Cochlear cleft

Last revised by Dr Francis Deng on 27 May 2020

The cochlear cleft is a curvilinear radiolucent area of incomplete endochondral ossification in the otic capsule adjacent to the cochlea. It is a variant most prominent in children that may also be visible in adults 1.

The cochlear cleft is a C-shaped structure in the otic capsule of the temporal bone that is parallel and lateral to the basal turn of the cochlea 2. It is located anterior to the oval window and underneath the cochleariform process.

The prevalence/prominence of the cochlear cleft decreases with age 2.

The cochlear cleft corresponds to fatty marrow spaces, consistent with a process of incomplete endochondral ossification 1. It is distinct from the fissula ante fenestram, which is slightly more posteriorly located and composed of connective tissue.

The structure is a normal variant without any relationship with hearing loss 3. It should not be confused for otosclerosis, which commonly affects the area anterior to the oval window or the pericochlear otic capsule.

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