Radiological parameters related to success of the round window approach in cochlear implantation: A retrospective study

Innovative computed tomography based mapping of the surgical posterior tympanotomy: An exploratory study

Robotic devices have recently enhanced cochlear implantation by improving precision resulting in reduced intracochlear damage during electrode insertion. This study aimed to gain first insights into the expected dimensions of the cone-like workspace from the posterior tympanotomy towards the round window membrane. This retrospective chart review analyzed ten postoperative CT scans of adult patients who were implanted with a CI in the past ten years. The dimensions of the cone-like workspace were determined using four landmarks (P1-P4). In the anteroposterior range, P1 and P2 were defined on the edge of the bony layer over the facial nerve and chorda tympani nerve, respectively. In the inferosuperior range, P3 was defined on the bony edge of the incus buttress and P4 was obtained at a distance of 0.45 mm between the facial nerve and the chorda tympani nerve. After selecting the landmarks, the calculations of the dimensions of the surgical access space were done in a standardized coordinate system and presented using descriptive statistics. The cone-like space is limited by two maximal angles, α and β. The average angle α of 19.84 (±3.55) degrees defines the angle towards the round window membrane between P1 and P2. The second average angle β of 53.56 (±10.29) degrees defines the angle towards the round window membrane between P3 and P4. Based on the angles the mean anteroposterior range of 2.25 (±0.42) mm and mean inferosuperior range of 6.73 (±2.42) mm. The distance from the posterior tympanotomy to the round window membrane was estimated at 6.05 (±0.71) mm. These findings present data on the hypothetical maximum workspace in which a future robotically steered insertion tool can be positioned for an optimal automated electrode insertion. A larger sample size is necessary before generalizing these dimensions to a population. Further research including preoperative CT scans is needed for planning robotic-steered cochlear implantation.

Round Window Visibility in Cochlear Implantation : Pre-operative Prediction Using Various Radiological Parameters

Purpose

The round window approach has become the most preferred route for electrode insertion in cochlear implant surgery; however, it is not possible at times due to difficult round window membrane (RWM) visibility. Our study aims to investigate the relationship between preoperative radiological parameters and the surgical visibility of the RWM in Cochlear implant patients.

Methodology

A prospective cross-sectional study of 31 patients, age < 6 years, with bilateral severe to profound sensorineural hearing loss was conducted at a tertiary care hospital. The preoperative HRCT temporal bone scan was studied, and the parameters evaluated were facial nerve location, facial recess width, and RWM visibility prediction. All patients were operated on via the posterior tympanotomy. The surgical RWM visibility was done after optimal drilling of the posterior tympanotomy recess. The relationship between the radiological parameters and surgical visibility of RWM was evaluated.

Results

The difference in the facial nerve location as per the type of RWM was found to be significant (p value < 0.05). However, the facial recess width was not significantly associated with RWM visibility. The radiological prediction of RWM visibility by tracing the prediction line over RWM was significantly associated with intraoperative RWM visibility.

Conclusion

The goal to look for preoperative scans is to predict the ease or difficulty of RWM visibility during surgery. The difficult visualization of the RWM, can result in dire intraoperative consequences. A comprehensive understanding of preoperative radiological parameters, coupled with meticulous surgical planning, is crucial to address these challenges effectively by focusing on enhancing RWM visualization.

The feasibility of cochlear implantation in early infancy

OBJECTIVES

To determine the key image anatomical parameters that are relevant to cochlear implantation (CI) using temporal bone high-resolution computed tomography (HRCT) scans and to identify age group differences in order to provide image anatomical support for early CI.

METHODS

The data of 346 temporal bone HRCTs of 173 children from 5 months to 18 years of age were retrospectively selected and reviewed. Parameters of the human temporal bone that are relevant to CI key surgical steps include mastoid thickness (MT), the facial recess width (FRW), and an angle representing the round window visibility. All measurements are performed on axial images.

RESULTS

There was no significant difference in the above morphological values by gender (p > 0,05). Two-sided FRW was not significantly different (p > 0,05), but MT and angle A were significantly different (p < 0,001). FRW and angle were independent of age (p > 0,05). However, MT had been found to exhibit postnatal development. The linear function of MT were calculated as y = 2463 × group(s) + 20,574 (p < 0,001).

CONCLUSIONS

Based on preoperative imaging analysis at different ages, middle ear development was stable at 5 months of age, allowing early CI in infancy with severe to severe hearing loss at this age. These data must be considered exploratory and more extensive clinical studies are needed.

Pneumolabyrinth as an Early Computed Tomographic Finding After Cochlear Implantation and its Clinical Significance

OBJECTIVE

To determine the incidence and volume of pneumolabyrinth using early temporal bone computed tomography (TBCT) findings and evaluate the correlation between pneumolabyrinth and various clinical variables.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary academic center.

PATIENTS

Fifty-three consecutive adult cochlear implantation (CI) recipients (53 ears) with normal inner ears who underwent high-resolution TBCT within 3 days after CI were included.

INTERVENTION

Axial TBCT images were used for detection and measurement of pneumolabyrinth.

MAIN OUTCOME MEASURES

Incidence and volume of pneumolabyrinth were evaluated. In addition, the following clinical variables were analyzed to evaluate the correlation with pneumolabyrinth volume: demographics, implant type, surgical approach, postoperative dizziness, and preservation of functional residual hearing.

RESULTS

Pneumolabyrinth was present in all patients, and the average volume was 8.496 mm3. Pneumolabyrinth was confined to the cochlea (pneumocochlea) in all patients except for one who also had pneumovestibule. The pneumolabyrinth volume in patients with postoperative dizziness was significantly larger than that in patients without postoperative dizziness (10.435 mm3 vs. 8.016 mm3; p = 0.029). Multivariate analysis showed that a larger volume of pneumolabyrinth was significantly associated with postoperative dizziness (odds ratio, 1.420; 95% confidence interval, 1.114-1.808; p = 0.005).

CONCLUSION

A certain volume of pneumolabyrinth was always present in the early stage after CI, and the volume of pneumolabyrinth measured using early TBCT findings was significantly associated with the occurrence of postoperative dizziness.

Round window anatomy predicts ease of cochlear implantation in children

OBJECTIVES

We aim to evaluate the utility of the Round Window Angle (RWA) as a predictor of difficulty and operative time in cochlear implantation.

METHODS

A retrospective study of pediatric patients that underwent cochlear implantation and CT temporal bone imaging from January 2008 to November 2019. Correlation, univariate, and multivariate analysis were conducted.

RESULTS

347 implantations met inclusion criteria. We found a difference in RWA for difficult (median: 101°, n = 5) and non-difficult (median: 74, n = 317) implantations (p < 0.0001). There was also a difference in RWA in patients with round windows visualized intra-operatively (p < 0.0197). When controlling for age and intraoperative round window visualization, logistic regression showed RWA was significantly associated with difficult insertion (OR: 1.687; p = 0.0246). Further, there was positive correlation between RWA and operative time (r = 0.1779, p = 0.0013) with patients with acute RWAs having shorter operative times (mean 115.7 ± 32.1 min) than those with obtuse RWA (mean 183.5 ± 97.0 min) (p = 0.0035). When accounting for surgeon and patient age, multivariate linear regression showed round window visualization (β = 3.456, p = 0.0006) and obtuse RWA (β = 6.172, p < 0.0001) was associated with an increase in operative time.

CONCLUSION

Further research is needed to identify difficult cochlear implantations to increase the success and reduce risks associated with the surgery. Our study reports the possibility that an obtuse RWA both significantly increases difficulty and time of operation due to decreased round window visualization.

Preimplant Hearing Threshold: An Important Predictor of Hearing Preservation in Cochlear Implantation With Lateral Wall Electrodes

OBJECTIVE

To evaluate the outcomes and association factors of long-term hearing preservation (HP) in cochlear implantation with lateral wall (LW) electrode arrays.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary academic center.

PATIENTS

Thirty-four consecutive ears from 32 patients with a ≤ 80 dB HL preoperative low-frequency pure-tone average of 250 to 500 Hz were included.

INTERVENTION

Cochlear implantation with LW electrode arrays and the intention of achieving HP.

MAIN OUTCOME MEASURES

HP classifications according to the HEARRING group and functional HP methods (≤ 85 dB HL of pure-tone threshold at 250 Hz) at 1 year postoperatively.

RESULTS

Based on the HEARRING classification, complete, partial, and minimal HP was achieved in 7 ears (21%), 12 ears (35%), and 4 ears (12%), respectively. Under functional classification, 14 ears (41%) exhibited functional hearing after surgery. The average threshold shift was 17.1 dB HL (SD = 16.9 dB HL). Among various clinical features, a ≤ 60 dB HL preimplant pure-tone threshold of 250 Hz was associated with HP outcome in both classifications (OR = 12.95, 95% CI = 1.29-130.01, p = 0.029 in HEARRING classification; OR = 14.36, 95% CI = 1.07-191.40, p = 0.044 in functional classification). The following parameters were not associated with HP (p > 0.05): patient demographics, surgical aspects (insertion route and depth), electrode array size, scalar electrode position, and presence of comorbidity.

CONCLUSION

With LW electrode arrays, HP was achieved in 68% of HEARRRING group patients and 41% of functional classification patients. A ≤ 60 dB HL preimplant pure-tone threshold of 250 Hz was significantly associated with an increased rate of long-term HP.

Combined preoperative HRCT parameters for prediction of round window visibility in pediatric cochlear implant patient

OBJECTIVE

To evaluate the add value of combined analysis of high resolution computed tomography (HRCT) temporal bone parameters in accurate prediction of round window (RW) visibility through posterior tympanotomy.

PATIENTS AND METHODS

a retrospective observational study was held in a tertiary center, conducted on 45 cochlear implant pediatric candidates between January 2017 and September 2019. Candidates were referred for CT temporal bone. They were classified into fully visible RW cases and partially or non-visible RW cases. Radiological measurements were compared between the two groups for prediction of RW visibility separate and in combination.

RESULTS

45 patients were included in the study (26 males (57.8%) and 19 females (42.2%)). Their median age was 4 years (2-12 years). There were 38 (84.4%) fully visible and 7 (15.6%) partially or non-visible RW cases. Kashio posterior line (n:32/3), fascial recess width (FRW) (mean: 4.9 (3.5-7.5)/4.2 (4-4.7) mm) and round window location (RWL) (3 (1-4)/2.8 (1-3)mm) measurements significantly differentiated between the two groups; (P value 0.034, 0.012 & 0.025 respectively). Posterior kashio line and cut off values of ≥4.75 mm of FRW & 2.95 mm of RWL were showed sensitivity 84.2%, 63.2% & 65.8%, and accuracy 80%, 68.9% &68.9% in prediction of RW visibility respectively. Combination of Kashio prediction line with cut off value ≥ 7.45 mm (sum of FRW & RWL) showed P value 0.003 with further improve in the sensitivity and overall accuracy in prediction of RW visibility from 84.2% to 80% up to 91.4% and 88.6% respectively.

CONCLUSION

combined parameters using Kashio line with FRW and RWL increases sensitivity and overall accuracy in prediction of RW visibility rather than single parameter.