Predictive Factors for Concurrent Tegmen Dehiscence in Superior Canal Dehiscence Syndrome

A novel perspective on geniculate ganglion fossa: Cone beam computed tomography analysis of pneumatization and dehiscence

OBJECTIVE

This study aimed to analyze the prevalence and patterns of geniculate ganglion fossa (GGF) pneumatization, as well as the dehiscence and thickness of its tegmen, while evaluating their anatomical correlations. The assessment was conducted using two coronal planes aligned with the histological division of the GGF.

METHODS

Seventy cone-beam computed tomography (CBCT) scans (140 sides) were analyzed. Two coronal planes through the GGF were used, based on its histology: an anterior plane through the ganglion and a posterior plane through the facial nerve fibers. Pneumatization was assessed by identifying air cells within a 2 mm range of the GGF, examining its superior, lateral, medial, and inferior walls, and classifying the pneumatization patterns. The GGF tegmen dehiscence was evaluated in both planes and categorized as intact, partial, or total. Based on combined findings, five dehiscence types were defined, ranging from type 1 (no dehiscence) to type 5 (complete dehiscence in both coronal planes). The classification reflects the progressive extent of tegmen dehiscence across these planes.

RESULTS

Type 1 (intact GGF tegmen) was the most common, observed in 47.1 % of cases, while partial dehiscence (types 2-4) and complete dehiscence (type 5) were found in 39.3 % and 13.6 % of cases, respectively. Pneumatization was predominantly lateral (95 %), corresponding to the epitympanum, while superior pneumatization within the GGF tegmen occurred in 33.6 % of cases. Circumferential pneumatization, involving all GGF walls, was very rare (1 case, left side). Superior pneumatization correlated with a significantly greater mean GGF tegmen thickness compared to non-pneumatized cases (2.6 ± 1.3 mm vs. 1.2 ± 0.7 mm). GGF tegmen dehiscence did not significantly influence tegmen tympani dehiscence (prevalence of 72.9 %), indicating no clear association.

CONCLUSION

Assessing GGF morphology in anterior and posterior planes, thus correlated with the histological division of its neural content, can enhance preoperative planning and help predict and minimize surgical risks in this complex and delicate region.

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.

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.

Association of the superior semicircular canal and tegmen tympani dehiscences and its relationship with the pneumatisation of the temporal bone

PURPOSE

To analyse the degree of pneumatisation of the temporal bone when there is an association between dehiscence of the superior semicircular canal and dehiscence of the tegmen tympani.

MATERIALS AND METHODS

We analysed a retrospective CT study of 124 selected cases. A single inclusion criterion was applied: the presence of a dehiscence of the tegmen tympani. On the other hand, the degree of temporal pneumatisation was assessed by axial and coronal planes, and has been divided into the following grades O, I, II and III, according to the status and relationship of the mastoid, the bony labyrinth, the petrous segment of the carotid canal and sigmoid sinus.

RESULTS

Of the 124 cases studied, 35 (28.2%) presented both dehiscences. In 26 of the 35 (47.3%), grade II pneumatisation, 4 (14,8%), grade I, and 5 (11,9%) grade III was observed, with a statistically significant relationship (p < 0.001). On the other hand, we did not find a significant relationship when relating both dehiscences in any age or sex group. However, when relating the degree of pneumatisation to sex, among those with grade III pneumatisation, the proportion of men (52.4%) was significantly higher than that of women (47.6%) (p = 0.017).

CONCLUSION

We have detected a statistically significant relationship between the coexistence of grade II pneumatisation and the presence of both dehiscences in the temporal bone.

Matched Cohort Study of Radiographic Superior Semicircular Canal Dehiscence and Tegmen Dehiscence and Obstructive Sleep Apnea

OBJECTIVE

To report the frequency of radiographic superior semicircular canal dehiscence (SSCD) and tegmen dehiscence in patients with and without obstructive sleep apnea (OSA).

STUDY DESIGN

Retrospective matched cohort study.

SETTING

Tertiary care center.

PATIENTS

Adults with OSA and fine-cut computed tomographic scans including the temporal bone were matched to patients without OSA by age, sex, and type of computed tomography (protocol, scanner type, slice thickness). Ears with otologic surgery or temporal bone tumors were excluded.

MAIN OUTCOME MEASURES

Prevalence of SSCD and tegmen dehiscence assessed by two independent reviewers.

RESULTS

The average body mass index of the OSA patients was 29.2 kg/m 2 with an average apnea-hypopnea index of 36.8. The control group had an average body mass index of 26.2 kg/m 2 . Of the 352 temporal bones, 34 (9.7%) had SSCD in the OSA cohort versus 37 (10.5%) in the control group ( p > 0.05). Seven OSA patients (25.6% of those with SSCD) had bilateral SSCD versus 8 controls (27.6% of those with SSCD; p > 0.05). The majority (87.3%) of dehiscences involved the temporal lobe, with the remaining involving the superior petrosal sinus or both. Of the 352 OSA ears, 90 (25.6%) had a tegmen dehiscence versus 95 (27.0%) in the control group ( p > 0.05). Neither group had a laterality preference for SSCD or tegmen dehiscence.

CONCLUSION

The prevalence of radiographic SSCD and tegmen dehiscences in OSA patients does not significantly differ from age- and sex-matched controls. This is in contrast to a previous case-control study finding patients with symptomatic SSCD to have higher rates of OSA. This may suggest that the effect size of OSA on SSCD prevalence may be limited despite OSA being a risk factor for elevated intracranial pressure.