Consensus Panel on a Cochlear Coordinate System Applicable in Histologic, Physiologic, and Radiologic Studies of the Human Cochlea

Abstract

Hypothesis An objective cochlear framework, for evaluation of the cochlear anatomy and description of the position of an implanted cochlear implant electrode, would allow the direct comparison of measures performed within the various sub-disciplines involved in cochlear implant research. Background Research on the human cochlear anatomy in relation to tonotopy and cochlear implantation is conducted by specialists from numerous disciplines such as histologists, surgeons, physicists, engineers, audiologists and radiologists. To allow accurate comparisons between and combinations of previous and forthcoming scientific and clinical studies, cochlear structures and electrode positions must be specified in a consistent manner. Methods Researchers with backgrounds in the various fields of inner ear research as well as representatives of the different manufacturers of cochlear implants (Advanced Bionics Corp, Med-El, Cochlear Corp) were involved in consensus meetings held in Dallas, March 2005 and Asilomar, August 2005. Existing coordinate systems were evaluated and requisites for an objective cochlear framework were discussed. Results The consensus panel agreed upon a 3-dimensional, cylindrical coordinate system of the cochlea using the “Cochlear View” as a basis and choosing a z-axis through the modiolus. The zero reference angle was chosen at the centre of the round window, which has a close relationship to the basal end of the Organ of Corti. Conclusions Consensus was reached on an objective cochlear framework, allowing the outcomes of studies from different fields of research to be compared directly.

Automated analysis of human cochlea shape variability from segmented μ CT images

“…The cochlear coordinate system (x, y, z) by Verbist et al (2010) provide a standard and unambiguous framework for anatomic studies of the cochlea.…”

Standardization of CT Depiction of Cochlear Implant Insertion Depth

“…The location of the implant position within the cochlea was described by using an approach based on consensus terminology for standard terms regarding cochlear anatomy. 10 Results were recorded by using a 4-quadrant system for each 360°turn of the cochlea (noted as numerals I-X), with the round window as a zero-degree reference point (Fig 2). For example, insertion into only the inferior quadrant of the first turn would be termed "quadrant I," insertion into the inferior quadrant of the second turn would be termed "quadrant V," and insertion into the posterior quadrant of the second turn would be termed "quadrant VIII" insertion.…”

“…10 Throughout the literature, especially when comparing otolaryngologic and radiologic textbooks, descriptions of cochlear anatomy vary significantly. This variation is especially seen when the cochlea is malformed, without the usual number of turns.…”

“…Ideally, the radiology report would routinely include objective measures of the CI tip insertion depth and a scalar chamber assignment so that these can be compared against the clinically desired position of the electrode tip. In 2010, a consensus panel comprising radiologists, otologists, and researchers developed a cochlear coordinate system 10 to have an objective method for comparing study and research outcomes by using a standard description of the cochlea. The consensus terminology developed for describing cochlear anatomy uses the round window as the zero-degree point.…”

Threshold Levels of Dual Electrode Stimulation in Cochlear Implants

“…To measure the exact position of the electrode contacts, a multiplanar reconstruction (MPR) was made (Verbist et al 2005). A system of coordinates, according to an international consensus (Verbist et al 2010), was entered in the postoperative MPR, using a custom Matlab application (MathWorks, Natick, MA) as described in a previous paper (SnelBongers et al 2011). All electrode contacts were marked by an experienced physician.…”