title: Imaging Modality of Choice for Pre-Operative Cochlear Imaging: HRCT vs. MRI Temporal Bone.
abstract: BACKGROUND
  Congenital inner ear malformations occur as a result of the arrest or aberrance of inner ear development due to the heredity, gene mutation or other factors. Ever since the availability of cochlear implants, pre-operative evaluation by imaging of temporal bone has gained much attention. Precise selection of the candidate for cochlear implant dependent on preoperative radiological investigations. Only CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) can provide a better picture of anatomy and pathology.
  
  
  OBJECTIVE
  To compare pre-operative imaging findings of both MRI and High Resolution Computed Tomography (HRCT) temporal bone and to find the best modality of choice in patients with bilateral profound Sensorineural Hearing Loss (SNHL).
  
  
  METHODS
  This was a prospective, longitudinal, observational study conducted between June 2010 to November 2012. A total of 144 temporal bones were evaluated in 72 children with bilateral profound SNHL with congenital inner ear malformations. Each temporal bone was considered as a single case (144 cases). All the patients underwent HRCT and high field MRI study. MRI study included T2 W axial 3D FIESTA (Fast Imaging Employing Steady-state Acquisition) sequence. Anatomic abnormalities in each temporal bone were described and noted. For complete and better evaluation of Vestibulo-Cochlear Nerve (VCN) additional 3D oblique parasagittal view was taken perpendicular to the internal auditory canal with a small Field Of View (FOV).
  
  
  RESULTS
  HRCT and MRI allowed accurate detection of inner ear malformations in children with bilateral SNHL. Majority of the patients presented with multiple structural abnormalities of inner ear. The common pathologies detected in the study were semicircular canal abnormality (89/144) followed by cochlear abnormalities (39/144). Most common cochlear abnormality was Mondini's deformity (14/144). MRI demonstrated absent of vestibulo-cochlear nerve in 15 cases.
  
  
  CONCLUSIONS
  Few abnormalities of inner ear are better illustrated on CT, while others are better showed on MRI. Hence, neither HRCT nor MRI of the brain and temporal bones appears to be adequate imaging modality rather they are complementary to each other for pre-operative imaging of cochlear implantation.
authors.affiliation: Senior Resident, Department of Radiology, Kasturba Medical College , Manipal, Karnataka, India .
authors.forename: Poornima
authors.initials: P
authors.lastname: Digge
authors.affiliation: Ex-Associate Professor, Department of Radiology, B J Medical College and Civil Hospital , Ahmedabad, India .
authors.forename: Rajendra N
authors.initials: RN
authors.lastname: Solanki
authors.affiliation: Professor, Department of Radiology, B J Medical College and Civil Hospital , Ahmedabad, India .
authors.forename: Dipali C
authors.initials: DC
authors.lastname: Shah
authors.affiliation: Professor, Department of ENT, B J Medical College and Civil Hospital , Ahmedabad, India .
authors.forename: Rajesh
authors.initials: R
authors.lastname: Vishwakarma
authors.affiliation: Associate Professor, Department of Radiology, Kasturba Medical College , Manipal, Karnataka, India .
authors.forename: Sandeep
authors.initials: S
authors.lastname: Kumar
keywords: Cochlea; Hearing loss; Magnetic resonance imaging; Sensorineural