Hyrtl's fissure.

Hyrtl's fissure is a transient anatomic landmark in the developing fetal petrous temporal bone and is usually closed by the normal progression of ossification in the 24th week of gestation. It occasionally persists into extrauterine life and has been reported as an unusual cause of a perilabyrinthine cerebrospinal fluid fistula. We present a case of a child presenting with bacterial meningitis because of a persistent Hyrtl's fissure. We have reviewed aspects of the fissure's developmental anatomy and previously published clinical cases. We have also explored the provenance of the eponym. We were unable to uncover evidence in support of the contention that Joseph Hyrtl was actually responsible for describing the structure commonly known as Hyrtl's fissure.