Turns of cochlea

The turns of the cochlea refer to the spiral segments of the cochlear duct as it winds around the modiolus (central axis). In humans, the cochlea typically makes 2.5 turns, but anatomical studies show that this can range from about 2.5 to nearly 3 turns in normal variation.The turns are conventionally defined as follows:

• Basal turn: The first and largest turn, beginning at the round window and encompassing approximately the first 360° (one full turn) of the spiral. This region is critical for cochlear implantation and is the site of high-frequency sound detection.[3-4]

• Middle turn: The second spiral, extending from about 360° to 720°, responsible for mid-frequency sound processing.

• Apical turn: The final segment, from 720° to the apex (typically up to 900° or more), responsible for low-frequency sound detection.