Timothy Booth

I believe the imaging evaluation of children with sensorineural hearing loss is difficult, often with quite subtle findings. I wanted to report on unique, objective measures to help in the diagnosis of cochlear malformations. Determining the number of cochlear turns can be difficult even for the experienced temporal bone imager. Scala communis is a common developmental malformation of the cochlea that results from the incomplete formation of the distal interscalar septum. The septum separates the turns of the cochlea, with the second portion delineating the upper basal from the upper middle cochlear turn.

The R2 notch, which represents the second portion of the interscalar septum, is an easily definable structure along the lateral margin of the cochlea and was easily assessed by all interpreters (including novice readers). Both a radiology and otolaryngology resident could accurately diagnose scala communis using both depth and angle as discriminators.

When the structure is shallow or obtuse, the radiologist should entertain the diagnosis of scala communis, which is often associated with incomplete partition type II. Scala communis should be suspected with an angle of ˃114 degrees and a depth of 3 mm or less.

I have received great feedback from many neuroradiologists about the utility of this finding and the enhanced ability to make this difficult diagnosis. The simple evaluation of this structure leads to improved care in this population, as scala communis may have surgical implications with an increased risk for a gusher, and addresses the need to accurately classify these malformations to predict patient outcomes.

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