Fissula ante fenestram

Last revised by Dr Daniel J Bell on 27 Jan 2021

The fissula ante fenestram (plural: fissula ante fenestras) is a small connective tissue-filled cleft in the otic capsule of the temporal bone, not typically visible on CT. The area around the fissula ante fenestram is the usual origin of fenestral otosclerosis.

Gross anatomy

The fissula ante fenestram is situated in the region anterior to the oval window 1. The structure is an irregular projection from the junction of the vestibule and scala vestibuli that extends to the periosteum of the middle ear just beneath the cochleariform process, where the tendon of the tensor tympani muscle turns laterally toward the malleus 2.

The fissula ante fenestram was previously thought to be related to the cochlear cleft 3, but recent studies have shown the latter to be a separate structure 4.

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

Anatomic trivia:

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

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. It is not 'fissulae' as some might erroneously believe.

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Cases and figures

  • Figure 1: labeled as FAF
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