Hyrtl fissure

Hyrtl fissure (also known as tympanomeningeal fissure) is a congenital infralabyrinthic fissure through the petrous temporal bone. It is a very rare cause of spontaneous CSF otorrhea and meningitis.

Development

This fissure is present in the developing fetal petrous temporal bone and is typically ossified by 24 weeks.

Radiographic features

CT

• the fissure can be seen on thin axial slices and coronal reformations
• CT cisternography can also help diagnose this rare condition

MRI

• heavily T2 weighted images are helpful

Nuclear medicine

• occasionally radionuclide cisternography can be used, but usually is second-line after CT cisternography (see above)

Treatment and prognosis

Once the diagnosis is established, attempts to surgically close the fissure can be planned .

History and etymology

Hyrtl described his eponymous fissure in 1936 .