caracterizada pelo desgaste da camada óssea que recobre o canal semicircular superior. São sintomas comuns da SDCSS a presença de vertigem associada à nistagmos induzidos por estímulos sonoros intensos ou por modificações das pressões intracraniana ou da orelha média. O objetivo deste trabalho é descrever os achados audiólogicos e vestibulares de dois pacientes com diagnóstico de Síndrome da Deiscência do Canal Semicircular Superior, com diagnóstico confirmado por meio de tomografia computadorizada. Foram realizadas meatoscopia, anamnese, audiometria tonal e vocal seguida das medidas de imitância acústica, Weber audiométrico, pesquisa do fenômeno de Túlio e manobra de Valsalva, realizados pela mesma pesquisadora em uma única sessão. Foram observados gap aéreo-ósseo, curva timpanométrica tipo A e reflexos acústicos presentes. O gap aéreo-ósseo apresenta-se com maior amplitude nas frequências baixas. As queixas auditivas não foram relatadas pelas pacientes como os primeiros sintomas. O Weber mostrou lateralização, nos dois casos, confirmando a presença de gap. O fenômeno de Túlio apresentou-se positivo para vertigem em ambos os casos. A manobra de Valsalva apresentou alteração em apenas um caso.

The new vestibular stimuli: sound and vibration-anatomical, physiological and clinical evidence

The classical view of the otoliths-as flat plates of fairly uniform receptors activated by linear acceleration dragging on otoconia and so deflecting the receptor hair bundles-has been replaced by new anatomical and physiological evidence which shows that the maculae are much more complex. There is anatomical spatial differentiation across the macula in terms of receptor types, hair bundle heights, stiffness and attachment to the overlying otolithic membrane. This anatomical spatial differentiation corresponds to the neural spatial differentiation of response dynamics from the receptors and afferents from different regions of the otolithic maculae. Specifically, receptors in a specialized band of cells, the striola, are predominantly type I receptors, with short, stiff hair bundles and looser attachment to the overlying otoconial membrane than extrastriolar receptors. At the striola the hair bundles project into holes in the otolithic membrane, allowing for fluid displacement to deflect the hair bundles and activate the cell. This review shows the anatomical and physiological evidence supporting the hypothesis that fluid displacement, generated by sound or vibration, deflects the short stiff hair bundles of type I receptors at the striola, resulting in neural activation of the irregular afferents innervating them. So these afferents are activated by sound or vibration and show phase-locking to individual cycles of the sound or vibration stimulus up to frequencies above 2000 Hz, underpinning the use of sound and vibration for clinical tests of vestibular function.

Relationship between Surgically Treated Superior Canal Dehiscence Syndrome and Body Mass Index

Objective

Examine the association between body mass index (BMI) and superior canal dehiscence (SCD) among patients who have undergone surgical repair for superior canal dehiscence.

Study Design

Retrospective comparison study.

Setting

Neurotology tertiary care center.

Subjects and Methods

Retrospective review of consecutive adult patients evaluated at our institution for SCD syndrome between November 2006 and August 2015. A control group who underwent imaging within the same period for reasons other than SCD was also included. Patient demographics, weight, and height were examined. We performed multiple subgroup analyses to investigate the relationship of BMI, surgery vs no surgery, and correlation between patient BMI and SCD size.

Results

Of the 268 patients with SCD, 99 underwent surgery; 96 of these patients had complete medical records and were eligible for inclusion. Eighty-eight patients were noted to have arcuate eminence defects, and the mean BMI of this surgical cohort was 28.09 ± 5.26 kg/m2. Nonsurgically treated patients with SCD with available data (n = 94) had a mean BMI of 27.97 ± 6.95 kg/m2. A control group of 204 patients who underwent computed tomography for non-SCD-related causes was analyzed, of whom 155 had available data with a mean BMI of 27.91 ± 6.38 kg/m2.

Conclusion

We demonstrate that adult patients who undergo surgery for SCD are not obese (mean BMI <30), and size of dehiscence poorly correlates with BMI. Our observations call into question the proposed theory that patient weight is a risk factor for the development of symptomatic SCD involving the arcuate eminence.

Enhanced Auditory Sensitivity to Body Vibrations in Superior Canal Dehiscence Syndrome

A key feature of superior canal dehiscence (SCD) syndrome is supranormal hearing of body sounds. The aim of the present study was to quantify this phenomenon and to ascertain whether auditory sensitivity to body vibrations can distinguish SCD patients. Hearing thresholds in response to vibration at the vertex, at the spinous process of the 7th cervical vertebra, and at the medial malleolus were tested in 10 SCD patients and 10 controls. Both patients and controls had insert earphones in both ears. The insert in the test ear was blocked while masking was presented to the other ear. Vibration in the frequency range of 125-1,000 Hz was presented to each of the 3 stimulation sites. The SCD patients were found to have significantly lower hearing thresholds compared with controls. The two study groups reacted differently with respect to frequency. The SCD patients showed an enhanced sensitivity for the lower stimulus frequencies. The difference was, however, rather independent of stimulus presentation site. The findings suggest that hearing thresholds in response to low-frequency body vibration at sites distant from the ears can distinguish SCD patients. The present findings may also support the idea that auditory sensation to body vibrations is a response related to soft tissue conduction.

Superior semicircular canal dehiscence syndrome

Superior semicircular canal dehiscence (SSCD) syndrome is an increasingly recognized cause of vestibular and/or auditory symptoms in both adults and children. These symptoms are believed to result from the presence of a pathological mobile "third window" into the labyrinth due to deficiency in the osseous shell, leading to inadvertent hydroacoustic transmissions through the cochlea and labyrinth. The most common bony defect of the superior canal is found over the arcuate eminence, with rare cases involving the posteromedial limb of the superior canal associated with the superior petrosal sinus. Operative intervention is indicated for intractable or debilitating symptoms that persist despite conservative management and vestibular sedation. Surgical repair can be accomplished by reconstruction or plugging of the bony defect or reinforcement of the round window through a variety of operative approaches. The authors review the etiology, pathophysiology, presentation, diagnosis, surgical options, and outcomes in the treatment of this entity, with a focus on potential pitfalls that may be encountered during clinical management.

Diagnostic performance of reformatted isotropic thin-section helical CT images in the detection of superior semicircular canal dehiscence

Purpose The purpose of this article is to assess the diagnostic performance of computed tomography (CT) reformatted images for detection of superior semicircular canal (SSC) dehiscence. Material and methods Forty-two patients, with sound- and/or pressure-induced vestibular symptoms, and 42 control participants underwent helical CT examination with a highly collimated beam (0.5 mm). Reformatted images of the vestibular labyrinth were obtained in the standard axial and coronal planes (group A images), and in a plane parallel and perpendicular to the SSC (group B images). Diagnostic performance obtained by evaluating the group A images alone and the group B images alone was analyzed by using the area under the receiver operating characteristic curve (AUC). Results The diagnostic performance of group A images was AUC = 0.929 with an overall accuracy of 92.9%. The diagnostic performance of group B images was AUC = 0.988 with an overall accuracy of 98.8%. The evaluation of group B images alone showed an improved diagnostic performance over the group A images alone. Conclusion Thin-section 0.5-mm collimation CT with reformatted images oriented in the plane parallel and perpendicular to the SSC improves diagnostic accuracy in assessing for SSC dehiscence in comparison to CT images with reconstructions limited to traditional axial and coronal planes.

Characteristics and clinical use of ocular and cervical vestibular evoked myogenic potentials for evaluating paediatric candidates for cochlear implants

Objective:

This study aimed to define the characteristics and use of ocular and cervical vestibular evoked myogenic potentials for evaluating paediatric cochlear implant candidates.

Methods:

Ocular and cervical vestibular evoked myogenic potentials of 34 paediatric cochlear implant candidates were analysed. All patients also underwent a routine audiological examination, including computed tomography.

Results:

In all, 27 patients with normal inner-ear structures had absent or impaired vestibular evoked myogenic potential responses. In paediatric candidates with inner-ear malformations, ocular and cervical vestibular evoked myogenic potentials had lower thresholds and higher amplitudes. Vestibular evoked myogenic potential responses in this cohort were classified into three groups. There was significant concordance between vestibular evoked myogenic potentials and temporal bone computed tomography findings.

Conclusion:

Ocular and cervical vestibular evoked myogenic potential waveforms were different in paediatric candidates with normal and abnormal inner-ear structures. Therefore, vestibular evoked myogenic potential responses can indicate temporal bone structure.

Risk of progressive hearing loss in untreated superior semicircular canal dehiscence

OBJECTIVE

Patients with incidental or minimally symptomatic superior semicircular canal dehiscence (SSCD) are usually observed, without surgical repair. However, it remains unknown whether a labyrinthine fistula of the superior semicircular canal is associated with progressive conductive or sensorineural hearing loss over time.

STUDY DESIGN

Retrospective review at two tertiary care academic referral centers.

METHODS

Adults analyzed were diagnosed with SSCD by high-resolution temporal bone computed tomography and vestibular evoked myogenic potential testing and observed with a minimum of two sequential audiograms. Patients with other potential causes of hearing impairment were excluded.

RESULTS

A total of 40 ears in 30 adult patients (median age: 59 years; 63% female) were analyzed. Median audiometric follow-up was 23 months (range 1-136 months). None experienced a sudden hearing loss over the follow-up period. In patients with audiometric follow-up of at least 20 months (median 34 months), the median change in air-conduction pure tone average and air-bone gap was 0.9 decibels (dB) per year (interquartile range [IQR] 0-2.1) and 0.7 dB per year (IQR 0-2.0), respectively. Speech discrimination scores did not differ when comparing median initial (100%) and median final (98%) scores (P = 0.77). There was no statistically significant change in bone-conduction thresholds at 0.5, 1, 2, and 4 kHz over the period of observation.

CONCLUSION

The risk of progressive hearing loss with observed SSCD is low during short- and intermediate-term follow-up. Further studies are necessary to determine whether late hearing loss occurs. Such information may be critical toward patient counseling regarding the need for and timing of surgery.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:1181-1186, 2017.

Adaptation and Compensation of Vestibular Responses Following Superior Canal Dehiscence Surgery

OBJECTIVE

To describe vestibulo-ocular function and compensatory mechanisms in the immediate postoperative period after superior canal dehiscence surgery.

STUDY DESIGN

Prospective longitudinal study.

SETTING

Tertiary medical center.

PATIENTS

Five patients who underwent plugging of superior semicircular canal via middle cranial fossa approach.

INTERVENTIONS

Bedside quantitative video head impulse testing (vHIT).

MAIN OUTCOME MEASURES

Dynamic measures of vestibulo-ocular reflex (VOR) function including VOR gain and compensatory saccades during vHIT.

RESULTS

Mean VOR gain of the ipsilateral superior semicircular canal (SC) decreased from 0.71 ± 0.1 preoperatively to 0.28 ± 0.07 on postoperative day (POD) 2-4 (p = 0.0031), consistent with plugging. There was also a significant immediate postoperative decrease of VOR gain for the other ipsilateral canals (posterior canal (PC) from gain 0.91 ± 0.33 down to 0.55 ± 0.14, p = 0.040; horizontal canal (HC) from 0.81 ± 0.08 down to 0.54 ± 0.19, p = 0.038). On PODs 1-2, compensatory saccades after testing the plugged SC occurred exclusively after the head stopped moving (overt) with latency of 186.2 ms ± 19.9 ms. By POD 7 saccade latency decreased to 141.0 ± 17.5 ms (p = 0.032), and saccades were occurring during the vertical head rotation (covert saccades). Follow-up >40 days was consistent with previous findings in that mean SC gain remained low. HC gain recovered fully, but some cases did not have full recovery of PC gain.

CONCLUSION

When the SC is plugged surgically, early quantitative vHIT demonstrates significantly reduced VOR gain for all of the ipsilateral canals. Possible mechanisms include labyrinthine inflammation and loss of perilymph at the time of surgery. Full recovery is typical for the horizontal canal but not always for the PC. Evidence of central compensation occurred by the elicitation of compensatory saccades and by reducing their latencies within the first week after surgery.

Characteristics of Wax Occlusion in the Surgical Repair of Superior Canal Dehiscence in Human Temporal Bone Specimens

HYPOTHESIS

Superior canal dehiscence (SCD) repair using surgical bone wax may result in variable outcomes if large wax volumes are applied.

BACKGROUND

SCD is a disorder characterized by a pathologic defect in the bony labyrinth of the superior semicircular canal (SSC), resulting in vestibular and/or auditory symptoms. Repair of SCD using bone wax can provide symptomatic relief, but surgical outcomes are variable. These observations may be associated with the inconsistency in the position and extension of intralabyrinthine bone wax during surgical repair.

METHODS

A pathological model of SCD was created using cadaveric human temporal bones and a microdrill. Defects in the arcuate eminence 0.5 to 3.5  mm in length were repaired by surgical occlusion with bone wax. The volume of wax used in the repair was quantified. The position of bone wax was evaluated by direct visualization and imaging (computed tomography [CT]). To visualize wax on CT, specimens were repaired using radiopaque wax.

RESULTS

Exceedingly small volumes of bone wax (3.0-5.0  mm2) reliably occluded the canal lumen. Multiple wax applications resulted in extension into the common crus and ampulla. The length of this extension was related to the number of applications.

CONCLUSIONS

Repair of SCD with bone wax occludes the bony defect completely in most patients. Wax can extend along the lumen of the superior canal beyond the limits of the dehiscence to reach the sensory neuroepithelium of the vestibular end organs. Limiting the number of wax applications is essential to avoid inadvertent injury to the delicate neurosensory systems.

Transmastoid resurfacing versus middle fossa plugging for repair of superior canal dehiscence: Comparison of techniques from a retrospective cohort

OBJECTIVE

To compare and contrast our experience with middle cranial fossa approach (MFR) and transmastoid approach with capping of the dehiscence (TMR) of superior semicircular canal dehiscence and to determine guidelines to help guide management of these patients.

METHODS

All patients from 2005 to 2014 with symptomatic superior semicircular canal dehiscence syndrome with dehiscence demonstrated on CT scan of the temporal bone who underwent surgical repair and had a minimum 3 months of follow up. Surgical repair via the MFR or TMR, preoperative CT temporal bone, preoperative, and postoperative cervical vestibular evoked myogenic potential (cVEMP) testing and anterior canal video head thrust testing (vHIT). Success of repair was stratified as complete success, moderate success, mild success, or failure based on resolution of all symptoms, the chief complaint, some symptoms, or no improvement, respectively.

RESULTS

A total of 29 ears in 27 patients underwent surgical repair of canal dehiscence. Complete or moderate success was seen in 71% of the MFR group compared to 80% of the TMR group. There were zero failures with the MFR group and no major intracranial complications. There were 2 failures out of 15 ears that underwent the TMR. Residual symptoms were most commonly vertigo or disequilibrium in the MFR and aural fullness or autophony in the TMR groups, respectively. MFR hospital stay was approximately 2 days longer. Average cVEMP threshold shifted 18 dB with surgical correction in the MFR group. A 29 dB average shift was seen in the TMR group. The MFR group had a significant reduction in their anterior canal gain compared to the TMR group.

CONCLUSIONS

TMR is a less invasive alternative to MFR. However, in our series, we have not seen any intracranial complications (aphasia, stroke, seizures, etc.) in our MFR patients. Interestingly, vestibular symptoms were better addressed than audiological symptoms by the TMR suggesting its usefulness as a less invasive option for patients with primarily vestibular complaints. Residual auditory symptoms in TMR patients may be due to the flow of acoustic energy from the superior canal to the mastoid cavity through an incompletely sealed third window.

Wideband acoustic immittance measurements in assessing crimping status following stapedotomy: A temporal bone study

OBJECTIVE

To ascertain if wideband acoustic immitance (WAI) measurements are useful in assessing crimping status following stapedotomy.

DESIGN

WAI measurements were obtained using the Mimosa Acoustics HearID system. Wideband chirp sound stimuli and a set of tone stimuli for nine frequencies between 0.2 and 6 kHz were used at 60 dB SPL. Five sets of measurements were performed on each temporal bone: mobile stapes, stapes fixation and stapedotomy followed by insertion of a tightly crimped, a loosely crimped and an uncrimped prosthesis.

STUDY SAMPLE

Eight fresh-frozen temporal bones were harvested from human cadaveric donors.

RESULTS

At lower frequencies, up to 1 kHz, stapes fixation decreased absorbance. Compared to the baseline absorbance, absorbance with stapes fixation dropped by 6 to 17% in absolute terms from the baseline value (p = 0.027). Absorbance was not affected in higher frequencies (p = 0.725). Stapedotomy changed the absorbance curve significantly compared to the normal condition with an increase of absolute absorbance values by 6 to 36% around 0.25-1 kHz (p-value <0.01). The crimping conditions did not differ from one another (p = 0.555).

CONCLUSION

WAI is not useful in distinguishing between tightly crimped, loosely crimped and uncrimped stapes prostheses following stapedotomy.

Middle Cranial Fossa Dehiscence as an Incidental Finding on CT

OBJECTIVES

This retrospective chart review demonstrates that the prevalence of middle cranial fossa (MCF) dehiscence on computed tomography (CT) scans increases with age.

METHODS

High-resolution temporal bone CT scans, which had been obtained for any otologic complaint, were reviewed independent of all clinical history. Scans showing soft tissue, fluid, trauma, or previous operations were excluded. The CTs from 183 patients (296 ears) were reviewed, blinded for age and body mass index (BMI). The MCF floor was divided into 7 regions and systematically inspected. Ages and BMIs of the patients were subsequently extracted from the medical record.

RESULTS

Logistic regression analysis confirmed increasing MCF dehiscence with age (P < .05, odds ratio [OR] = 1.07, R = .584). Over all ages (range, 1-88 years; average, 38.5), 32% of MCF floors were dehiscent at any 1 site. For age 60 and over, 55% were dehiscent. The most common sites of MCF dehisence were directly above the malleus head and above the additus ad antrum (35% and 28%, respectively). Superior canal dehiscence (SCD) was seen in 7% of all patients and only in the context of MCF dehiscence. The prevalence of MCF dehiscence increased with age when patients were analyzed by BMI <25, BMI = 25-30, and BMI >30 (P < .003, P < .04, P = .03).

CONCLUSION

The increase of middle cranial fossa dehiscence with respect to age is statistically significant. Over all ages, approximately 32% of ears show dehiscence. Over 60 years, approximately 55% show dehiscence. The odds of having dehiscence double with a 10-year difference in age. The most common sites along the MCF floor are in the epitympanum over the malleus head and the additus ad antrum. There was a statistically significant increase in MCF dehiscence with age when patients with equivalent BMIs are compared.

Vestibular-evoked myogenic potentials in chronic noise-induced hearing loss

Objective

To investigate the effect of chronic noise exposure on vestibular-evoked myogenic potentials.

Study Design

Prospective study.

Subjects and Methods

Twenty patients with chronic noise-induced hearing loss, presenting as bilateral notched audiogram at 4 kHz, underwent audiometry, caloric, and vestibular-evoked myogenic potential tests.

Results

Caloric and vestibular-evoked myogenic potential tests revealed abnormal responses in nine (45%) and 10 (50%) patients, respectively. However, when both results were considered together, the abnormal rate reached 70% (14 of 20). The hearing threshold of 4 kHz significantly associated with vestibular-evoked myogenic potential results (ie, vestibular-evoked myogenic potential was abnormal in patients with greater degrees of hearing loss), but not with caloric responses.

Conclusion

Patients with bilateral 4-kHz notched audiogram and hearing threshold of 4 kHz >40 dB may show abnormal (absent or delayed) vestibular-evoked myogenic potentials, indicating that the vestibular part, especially the sacculocollic reflex pathway, has also been damaged.