Home Ahead of print Instructions Contacts
About us Current issue Submit article Advertise  
Editorial board Archives Subscribe Login   


 
 Table of Contents  
CASE REPORT
Year : 2017  |  Volume : 23  |  Issue : 3  |  Page : 211-215

Multimodality approach in evaluation of common crus aplasia


1 Department of Radiology and Imaging Sciences, Sri Ramachandra Medical College and Research Institute, Chennai, Tamil Nadu, India
2 Department of ENT, Head and Neck Surgery, Sri Ramachandra Medical College and Research Institute, Chennai, Tamil Nadu, India

Date of Web Publication31-Aug-2017

Correspondence Address:
Sai Kiran Pendem
Department of Radiology and Imaging Sciences, Sri Ramachandra Medical College and Research Institute, Chennai - 600 116, Tamil Nadu
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/indianjotol.INDIANJOTOL_140_15

Rights and Permissions
  Abstract 

Common crus aplsia is a rare congenital anomaly caused due to abnormal reabsorption of neuroectodermal tissue of membranous common crus. Three patients came to the Department of Otorhinolaryngology with the complaints of poor response to sound. Audiometry examination revealed bilateral sensorineural hearing loss. They were referred to radiology department for high resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) temporal bone as a part of preoperative cochlear implant work up. In the present study, we discuss the HRCT and MRI findings helpful in the diagnosis of this rare anomaly in three cases.

Keywords: Aplasia, Cochlea, Common crus, Semicircular canals, Vestibule


How to cite this article:
Pendem SK, Rangasami R, Mohanty S S, Radhakrishnan PR. Multimodality approach in evaluation of common crus aplasia. Indian J Otol 2017;23:211-5

How to cite this URL:
Pendem SK, Rangasami R, Mohanty S S, Radhakrishnan PR. Multimodality approach in evaluation of common crus aplasia. Indian J Otol [serial online] 2017 [cited 2020 Feb 25];23:211-5. Available from: http://www.indianjotol.org/text.asp?2017/23/3/211/213863


  Introduction Top


The posteromedial end of the superior semicircular canal joins with the anteromedial end of the posterior semicircular canal to form common crus. The absence of common crus is a rare congenital anomaly with incidence of 9.68% in children with congenital sensorineural hearing loss (SNHL).[1] It is known that common crus aplasia (CCA) can be associated with lateral semicircular canal (LSCC) dysplasia.[2] Three-dimensional (3D) techniques such as minimum intensity projection (MIP), volume rendering (VR) of high resolution computed tomography (HRCT), and 3D VR of constructive interference in steady state (CISS) in magnetic resonance imaging (MRI) are helpful in improved diagnosis of cochleovestibular anomalies.[1],[2] Few studies have reported CCA with inner ear anomalies. We present a case series of three children with SNHL with CCA and congenital anomalies of inner ear according to the classification proposed by Sennaroglu et al.[3]


  Case Reports Top


All the three patients presented to the otorhinolaryngology department with a history of poor response to sound since birth. Audiometry examination revealed bilateral SNHL. There were no vestibular disorders noted on clinical examination. There were no associated facial dysmorphism or anomalies in other body parts. They were referred for HRCT and MRI temporal bone for cochlear implant work up.

Protocol and technical details

Parental informed consent was obtained for all three cases. Institutional Ethical Committee approval was obtained.

Computed tomography protocol

Imaging was performed using Philips Brilliance 16-slice Computed tomography (CT) scanner (Brilliance CT, Philips medical systems, OH, Cleveland, USA). The axial sections of temporal bone were acquired at 120 kVp, 250 mA, with thickness of 0.7 mm. and matrix of 512 × 512.

Magnetic resonance imaging protocol

Imaging was performed using Siemens Magnetom Avanto 1.5 tesla MRI scanner (Siemens Health care, Erlangen, Germany). CISS images were acquired using 0.75 mm thickness with no gap and imaging parameters of TR-5.8 ms, TE-2.7 ms, flip angle of 70°, and matrix of 256 × 198.

The VR images of the CISS sequence were done in Siemens work station.

Case 1

A 4-year-old boy with history as mentioned above HRCT and MRI demonstrated following findings.

Right side

Semicircular canals: LSCC was dilated and fused with dilated vestibule suggesting LSCC and vestibular dysplasia. Bony Island of LSCC measured on axial HRCT image was 0.5–0.8 mm (normal: 2.0–2.5 mm) [Figure 1]a superior semicircular canal (SSCC) was hypoplastic. Common crus was absent. Posterior semicircular canal (PSCC) was normal [Figure 1]c
Figure 1: A 4-year-old boy with history of bilateral sensorineural hearing loss. (a) Axial high resolution computed tomography image show dysplastic lateral semicircular canal on both sides (white arrows). Internal auditory canal is widened (asterisks). Vestibular aqueduct is dilated on right side and is normal on left side (arrow heads). (b) Axial high resolution computed tomography image show incomplete partition-I on both sides (black arrows). (c and d) Volume rendering image of right (purple colour) and left (dark brown colour) sides show dysplastic lateral semicircular canals (asteriks). Common crus is absent on both sides (open white arrows). Superior semicircular canal is hypoplastic on right side (white arrow head)

Click here to view


Cochlea

Cochlea appeared cystic were fused with the absence of modiolus and were seen to be separate from vestibule suggesting incomplete partition (IP) Type I [Figure 1]b. Vestibular aqueduct (VA) was minimally dilated. Internal auditory meatus was widened [Figure 1]a.

Left side

Semicircular canals: LSCC was dilated and fused with dilated vestibule suggesting LSCC and vestibular dysplasia. Bony Island of LSCC measured on axial HRCT image was 1.1–1.3 mm [Figure 1]a. Common crus was absent. Both Posterior and superior semicircular canals showed focal stenosis just below the junction [Figure 1]d.

Cochlea

Cochlea appeared cystic with absence of modiolus and was seen to be separate from vestibule suggesting IP Type I [Figure 1]b. VA was normal. Internal auditory canal (IAC) was widened [Figure 1]a.

Case 2

A 6-year-old boy with history as mentioned above HRCT and MRI demonstrated following findings.

Right side

Semicircular canals: LSCC was dilated and fused with dilated vestibule suggesting LSCC and vestibular dysplasia. Bony island of LSCC measured on HRCT axial image was 1.1–1.3 mm [Figure 2]a Common crus was present. Posterior and superior semicircular canals were normal [Figure 3]a.
Figure 2: A 6-year-old boy with history of bilateral sensorineural hearing loss. (a) Axial high resolution computed tomography image shows reduced bony island of the lateral semicircular canal on right side (white arrow); the bony island of the lateral semicircular canal is absent on left side (white arrow head). Internal auditory canal is narrowed on both sides (asterisks). (b) Axial high resolution computed tomography image shows hypoplastic cochlea on right side (black arrow); the cochlea is cystic and fused with vestibule on left side (black arrow head)

Click here to view
Figure 3: A 6-year-old boy with history of bilateral sensorineural hearing loss.(a) Volume rendering image of right side (purple colour) show dysplastic lateral semicircular canal (asterik). Common crus is present (white arrow). (b) Volume rendering image of left side shows dysplastic lateral semicircular canal (asterik). Common crus is absent (white arrow head). (c) Oblique sagittal magnetic resonance image of constructive interference in steady state sequence of right side show absence of cochlear nerve (open arrow) (d) Oblique sagittal magnetic resonance image of constructive interference in steady state sequence of left side show absence of cochlear nerve (open arrow) and single vestibular nerve

Click here to view


Cochlea

Cochlea appeared hypoplastic [Figure 2]b. Cochlear nerve was not visualized [Figure 3]c. IAC was narrowed. VA was normal.

Left side

Semicircular canals

LSCC and vestibular dysplasia was seen. Bony island of LSCC was absent [Figure 2]a. Common crus was absent. Posterior and superior semicircular canals were normal [Figure 3]b.

Cochlea

Cochlea appeared cystic with absence of modiolus and was fused with vestibule suggesting Common cavity deformity [Figure 2]b. IAC was narrowed. Cochlear nerve was not visualized. Vestibular nerve was appeared as single [Figure 3]d. VA was normal.

Case 3

A 9-year-old boy with history as mentioned above HRCT and MRI demonstrated following findings.

Semicircular canals

Bilateral LSCC s were dilated and fused with vestibule. CCA was noted on both sides. Posterior and superior semicircular canals were seen [Figure 4]a and [Figure 4]b.
Figure 4: A 9-year-old boy with history of bilateral sensorineural hearing loss. (a and b) Volume rendering images of right and left sides shows dysplastic lateral semicircular canal (asterisks). Common crus is absent (white arrows). (c and d) Axial high resolution computed tomography images of the right and left ears shows normal cochlea (black arrows) on both sides

Click here to view


Cochlea

Cochlea was normal on both sides. IAC was normal. VA was normal [Figure 4]c and [Figure 4]d.

[Table 1] shows the summary of findings demonstrated on HRCT and MRI for the three cases.
Table 1: Summary of findings demonstrated in high resolution computed tomography and magnetic resonance imaging

Click here to view



  Discussion Top


HRCT and MRI temporal bone have become routine part of preoperative cochlear implant work up for diagnosing congenital anomalies of inner ear in children with SNHL.

Embryology of inner ear

At the 3rd week of gestation, otic placode develops from the ectodermal layer on either side of the rhombencephalon. By the 4th week, the otic placode invaginates into the connective tissue adjacent to the rhombencephalon to form the otic cyst or otic vesicle. Otocyst starts to differentiate by the 5th week. At around 6th week, the cochlea and semicircular canals were identified. The cochlear duct achieves the full 2.5 turns at 9–11 weeks. The development of the cochlea is completed between 22nd and 25th weeks. Thus, the human labyrinth achieves adult size at birth and does not grow further.[4],[5],[6]

Jackler et al.[7] proposed the classification of inner ear abnormalities, based on a linear developmental model towards normal anatomy and most likely time at which developmental arrest occurs during embryogenesis. Sennaroglu and Saatci [3] further modified this classification. They stated five groups of malformations; which include cochlear, vestibular, semicircular canal, IAC, vestibular, and cochlear duct malformations.

The classification of Cochleo-vestibular malformations according to Sennaroglu et al. was shown in [Table 2].
Table 2: Classification of cochlear anomalies according to Sennaroglu et al.

Click here to view


Semicircular canal anomalies

They can be either completely absent/hypoplastic or enlarged. The most common anomaly is short LSCC being confluent with vestibule known as LSCC-vestibular dysplasia.

Large vestibular aqueduct syndrome

It is the most common inner ear anomaly occurring in children with congenital SNHL. Usually presents bilaterally. It is defined as having a width of more than 1.5 mm measured at the mid-point between common crus and external aperture.

Benton and Bellet [8] proposed that occurrence of CCA is not related to developmental arrest of otic placode. It is caused due to abnormal reabsorption of neuro-ectodermal tissue of membranous crus which results in insufficient stimulation for the surrounding mesenchyme to get differentiated in to cartilage and finally to bone.

Manfré et al.[9] reported a case with unilateral CCA associated with Goldenhar syndrome (Occuloauriculo vertebral dysplasia). On CT and MRI imaging they have identified CCA on the right side with LSCC-vestibular dysplasia. There were no cochlear anomalies.

Kim et al.[2] retrospectively studied the findings of 3D volume rendered images obtained from CISS sequence in six cochlear implant candidates who had been diagnosed with CCA. They stated that 3D VR images can help in better comprehension of CCA compared to two-dimensional axial sections and MIP techniques. The six cases with CCA were found to be associated with cochlear anomalies such as cochlear hypoplasia and IP.

Emmrich et al.[1] have described the usefulness of 3D CT VR technique in evaluation of CCA. They stated that it is difficult to identify the CCA on axial and coronal sections on CT scan and would require 3D reconstructed VR images for better visualization of this anomaly.

In our study, unilateral aplasia was found in the second case. Kim et al.[2] have also reported a case with unilateral aplasia. It is difficult to understand the occurrence of unilateral aplasia as the development of inner ear occurs simultaneously on both sides.

All the three cases showed lateral semicircular-vestibular dysplasia which is in accordance with the known fact that it is associated with CCA. As LSCC is the last to be formed any developmental malformations happened during development of posterior and LSCC will also affect the LSCC which is evident from our study.

In our study, we have used combined HRCT and MRI findings to diagnose these malformations. Volume rendered MRI obtained from CISS sequence was extremely useful to confirm the CT diagnosis. Further, they could show area of stenosis in the semicircular canals. The oblique sagittal magnetic resonance sections obtained perpendicular to the vestibulo-cochlear and facial nerves would help in better understanding of the hypoplasia/agenesis of the nerves. The accurate diagnosis of inner anomalies associated with CCA and in evaluating status of nerves would be helpful for ENT surgeon in determining the implantation side and choosing the length of the electrode array.


  Conclusion Top


Our study shows that HRCT and MRI imaging with advanced rendering techniques such as VR techniques were quiet useful for radiologists in studying the complex anatomy of cochleo-vestibular structures and improve the confidence in accurate diagnosis and classification of cochlea-vestibular anomalies. These findings would help the surgeon in making choice of implantation side and determining the length of cochlear implant according to the cochlear duct length in cochlear anomalies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Emmrich JV, Fatterpekar GM, Shlionsky A, Som PM. 3D CT evaluation of common crus aplasia. AJNR Am J Neuroradiol 2009;30:1127-30.  Back to cited text no. 1
[PUBMED]    
2.
Kim HJ, Song JW, Chon KM, Goh EK. Common crus aplasia: Diagnosis by 3D volume rendering imaging using 3DFT-CISS sequence. Clin Radiol 2004;59:830-4.  Back to cited text no. 2
[PUBMED]    
3.
Sennaroglu L, Saatci I. A new classification for cochleovestibular malformations. Laryngoscope 2002;112:2230-41.  Back to cited text no. 3
[PUBMED]    
4.
Jeffery N, Spoor F. Prenatal growth and development of the modern human labyrinth. J Anat 2004;204:71-92.  Back to cited text no. 4
[PUBMED]    
5.
Yiin RS, Tang PH, Tan TY. Review of congenital inner ear abnormalities on CT temporal bone. Br J Radiol 2011;84:859-63.  Back to cited text no. 5
[PUBMED]    
6.
Bartel-Friedrich S, Wulke C. Classification and diagnosis of ear malformations. Gms Curr Top Otolaryngol Head Neck Surg 2009;6:1-21.  Back to cited text no. 6
    
7.
Jackler RK, Luxford WM, House WF. Congenital malformations of the inner ear: A classification based on embryogenesis. Laryngoscope 1987;97:2-14.  Back to cited text no. 7
[PUBMED]    
8.
Benton C, Bellet PS. Imaging of congenital anomalies of the temporal bone. Neuroimaging Clin N Am 2000;10:35-53, vii-viii.  Back to cited text no. 8
[PUBMED]    
9.
Manfré L, Genuardi P, Tortorici M, Lagalla R. Absence of the common crus in Goldenhar syndrome. AJNR Am J Neuroradiol 1997;18:773-5.  Back to cited text no. 9
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2]



 

Top
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
Abstract
Introduction
Case Reports
Discussion
Conclusion
References
Article Figures
Article Tables

 Article Access Statistics
    Viewed1495    
    Printed11    
    Emailed0    
    PDF Downloaded99    
    Comments [Add]    

Recommend this journal