Human cochleae with three turns: an unreported malformation.

OBJECTIVE

The objective of this histologic study of archival temporal bone sections was to describe the morphology of human cochleae found with three turns, a previously unreported anomaly, found in three pairs of temporal bones.

METHODS

The authors conducted histopathologic processing and measurement of basilar membrane length. Basilar membrane length was compared with that found in six normal control bones.

RESULTS

Cochleae with three complete turns, rather than the usual two and a half turns, are described for the first time. All had longer than normal basilar membranes, with a mean length of 40.6 mm compared with a mean of 33.8 mm in the normal bones.

CONCLUSIONS

Human cochleae with three turns exist as an unreported anomaly. This is a new category of anomaly, not likely based on interruption of development.