Radiological Classification of the Facial Nerve

Study Overview
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Brief Summary
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Cortical mastoidectomy and posterior tympanotomy is a classic approach for cochlear implant. Intimate knowledge of the relevant surgical anatomy of the temporal bone and facial recess is important to safely perform the posterior tympanotomy. Anatomical variation of facial nerve such as lateral or anterior position of vertical segment of facial nerve, will render this approach challenging. In this research, investigators proposed a Radiological Classification system of the position of vertical segment of facial nerve in relation to the lateral semicircular canal to predict difficult cases with narrow facial recess.

Detailed Description
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Cochlear implantation done by mastoidectomy, posterior tympanotomy and round window membrane insertion or cochleostomy, if we have to. In cases with very laterally placed vertical segment of the facial nerve a trans- mastoid trans- attic approach used with trans canal monitoring as an alternative approach. Position of the vertical segment of the facial nerve (VFN) determined by coronal view HRCT of temporal bone, bone window of 0.6 mm thickness by using the cut posterior to the internal auditory canal at the level of lateral semicircular canal (LSCC) and then drawing a line parallel to the bony canal of the VFN and another parallel line on the outer bony wall of lateral semicircular canal (LSCC), and comparing level of both. The location of the facial nerve classified into normal if the FN is medial, same level or lateral to LSCC . Investigators referred the laterally placed FN (LPFN) when the whole vertical segment of facial nerve is lateral to LSCC. In addition, distance between VFN and LSCC was measured in cases of laterally placed FN. Investigators proposed a radiological classification system of the mastoid segment of facial nerve to predict round window niche accessibility through posterior tympanotomy pre-operatively by using coronal view computed tomography scan of temporal bone. Facial nerve position classified into 3 types in relation to LSCC: TYPE I Medial to LSCC TYPE II Same level of LSCC TYPE III Laterally placed to LSCC III a) Less than 2mm III b) More than 2mm

Official Title
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Radiological Classification of the Vertical Segment of Facial Nerve in Cochlear Implant Surgery

Conditions
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Severe to Profound Sensorineural Hearing Loss, Undergoing Cochlear Implant Surgery

Intervention / Treatment
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* Other: cochlear implant surgery


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All patient who underwent cochlear implant surgery with preoperative computed tomography scan and high resolution CT scan of temporal bone Exclusion Criteria: None

Ages Eligible for Study
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Minimum Age: 1 Year
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Cochlear Implant<br>Patients with severe to profound sensorineural hearing loss who underwent cochlear implant surgery | Other: cochlear implant surgery<br>* patients with severe to profound sensorineural hearing loss who underwent cochlear implant surgery<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Radiological classification of vertical segment of facial nerve | - Radiological classification of vertical segment of facial nerve by studying temporal bone CT scan using an implemented scoring system TYPE I Medial to LSCC TYPE II Same level of LSCC TYPE III Laterally placed to LSCC III a) Less than 2mm III b) More than 2mm | 48 hours before surgery | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Surgical approach in cochlear implantation | The surgical approach used for cochlear implantation | For 4 hours after start of surgery |