Hyrtl's fissure: a case of spontaneous cerebrospinal fluid otorrhea.

Spontaneous CSF otorrhea is a relatively rare entity. Adequate diagnosis and treatment are needed to avoid life-threatening complications such as meningitis. Because diagnosis is based on CT findings, identification of the different pathways of congenital fistulas requires detailed knowledge of embryology and anatomy. The facial canal, petromastoid canal, and tympanomeningeal (Hyrtl's) fissure can be responsible for CSF fluid otorrhea in the absence of any abnormality of the adjacent membranous labyrinth. We report the first documented and imaging case of Hyrtl's fissure and its treatment.