A study on modelling cochlear duct mid-scalar length based on high-resolution computed tomography, and its effect on peri-modiolar and mid-scalar implant selection

Abstract

ObjectiveTo determine cochlear duct mid-scalar length in normal cochleae and its role in selecting the correct peri-modiolar and mid-scalar implant length.MethodsThe study included 40 patients with chronic otitis media who underwent high-resolution computed tomography of the temporal bone. The length and height of the basal turn, mid-modiolar height of the cochlea, mid-scalar and lateral wall length of the cochlear duct, and the ‘X’ line (the largest distance from mid-point of the round window to the mid-scalar point of the cochlear canal) were measured.ResultsCochlear duct lateral wall length (28.88 mm) was higher than cochlear duct mid-scalar length (20.08 mm) (p < 0.001). The simple linear regression equation for estimating complete cochlear duct length was: cochlear duct length = 0.2 + 2.85 × X line.ConclusionUsing the mid-scalar point as the reference point (rather than the lateral wall) for measuring cochlear duct mid-scalar length, when deciding on the length of mid-scalar or peri-modiolar electrode, increases measurement accuracy. Mean cochlear duct mid-scalar length was compatible with peri-modiolar and mid-scalar implant lengths. The measurement method described herein may be useful for pre-operative peri-modiolar or mid-scalar implant selection.

Computed Tomography–Based Measurements of the Cochlear Duct: Implications for Cochlear Implant Pitch Tuning

“…Accurate measurement of CDL is highly germane to CI electrode array design, preoperative selection of electrode arrays (Erixon & Rask-Andersen 2013; Pamuk et al 2019), and postoperative frequency mapping (Jiam et al 2016a, 2019). Whereas CDL measurements were previously obtained from direct measurements of histological sections (Bredberg 1965; Ulehlova et al 1987; Wright et al 1987; Sridhar et al 2006; Stakhovskaya et al 2007; Verbist et al 2010), CDL measurements are increasingly calculated today using indirect imaging-based reconstructions of the cochlea (Erixon et al 2009; Erixon & Rask-Andersen 2013; Pearl et al 2014; Alexiades et al 2015) and spiral coefficients using 3D CT-based reconstructions of the inner ear (Wurfel et al 2014; Koch et al 2017b; Lexow et al 2018).…”

Radiological measurement of cochlear dimensions in cochlear hypoplasia and its effect on cochlear implant selection

“…Our previous study examined cochlear dimensions in the normal cochlea. 8 However, to the best of our knowledge, the literature does not include any data on hypoplastic cochlear dimensions. Prior to implantation of a cochlear implant, accurate measurement of the cochlear canal length is extremely important for selecting a cochlear implant electrode of optimal length.…”