Using temporal bone computed tomography to predict sensorineural hearing loss in otic capsule-sparing temporal bone fracture

Improved Prediction of Hearing Loss after Temporal Bone Fracture by Applying a Detailed Classification for Otic Capsule-Violating Fracture: A Wide Scope Analysis with Large Case Series

INTRODUCTION

This study aimed to analyze the predictability of temporal bone (TB) fracture-associated hearing loss by applying a detailed classification separating individual injury of the cochlea, vestibule, and semicircular canals (SCC).

METHODS

In this retrospective study, patients with otic capsule-violating (OCV) fractures were further classified as OCV-C(VS) when the cochlea was involved regardless of vestibule or SCC involvement, OCV-V(S) when the vestibule was involved regardless of SCC involvement, and OCV-S when the fracture only involved SCC. Hearing changes were compared by applying the above-mentioned classification, and TB fracture-induced facial palsy was also analyzed.

RESULTS

A total of 119 patients were included. Patients with OCV fractures had significantly worse bone conduction (BC) and air conduction (AC) thresholds (59.1 ± 25.3 and 87.0 ± 29.5 dB) than those with otic capsule-sparing (OCS) fractures (20.1 ± 17.9 and 36.5 ± 21.9 dB; p < 0.001 for each comparison). The BC and the AC thresholds of OCV-C(VS) (77.5 ± 11.0 and 114.2 ± 14.3 dB) and OCV-V(S) (69.3 ± 27.7 and 98.0 ± 22.2 dB) were significantly higher than OCV-S (40.1 ± 22.9 and 62.1 ± 25.6 dB; p < 0.001 for each comparison). The BC hearing thresholds were not significantly improved in the last pure tone audiometry when compared for total, OCV, or OCS cases. The AC threshold significantly improved in OCS cases. In a considerable number of cases with facial palsy, causative fracture lines involved the geniculate ganglion or tympanic segment without the involvement of the otic capsule. Most cases showed significant improvement; however, recovery was limited in cases with obvious fallopian canal disruption.

CONCLUSIONS

The cases with sole involvement of SCC had significantly better hearing thresholds than those with cochlear or vestibule involvement, even in OCV fracture cases.

Clinical-radiological Correlation in Temporal Bone Fractures

INTRODUCTION

The diagnosis of temporal bone fractures (TBF) is based on radiological imaging. The most widely used classification divides fractures into longitudinal, transverse, and mixed. In recent years, other classifications have emerged to better predict clinical manifestations.

OBJECTIVES

To review computed tomography (CT) images of TBF, define their radiological pattern, and study the concordance of the observed findings with those described in the radiological report. To analyse the association between fracture types and clinical findings. To study the impact of mastoid pneumatization on fracture characteristics.

METHODS

Retrospective study of 110 TBF diagnosed with CT between January 2016 and May 2019.

RESULTS

Fifty-two transverse (47%), 34 longitudinal (30%), and 19 mixed fractures (17%) were identified with good interobserver agreement (k = .637). Longitudinal fractures were associated with conductive hearing loss (P < .001) and transverse fractures with sensorineural hearing loss (P = .005). Of the fractures, 8.2% showed involvement of the otic capsule, and were associated with sensorineural hearing loss (P < .001), facial paralysis (P = .019) and vertigo (P= .035). Fractures were more frequent in cases of greater pneumatization, and the involvement of the otic capsule in cases of very good pneumatization (P = .024).

CONCLUSIONS

The traditional classification of TBF is reproducible. Its association with clinical findings improves when the involvement of the otic capsule is also analysed. Mastoid pneumatization is not a protective factor for TBF or for involvement of the otic capsule.

Traumatic dislocation of middle ear ossicles: A new computed tomography classification predicting hearing outcome

Objectives

To assess the feasibility of radiologic measurements and find out whether hearing outcome could be predicted based on computer tomography (CT) scan evaluation in patients with temporal bone fractures and suspected ossicular joint dislocation.

Methods

We assessed 4002 temporal bone CT scans and identified 34 patients with reported ossicular joint dislocation due to trauma. We excluded those with no proven traumatic ossicular dislocation in CT scan and patients with bilateral temporal bone fractures. We measured four parameters such as malleus-incus axis distance, malleus-incus angle at midpoints, malleus- incus axis angle and ossicular joint space. The contralateral healthy side served as its own control. Hearing outcome 1–3 months after the index visit was analyzed. We assessed diagnostic accuracy and performed a logistic regression using radiologic measurement parameters for outcome prediction of conductive hearing loss (defined as >20dB air-bone gap).

Results

We found excellent inter-rater agreement on the measurement of axis deviation between incus and malleus in CT scans (interclass correlation coefficient 0.81). The larger the deviation of incus and malleus axis, the higher probability of poor hearing outcome (odds ratio (OR) 2.67 per 0.1mm, p = .006). A cut-off value for the axis deviation of 0.25mm showed a sensitivity of 0.778 and a specificity of 0.94 (p < .001) for discrimination between poor and good hearing outcome in terms of conductive hearing loss.

Conclusion

Adequate assessment of high resolution CT scans of temporal bone in which ossicular chain dislocation had occurred after trauma was feasible. Axis deviations of the incus and the malleus were strongly predictive for poor hearing outcome in terms of air conduction 1–3 months after trauma. We propose a 3-level classification system for hearing outcome prediction based on radiologic measures.

The potential protective effects of temporal bone pneumatization: A shock absorber in temporal bone fracture

Objectives

We hypothesize that when temporal bone fractures occur, the pneumatic cells in the temporal bone are able to absorb most of the impact force during a traumatic event. This study aims to correlate the degree of pneumatization of the temporal bone with the severity of temporal bone fracture (TBF).

Methods

Charts and computed tomography scans representing 54 TBFs, diagnosed from 2012 to 2017 at a single tertiary hospital, were retrospectively reviewed. Temporal bone pneumatization (TBP) in the petrous apex and mastoid region was evaluated using previously published classification systems. TBP classifications and fracture types were correlated with TBF complications such as sensorineural hearing loss (SNHL), facial nerve palsy (FNP), and vestibular dysfunction.

Results

Patients with increased pneumatization of the temporal bone had significantly fewer and less severe SNHL. SNHL more strongly correlated with the degree of pneumatization in the mastoid (P = 0.005) than that in the petrous apex (P = 0.024). On the other hand, the degree of TBP correlated poorly with FNP and vestibular dysfunction. However, the mastoid hypopneumatization demonstrated significant correlation with otic-capsule violations (P = 0.002). Fractures with otic-capsule violation were 4 times more likely to have vestibular dysfunction (P = 0.043) and 3 times more likely to have SNHL (P = 0.006). FNP was not associated with otic-capsule violating fractures but was 3.5 times more common in comminuted fractures (P = 0.025).

Conclusions

The degree of temporal bone pneumatization was negatively correlated to the incidence of otic-capsule violation and the severity of hearing impairment in patients with temporal bone fracture. This study substantiated the potential protective effect of temporal bone pneumatization in TBFs.