Fissula ante fenestram

The fissula ante fenestram (FAF), also known as the cochlear cleft, is a small connective tissue-filled cleft located where the tendon of the tensor tympani muscle turns laterally toward the malleus. It is situated immediately anterior to the oval window, and posterior to the cochleariform process ¹. 

The fissula ante fenestram is the usual origin of fenestral otosclerosis.

Anatomic trivia:

• it is the only structure named fissula in the human body
• it has not been found in any other animal

A structure called the fossula post fenestram is also described in histological studies and refers to a different but anatomically-proximate structure.

History and etymology

It is derived from the classical Latin:

• fissula meaning a 'small cleft'
• ante meaning 'forwards of'
• fenestram (accusative form of fenestra) meaning 'window'.

Hence, it literally means 'the small cleft forwards of the window'.

The plural, although rarely seen, is fissula ante fenestras.