Auditory Outcomes Following Transmastoid and Middle Cranial Fossa Approaches for Superior Semicircular Canal Dehiscence Repair

Patient Sex Mediates the Influence of Patient Age on Superior Canal Dehiscence Repair Outcome

OBJECTIVE

To investigate the independent and interactive effects of patient age and sex on superior canal dehiscence (SCD) repair outcomes.

METHODS

This was a cohort study of consecutive SCD repairs via the middle fossa approach at an institution between 2011 and 2022. We constructed multivariable regression models assessing surgical outcomes with age and sex as the primary predictors. Models controlled for surgery duration, follow-up duration, and relevant surgical and medical history. Subsequently, we repeated each model with the incorporation of an interaction term between patient age and sex.

RESULTS

Among 402 repairs, average age was 50 years, and 63% of cases were females. There was a significant interaction between patient age and sex with respect to symptom resolution score (SRS) (adj. β 0.80, 95% C.I. 0.04-1.56). Older age was associated with lower SRS among females (-0.84, -1.29 to -0.39 point per year) but not significantly associated with SRS among males (0.04, -0.65 to 0.56 point per year). Furthermore, older age independently predicted a greater magnitude of increase in air conduction at 8000 Hz following surgery regardless of sex (adj. β 2.1, 0.2-4.0 dB per 10-year increase).

CONCLUSIONS

This is the first study on the interactive effect between patient age and sex with respect to SCD repair outcomes. Older age predicted poorer symptomatic response among female patients but did not predict symptomatic response among male patients. Furthermore, older age predicted more severe high-frequency hearing loss following SCD repairs among both female and male patients.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:3363-3370, 2024.

Comparing Approaches for Repair of Superior Semicircular Canal Dehiscence

OBJECTIVE

Compare outcomes for subjects who underwent middle cranial fossa (MCF) or transmastoid (TM) repair of superior semicircular canal dehiscence (SSCD).

STUDY DESIGN

Retrospective cohort study.

SETTING

Quaternary-care, academic neurotology practice.

METHODS

Subjects who underwent MCF or TM repair of SSCD between December 1999 and April 2023 were identified. Main outcome measures included demographic data, length of surgery and hospital stay, clinical presentation, and audiometric testing.

RESULTS

Ninety-three subjects (97 ears) who underwent surgery for SSCD met inclusion criteria: 58.8% (57) via MCF, 39.2% (38) via TM, and 2.0% (2) via TM + MCF. Median operative time was shorter for the TM (35) compared to the MCF (29) approach (118 vs 151 minutes, P < .001). Additionally, median hospital stays were shorter for TM (36) compared to the MCF (56) approach (15.3 vs 67.7 hours, P < .001). Overall, 92% (49/53) of MCF and 92% (33/36) of TM surgeries resulted in an improvement or resolution of one or more symptoms (P = .84). There was no significant preoperative to postoperative change in the median air conduction pure-tone average (PTA), air-bone gap, or word recognition score in both the MCF and TM groups (P > .05). Improvements of >10 dB in the pre- to postoperative absolute change in bone conduction PTA were noted in 3 subjects in the MCF group and 4 subjects in the TM group (P = .49).

CONCLUSION

The TM approach for SSCD demonstrates shorter operative times and length of hospital stay. The TM and MCF approaches have comparable audiometric and clinical outcomes.

Narrowing of Low-Frequency Air-Bone Gap and Its Association with Symptom Resolution Following Superior Canal Dehiscence Repair

OBJECTIVE

Low-frequency air-bone gap (LABG) on pure tone audiometry is an expected clinical finding of superior canal dehiscence (SCD) syndrome. We investigate how narrowing of LABG following SCD repairs translates to symptom resolution.

STUDY DESIGN

Cohort study.

SETTING

Tertiary Care Center.

METHODS

We analyzed consecutive SCD repairs at an institution between 2012 and 2022. Pure tone audiometry and symptom questionnaires were administered pre- and post-operatively. The independent variable assessed whether the LABG narrowed (≥5 dB) following surgery. Outcome measures were rates of Overall Symptom Improvement (OSI, net resolution of ≥1 symptom) and Symptom Resolution Score (SRS, % symptoms resolved). We conducted multivariable regression analyses with LABG narrowing as the primary predictor. All models controlled for demographics, bilateral disease, prior ear surgery, and follow-up.

RESULTS

Among total of 217 repairs analyzed, 161 (74%) reached OSI, and mean SRS was 39 (out of 100). LABG narrowing at 250 Hz (65%), 500 Hz (52%), and 1000 Hz (47%) was associated with a 41-point (β 95% confidence interval [CI] 5-77) increase in auditory, 15-point (β 95% CI 1-30) increase in auditory, and 23-point (β 95% CI 2-45) increase in vestibular SRS, respectively. However, LABG narrowing was not significantly associated with the rates of auditory and vestibular OSI at all frequencies assessed.

CONCLUSION

Lack of LABG narrowing following repair was associated with the persistence of a greater proportion of preoperative symptoms but similar likelihood of OSI. This relationship was more prominent for auditory symptoms at 250 to 500 Hz and for vestibular symptoms at 1000 Hz. Additional research is warranted to elucidate the mechanism through which symptoms resolve despite LABG persistence.

Hearing Results after Transmastoid Superior Semicircular Canal Plugging for Superior Semicircular Canal Dehiscence: A Meta-Analysis

OBJECTIVE

The transmastoid plugging of a superior semicircular canal is considered a safe and effective technique for the management of superior semicircular canal dehiscence (SSCD). The aim of this meta-analysis is to assess the postoperative hearing outcomes after the transmastoid plugging of the superior semicircular canal. Search method and data sources: A systematic database search was performed on the following databases until 30 January 2023: MEDLINE, Embase, Cochrane Library, Web of Science, CINAHL, ICTRP, and clinicaltrials.gov. A systematic literature review and meta-analysis of the pooled data were conducted. We also included a consecutive case series with SCDS for those who underwent transmastoid plugging treatment at our clinic.

RESULTS

We identified 643 citations and examined 358 full abstracts and 88 full manuscripts. A total of 16 studies were eligible for the systematic review and 11 studies for the meta-analysis. Furthermore, 159 ears (152 patients) were included. The postoperative mean air conduction threshold remained unchanged (mean difference, 2.89 dB; 95% CI: -0.05, 5.84 dB, p = 0.58), while the mean bone conduction threshold was significantly worse (mean difference, -3.53 dB; 95% CI, -6.1, -0.95 dB, p = 0.9).

CONCLUSION

The transmastoid plugging technique for superior semicircular canal dehiscence syndrome, although minimally worsening the inner ear threshold, is a safe procedure in terms of hearing preservation and satisfactory symptom relief.

Audiometric Outcomes After the Middle Cranial Fossa Repair of Superior Semicircular Canal Dehiscence

OBJECTIVE

To evaluate the audiometric outcomes after the middle cranial fossa approach (MCF) for superior canal dehiscence (SCD) repair.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral center.

PATIENTS

SCD cases presented to a single institution between 2012 and 2022.

INTERVENTIONS

The MCF repair of SCD.

MAIN OUTCOME MEASURES

Air conduction (AC) threshold (250-8,000 Hz), bone conduction threshold (BC) (250-4,000 Hz), and air bone gap (ABG) (250-4,000 Hz) at each frequency, pure tone average (PTA) (500, 1,000, 2,000, 3,000 Hz).

RESULTS

Among 202 repairs, 57% were bilateral SCD disease and 9% had previous surgery on the affected ear. The approach significantly narrowed ABG at 250, 500, and 1,000 Hz. The narrowing of ABG was achieved by both decreased AC and increased BC at 250 Hz, but mediated primarily by increased BC at 500 Hz and 1,000 Hz. Among cases without previous ear surgery, mean PTA remained in the normal hearing range (mean: preop, 21 dB; postop, 24 dB) and clinically important hearing loss (PTA increased by ≥10 dB) after the approach was noted in 15% of cases. Among cases with previous ear surgery, mean PTA remained in the mild hearing loss range (mean: preop, 33 dB; postop, 35 dB) and clinically important hearing loss after the approach was noted in 5% of cases.

CONCLUSION

This is the largest study to date examining the audiometric outcomes after the middle cranial fossa approach for SCD repair. Findings of this investigation support that the approach is effective and safe with long-term hearing preservation for most.

Computed tomography approximated superior semicircular canal dehiscence size and location and their association with clinical presentation

OBJECTIVE

This study investigates the relationship of superior semicircular canal dehiscence (SSCD) size and location with patient symptomatology and audiometry.

METHODS

We retrospectively reviewed SSCD cases presented to a tertiary institution between 2011 and 2022. Dehiscence length and width measured on high-resolution temporal bone computed tomography imaging were used to calculate an approximate dehiscence area (ADA). Dehiscence location was classified employing a six-grade system. Multivariable regression analyses were performed with symptomatology and audiogram metrics as outcome variables and ADA and dehiscence location as the primary covariates of interest.

RESULTS

A total of 402 SSCD were included in the analysis. Controlling for patient age, sex, dehiscence laterality, and location, greater ADA was independently associated higher rates of autophony (aOR 1.39; 95% C.I. 1.14-1.71; P = 0.004) and hyper-amplification (aOR 1.39; 1.14-1.70; P = 0.004). Additionally, dehiscences with greater ADA exhibited significantly lower bone conduction threshold at 500 Hz (adjusted β -1.75, P = 0.006) and 1000 Hz (adjusted β -1.61, P = 0.018) and significantly wider air-bone gap at 500 Hz (adjusted β 2.22, P < 0.001) and 1000 Hz (adjusted β 1.00, P = 0.039). Dehiscence location was not independently associated with any outcome variable examined when accounting for dehiscence size.

CONCLUSION

The size of dehiscence is more independently related to clinical presentations than the anatomical location of the dehiscence in the superior semicircular canal. Greater dehiscence size is associated with symptomatology and audiometry consistent with more severe bone conduction hyperacusis.

New model of superior semicircular canal dehiscence with reversible diagnostic findings characteristic of patients with the disorder

Background

Third window syndrome is a vestibular-cochlear disorder in humans in which a third mobile window of the otic capsule creates changes to the flow of sound pressure energy through the perilymph/endolymph. The nature and location of this third mobile window can occur at many different sites (or multiple sites); however, the most common third mobile window is superior semicircular canal dehiscence (SSCD). There are two essential objective diagnostic characteristics needed to validate a model of SSCD: the creation of a pseudoconductive hearing loss and cVEMP increased amplitude and decreased threshold.

Methods

Adult Mongolian gerbils (n = 36) received surgical fenestration of the superior semicircular canal of the left inner ear. ABR and c+VEMP testing were carried out prior to surgery and over acute (small 1 mm SSCD, 1-10 days) or prolonged (large 2 mm SSCD, 28 days) recovery. Because recovery of function occurred quickly, condenser brightfield stereomicroscopic examination of the dehiscence site was carried out for the small SSCD animals post-hoc and compared to both ABRs and c+VEMPs. Micro-CT analysis was also completed with representative samples of control, day 3 and 10 post-SSCD animals.

Results

The SSCD created a significant worsening of hearing thresholds of the left ear; especially in the lower frequency domain (1-4 kHz). Left (EXP)/right (CTL) ear comparisons via ABR show significant worsening thresholds at the same frequency representations, which is a proxy for the human pseudoconductive hearing loss seen in SSCD. For the c+VEMP measurements, increased amplitude of the sound-induced response (N1 2.5 ms and P1 3.2 ms) was observed in animals that received larger fenestrations. As the bone regrew, the c+VEMP and ABR responses returned toward preoperative values. For small SSCD animals, micro-CT data show that progressive osteoneogenesis results in resurfacing of the SSCD without bony obliteration.

Conclusion

The large (2 mm) SSCD used in our gerbil model results in similar electrophysiologic findings observed in patients with SSCD. The changes observed also reverse and return to baseline as the SSCD heals by bone resurfacing (with the lumen intact). Hence, this model does not require a second surgical procedure to plug the SSCD.