On the number of turns in human cochleae.

OBJECTIVE

The number of human cochlear turns is generally accepted being 2 1/2, although cases with up to 2 3/4 or even 3 turns are known from literature. This study was performed to evaluate the actual number of cochlear turns and its variance.

METHODS

Histologic temporal bone series from the "Wittmaack temporal bone collection" (Hamburg, Germany) were examined, and the number of scala media segments was counted using the midmodiolar sections. These data were evaluated in reference to the cochlear spiral to obtain the number of cochlear turns.

RESULTS

Sixty-five percent of the investigated specimens had more than 2 1/2 cochlear turns, of which, 11% had more than 2 3/4 turns.

CONCLUSION

The number of human cochlear turns shows a higher variance than is represented in literature. Cases with up to 3 turns can be regarded as upper limit of the normal range. This finding may carry further implications for cochlear implantation to focus on the development of individually shaped electrode carriers and stimulation strategies.