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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 3  |  Issue : 2  |  Page : 517-526

Role of computed tomography and magnetic resonance imaging in the assessment of temporal bone pre-cochlear and postcochlear implantation


1 Department of Radiodiagnosis, Faculty of Medicine (For Boys), Al-Azhar University, Cairo, Egypt
2 Department Otorhinolaryngology, Military Medical Academy and Al Galaa Military Hospital, Cairo, Egypt

Date of Submission06-Apr-2019
Date of Acceptance09-Jul-2019
Date of Web Publication24-Oct-2019

Correspondence Address:
MD Mohamed S Elfeshawy
El Mahalla El Kobra, Gharbyia, Cairo
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjamf.sjamf_29_19

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  Abstract 


Introduction Multidetector computed tomography (CT) and MRI play a critical role in the evaluation and management of different causes of hearing loss, which require many therapeutic techniques including cochlear implantation. Multidetector CT has proven its efficacy in the postoperative imaging of cochlear implant patients. CT confirms the intracochlear position of the implant. It has also been shown that malpositioning and kinking can be detected by CT imaging.
Aim of the work To evaluate the role of various imaging modalities (CT and MRI) in the preoperative and postoperative evaluation of cochlear implant candidates. Patients and methods The study included a total of 20 patients referred to the Radiodiagnosis Department from the ENT Department in Al Galaa Military Hospital. CT and MRI were performed for the assessment of the cochlear state before cochlear implantation operation. Postoperative CT was done to underline the position of the implanted electrode.
Setting and design This study involves prospective, randomized, controlled trials.
Ethics Informed consent from a parent or guardian.
Results This study included 20 patients with bilateral severe to profound sensorineural hearing loss. The study was performed on eight (40%) men and 12 (60%) women. Only 17 (85%) patients underwent cochlear implantation, the other three (15%) cases were diagnosed as Michel deformity, Cochlear hypoplasia, and Labyrinthine ossificans. Full electrode array insertion was reported in all cases who underwent cochlear implantation.
Conclusion Preoperative CT and MRI assessment is critical for determining implant candidacy. Postoperative CT confirms the intracochlear position of the implant.

Keywords: cochlear implantation, computed tomography, magnetic resonance imaging, petrous, postoperative, preoperative, temporal bone


How to cite this article:
El-Zayat TM, Elfeshawy MS, Khashaba AH, El-Raouf ME. Role of computed tomography and magnetic resonance imaging in the assessment of temporal bone pre-cochlear and postcochlear implantation. Sci J Al-Azhar Med Fac Girls 2019;3:517-26

How to cite this URL:
El-Zayat TM, Elfeshawy MS, Khashaba AH, El-Raouf ME. Role of computed tomography and magnetic resonance imaging in the assessment of temporal bone pre-cochlear and postcochlear implantation. Sci J Al-Azhar Med Fac Girls [serial online] 2019 [cited 2019 Nov 13];3:517-26. Available from: http://www.sjamf.eg.net/text.asp?2019/3/2/517/269851




  Introduction Top


The cochlear implant is a highly technological surgical device that is inserted in the cochlea of patients with severe to profound bilateral sensorineural hearing loss (SNHL) and that have not benefited from conventional sound amplification hearing aids [1].

Candidates for the cochlear implant undergo preoperative assessment involving clinical, speech therapeutic, psychological, social criteria, and imaging of the cochlear region to identify the etiology of hearing loss, findings that may contraindicate surgery and helping to select the ear to be implanted [2].

Cochlear implants aim to provide complex sound analysis by stimulating auditory cortex over a wide range of frequencies. To achieve this goal, the implant must be placed well within the cochlear lumen. Therefore, a detailed preoperative and postoperative radiological assessment of the temporal bone has become vital for cochlear implantation [3].

Multidetector computed tomography (MDCT) and MRI play a critical role in the evaluation and management of different causes of hearing loss, which require many therapeutic techniques including cochlear implantation [4].

Multislice CT has proven its efficacy in the postoperative imaging of cochlear implant patients. CT confirms the intracochlear position of the implant. It has also been shown that malpositioning and kinking can be detected by CT imaging [5].


  Patients and methods Top


  1. This study including 20 patients (eight men and 12 women) with severe to profound bilateral SNHL during the period from July 2017 to December 2018.
  2. The age of the total sample ranged from 1 to 45 years, the mean age was 8.05 years.
  3. All patients were referred from the ENT Department of Al Galaa Military Hospital. CT and MRI were performed as part of preoperative assessment in the Radiodiagnosis Department.
  4. CT was done after cochlear implantation to ensure the intracochlear position of inserted electrode.
  5. Written consent was taken from patients to participate in this study. Along with ethical comity approval.
  6. Imaging for the pediatric population was performed under sedation or short-acting general anesthesia. Low-dose pediatric HRCT protocols are used to keep radiation doses to a minimum.


Patient selection (inclusion criteria)

  1. Patients with bilateral, severe to profound, prelinguistic or postlinguistic SNHL and who demonstrate limited benefit from amplification.
  2. Clinical and imaging evaluation were done to select those patients who will benefit the most from implantation.
  3. The decision to operate is made after a thorough evaluation by a multidisciplinary team.


Exclusion criteria

Active, middle ear disease, congenital aural dysplasia, and patients medically unfit for undergoing cochlear implantation.

Patient preparation

  1. Detailed history was taken from the parents/patient.
  2. Preoperative assessment involving clinical, speech therapeutic, psychological, social criteria, and imaging (CT and MRI) of the cochlear region.
  3. Detailed explanation of the procedure to the parents/patient.
  4. Obtaining informed consent from the parents/patient.


Computed tomographic imaging technique

  1. Imaging for the pediatrics population was performed under sedation or short-acting general anesthesia.
  2. All patients were examined by multiple detector computed tomography (MDCT) in supine with head first and then axial images were obtained from the top of the petrous apex to the inferior tip of the mastoid bone with the patient’s neck semiflexed. The images were transferred to a workstation were multiplanar reformation (MPR) images were conducted for image analysis.
  3. All patients were examined by MDCT scanning using CT machines with 128 dual detector rows (Somatom Definition Edge; Siemens, Siemens Healthcare GmbH, Henkestr, Erlangen, Federal Republic of Germany)


The following parameters were used:



Technique MRI

  1. All patients were examined by MRI scanning using (1.5 T GE Signa Explorer, 60 cm; GE).
  2. The ideal MRI scan would be short in duration and nonstrenuous for the patient and technician. It provides a high signal-to-nose ratio, and consistent signal intensities throughout the scan.
  3. Imaging for the pediatric population was performed under sedation or short-acting general anesthesia.
  4. For neuro-otologic MRI examinations, a standard head coil is used. Superficial coils that display the temporal bone in detail can also be used, but in order to also include the brain stem and brain it is necessary to switch to a standard head coil. Currently, multichannel coils that enable parallel imaging are used for this purpose.


MRI was performed with the following sequences:



Computed tomography and magnetic resonance image analysis

Each case was assessed for:
  1. Different abnormalities requiring cochlear implantation.
  2. Congenital versus acquired lesions.
  3. Whether cochlear implantation would be useful for the patient or not.


Postoperative multidetector computed tomography

Generation of two-dimensional reformations and three-dimensional reconstruction to visualize the electrode array within the cochlea or not.


  Results Top


This study included 20 patients with bilateral severe to profound SNHL. The study was performed on eight (40%) men and 12 (60%) women. The age of the total sample ranged from 1 to 45 years, the mean age was 8.05 years.

[Table 1] shows that in our study:
  1. The most common age group is from 1 to 3 years representing 65% of cases.
  2. Women were more affected than men representing 60% of the cases.
Table 1 Distribution of patients according to their age and sex group

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The patients were divided according to the onset of hearing loss into two main categories ([Table 2]): prelingual (deafness before the patients begin to speak) and postlingual (deafness after acquisition of speech).
Table 2 Distribution of patients according to the onset of hearing loss

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[Table 2] shows that:
  1. The most common onset is the prelingual representing 60% of cases.


The patients were classified according to etiological factors of SNHL into two groups: congenital and acquired causes ([Table 3]).
Table 3 Frequency of etiological factors of sensorineural hearing loss among the study group

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[Table 3] shows that:
  1. The most common etiological factor for SNHL was congenital (found in 12 patients representing 65% of the total number of patients).


Preoperative multidetector computed tomography and MRI assessment

Most causes of hearing impairment including the external auditory canal, middle ear space, and the cochlea are best visualized with CT scan and MRI of the temporal bone [4].

[Table 4] shows that:
  1. Most of the patients had normal study of the inner ear (14 out of 20 patients).
  2. Congenital malformation of the inner ear was detected in only five cases representing 25% of cases.
Table 4 Multidetector computed tomography and MRI findings of the inner ear of the 20 patients

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In our study

Only 17 (85%) patients underwent cochlear implantation ([Table 5]), the other three cases were diagnosed as follows:
  1. Michel deformity: this case has been excluded from undergoing cochlear implantation because of absence of vestibulocochlear structures bilaterally.
  2. Cochlear hypoplasia: this case has been excluded from undergoing cochlear implantation because it has bilateral cochlear hypoplasia (only one turn or a partial turn is seen) and bilateral hypoplastic cochlear nerves.
  3. Labyrinthine ossificans: this case has been excluded from undergoing cochlear implantation because of bilateral and completely ossified both cochlea which affects insertion of the wire during cochlear implantation operation.
  4. [Table 5] shows that 17 (85%) patients underwent cochlear implantation.
Table 5 Patients who underwent cochlear implantation

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Postoperative multidetector computed tomography assessment

MDCT is necessary to underline the position of the implanted electrode, ensure intracochlear position, and to detect electrode kinking and may serve as a reference.

Full electrode array insertion was reported in all cases that underwent cochlear implantation ([Figure 1],[Figure 2],[Figure 3],[Figure 4],[Figure 5],[Figure 6],[Figure 7],[Figure 8],[Figure 9],[Figure 10],[Figure 11],[Figure 12],[Figure 13],[Figure 14],[Figure 15],[Figure 16],[Figure 17],[Figure 18]).
Figure 1 Axial CT of Mondini abnormality including: abnormal cochlea. Only 1.5 turns (instead of the normal 2.5 turns). Normal basal turn with a cystic apex in place of the distal 1.5 turns. Vestibular abnormalities: enlarged vestibule. Enlarged vestibular aqueduct (reaches 3.5 mm) containing a dilated endolymphatic sac. Normal semicircular canals. CT, computed tomography.

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Figure 2 Case no. 1: Axial T2 high-resolution MRI features of Mondini abnormality.

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Figure 3 Case no. 1: CT scan images show complete insertion of the electrode and reaching the basal cochlear turn. CT, computed tomography.

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Figure 4 Case no. 2 axial and coronal CT images bilateral cochlear hypoplasia is considered in terms of a small cochlear bud of variable length (usually 1–3 mm). It has only one turn or a partial turn is seen. Vestibule and semicircular canals are malformed with a dilated vestibule. Symmetrically dilated internal auditory canals bilaterally. Dilated cochlear aqueduct. Normal vestibular aqueduct. CT, computed tomography.

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Figure 5 Case no. 2: serial axial T2 high-resolution and sagittal oblique show cochlear hypoplasia, malformed vestibule and semicircular canals, bilateral, dilated internal auditory canals and bilateral hypoplastic cochlear nerves.

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Figure 6 Case no. 3: axial and coronal CT scan images show absence of vestibulocochlear structures (Michel deformity). CT, computed tomography.

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Figure 7 Case no. 3: axial and coronal T2 and 3D FIESTA images show absence of vestibulocochlear structures and cochlear nerve deficiency. CT, computed tomography; FIESTA, fast imaging employing steady-state acquisition.

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Figure 8 Case no. 4: axial CT images show bilateral isolated vestibular aqueduct dilatation. CT, computed tomography.

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Figure 9 Case no. 4: axial T2 FSE MRI bilateral large endolymphatic sac anomaly.

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Figure 10 Case no. 4: CT scan images show complete insertion of the electrode and reaching the basal cochlear turn. CT, computed tomography.

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Figure 11 Case no. 5: a 3-year-old girl presented with postlingual severe to profound SNHL. The patient had past history of meningitis. CT scan images show normal inner ear structures, normal bilateral IAC, and both cochlea and normal vestibule on both sides. CT, computed tomography; SNHL, sensorineural hearing loss.

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Figure 12 Case no. 5: MRI scan images (a) axial T2 high resolution, (b) coronal T2 high resolution, (c) right sagittal oblique T2 high resolution, (d) left sagittal oblique T2 high resolution show normal inner ear structures.

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Figure 13 Case no. 5: postcochlear implant. Serial axial cuts (a, b, and c) and coronal cut (d) show complete insertion of the electrode and reaching the basal cochlear turn.

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Figure 14 Case no. 6: a 2-year-old male child presented with prelingual severe to profound SNHL. The patient had past history of meningitis. CT scan images show normal inner ear structures, normal bilateral IAC, and both cochlea and normal vestibule on both sides. CT, computed tomography; SNHL, sensorineural hearing loss.

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Figure 15 Case no. 6: MRI scan images (a) axial T2 high resolution, (b) coronal T2 high resolution, (c) right sagittal oblique T2 high resolution, (d) left sagittal oblique T2 high resolution show normal inner ear structures.

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Figure 16 Case no. 6: postcochlear implant. Selected coronal cut (a) and serial axial cuts (b and c) show complete insertion of the electrode and reaching the basal cochlear turn.

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Figure 17 Case no. 7: a 16-year- old male patient presented with postlingual severe to profound SNHL. Axial (a and b) and coronal (c) CT scan images show complete ossification of both cochlea. CT, computed tomography; SNHL, sensorineural hearing loss.

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Figure 18 Case no. 7: axial T2 high resolution show loss of normal fluid filled spaces of membranous labyrinth on both sides.

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  Discussion Top


Cochlear implantation is the standard procedure for managing severe to profound SNHL [6].

Cochlear implants are recommended for children as young as 12 months and there is no upper age limit [7].

Multiple models of cochlear implant devices are present. All are multichannel intracochlear array devices [8].

The aim of this study was to evaluate the role of various imaging modalities (CT and MRI) in the preoperative and postoperative evaluation of cochlear implant candiates.

All cases (20 cases) underwent preoperative MDCT and MRI of both temporal bones.

Only 17 cases underwent postoperative MDCT.

In our study, we agree with Lane and colleagues, who found that the use of oblique sagittal reconstructions with different angles had solved the problem with volume-averaging effect at SCC imaging and diagnosis of dilated vestibular aqueduct. Moreover, oblique sagittal reconstruction can depict the entire length of the tympanic and mastoid segments of the facial nerve [9].

In our study, we agree with Chavhan and colleagues that CISS/FIESTA-C has become a sequence of choice for evaluating the cranial nerves. Cerebellopontine angle cistern lesions and cranial nerves VII and VIII in the internal auditory canal and labyrinth are best evaluated with CISS/FIESTA-C [10].

In our study, most children with congenital SNHL showed normal inner ear morphology with congenital inner ear anomalies reported in 41.6%. This findings agree with Haung et al. [11], who explained that the hearing loss is often at the microscopic level and does not affect the appearance of the bony otic capsule or membranous inner ear.

In our study, we agree with Morzaria et al. [12] who reported that meningitis is the most common postnatal cause of acquired bilateral SNHL, as the eight patients presented to us with postlingual hearing loss, all of them were postmeningitic.

In our study, the most common cause of the SNHL was congenital causes (representing 60% of cases) and then acquired causes (representing 40% of cases). This slightly differs from McClay et al. [13] who reported that the SNHL described in children was due to genetic cause in 50% of their sample while acquired and unknown causes represented 50%.

In our study, we agree with Mackeith et al. [14] that combined MDCT and MRI is better as MRI can assess the cochlear nerve anomalies like nerve absence and early stages of postmeningitic labyrinthine fibrosis.

In the current study, out of the 12 patients with congenital SNHL only five (41.6%) patients showed congenital malformation of their inner ears ranged from IP II, dilated vestibular aqueducts, Michel deformity, and cochlear hypoplasia. This result differs from that of Gupta et al. [15] who reported that congenital malformations of the inner ear are rare anomalies. So they can be identified on imaging in about 20% of patients with congenital SNHL.In our study, we agree with Broomfield and colleagues that certain abnormalities of the inner ear are better depicted on CT, while others are better seen on MRI. Hence, neither MDCT nor MRI of the brain and temporal bones appears to be adequate as a single imaging modality but they are complementary to each other for preoperative imaging of cochlear implantation [16].

In our study, we agree with Arweiler-Harbeck and colleagues that MDCT has proven its efficacy in the postoperative imaging of cochlear implant patients. CT confirms the intracochlear position of the implant. It has also been shown that malpositioning and kinking can be detected by CT imaging [17].

In our study, full electrode array insertion was reported in all cases who underwent cochlear implantation which agrees with Ying et al. [18] who reported that misplacement of the electrode is rarely occur.


  Conclusion Top


Preoperative CT and MRI assessment of children with severe or profound SNHL is critical for determining implant candidacy. Both have their proponents. MDCT demonstrates the bony architecture of the temporal bone, while MRI is helpful for identifying membranous labyrinth and soft tissue abnormalities.

MDCT has proven its efficacy in the postoperative imaging of cochlear implant patients. CT confirms the intracochlear position of the implant. It has also been shown that malpositioning and kinking can be detected by CT imaging.

Acknowledgements

Source(s) of support: Radiodiagnosis Departments, Al Hussein Univeristy Hospital.

Organization: Faculty of Medicine for Boys.

Place: Al Hussein Univeristy Hospital.

Date: 07/04/2019

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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2.
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Chaturvedi A, Mohan C, Mahajan SB, Kakkar V. Imaging of cochlear implants. J Radiol Imag 2006; 16:85–392.  Back to cited text no. 3
    
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Verbist BM, Joemai RM, Teeuwisse WM. Evaluation of 4 multisection CT systems in postoperative imaging of a cochlear implant: a human cadaver and phantom study. Am J Neuroradiol 2008; 29:1382–1388.  Back to cited text no. 5
    
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Balkany TJ. Cochlear implants for sensorineural hearing loss. Hosp Phy 2002; 38:22–32.  Back to cited text no. 7
    
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Young JY, Ryan ME, Young NM. Preoperative imaging of sensorineural hearing loss in pediatric candidates for cochlear implantation. RadioGraphies 2014; 34:E133–E149.  Back to cited text no. 8
    
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Lane JI, Lindell EP, Witte RJ, DeLone DR, Driscoll CL. Middle and inner ear: improved depiction with multiplanar reconstruction of volumetric CT data. Radiographics 2006; 26:115–124.  Back to cited text no. 9
    
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Chavhan GB, Babyn PS, Singh M, Vidarsson L, Shroff M. MR imaging at 3.0 T in children: technical differences, safety issue, and initial experience. Radiographics 2009; 29:1451–1466.  Back to cited text no. 10
    
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Haung BY, Zadanski C, Castillo M. Pediatric sensorineural-hearing loss, part 1: practical aspects for neuroradiologists. Am J Neuroradiol 2012; 33:211–217.  Back to cited text no. 11
    
12.
Morzaria S, Westerberg BD, Kozak FK. Systematic review of the etiology of bilateral sensorineural hearing loss in children. Int J Pediatr Otorhino-laryngol 2004; 68:1193–1198.  Back to cited text no. 12
    
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McClay JE, Booth TN, Parry DA. Evaluation of pediatric Sensorineural hearing loss with magnatic resonance imaging. Arch Otolaryngol Head Neck Surg 2008; 146:180–190.  Back to cited text no. 13
    
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Mackeith S, Joy R, Robinson P. Pre-operative imaging for cochlear implantation: magnetic resonance imaging, computed tomography, or both? Cochlear Implants Int 2012; 13:133–136.  Back to cited text no. 14
    
15.
Gupta SS, Maheshwari SR, Kirtane MV. Pictorial review of MRI/CT Scan in congenital temporal bone anomalies, in patients for cochlear implant. Indian J Radiol Imaging 2009; 19:99–106.  Back to cited text no. 15
    
16.
Broomfield SJ, Da Cruz M, Gibson WP. Cochlear implants and magnetic resonance scans: a case report and review. Cochlear Implants Int 2013; 14:51–55.  Back to cited text no. 16
    
17.
Arweiler-Harbeck D, Mönninghoff C, Greve J. Imaging of electrode position after cochlear implantation with flat panel CT. ISRN Otolaryngol 2012; 2012:728205.  Back to cited text no. 17
    
18.
Ying YL, Lin JW, Oghalai JS. Cochlear implant electrode misplacement: incidence, evaluation, and management. Laryngoscope 2013; 123:757–766.  Back to cited text no. 18
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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