Keywords
cochlear implantation - hearing loss - inner ear malformations - imaging - radiology
Introduction
Inner ear and vestibulocochlear nerve malformations may lead to congenital sensorineural
hearing loss (SNHL).[1] Hearing loss is the most common sensory disability in children. It is considered
that 1 in 1,000 children has severe or profound deafness at birth and 90% of birth
hearing loss are sensorineural.[2]
The reported prevalence of inner ear malformations (IEMs) in individuals with congenital
hearing loss varies from 2.3 to 28.4%.[3] A variety of congenital anomalies are seen, syndromic and nonsyndromic.[4] These anomalies have been grouped according to various classifications and the most
used is proposed by Sennaroglu.[5],[6]
In cases of severe-to-profound deafness, cochlear implant is proven to be the most
beneficial in children. For this management, IEMs may not only affect the decision
to perform the implant procedure but also increase the risk of complications.[1] In Côte d'Ivoire, our cochlear implantation experience is recent (December 2015),
and the first cochlear implantations at Bingerville Mother-Child Hospital were performed
in 2020. Moreover, no study has been carried regarding the inner ear anomalies in
our setting. The lack of data on malformations therefore justifies this study. Thus,
the objectives were to determine the prevalence and the types of inner ear and/or
cochlear nerve abnormalities in children with severe or profound SNHL in Côte d’Ivoire.
Methods
This is a descriptive cross-sectional study with a review of the medical files of
children under 15 years old, candidates for cochlear implantation, who presented to
our hospital for a preimplantation imaging assessment (computed tomography [CT] and
magnetic resonance imaging [MRI]), from January 2019 to December 2021. All cochleovestibular
or cochlear nerve malformations, isolated or associated, were included in the study.
Malformations isolated from the windows, abnormal hyperdensity, or ossified lesions
were not retained. They were categorized by side (unilateral, bilateral), site (cochlea,
vestibule, semicircular canal, entire labyrinth), and Sennaroglu classification.[5],[6]
The variables to be studied were reason for consultation, risk factors, types of inner
ear abnormalities classified and analyzed according to degree of SNHL, gender, and
age at diagnosis. Significant risk factors and history corresponded to the presence
of parameters that could impact the occurrence of cochleovestibular malformations:
TORCH (TOxoplasmosis, Rubella, Cytomegalovirus, Herpes simplex virus) infection during
pregnancy and other microorganisms; gestational age less than 34 weeks, birth defects
of the head and neck.
After collection, data was tabulation using Microsoft Excel Worksheet and analyzed
statistically using Statistical Package for Social Studies (SPSS) Version-23. Results
were analyzed using descriptive statistic including frequencies, percentages, mean,
and standard deviation. Chi-squared and Fischer’s exact tests were used to see association
(p-value < 0.05).
The study was conducted after administrative approvals were obtained; and the anonymity
of the tools and data collected was ensured.
Results
Prevalence
During this study, we identified 81 patients (162 ears) with available clinical information
and imaging results. Among these children, nine (9) had cochleo-vestibular malformations,
that is, a prevalence of 11.1%.
Sociodemographic and Clinical Data of Malformations Cases
They are summarized into [►Table 1].
Table 1
Sociodemographic and clinical data
|
Age
|
Sex
|
Sibling rank
|
Consultation reason
|
Age at diagnosis of deafness
|
ENT and general examination
|
|
Case 1
|
25 mo
|
Female
|
1st
|
Language delay
|
12 mo
|
Auricular anomalies + cervical fistulas + congenital PFPa
|
|
Case 2
|
42 mo
|
Male
|
1st
|
Language delay
|
20 mo
|
Normal
|
|
Case 3
|
29 mo
|
Male
|
1st
|
Language delay
|
12 mo
|
Normal
|
|
Case 4
|
55 mo
|
Male
|
1st
|
Language delay + hearing loss
|
24 mo
|
Normal
|
|
Case 5
|
168 mo
|
Female
|
5th
|
Hearing loss
|
141 mo
|
Normal
|
|
Case 6
|
39 mo
|
Male
|
1st
|
Hearing loss
|
36 mo
|
Normal
|
|
Case 7
|
53 mo
|
Male
|
1st
|
Language delay
|
45 mo
|
Autism spectrum disorder
|
|
Case 8
|
112 mo
|
Female
|
1st
|
Language delay + hearing loss
|
60 mo
|
Normal
|
|
Case 9
|
39 mo
|
Female
|
2nd
|
Language delay
|
30 mo
|
Normal
|
Abbreviation: PFP, peripheral facial paralysis.
The patients were unschooled except for one. Case 6 had a pathological history such
as diffuse brain damage. No significant risk factor was identified in these nine patients.
The age of the patients ranged from 2 to 14 years, with mean age of 5.2 years (62.4
months) and a standard deviation of 4.6 years. There were five males for four females
(sex ratio: 1.25).
The reason for consultation was a language delay in 7/9 cases. The age at diagnosis
ranged from 1 to 12 years with a mean age of 3.5 years (42.2 months). Among the 16
ears with malformations, 11 had profound hearing loss, 4 had severe hearing, and 1
had moderate hearing loss. A branchio-oto-renal syndrome (auricular abnormalities,
bilateral prehelical and second branchial arch fistulas, small right kidney) with
congenital deafness was identified (case 1). A persistence of the ductus arteriosus
was noted in case 5.
Radiological Assessment
A petrous CT scan was performed in all patients (100%) and an MRI of the inner ear
and brain in eight cases (88.9%). All patients had multiple IEMs except case 8. Seven
children had bilateral anomalies of the inner ear and/or cochlear nerve and two had
unilateral anomalies, for a total of 16 malformed ears. A total of 40 types of IEM
were identified in these 16 ears ([►Table 2]). Abnormalities were on the right side in 23 cases (57.5%) and on the left side
in 17 cases (42.5%). In four cases, brain MRI also showed frontal and/or biparietal
leukomalacia, predominantly on the left side.
Table 2
Distribution of malformations according to their frequency
|
Case 1
|
Case 2
|
Case 3
|
Case 4
|
Case 5
|
Case 6
|
Case 7
|
Case 8
|
Case 9
|
(n) % of 40 IEM
|
|
Enlarged IAC
|
|
|
|
|
1
|
|
|
|
|
(1) 2.5
|
(5) 12.5%
|
|
IAC abnormalitiesa
|
1
|
|
|
2
|
|
|
|
|
|
(3) 7.5
|
|
Vascular-nervous conflict in IAC
|
|
|
|
1
|
|
|
|
|
|
(1) 2.5
|
|
Hypoplastic cochlear nerve
|
|
|
|
|
|
1
|
|
2
|
|
(3) 7.5
|
(3) 12.5%
|
|
Complete labyrinthine aplasia
|
|
1
|
|
|
|
|
|
|
|
(1) 2.5
|
(1) 2.5%
|
|
Cochlear aplasia
|
|
1
|
|
|
|
|
|
|
|
(1) 2.5
|
(12) 30%
|
|
Cochlear hypoplasia
|
|
|
2
|
|
1
|
|
1
|
|
|
(4) 10.0
|
|
Modiolus malformationsb
|
|
|
2
|
|
1
|
|
|
|
2
|
(5) 12.5
|
|
Cochlea with less than 2 turns
|
1
|
|
|
|
|
|
|
|
|
(1) 2.5
|
|
Dilated cochlear duct
|
|
|
|
|
1
|
|
|
|
|
(1) 2.5
|
|
Common cavity (cystic cavity)
|
1
|
|
|
|
|
|
|
|
|
(1) 2.5
|
(1) 2.5%
|
|
Bone vestibular dysplasia (utricle and saccule)
|
|
|
1
|
|
1
|
|
|
|
|
(1) 2.5
|
(3) 7.5%
|
|
Dilated vestibule
|
|
|
1
|
|
1
|
|
|
|
|
(2) 5.0
|
|
SCCl hypoplasia
|
|
|
2
|
|
1
|
|
|
|
|
(3) 7.5
|
(11) 27.5%
|
|
SCCs hypoplasia or aplasia
|
|
|
2
|
|
1
|
|
|
|
2
|
(5) 12.5
|
|
SCCp hypoplasia or aplasia
|
|
|
1
|
|
|
1
|
|
|
1
|
(3) 7.5
|
|
SCCs bone capsule dehiscence
|
|
|
|
|
1
|
|
1
|
|
|
(3) 7.5
|
(3) 7.5%
|
|
Enlarged (or dilated) vestibular aqueduct
|
|
|
|
1
|
|
|
|
|
|
(1) 2.5
|
(1) 2.5%
|
|
Outer and middle ears abnormalities associated
|
|
–Prolapse of jugular vein
|
1 Yes
|
Yes
|
|
Yes
|
1
2
Yes
|
2
|
|
–Moderate atresia of EMAs
|
|
–Ossicular dysmorphism (stapes) and narrow oval window
|
|
Brain abnormalities
|
|
Leukomalacia
|
|
Abbreviations: IEMs, inner ear malformations; SCC, squamous cell carcinoma.
aInternal auditory canal (IAC): 1 horizontalization, 2 narrows.
bModiolus: 4 incomplete, 1 short.
|
Reporting to the 16 ears with IEMs, there are 1 ear with complete anomaly of the labyrinthine
(6.25%), 1 ear with common cavity (6.25%), 8 ears with abnormalities of the cochlea
(50%), 8 ears with vestibular abnormalities (50%), 5 ears with abnormalities of the
internal auditory canal (31.25%), 1 vestibular aqueduct abnormality (6.25%), and 3
ears with cochlear nerve abnormalities (18.75%). One ear had at least one abnormality
at each site on the same side (case 6).
The IEMs distribution according to Sennaroglu and Bajin classification[5] is summarized in [►Table 3]
Table 3
IEMs distribution according to Sennaroglu and Bajin classification
|
Effective
|
Percentage
|
|
Complete anomaly of the labyrinthine (or Michel deformity)
|
|
1
|
6.25
|
|
Common cavity
|
|
1
|
6.25
|
|
Cochlear aplasia
|
|
1
|
6.25
|
|
Incomplete partition
|
IP type II (Mondini deformity)
|
1
|
6.25
|
|
IP type I
|
1
|
6.25
|
|
Cochlear hypoplasia
|
CH type II
|
3
|
18.75
|
|
CH type III
|
1
|
6.25
|
|
Isolated SCC hypoplasia
|
|
2
|
12.50
|
|
Isolated narrow IAC
|
|
1
|
6.25
|
|
Narrow IAC associated with SCCs bone capsule dehiscence
|
|
1
|
6.25
|
|
Hypoplastic cochlear nerve associated with SCCs bone capsule dehiscence
|
|
1
|
6.25
|
|
Isolated hypoplastic cochlear nerve
|
|
2
|
12.50
|
Abbreviations: CH, cochlear hypoplasia; IAC, internal auditory canal; IEMs, inner
ear malformations; IP, Incomplete partition; SCC, semicircular canal.
Malformations of the Inner Ear according to Degree of Deafness, Age, and Sex of Patients
The p-value compares the rate of child with age at diagnosis inferior to 2 years in those
with malformations and those without, and the rate of male in those with malformations
and those without ([►Table 4]).
Table 4
Age of diagnosis/sex and presence of inner ear malformations
|
Age of diagnosis Sex
|
|
≤ 2 years
|
n (%)
|
> 2 years
|
n (%)
|
Male
|
Feminine
|
|
Malformations, yes
|
8 (50)
|
4 (50)
|
9 (56.3)
|
7 (43.7)
|
|
Malformations, no
|
24 (16.4)
|
122 (83.6)
|
76 (52.1)
|
70 (47.9)
|
|
Fisher’s exact test
p-Value = 0.004; RR = 4.06
|
Chi-squared test = 0.10 < 3.84
p-Value = 0.75
|
Abbreviation: RR, relative risk.
There was a significant association (p-value < 0.05) between age at diagnosis and IEM. The occurrence of IEMs was not gender
related (p-value > 0.05).
The association between the degree of hearing loss and IEMs is presented in [►Table 5].
Table 5
Degree of SNHL and presence of inner ear malformations
|
Profound and severe deafness, n (%)
|
Other level of deafness, n (%)
|
p-Valuea
|
|
Malformations, yes
|
15 (93.7)
|
01 (06.3)
|
0.008
|
|
Malformations, no
|
88 (50.3)
|
58 (39.7)
|
|
Abbreviations: RR, relative risk; SNHL, sensorineural hearing loss.
aFisher’s exact test; RR: 8.59 > 1.
There was a significant correlation (p-value < 0.05) between IEM and degree of deafness: IEM was associated with severe
and profound hearing loss.
Discussion
We found a prevalence of 11.1% of malformations in children’s candidates for cochlear
implantation, which is within the range of prevalence reported worldwide: 7.5 to 20%.[7]–[9] With a prevalence of 3.7% in cases of unilateral SNHL, the study by Masuda and Usui[10] showed a significant increase in the prevalence of malformations in the case of
bilateral SNHL.
Gender does not seem to be a predisposing factor for ear malformations either in our
study or in the literature.[4],[10] However, studies concerning the prevalence by sex of the different malformations
in general are lacking, apart from those on the anomalies of the external ear that
note a male predominance.[11] More than the age of the patients included, the present study demonstrated a significant
correlation between IEMs and early age at diagnosis. The children were mostly the
first born in the family (7/9 cases), like in other studies on deafness.[12],[13] Children were mostly out of school, perhaps because of the hearing loss?
The main reason for consultation in children’s SNHL was a language delay according
to Ridal et al.[14] The profound deafness would favor early diagnosis, even in under-equipped countries,
because of the main impact on the language development of young children. We did not
note any pathological history in our work, due to the size of our sample. However,
the role of pregnancy and childbirth conditions as well as prenatal infections, in
particular TORCH, are known to be responsible of congenital craniofacial malformations,
including auricular. Indeed, ear malformations may have not only an acquired background
(infections, chemical agents, irradiation, etc.) but also a genetic origin. Theses
malformations can affect outer/middle ant inner ear, sometimes in combination. But
the different embryogenesis of the outer/middle ear and the inner ear explains malformations
in outer and/or middle ear without IEMs.[3] An association with other malformations (cervical, renal, cardiac, etc.) is noted
in two patients, which may be part of so-called syndromic genetic deafness described
in 10 to 30% of cases of genetic deafness.[3] The IEMs were associated with profound and/or severe degree sensorineural deafness
in majority of cases, with varying rates.[8],[10]
CT is the first-line examination in the exploration of the ear in children, but CT
and MRI must be complementary in the preoperative assessment. MRI essentially makes
it possible to look for an anomaly of the cochlear nerve or of the labyrinthine membranous
structures and of the brain.[1],[4] In most cases, the underlying disorders involve the membranous labyrinth at a microscopic
level and therefore radiological examinations are entirely normal.[1] The most used classification is that in eight groups.[1],[5],[6] Majority of patients demonstrated multiple abnormalities.[5] The prevalence of any type of IEMs is variable with large differences in the proportions
reported by studies. In our series, the most common abnormalities were SCC malformations,
including SCC hypoplasia and dehiscence of superior SCC bone capsule. In second position,
we had cochlear malformations with cochlear hypoplasia type II or III (25%) while
incomplete partitions were the most frequent malformations in studies by Sennaroglu
and Sun.[7],[15] Conversely, the most common malformations were dilated vestibules for other authors.[9],[16] An enlarged vestibular aqueduct has been reported at high rates (40–56%) in several
studies, whereas they represent only 2.5% of the malformations in our series.[9],[15],[17] No documented explanation could justify these significant differences.
Conclusion
This study shows that 11.1% of children with profound SNHL have inner ear malformations.
SCC anomalies and cochlear hypoplasia were the most common. A precise description
of these malformations during the imaging assessment is particularly useful for cochlear
implantation, for better planning of this surgery.
