Clinical Manifestations of Superior Semicircular Canal Dehiscence

Superior Semicircular Canal Dehiscence Syndrome without Vestibular Symptoms

Introduction Superior semicircular canal dehiscence syndrome is mainly characterized by vestibular symptoms induced by intense sound stimuli or pressure changes, which occur because of dehiscence of the bony layer covering the superior semicircular canal.

Case Report Here, we report a case of the syndrome with pulsatile tinnitus and ear fullness, in the absence of vestibular symptoms.

Discussion Signs and symptoms of the syndrome are rarely obvious, leading to the requirement for a minimum workup to rule out or make diagnosis more probable and thus avoid misconduct.

Transmastoid repair of superior semicircular canal dehiscence

Objective/Hypothesis Superior semicircular canal (Sup SC) dehiscence syndrome is a rare condition, causing a variety of auditory and vestibular symptoms. The traditional surgical management is a middle cranial fossa, extradural approach to resurface the Sup SC. Recently, a transmastoid approach for plugging of the Sup SC has been developed. We present further data supporting the use of the transmastoid approach in preference to the middle fossa approach. Design This is a retrospective multi-institutional case series. Method We included 10 patients in this case series from two tertiary otology institutions. Sup SC dehiscence was confirmed by correlation of clinical symptoms with positive audiometric, vestibular evoked myogenic potential, and computed tomography findings. A transmastoid approach was used for plugging of the Sup SC. Either a single fenestration was created at the site of dehiscence or separate fenestrations sited ampullopetal and ampullofugal to the dehiscence. Results All patients who underwent this procedure had good symptom control and hearing preservation postoperatively. Conclusion In patients with adequate temporal bone pneumatization, the transmastoid approach provides a safe and effective alternative to the middle cranial fossa approach. This series has demonstrated excellent symptom control and preservation of hearing with the transmastoid approach.

Quantification of hearing loss associated with superior semi-circular canal dehiscence

INTRODUCTION

Superior semi-circular canal dehiscence (SSCD) is a known cause of hearing loss. This study quantifies hearing loss in SSCD ears in a frequency-specific fashion.

METHODS

A meta-analysis of English language literature pertaining to SSCD was performed, with extraction and evaluation of available human audiometric data. Our own institution's case series of SSCD patients was also similarly analysed. Hearing loss in SSCD ears was compared to same patient control ears and to age-matched normative audiometric data.

RESULTS

Ears with SSCD had statistically significant worse hearing as compared to both normative data and to own normal ear controls at 2000 Hz and below. The effect appears to diminish with increasing frequency.

DISCUSSION

The presence of statistically significant conductive hearing loss in the low frequencies was confirmed for SSCD ears. SSCD may also predispose ears to high frequency sensorineural hearing loss.

Air-conducted oVEMPs provide the best separation between intact and superior canal dehiscent labyrinths

OBJECTIVE

First, to define the best single-step suprathreshold screening test for superior canal dehiscence syndrome (SCDS); second, to obtain further insight into the relative sensitivity of vestibular afferents to sound vibration in the presence of a superior canal dehiscence.

STUDY DESIGN

Prospective study.

SETTING

Tertiary referral center.

PATIENTS

Eleven patients with surgically confirmed SCDS (mean, 50 yr; range, 32-66 yr) and 11 age-matched, healthy subjects (right ear only) with no hearing or vestibular deficits (mean, 50 yr; range, 33-66 yr).

INTERVENTION

All subjects completed ocular and cervical vestibular evoked myogenic potential (o- and cVEMP) testing in response to air conduction (click and 500 Hz tone burst) and midline bone conduction (reflex hammer and Mini-shaker) stimulation.

MAIN OUTCOME MEASURES

OVEMP n10 amplitude and cVEMP corrected peak-to-peak amplitude.

RESULTS

OVEMP n10 amplitudes were significantly higher in SCDS when compared with healthy controls in response to all stimuli with the exception of reflex hammer. Likewise, cVEMP-corrected peak-to-peak amplitudes were significantly higher in SCDS when compared with healthy controls for air conduction stimulation (click and 500 Hz toneburst). However, there were no significant differences between groups for midline taps (reflex hammer or mini-shaker). Receiver operating characteristic curves demonstrated that oVEMPs in response to air conduction stimulation provided the best separation between SCDS and healthy controls.

CONCLUSION

OVEMPs in response to air conduction stimulation (click and 500 Hz toneburst) provide the best separation between SCDS and healthy controls and are therefore the best single-step screening test for SCDS.

Ocular versus cervical VEMPs in the diagnosis of superior semicircular canal dehiscence syndrome

OBJECTIVES

To determine whether cervical vestibular evoked myogenic potential (cVEMP) thresholds or ocular VEMP (oVEMP) amplitudes are more sensitive and specific in the diagnosis of superior semicircular canal dehiscence syndrome (SCDS).

STUDY DESIGN

Prospective case-control study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Twenty-nine patients with SCDS (mean age 48 yr; range, 31-66 yr) and 25 age-matched controls (mean age 48 yr; range, 30-66 yr).

INTERVENTION(S)

cVEMP and oVEMP in response to air-conducted sound. All patients underwent surgery for repair of SCDS.

MAIN OUTCOME MEASURE(S)

cVEMP thresholds; oVEMP n10 and peak-to-peak amplitudes.

RESULTS

cVEMP threshold results showed sensitivity and specificity ranging from 80% to 100% for the diagnosis of SCDS. In contrast, oVEMP amplitudes demonstrated sensitivity and specificity greater than 90%.

CONCLUSION

oVEMP amplitudes are superior to cVEMP thresholds in the diagnosis of SCDS.

An Indicator of Probable Semicircular Canal Dehiscence

The n10 component of the ocular vestibular evoked myogenic potential (oVEMP) to sound and vibration stimuli is a crossed response that has enhanced amplitude and decreased threshold in patients with CT-verified superior semicircular canal dehiscence (SSCD). However, demonstrating enhanced VEMP amplitude and reduced VEMP thresholds requires multiple trials and can be very time consuming and tiring for patients, so a specific indicator of probable SCD that is fast and not tiring would be preferred. Here we report a 1-trial indicator: that the oVEMP n10 in response to a very high frequency stimulus (4000 Hz), either air-conducted sound (ACS) or bone conducted vibration (BCV), is such a fast indicator of probable SCD. In 22 healthy subjects, oVEMP n10 at 4000 Hz was not detectable; however, in all 22 CT-verified SSCD patients tested, oVEMP n10 responses were clearly present to 4000 Hz to either ACS or BCV stimuli.

Recurrent spontaneous attacks of dizziness

PURPOSE OF REVIEW

This article describes the common causes of recurrent vertigo and dizziness that can be diagnosed largely on the basis of history.

RECENT FINDINGS

Ninety percent of spontaneous recurrent vertigo and dizziness can be explained by six disorders: (1) Ménière disease is characterized by vertigo attacks, lasting 20 minutes to several hours, with concomitant hearing loss, tinnitus, and aural fullness. Aural symptoms become permanent during the course of the disease. (2) Attacks of vestibular migraine may last anywhere from minutes to days. Most patients have a previous history of migraine headaches, and many experience migraine symptoms during the attack. (3) Vertebrobasilar TIAs affect older adults with vascular risk factors. Most attacks last less than 1 hour and are accompanied by other symptoms from the posterior circulation territory. (4) Vestibular paroxysmia is caused by vascular compression of the eighth cranial nerve. It manifests itself with brief attacks of vertigo that recur many times per day, sometimes with concomitant cochlear symptoms. (5) Orthostatic hypotension causes brief episodes of dizziness lasting seconds to a few minutes after standing up and is relieved by sitting or lying down. In older adults, it may be accompanied by supine hypertension. (6) Panic attacks usually last minutes, occur in specific situations, and are accompanied by choking, palpitations, tremor, heat, and anxiety. Less common causes of spontaneous recurrent vertigo and dizziness include perilymph fistula, superior canal dehiscence, autoimmune inner ear disease, otosclerosis, cardiac arrhythmia, and medication side effects.

SUMMARY

Neurologists need to venture into otolaryngology, internal medicine, and psychiatry to master the differential diagnosis of recurrent dizziness.

Radiographic evaluation of the tegmen in patients with superior semicircular canal dehiscence

OBJECTIVE

To determine a radiographic association between superior semicircular canal dehiscence (SSCD) and tegmen dehiscence (TD).

STUDY DESIGN

Retrospective case-control series.

SETTING

Tertiary referral center.

PATIENTS

Patients seen between 2003 and 2010 with radiographic SSCD were compared with cochlear implant recipient controls.

INTERVENTION

The tegmen and superior semicircular canal were evaluated on computed tomographic temporal bone scans.

MAIN OUTCOME MEASURE

If detected, the widest point of the SSCD was measured. The tegmen was graded on a 5-point scale. After analysis, a radiographic TD was defined as any single area of absent tegmen greater than 5 mm, multiple areas of absent tegmen, or evidence of meningocele. Age, sex, and body mass index were also noted.

RESULTS

Thirty-eight patients with SSCD and 41 cochlear implant controls were identified. Seventy-six percent (29/38) of patients with unilateral or bilateral SSCD had a radiographic TD on at least 1 side compared with 22% (9/41) of the comparison group. Ninety-four percent (7/18) of patients with bilateral SSCD had a TD on at least 1 side. Patients with SSCD had a 10.2 times (p < 0.001) higher odds of having radiographic TD in either ear compared to the controls. Among patients with any SSCD, for every millimeter increase in the width of dehiscence, the relative risk for any TD increased more than 2-fold (odds ratio, 2.5; p = 0.019). Age, sex, and a body mass index greater than 30 did not confound the association between SSCD and TD.

CONCLUSION

There is a strong radiologic association between SSCD and TD, suggesting a similar etiologic process. The tegmen should be carefully evaluated in patients with SSCD. We have also proposed a new system for radiographically grading the integrity of the tegmen.

Superior canal dehiscence patients have smaller mastoid volume than age- and sex-matched otosclerosis and temporal bone fracture patients

Background and Objectives

The purpose of the study was to compare the mastoid air-cell volume of the patients with superior semicircular canal dehiscence syndrome (SCDS) and that of the control patients with otosclerosis and temporal bone (TB) fracture.

Subjects and Methods

Ten patients with SCDS were enrolled and 10 patients with bilateral otosclerosis and TB fracture were selected as control groups by age and sex matching. To measure the mastoid air-cell volume, 3D reconstruction software was used.

Results

In 10 patients with SCDS, the mean age was 44.5 years, ranging from 16 to 79 years (M : F=4 : 6). Mean mastoid air-cell volume in the SCDS side was 3319.9 mm³, whereas 4177.2 mm³ in the normal side (p=0.022). Mean mastoid air-cell volume in the right side of otosclerosis patients was 6594.3 mm³ and it was not different from 6380.5 mm³ in the left side (p=0.445). Mean mastoid air-cell volume in normal side of TB fracture was 6477.2 mm³. The mastoid air-cell volume in the SCDS side was significantly smaller than that of otosclerosis and TB fracture patients (p=0.009, p=0.002, respectively). The mastoid air-cell volume in the normal side of SCDS was significantly smaller than that of TB fracture (p=0.019), but not significant with that of otosclerosis (p=0.063).

Conclusions

Our findings revealed that the mastoid air-cell volume in the SCDS side was significantly smaller than control group, which suggest that the decreased mastoid pneumatization is closely related to the generation of SCDS.

Characteristics and management of superior semicircular canal dehiscence

Objectives To review the characteristic symptoms of superior semicircular canal dehiscence, testing and imaging of the disease, and the current treatment and surgical options. Results and Conclusions Symptoms of superior semicircular canal dehiscence (SSCD) include autophony, inner ear conductive hearing loss, Hennebert sign, and sound-induced episodic vertigo and disequilibrium (Tullio phenomenon), among others. Potential etiologies noted for canal dehiscence include possible developmental abnormalities, congenital defects, chronic otitis media with cholesteatoma, fibrous dysplasia, and high-riding jugular bulb. Computed tomography (CT), vestibular evoked myogenic potentials, Valsalva maneuvers, and certain auditory testing may prove useful in the detection and evaluation of dehiscence syndrome. Multislice temporal bone CT examinations are normally performed with fine-cut (0.5- to 0.6-mm) collimation reformatted to the plane of the superior canal such that images are parallel and orthogonal to the plane. For the successful alleviation of auditory and vestibular symptoms, a bony dehiscence can be surgically resurfaced, plugged, or capped through a middle fossa craniotomy or the transmastoid approach. SSCD should only be surgically treated in patients who exhibit clinical manifestations.

Prevalence of radiographic semicircular canal dehiscence in very young children: an evaluation using high-resolution computed tomography of the temporal bones

BACKGROUND

Previous studies suggest that semicircular canal dehiscences (SCDs) have a developmental origin.

OBJECTIVE

We hypothesized that if SCDs originate during development, incidence of radiographic SCDs in young children will be higher than in adults.

MATERIALS AND METHODS

Thirty-four temporal bone HRCTs of children younger than 2 years and 40 temporal bone HRCTs of patients older than 18 years were reformatted and re-evaluated for presence of SCD or canal thinning. Results were compared with indications for HRCT and clinical information.

RESULTS

SCDs were detected in 27.3% of children younger than 2 years of age (superior, 13.8%; posterior, 20%) and in 3% of adults (P  < 0.004). Of children with one radiographic dehiscence, 55.6% had multiple and 44% had bilateral SCDs on HRCT. No lateral canal SCDs were present. Thinning of bone overlying the semicircular canals was found in 44% of children younger than 2 years and 2.5% of adults (P < 0.0001).

CONCLUSION

SCDs are more common on HRCTs of very young children. This supports the hypothesis that SCDs originate from discontinuation of bone deposition/maturation. However, SCDs on imaging do not necessarily correlate with canal dehiscence syndrome and should therefore be interpreted carefully.

Superior canal dehiscence size: multivariate assessment of clinical impact

OBJECTIVE

To examine the association between dehiscence length in patients with superior semicircular canal dehiscence syndrome and their clinical findings, including objective audiometric and vestibular testing results.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

Patients included in this study were diagnosed with superior semicircular canal dehiscence syndrome and underwent surgical repair of the dehiscence through middle fossa craniotomy. The dehiscence length was measured intraoperatively in all cases.

MAIN OUTCOME MEASURES

Correlation between dehiscence length with pure-tone average (PTA), average bone-conduction threshold, maximal air-bone gap, cervical vestibular evoked myogenic potential thresholds, and presenting signs and symptoms.

RESULTS

The correlation between dehiscence length and maximal air-bone gap was statistically significant on both univariate and multivariate regression analyses. The correlations between dehiscence length and PTA, average bone-conduction threshold, cervical vestibular evoked myogenic potential threshold, and presenting signs and symptoms were not statistically significant.

CONCLUSION

The dehiscence length correlated positively with the maximal air-bone gap in patients with superior semicircular canal dehiscence. The correlation was statistically significant. The dehiscence length did not correlate with the other variables examined in this study.

Clinical factors associated with prolonged recovery after superior canal dehiscence surgery

OBJECTIVE

To identify clinical factors associated with prolonged recovery after superior canal dehiscence surgery.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary care academic medical center.

PATIENTS

Thirty-three patients that underwent surgery for SCDS were identified from a database of 140 patients diagnosed with SCD (2000-2010) at the Massachusetts Eye and Ear Infirmary (U.S.A.). The diagnosis of SCDS was based on clinical signs and symptoms, audiometric and vestibular testing and high-resolution temporal bone computed tomography.

INTERVENTION

For the primary repair, the superior canal was plugged in 31 patients through a middle fossa craniotomy approach and in 1 patient through a transmastoid approach. In 1 patient, the SCD was resurfaced through a middle fossa craniotomy approach.

MAIN OUTCOME MEASURES

Postoperative clinical signs and symptoms and factors that may influence duration of disequilibrium after surgery.

RESULTS

Thirty-three patients (15-71 yr; mean, 43 yr) underwent surgery for SCDS on 35 ears (2 bilateral). Mean follow-up was 28.7 months (range, 3 mo to 10 yr); 33 of 33 (100%) patients experienced initial improvement of the chief complaint. Three patients required revision surgery, improving symptoms in 2 patients. Six patients had dizziness lasting more than 4 months postoperatively, and all had bilateral SCD, migraines, and a dehiscence of 3 mm or greater.

CONCLUSION

Surgical plugging of SCD is an effective management option to provide long-term improvement of the chief complaint in SCDS patients. Patients with bilateral SCD, a history of migraines, and larger defects may be at risk of prolonged recovery and should be appropriately counseled.

Balance dysfunction and recovery after surgery for superior canal dehiscence syndrome

OBJECTIVE

To characterize (1) the impairment and recovery of functional balance and (2) the extent of vestibular dysfunction and physiological compensation following superior canal dehiscence syndrome (SCDS) surgical repair.

DESIGN

Prospective study.

SETTING

Tertiary referral center.

PARTICIPANTS

Thirty patients diagnosed as having SCDS.

INTERVENTIONS

Surgical plugging and resurfacing of SCDS.

MAIN OUTCOME MEASURES

Balance measures were assessed in 3 separate groups, each with 10 different patients: presurgery, postoperative short-term (<1 week), and postoperative long-term (≥6 weeks). Vestibular compensation and function, including qualitative head impulse tests (HITs) in all canal planes and audiometric measures, were assessed in a subgroup of 10 patients in both the postoperative short-term and long-term phases.

RESULTS

Balance measures were significantly impaired immediately but not 6 weeks after SCDS repair. All patients demonstrated deficient vestibulo-ocular reflexes for HITs in the plane of the superior canal following surgical repair. Unexpectedly, spontaneous or post-head-shaking nystagmus beat ipsilesionally in most patients, whereas contrabeating nystagmus was noted only in patients with complete canal paresis (ie, positive HITs in all canal planes). There were no significant deviations in subjective visual vertical following surgical repair (P = .37). The degree of audiometric air-bone gap normalized 6 weeks after surgery.

CONCLUSIONS

All patients undergoing SCDS repair should undergo a postoperative fall risk assessment. Nystagmus direction (spontaneous and post-head-shaking) seems to be a good indicator of the degree of peripheral vestibular system involvement and central compensation. These measures correlate well with the HIT.

Mutation analysis of Netrin 1 and HMX3 genes in patients with superior semicircular canal dehiscence syndrome

CONCLUSION

In spite of its absence in the control population, there is questionable evidence for the alteration c.114C->T in the HMX3 gene being implicated in the development of superior semicircular canal dehiscence (SSCD). However, the concept of a complex disease is valid for SSCD and a possible molecular origin can neither be confirmed nor excluded by the results of this study.

OBJECTIVES

SSCD was first described in 1998 by Minor et al. While the etiology is not clear, findings from both temporal bone CT and histologic studies suggest a congenital or developmental origin. In recent years, a couple of genes regulating inner ear morphogenesis have been described. Specifically, Netrin-1 and HMX3 have been shown to be critically involved in the formation of the SCC. Molecular alterations in these two genes might lead to a disturbed development of this canal and might represent an explanation for SSCD.

METHODS

DNA was extracted from whole blood of 15 patients with SSCD. The coding sequences of Netrin-1 and HMX3 were amplified by PCR and sequenced.

RESULTS

One sequence alteration, heterozygous c.114C->T (conservative change without alteration of amino acid) in exon 1 of HMX3, was detected in 2 of 15 patients but not in 300 control chromosomes. The study was supported in part by the Emilia-Guggenheim-Schnurr-Foundation, Basel, Switzerland.

Influence of aging and menopause in the origin of the superior semicircular canal dehiscence

OBJECTIVE

Determine if aging and menopause, known to be associated with bone resortion, also are associated with superior semicircular canal dehiscence.

DESIGN

Observational study.

SETTING

Study conducted in 3 tertiary Spanish hospitals.

PATIENTS

Nonselected consecutive patients of all ages.

INTERVENTIONS

Thin-section multi-detector row computed tomographic scan of the temporal bones.

MAIN OUTCOME MEASURE

The minimum thickness of the bone covering the roof of the superior semicircular canal (SSC) measured in each temporal bone. The outcome was studied both as a continuous and as a dichotomous variable: thin (<0.6 mm) and normal (≥ 0.6 mm).

RESULTS

Five hundred eighty-two ears of 312 patients were included in the study. Fifty-five percent of the sample were women. Patient's age ranged from 2 to 88 years. A 40-year age difference between ears was associated with a decreased thickness of bone covering the SSC of 0.10 mm, which is 10% of the average thickness of such bone. The thickness of the bone overlying the SSC of subjects younger than 45 years was an average of 1.14 mm (SD, 0.52 mm), whereas that of the subjects older than 45 years was equal to 1.02 mm (SD, 0.45 mm; p = 0.006). The percentage of ears with thin bone coverage of SSC was 7.1% in subjects younger than 45 years and 13.8% in those older than 45 years (p = 0.013).

CONCLUSION

Our data support the hypothesis that there is a slight osteopenia of the roof of the superior semicircular canal associated with aging, and this effect seems to be more pronounced in menopausal women.

Utility of cVEMPs in bilateral superior canal dehiscence syndrome

OBJECTIVES/HYPOTHESIS

To determine the utility of cervical vestibular evoked myogenic potential (cVEMP) thresholds in the surgical management of bilateral superior canal dehiscence syndrome (SCDS).

STUDY DESIGN

Retrospective review.

METHODS

We identified patients who underwent surgical treatment for SCDS from our database of 147 patients diagnosed with superior canal dehiscence (SCD) between 2000 and 2011 at our institution. The diagnosis of SCDS was based on clinical signs and symptoms, audiometric and cVEMP testing, and high-resolution computed tomography.

RESULTS

We identified 38 patients who underwent SCD surgery in 40 ears (2 bilateral). In seven patients with bilateral SCD, the more symptomatic ear had lower cVEMP thresholds, a larger air bone gap and a lateralizing tuning fork. In 13 patients with perioperative cVEMP testing, thresholds increased in 12 patients following primary repair, and no threshold shift was seen in one patient with persistence of symptoms after revision surgery. Audiometric data showed a significant mean decrease of the low-frequency air-bone gap and a mild (high-frequency) bone conduction loss after surgical repair.

CONCLUSIONS

We found that, 1) preoperative cVEMP thresholds, the magnitude of the air-bone gap and tuning-fork testing are important to confirm the worse ear in patients with bilateral SCD, 2) elevation of cVEMP thresholds following surgery correlates with improvement of symptoms and underscores the importance of postoperative testing in patients with bilateral disease or recurrence of symptoms and, 3) SCD plugging is associated with a partial closure of the air-bone gap and a mild (high-frequency) sensorineural hearing loss.

Surgical treatment of posterior semicircular canal dehiscence syndrome caused by jugular diverticulum

Objective:

We report a rare case of posterior semicircular canal dehiscence caused by a jugular diverticulum, and we describe its surgical treatment using a dehiscence resurfacing manoeuvre.

Method:

The clinical findings, surgical procedure and outcomes are presented.

Results:

A 66-year-old man presented with disequilibrium, sound-induced vertigo, a reduced ocular vestibular evoked myogenic potential threshold, and pressure-induced vertical and torsional nystagmus. Computed tomography revealed a right posterior semicircular canal dehiscence caused by a diverticulum of the jugular bulb. The defect in the posterior semicircular canal was localised and resurfaced with bone paté, temporalis muscle fascia and conchal cartilage, under direct visualisation. Post-operatively, the patient's symptoms disappeared and his ocular vestibular evoked myogenic potential threshold normalised.

Conclusion:

This case illustrates that posterior semicircular canal dehiscence can be surgically managed by resurfacing the defect site via a transmastoid approach.

Accuracy of computed tomography detection of superior canal dehiscence

HYPOTHESIS

High-resolution temporal bone computed tomography (CT) may erroneously demonstrate a superior semicircular canal dehiscence (SSCD) where none exists and inaccurately display the size of a dehiscence.

BACKGROUND

CT is an integral component of the diagnosis of SSCD. The prevalence of dehiscence as measured on computed tomographic scan is approximately eightfold higher than that on histologic studies, suggesting that CT may have a relatively low specificity for identifying canal dehiscence. This, in turn, can lead to an inappropriate diagnosis and treatment plan.

METHODS

We quantified the accuracy of CT in identifying a dehiscence of the superior semicircular canal in a cadaver model using microCT as a gold standard. The superior canals of 11 cadaver heads were blue lined. Twelve of the 22 ears were further drilled to create fenestrations of varying sizes. Heads were imaged using medical CT, followed by microCT scans of the temporal bones at 18-µm resolution. Diagnosis of dehiscence and measurements of dehiscence size were performed on clinical CT and compared with that of microCT.

RESULTS

Clinical CT identified 7 of 8 intact canals as dehiscent and tended to overestimate the size of smaller fenestrations, particularly those surrounded by thin bone.

CONCLUSION

These findings confirm that medical CT cannot be used as the exclusive gold standard for SSCD and that, particularly for small dehiscences on CT, clinical symptoms must be clearly indicative of a dehiscence before surgical treatment is undertaken. Preoperative counseling for small dehiscences may need to include the possibility that no dehiscence may be found despite radiologic evidence for it.

Transmastoid semicircular canal occlusion: a safe and highly effective treatment for benign paroxysmal positional vertigo and superior canal dehiscence

OBJECTIVES/HYPOTHESIS

Transmastoid occlusion of the superior semicircular canal in superior semicircular canal dehiscence (SSCD) syndrome and the posterior semicircular canal in intractable benign paroxysmal positional vertigo (BPPV) will produce resolution of preoperative symptoms.

STUDY DESIGN

Retrospective review, quality assurance.

METHODS

Sixteen patients with SSCD and 61 patients (65 ears) with intractable BPPV who underwent canal occlusion were reviewed. All patients underwent occlusion of the affected semicircular canal through a transmastoid approach.

RESULTS

Preoperative symptoms (vestibular, 13 patients; pulsatile tinnitus, 2 patients; or hyperacusis, 1 patient) were greatly improved or completely resolved in 15 of the 16 SSCD patients who underwent transmastoid occlusion of the superior canal. Hearing was preserved in 14 patients and improved in two patients. Vestibular symptoms were resolved in all intractable BPPV patients who underwent transmastoid occlusion of the posterior canal. One patient had a late recurrence of atypical BPPV. Almost all BPPV patients with normal preoperative hearing have an initial transient postoperative hearing loss, which when tested for is usually a mild to moderate mixed loss. Delayed sensorineural hearing loss was noted in three patients; one loss was profound whereas two were mild.

CONCLUSIONS

The transmastoid approach to canal plugging is successful in the treatment of symptoms in both SSCD and intractable BPPV, and is a familiar approach for the otologist. This is a viable alternative to the middle fossa approach for SSCD, thereby avoiding a craniotomy. Transmastoid is the definitive approach for posterior canal occlusion.

Comparison of ear-canal reflectance and umbo velocity in patients with conductive hearing loss: a preliminary study

OBJECTIVE

The goal of the present study was to investigate the clinical utility of measurements of ear-canal reflectance (ECR) in a population of patients with conductive hearing loss in the presence of an intact, healthy tympanic membrane and an aerated middle ear. We also sought to compare the diagnostic accuracy of umbo velocity (VU) measurements and measurements of ECR in the same group of patients.

DESIGN

This prospective study comprised 31 adult patients with conductive hearing loss, of which 14 had surgically confirmed stapes fixation due to otosclerosis, 6 had surgically confirmed ossicular discontinuity, and 11 had computed tomography and vestibular evoked myogenic potential confirmed superior semicircular canal dehiscence (SCD). Measurements on all 31 ears included pure-tone audiometry for 0.25 to 8 kHz, ECR for 0.2 to 6 kHz using the Mimosa Acoustics HearID system, and VU for 0.3 to 6 kHz using the HLV-1000 laser Doppler vibrometer (Polytec Inc, Waldbronn, Germany). We analyzed power reflectance |ECR| as well as the absorbance level = 10 × log10(1 - |ECR|). All measurements were made before any surgical intervention. The VU and ECR data were plotted against normative data obtained in a companion study of 58 strictly defined normal ears ().

RESULTS

Small increases in |ECR| at low-to-mid frequencies (400-1000 Hz) were observed in cases with stapes fixation, while narrowband decreases were seen for both SCD and ossicular discontinuity. The SCD and ossicular discontinuity differed in that the SCD had smaller decreases at mid-frequency (∼1000 Hz), whereas ossicular discontinuity had larger decreases at lower frequencies (500-800 Hz). SCD tended to have less air-bone gap at high frequencies (1-4 kHz) compared with stapes fixation and ossicular discontinuity. The |ECR| measurements, in conjunction with audiometry, could successfully separate 28 of the 31 cases into the three pathologies. By comparison, VU measurements, in conjunction with audiometry, could successfully separate various pathologies in 29 of 31 cases.

CONCLUSIONS

The combination of |ECR| with audiometry showed clinical utility in the differential diagnosis of conductive hearing loss in the presence of an intact tympanic membrane and an aerated middle ear and seems to be of similar sensitivity and specificity to measurements of VU plus audiometry. Additional research is needed to expand upon these promising preliminary results.

Imaging of ancient Egyptian mummies' temporal bones with digital volume tomography

The radiographic imaging of ancient Egyptian mummies has always been of great interest. Computed tomography is the method of choice to demonstrate bony pathologies with high quality. As digital volume tomography (DVT) is an extension of panoramic tomography with a very high resolution, its qualities were evaluated by examination of temporal bones of Egyptian mummy skulls. Ten Egyptian mummy skulls from the Zoological Collection Marburg, estimated 1,700-5,000 years of age, from Abydos, Philae, Theben-West and Sakkarah, were examined by DVT (3D Accuitomo, Morita, Japan). Through a rotation 360° of the X-ray source around the region of interest, a cylinder of 3 × 4 cm was captured as a three-dimensional volume. The gained data were analyzed with the help of special software on a PC. The angles of the axial, coronal and sagittal sections were arbitrarily changed to represent single structures with high resolution of 0.125 mm to analyze specific anatomical structures. In all skulls, conditions of the temporal bone and its anatomical structures were evaluated and normal as well as pathological findings evaluated in detail. The analysis of special landmarks such as the ossicular chain, cochlea, external, and internal auditory canal, facial nerve canal, and semicircular canals showed an intact ossicular chain in six temporal bones, while only isolated and dislocated ossicles were found in eight temporal bones. Besides one dehiscence of the superior semicircular canal in one temporal bone which might have led to vertigo and deafness at lifetime, all other findings were normal. Fragments of foreign bodies additionally found in the labyrinth, external ear canal and intracranially were attributed to postmortem damage. Digital volume tomography extends the imaging possibilities of CT for paleoradiological evaluation of temporal bones. With its high resolution, geometric accuracy, reconstruction capabilities, rapidness, and comparably low costs, even small bony pathologies are precisely demonstrated in a limited area. Investigations of larger numbers of specimen might reveal further details of ancient history for further interdisciplinary investigation of anthropologists, Egyptiologists, otolaryngologists, and radiologists.

Second-side surgery in superior canal dehiscence syndrome

OBJECTIVE

Bilateral superior canal (SC) dehiscence syndrome poses a challenge because bilateral SC dehiscence (SCD) plugging might be expected to result in oscillopsia and disability. Our aims were as follows: 1) to evaluate which symptoms prompted patients with bilateral SCD syndrome (SCDS) to seek second-side surgery, and 2) to determine the prevalence of disabling imbalance and oscillopsia after bilateral SC plugging.

STUDY DESIGN

Prospective observational study.

SETTING

Tertiary referral center.

PATIENTS

Five patients with bilateral SCDS based on history, audiometric and physiologic testing, and computed tomographic findings. This includes all of our patients who have had second-side plugging surgery to date.

INTERVENTION(S)

Bilateral sequential middle fossa craniotomy and plugging of SCs.

MAIN OUTCOME MEASURE(S)

Cochleovestibular symptoms, cervical and ocular vestibular-evoked myogenic potential testing, dizziness handicap inventory, short-form 36 Health Survey, dynamic visual acuity testing.

RESULTS

The most common symptoms prompting second-side surgery were sound- and pressure-induced vertigo and autophony. Three of the 5 patients reported that symptoms shifted to the contralateral ear immediately after plugging the first side, whereas in 2 patients, contralateral symptoms developed several years after the first SC plugging. Two of 4 patients experienced ongoing oscillopsia after bilateral SCDS surgery; however, all patients reported relief from their SCD symptoms and were glad that they had pursued bilateral surgery.

CONCLUSION

In patients with bilateral SCDS, sound- and pressure-induced vertigo most commonly prompted second-side surgery. Despite some degree of oscillopsia after bilateral SCDS surgery, patients were very satisfied with second-side surgery, given their relief from other SCDS symptoms.

Histopathology of the temporal bone in a case of superior canal dehiscence syndrome

OBJECTIVES

We describe the histopathologic findings in the temporal bones of a patient who had, during life, received a diagnosis of superior canal dehiscence (SCD) syndrome.

METHODS

The patient was found to have SCD syndrome at 59 years of age. She became a temporal bone donor, and died of unrelated causes at 62 years of age. Both temporal bones were prepared in celloidin and examined by light microscopy.

RESULTS

The patient developed bilateral aural fullness, pulsatile tinnitus, and difficulty tolerating loud noises after minor head trauma at 53 years of age. The symptoms were worse on the right. She also had Valsalva-induced dizziness and eye movements, as well as sound-induced dizziness (more prominent on the right). Audiometry showed a small air-bone gap of 10 dB in the right ear. Vestibular evoked myogenic potential testing showed an abnormally low threshold of 66 dB on the right, and a computed tomography scan showed dehiscence of the superior canal on the right. Histopathologic examination of the right ear showed a 1.4 x 0.6-mm dehiscence of bone covering the superior canal. Dura was in direct contact with the endosteum and the membranous duct at the level of the dehiscence. No osteoclastic process was evident within the otic capsule bone surrounding the dehiscence. The left ear showed thin but intact bone over the superior canal. Both ears showed focal microdehiscences of the tegmen tympani and tegmen mastoideum. The auditory and vestibular sense organs on both sides appeared normal. No endolymphatic hydrops was observed.

CONCLUSIONS

The findings were consistent with the hypothesis put forth by Carey and colleagues that SCD may arise from a failure of postnatal bone development, and that minor trauma may disrupt thin bone or stable dura over the superior canal.

Superior semicircular canal dehiscence: a possible pathway for intracranial spread of infection

Otogenic brain abscesses account for 31.4% of all cerebral abscesses: bone erosion due to coalescent otomastoiditis or cholesteatomas, osteothrombophlebitis, and hematogenous spreading are the most frequent pathways of infection. We briefly reported and discussed the first case of otogenic brain abscess due to infectious labyrinthitis that (likely) spread intracranially through a dehiscence of the superior semicircular canal.

Superior semicircular canal occlusion-Transmastoid approach

INTRODUCTION

The condition superior semi-circular canal dehiscence was first described by Minor et al. in 1998.

PRESENTATION OF CASE

We describe a novel surgical approach to the management of superior semicircular canal dehiscence. Our surgical technique involves a transmastoid rather than middle cranial fossa approach to the superior semicircular canal.

CONCLUSION

We conclude that the transmastoid approach, if anatomically feasible, carries significant advantages compared to middle cranial fossa craniotomy approach for the management of superior semicircular canal dehiscence.

Carotid artery-cochlear dehiscence: a review

This case report describes carotid-cochlear dehiscence, a rare and possibly fatal condition if missed or ignored on initial work-up of several otologic procedures. Thinning of the bony plate separating the carotid canal from other anatomic structures can occur anywhere along the course of the canal, including the carotid-cochlear bony plate. This condition should be recognized by all otolaryngologists in that it can mimic other otologic pathologies. The aim of this report was to call attention to this condition and its associated mimicking symptoms and inform on its proper management. The idea for this review was formed from the case of a patient who presented with pulsatile tinnitus and was found to have carotid-cochlear dehiscence. Carotid-cochlear dehiscence is a rare anatomic variation of which the neurotologic surgeon should be aware. This condition can mimic common otolaryngologic pathologies that regularly present themselves in clinical settings. We present what we believe to be the fourth reported case of carotid-cochlear dehiscence in the literature. The patient presented having only the complaint of pulsatile tinnitus and was later diagnosed with this rare condition. We advocate a thorough preoperative work-up, including high-resolution computed tomography and careful operative planning in a case-specific manner. This is especially important when common pathologies do not become apparent after careful investigation.

Superior semicircular canal dehiscence syndrome as assessed by oVEMP and temporal bone computed tomography imaging

To evaluate the role of oVEMP and multidetector CT scan in patients with superior canal dehiscence syndrome. Prospective study was conducted on nine patients with superior canal dehiscence syndrome (5 females, 4 males) age ranged 19-49 with mean age of 32.7 ± 9.3 years, complaining of intolerance to loud sounds and/or oscillopsia. The mean duration of illness was 18.7 ± 6.9 months, nine normal individuals as control (age and gender matched) were also included in the study. All of them underwent oVEMP and MDCT scan. Patients were of bilateral normal hearing sensitivity with no conductive impairment. All of the studied subjects (patients and controls) had identifiable contralateral oVEMP responses. MDCT scan showed dehiscence in all the patients. The dehiscence was unilateral (n = 7) and bilateral [n = 2 the other ear had a defect of 2 mm and thus was excluded from the study for fear or false diagnosis of Superior semicircular canal dehiscence syndrome (SCDS)]. Unlike the normal subject (nI = 0.94 µV ± 0.03 and pI = -0.42 µV ± 0.09), with stimulation of the affected side in SCDS, there were augmented amplitude responses (nI = 2.64 µV ± 0.35 and pI = -3.10 µV ± 0.44) in the eye contralateral to the stimulus "contralateral to the lesion". Mean oVEMP threshold for SCDS ears were 82.5 ± 7.55 dBnHL compared to 100 ± 5.77 dBnHL of the control ears. We concluded that combination of physiological and anatomical information from oVEMP and MDCT increased accuracy for diagnosis of dehiscence of superior semicircular canal.

[Sudden onset vertigo: imaging work-up]

Vertigo and dysequilibrium are a frequent cause of medical consultation. Clinical evaluation is essential. Some cases of vertigo are diagnosed clinically while others require imaging, sometimes emergently (suspected stroke). MRI is the imaging modality of choice to assess the labyrinth (labyrinthitis? labyrinthine hemorrhage?), internal auditory canal (vestibular schwannoma? other tumor?…) and brain parenchyma including all structures of the auditory pathways: vestibular nuclei, vestibulocerebellar tract, tracts involved with ocular motricity, vestibular cortex… Multiple central etiologies exist: stroke, multiple sclerosis, tumor… However, some etiologies are best depicted with CT, especially lesions of the labyrinth: cholesteatoma, trauma, suspected dehiscence of the superior semicircular canal, suspected labyrinthine fistula… Finally, imaging may be negative (Benign Paroxysmal Positional Vertigo, Meniere's disease, vestibular neuritis, migraine…), merely reducing the differential diagnosis.