Tegmen

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The tegmen is the thin osseous plate that separates the middle cranial fossa from the tympanic and mastoid cavities of the temporal bone. It is comprised of two or three parts :

  • tegmen tympani (roof of the tympanic cavity)
  • tegmen mastoideum (roof of the mastoid cavity)
  • tegmen antri (roof of the antrum), which is often described as part of either tegmen tympani or tegmen mastoideum ; uncommonly described separately

Embryologically, the tegmen is formed by the junction of the petrous and squamous parts of the temporal bone .

Related pathology

Dehiscence of the tegmen in conjunction with dural weakening can lead to meningocele, meningoencephalocele, or CSF fistula into the middle ear (with effusion and CSF otorrhea) or rarely mastoid air cells .