Keywords
cochlear implant - imaging - HRCT - MRI - temporal bone - Veria technique - basal
turn angle
Introduction
Inner ear hearing loss is the second most prevalent chronic disease worldwide after
arthritis. Incidence of sensorineural hearing loss (SNHL) in adult population of western
nations is almost 15%.[1] The prevalence of deafness in Southeast Asia ranges from 4.6 to 8.8%. In India,
63 million people (6.3%) suffer from significant auditory loss. Nationwide disability
surveys have estimated that hearing loss is the second most common cause of disability.
Cochlear implant is surgically implanted electronic device that provides a sense of
sound to a person who is profoundly deaf or severely hard of hearing in both ears.
Cochlear implantation has become an accepted treatment for severe to profound deafness
in patients who derive only minimal benefit from conventional amplification. In India,
although the number of children having bilateral SNHL is high, still cochlear implantation
is not commonly done due to the high costs for the implant, as well as subsequent
speech therapy.[2] It is important to be familiar with the various available imaging options and with
findings that could significantly impact or even preclude implantation. High-resolution
computed tomography (HRCT) and magnetic resonance imaging (MRI) are regularly used
for cochlear implant preoperative evaluation for the evaluation of inner ear malformations,
surgical planning, and to prevent intraoperative complications. In this study, we
have discussed the various anatomical details of middle and inner ear by both CT and
MRI in patients having bilateral SNHL which have an important role and are used as
a guide during the surgery as well as prevent complications in cochlear implantation
by Veria technique.
Objectives
-
To determine the various radiological measurements through high-resolution imaging
(CT and MR) for cochlear implantation candidacy.
-
Association between imaging findings and the level of difficulty encountered during
surgery by Veria technique.
Materials and Methods
Prospective study was conducted in a tertiary care center in North India from July
2015 to December 2017. A total of 55 patients were included in the study. After approval
from institutional ethic committee, informed consent was taken from the patients.
HRCT temporal bone and MRI head was done in cochlear implant candidates.
Inclusion Criteria
A prime candidate for inclusion is described as:
-
Age 1 to 5 years for prelingual and > 1 year for postlingual and perilingual.
-
Having severe to profound SNHL in both ears.
-
Family willing to work toward speech and language skills with therapy.
Exclusion Criteria
The exclusion criteria were: eMedically unfit for surgery.
Imaging Protocol
HRCT temporal bone and MRI images were evaluated in axial planes reconstructed parallel
to the long axis of the lateral semicircular canals (SCCs). Coronal and sagittal sections
were viewed perpendicular to the plane of the axial images. Imaging of pediatric population
was performed under sedation or short-acting general anesthesia and both CT scan and
MRI was done under single sedation.
HRCT Temporal Bone Protocol
64-detector row CT scanner (Brilliance 190 P 64; Phillips Medical Systems, Netherlands)
was used for all HRCT investigations. The patient lay in supine position. No gantry
tilt was used to facilitate free reconstructions of the images. All the images was
reviewed with a high-resolution bone algorithm for separate documentation of the right
and left ears. Axial images were obtained from the apex of the petrous bone to the
inferior tip of the mastoid. Coronal reformatted images were obtained from the anterior
margin of the petrous apex to the posterior margin of the mastoid. On a multidetector
CT scanner, the raw axial image data set was reconstructed with a section thickness
of as low as 0.3 mm with bone windows setting. Low-dose CT scan could have been performed
but because of the dense petrous bone and high-resolution requirement, quality of
images would have been compromised. No contrast injection was given.
MRI Protocol
In the same session, all patients underwent MRI on 3T MR scanner (Signa HDXT, GE Healthcare,
United States) by using head coil. Patients were positioned in the supine position
with head in the head coil and 3-plane localizer was obtained. Axial scanning was
performed from vertex to the line of foramen magnum in a plane parallel to the anterior
and posterior margin of corpus callosum (AC-PC line). Routine brain sequences were
acquired to display any brain pathology and central acoustic pathway anatomy from
the cochlear nuclei to the temporal acoustic area. Axial T2-weighted PROPELLAR was
done with the following parameters: TR/TE/, 5600/95.5/Ef; NEX, 1; slice thickness,
5 mm; gap, 0.5; matrix, 320 × 320; field of view (FOV), 24 cm. Axial T1-weighted fluid-attenuated
inversion recovery (FLAIR) sequence was done with the following parameters: TR/TE/,
1254/11.6/Ef; NEX, 1; slice thickness, 5 mm; gap 0.5; matrix,512 × 256; FOV, 24 cm.
Axial T2 FLAIR sequence was taken with the following parameters: TR/TE/, 8802/85.4/Ef;
NEX, 1; slice thickness, 5 mm; gap, 0.5; matrix, 256 × 160; FOV, 24 cm. Axial diffusion-weighted
1 sequence was used with the following parameters: TR/TE/, 5600/72.4/FE; NEX, 1; slice
thickness, 5 mm; gap, 0.5; matrix, 128 × 160; FOV, 24 cm. In addition to above sequences,
following specific MRI protocol was used for evaluation of inner ear anatomy and cochlear
nerve. Axial three-dimensional (3D) fast imaging enabling steady-state acquisition
(FIESTA) sequence (TR/TE/, 4.8/1.8/Fr; NEX, 2; slice thickness, 1 mm; gap,–0.5 overlapping;
matrix, 320 × 256; FOV, 20 cm) was performed to cover internal auditory canal (IAC)
from hippocampus up to the C-1 vertebral body. Oblique sagittal reformations were
done along the plane perpendicular to the course of the seventh and eighth nerves
in the IAC and cerebellopontine angle with 3D maximum intensity projection reconstructions.
A 3D FIESTA sequence was also acquired in a coronal plane parallel to the line along
the right and left IAC to cover the IAC from posterior wall of sphenoid sinus up to
the line of fourth ventricle. Postcontrast sequence was not needed. The total scanning
time was approximately 20 to 25 minutes for each patient.
Basal turn angulations: To estimate the rotated/tilting/misaligned cochlea, we have measured an angle called
the basal turn angle (BTA). We have drawn two lines:
Then the angle was measured between these two lines ([Fig. 1]).
Fig. 1 (A) Computed tomography (CT) scan (axial view of temporal bone): right, basal turn angle
(BTA) of 53.8 degrees, and left, BTA of 50.1 degrees. (B) Distance between the tympanic segment of facial nerve and posterior wall of external
auditory canal (EAC) at the level of incudostapedial joint (4.55 mm) (white arrow:
I-S joint, orange arrow: tympanic segment of facial nerve). (C) Coronal fast imaging enabling steady-state acquisition (FIESTA) magnetic resonance
imaging (MRI) image showed normal bilateral cochlear turns (arrows). (D) Coronal FIESTA MRI image showed normal bilateral internal auditory canal (IAC) (blue
arrow) with normal vestibule-cochlear complex, vestibule, and superior (red arrow)
and lateral (yellow arrow) semicircular canal.
Imaging Findings
We have grouped the patients into two categories (i.e., normal and abnormal) based
on the imaging findings on CT and MRI. Patients with acquired disease in ear and congenital
inner ear malformation were considered as abnormal imaging finding.
Surgical difficulty: Surgical difficulty score of all the patients who underwent surgery was assessed
by the operating surgeon on 0 to 10 scales, where 10 was most difficult score. Later,
the score was divided into three groups where 0 to 4 was considered no difficulty,
5 to 8 mild to moderate difficulty, and ≥9 severe difficulty. For the final analysis,
overall patients were divided into two groups, that is, difficult (≥5) and not difficult
(≤4).
Statistical Analysis
Normality of the continuous data was tested using Z score and variables were considered normal when Z score was within ±3.29. Descriptive statistics of the continuous variable was presented
in mean ± standard deviation/median (interquartile range) while categorical variable
in frequency and percentages. To compare the means between two groups, independent
samples t-test was used, while for nonnormal data, Mann–Whitney U test was used. To test the association/compare the proportions between two variables,
chi-square test/Fisher’s exact test was used as appropriate. Univariate and multivariate
binary logistic regression analysis was used to find out the predictors of the surgical
difficulty. Odds ratio and adjusted odds ratio (AOR) of the surgical difficulty was
calculated for the predictors. All the significant variables (predictors) found in
multivariate analysis for the surgical difficulty were used in receiver operating
characteristics (ROC) curve analysis. Area under curve (AUC) and appropriate cutoff
values was selected to identify the surgical difficulty with corresponding sensitivity
and specificity. Minimum 95% confidence interval (CI) or p-value < 0.05 was considered as statistically significant. Statistical Package for
Social Sciences, version 23 (SPSS-23, IBM, Chicago, United States) was used for data
analysis.
Results
Fifty-six patients having bilateral SNHL were included in the study. Out of these
56 patients, 55 patients had undergone imaging followed by the cochlear implants by
Veria technique ([Fig. 2]), while 1 patient who was diagnosed having Michel’s deformity was referred for brain
stem implant. Patients age ranged between 1 and 48 years with maximum patients in
the age group of ≤5 years (prelingual) (n = 31, 56.4%) followed by > 10 years (n = 14, 25.5%) and 6 to 10 years (n = 10, 18.2%) with a gender distribution of 29 males (52.7%) and 26 (47.3%) females.
There was significant (p = 0.016) difference in percentage of male patients between three age groups, that
is, 41.5% (≤5 years), 40% (6–10 years), and 85.7% (> 10 years). In this study, out
of 17 patients, those showing abnormality, 7 patients showed some type of acquired
disease which included otomastoiditis (n = 5) and otosclerosis (n = 2), while 10 patients showed various type of congenital inner ear malformation
([Table 1]). Out of 10 cases having congenital inner ear malformation, Mondini’s dysplasia,
type I incomplete partition ([Fig. 3]), and bilateral enlarged vestibular aqueduct were found in 3 of 3 cases (each 30%)
while Michel deformity was found in 1 case (10.0%) ([Table 2]
[Fig. 4]). The above radiological outcomes was insignificantly correlated with age, sex,
BTA, external auditory canal (EAC), and IAC measurements of the candidates (p > 0.05).
Table 1
Imaging findings in the study patients
|
Findings
|
Number of patients (N = 55)
|
|
Note: In abnormal imaging finding, multiple abnormality is included.
|
|
Normal
|
38 (70.18%)
|
|
Abnormal
|
Otomastoiditis
|
5
|
17(29.82%)
|
|
Otosclerosis
|
2
|
|
Poor mastoid
|
6
|
|
High jugular bulb
|
4
|
|
Congenital inner ear
|
10
|
Table 2
Distribution of congenital malformation in the patients
|
Type
|
No. of cases
|
|
Michel deformity
|
1 (10.0%)
|
|
Type I incomplete partition
|
3 (30.0%)
|
|
Mondini's dysplasia
|
3 (30.0%)
|
|
Bilateral enlarged vestibular aqueduct syndrome
|
3 (30.0%)
|
|
Total
|
10 (100%)
|
Fig. 2 Veria technique. (A) Tunnel made parallel to external auditory canal (EAC) using Trifon bur. (B) Cochleostomy through EAC after raising tympano-meatal flap. (C) Cochleostomy. (D) Electrodes passed trough tunnel made parallel and inserted into cochlea through
cochleostomy.
Fig. 3 (A–C) Axial high-resolution computed tomography (HRCT) and (D) magnetic resonance imaging (MRI) axial fast imaging enabling steady-state acquisition
(FIESTA) showed cystic bilateral vestibule and cochlea (8 appearances)–finding S/O
type I incomplete partition defect.
Fig. 4 Michel deformity. (A) High-resolution computed tomography (HRCT) axial absence of normally visualized
vestibule and cochlear turns in right petrous temporal bone (arrow). Corresponding
(B) magnetic resonance imaging (MRI) axial fast imaging enabling steady-state acquisition
(FIESTA) image of same patient showed findings similar to HRCT.
Distance between the Tympanic Segment of Facial Canal and Post Wall of EAC
We measured the distance between the tympanic segment of facial canal and posterior
wall of EAC (midpoint between level of I-S joint corresponding to EAC and exit of
chordae tympani nerve at the level of EAC) in 55 studied cases. Of the 55 cases, 54
(98.2%) showed that the distance was more than 3 mm with a mean of 4.55 ± 0.57 mm
([Fig. 5]). Only in one case (1.8%) who had congenital inner ear malformation (Michel deformity),
the distance was 2.7 mm. It was also found that the mean distance was greater in older
(> 5 years, 4.58 ± 0.62 mm) than younger age group (≤5 years, 4.55 ± 0.49 mm), although
the difference was not statistically significant (independent samples t-test, p = 0.860). In patient having inner ear malformation, mean was 3.90 ± 0.44 mm. In patients
having acquired disease, mean distance was 4.30 ± 0.47 mm. Similarly, coronal FIESTA
MRI image was used to show normal bilateral cochlear turns and coronal FIESTA MRI
image for normal bilateral IAC with normal vestibule-cochlear complex, vestibule,
and superior and lateral SCC.
Fig. 5 Distance between tympanic segment of facial nerve and posterior border of external
auditory canal (EAC).
Comparisons between Surgical Groups (Difficult/Smooth)
Out of the 55 patients who had undergone surgery, 13 (23.6%) patients’ surgery was
marked as difficult (11 patients associated with mild to moderate difficulty and 2
patients with severe difficulty) ([Fig. 6]). Age and sex of the patients were compared between two surgical groups (smooth
and difficult), and we found that there was no significant difference in distribution
of age (p = 0.359) ([Fig. 7]) and proportions of male/females (p = 0.926) between the two surgical groups ([Table 3]).
Table 3
Demographic variables and HRCT measurement of clinical variables and its association
with surgical outcomes
|
Variables
|
Total
(N = 55)
|
Smooth
(n = 42)
|
Difficult
(n = 13)
|
p-Value
|
|
Abbreviations: BTA, basal turn angle; EAC, external auditory canal; F, female; HRCT,
high-resolution computed tomography; IAC, internal auditory canal; M, male.
Note: p < 0.05 significant.
|
|
BTA
|
55.98 ± 3.43
|
56.90 ± 2.26
|
53 ± 4.76
|
0.032
|
|
Age
|
5 (3–14)
|
5 (3–15)
|
4 (2–15)
|
0.359
|
|
Sex (M/F)
|
29/26
|
22/20
|
7/6
|
0.926
|
|
EAC (mm)
|
6.53 ± 0.77
|
6.69 ± 0.69
|
6.01 ± 0.80
|
0.004
|
|
Distance between facial canal and EAC
|
4.56 ± 0.55
|
4.70 ± 0.51
|
4.09 ± 0.39
|
0.001
|
|
IAC (mm)
|
3.67 ± 0.54
|
3.75 ± 0.57
|
3.41 ± 0.33
|
0.009
|
Fig. 6 Difficulty was experienced in terms of insertion and implantation of internal auditory
canal (IAC). Postoperative X-ray transorbital view with cochlear implant in situ.
Right side image shows cochlear implant electrodes in IAC, left side image shows cochlear
implant electrodes in cochlea.
Fig. 7 Line graph showing mean value of age, basal angle, external auditory canal (EAC),
distance between the facial canal (FC) and post wall of EAC, and internal auditory
canal (IAC) in two surgical feasibility groups.
The mean score of BTA (p = 0.032), EAC (p = 0.004), and IAC (p = 0.009) and the distance between tympanic segment of facial canal to EAC (p = 0.001) as well as proportions of poor mastoid pneumatization (p = 0.002), having high jugular bulb (p = 0.011) and abnormal vestibule/vestibular aqueduct (p = 0.037), were significantly different between the groups ([Tables 3]
[4]
[5]
[Fig. 7]).
Table 4
HRCT and MRI findings and its association with surgical outcomes
|
Variables
|
Smooth
(n = 42)
|
Difficult
(n = 13)
|
Total
(N = 55)
|
p-Value
|
|
Abbreviations: HRCT, high-resolution computed tomography; MRI, magnetic resonance
imaging.
Note: Fisher’s exact test used, p < 0.05 significant.
|
|
Mastoid pneumatization (poor)
|
1 (2.4)
|
5 (38.5)
|
6 (10.9)
|
0.002
|
|
Middle ear cavity (abnormal)
|
2 (4.8)
|
3 (23.1)
|
5 (9.1)
|
0.080
|
|
Otosclerosis
|
0 (0)
|
2 (15.4)
|
2 (3.6)
|
0.053
|
|
High jugular bulb
|
0 (0)
|
3 (23.1)
|
3 (5.5)
|
0.011
|
|
Sigmoid sinus (abnormal)
|
2 (4.8)
|
2 (15.4)
|
4 (7.2)
|
0.234
|
|
Vestibule/vestibular aqueduct (abnormal)
|
1 (2.4)
|
3 (23.1)
|
4 (7.3)
|
0.037
|
|
Cochlea (abnormal)
|
1 (2.4)
|
2 (15.4)
|
3 (5.5)
|
0.136
|
|
Vestibule
|
2 (4.8)
|
2 (15.4)
|
4 (7.2)
|
0.234
|
|
Endolymphatic duct/sac
|
2 (4.8)
|
3 (23.1)
|
5 (9.1)
|
0.080
|
Table 5
Predictors of the difficult surgical process in the cochlear patients (N = 55)
|
Variables
|
Univariate analysis
|
Multivariate analysis
|
|
OR
|
Lower
|
Upper
|
AOR
|
Lower
|
Upper
|
p-Value
|
|
Abbreviations: AOR, adjusted odds ratio; BTA, basal turn angle; EAC, external auditory
canal; FC, facial canal; IAC, internal auditory canal; OR, odds ratio.
Note: p < 0.05 significant.
|
|
EAC
|
0.25
|
0.09
|
0.71
|
0.13
|
0.03
|
0.58
|
0.007
|
|
BTA
|
0.68
|
0.52
|
0.89
|
0.64
|
0.43
|
0.97
|
0.034
|
|
Distance between FC and EAC
|
0.08
|
0.02
|
0.43
|
0.10
|
0.01
|
0.91
|
0.041
|
|
IAC (mm)
|
0.21
|
0.04
|
0.98
|
–
|
–
|
–
|
–
|
|
Mastoid pneumatization (poor)
|
25.63
|
2.63
|
249.72
|
–
|
–
|
–
|
–
|
|
Vestibule/vestibular
aqueduct (abnormal)
|
12.30
|
1.15
|
131.10
|
–
|
–
|
–
|
–
|
Association between Surgical Difficulty and Clinical Variables
In [Table 5], association between the two groups of surgical difficulty and clinical variables
was tested using chi-square test/Fisher’s exact test. Result indicated that variables,
namely, EAC, BTA, distance between facial canal to EAC, IAC, poor mastoid pneumatization,
and abnormal vestibule/vestibular aqueduct were significantly associated with surgical
difficulty (p < 0.05).
Predictors of the Surgical Feasibility
The surgical difficulty and clinical variables, namely, EAC, BTA, distance between
facial canal to EAC, IAC, poor mastoid pneumatization, and abnormal vestibule/vestibular
aqueduct were significantly associated (p < 0.05). Univariate and multivariate binary logistic regression analysis was used
to calculate the odds ratio and AOR of the predictors to having surgical difficulty.
In univariate binary logistic regression analysis, result showed that higher size
of the EAC, BTA, distance between tympanic segment of facial canal to EAC, and IAC
were a protecting factor, while poor mastoid pneumatization and abnormal vestibule/vestibular
aqueduct were risk factors of the surgical difficulty. In multivariate analysis, out
of the six significant factors that were found in univariate analysis, only three
variables, namely, higher size of the EAC (AOR = 0.13, 95% CI = 0.03–0.58, p = 0.007), higher BTA (0.64, 95% CI = 0.43–0.97, p = 0.007), and higher distance between facial canals to EAC (0.10, 95% CI = 0.01–0.91,
p = 0.041), showed inverse relationship with difficult surgery and were found to be
statistically significant ([Table 5]).
Diagnostic Accuracy of the Predictors for Surgical Difficulty
ROC curve was used to test the diagnostic accuracy as well as to find out the appropriate
cutoff value of the surgical difficulty predictors. Result showed that distance between
tympanic segment of facial canal to EAC (AUC = 88%) was the highest predictor of diagnostic
accuracy followed by BTA (AUC = 77%) and EACs (AUC = 76%) ([Fig. 8]). For getting balancing sensitivity and specificity of the predictors, cutoff value
of 6.25 (sensitivity = 76.9%, specificity = 78.6%) of the distance between facial
canals to EAC, 4.45 (sensitivity = 84.6%, specificity = 81%) for BTA, and 55.25 (sensitivity
= 61.5%, specificity = 73.8%) for EACs were considered as the best.
Fig. 8 Area under the curve (of the receiver operating characteristics [ROC] curve) showing
comparisons in diagnostic accuracy of the predictors of the surgical difficulty.
Discussion
Cochlear implantation is a standard procedure for the rehabilitation of patients with
SNHL.[3] It has become an accepted treatment in patients with profound SNHL. Radiologists
have assumed a larger role in evaluating these patients as the number of procedures
increase.[4] The aim of our study was to evaluate the role of HRCT and MRI in the postoperative
assessment of surgical difficulty in cochlear implantation. Various studies have been
undertaken to establish the role of CT scan and MRI in preoperative evaluation of
cochlear implant candidates and its imaging findings that are likely to affect the
eligibility for implantation, risk, and surgical approach. A cross-sectional study
was conducted by Lima Júnior et al to investigate the accuracy of imaging studies
as predictors of possible complications of surgery. They found that the preoperative
radiological evaluation by CT was effective in identifying anatomic abnormalities,
allowing surgeons to avoid, or at least be aware of, possible complications. This
study demonstrated that CT and MRI were superior to CT alone.[5] A similar experience was observed in our study, where CT and MRI were found superior
in decision making as compared with the CT alone to evaluate the candidacy of the
cochlear implants. CT and MRI for evaluation of cochlear implant candidates require
consideration of a variety of clinical and radiographic factors. Candidates with SNHL
who met established audiologic criteria for cochlear implantation may have unique
audiologic, medical, and anatomic characteristics that necessitate special consideration
regarding cochlear implantation candidacy and outcome.[6]
[7] In our study, 69.1% patients had no radiological abnormality, while 30.9% patients
showed some type of abnormality including acquired disease and congenital malformation.
Note that 18% (n = 10) patients showed various type of congenital inner ear malformation on CT and
MRI. Similar result was observed in Chaturvedi et al, where, 16.7% patients showed
various types of congenital inner ear malformations.[8] In our study, cochlea/cochlea-vestibular deficiency, endolymphatic duct dilatation,
and vestibule/SCC anomaly were found in 12.5, 10.5, and 5.8%, respectively, as compared
with 25, 12, and 7% reported by Lin et al.[9] Our finding is also comparable with Agarwal et al.[10] Surgical difficulty was negatively associated with higher size of EAC, distance
between tympanic segment of facial canal to EAC, and BTA (p < 0.05), which indicated that patients with narrow size of the above parameters increase
the difficulty of the surgery while no association was observed with age and sex (p > 0.05). Similarly, poor mastoid pneumatization, abnormal middle ear cavity, and
abnormal vestibule/vestibular aqueduct were more commonly associated with surgical
difficulty (p < 0.05). Our finding was comparable with the study conducted by in Wu et al.[11] Joshi et al also published the role of imaging in preoperative evaluation of cochlear
implantation. They found that imaging has important role in the evaluation of congenital
SNHL. A broad spectrum of inner ear malformations has been described and linked to
development at different stages of embryogenesis, and various systems have been proposed
for classifying them.[12] In our study, ROC curve revealed that distance between facial canals to EAC (AUC
= 88%) can be considered as a good predictor of surgical difficulty followed by BTA
(AUC = 77%) and EACs (AUC = 76%) ([Table 6]). Although similar study to predict the surgical difficulty through AUC could not
be found.
MRI and CT both have roles in the preoperative assessment of inner ear abnormalities,
cochlear nerve deficiency, and variant anatomy that might affect the decision to implant
and the prognosis for auditory improvement and increased risk for complications. They
might also affect the surgical approach and made implantation difficult.[13]
[14] An organized report in cochlear implant patients should provide the surgeon with
clear and concise information with special focus on the surgeon’s expectations to
prepare a clinically relevant report. A constant communication between the imaging
specialist and the cochlear implant surgeon improves image interpretation and ensures
a successful implantation.[15]
Table 6
Diagnostic accuracy of the surgical difficulty predictors
|
Variables
|
AUC-ROC
(95% CI)
|
p-Value
|
Cutoff
|
Sensitivity
|
Specificity
|
|
Abbreviations: AUC-ROC, area under the curve calculated by receiver operating characteristics
curve; CI, confidence interval; EAC, external auditory canal.
Note: Lower values indicate more surgical difficulty, p < 0.05 significant.
|
|
EACs in mm
|
0.76 (0.59–0.92)
|
0.006
|
6.25
|
76.9
|
78.6
|
|
6.85
|
84.6
|
35.7
|
|
Distance (mm) between facial canals and EAC
|
0.88 (0.79–0.97)
|
< 0.001
|
4.55
|
92.3
|
71.4
|
|
4.45
|
84.6
|
81.0
|
|
Basal turn angle
|
0.77 (0.62–0.92)
|
0.004
|
57.55
|
84.6
|
47.6
|
|
55.25
|
61.5
|
73.8
|
Conclusion
Anatomy of temporal bone and cochlea by HRCT and MRI are decisive factors in the surgical
planning for the cochlear implantation team. Radiologist experienced in the anatomy
of temporal bone plays a major role with direct impact on the success of the surgical
intervention, helping the surgeon planning the operation and predicting potential
complications in cochlear implant candidates. HRCT and MRI are recommended in all
patients for preimplant analysis of the temporal bone morphology. BTA and distance
between tympanic segment of facial nerve and EAC (midpoint between level of I-S joint
corresponding to EAC and exit of chordae tympanic at level of EAC) are important predictors
for evaluating intra- and postoperative complications.
