الفهرس 
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Abstract
The location of middle cranial fossa dural plate is an important surgical landmark especially during tympanomastoidectomy. Awareness of level of tegmen particularly if it is low in position is very important for the surgeon in the preoperative period to decrease the risk of iatrogenic dural plate injury or trauma.
The aim of this study is to illustrate the level of tegmen in patients with chronic otitis media (COM) and to study different factors which can affect depth of middle cranial fossa dural plate.
In this prospective study, we identified the middle cranial fossa dural plate in CT scan, and then measured the depth of the dural plate beyond the point of greatest protrusion of the superior semicircular canal into the middle cranial fossa.
Results revealed that: There was significant difference in depth of the middle cranial fossa dural plate between normal and CSOM ears. Tegmen level in CSOM ears was significantly lower than the tegmen level in normal ears, but there was no significant difference in depth of the middle cranial fossa dural plate between normal and CSOM ears with cholesteatoma.
In patients with unilateral COM, there was significant difference in depth of the middle cranial fossa dural plate between normal and CSOM ears in the same patient. Tegmen level in CSOM ears was significantly lower than the tegmen level in normal ears. There was no significant difference in depth of the middle cranial fossa dural plate between normal and CSOM ears with cholesteatoma in the same patient.
There was no significant difference in depth of the middle cranial fossa dural plate between normal ears in patients with unilateral COM and normal ears of normal subjects.
There was no significant difference in the mean of dural plate depth between CSOM ears and CSOM with cholesteatoma ears.
There was no significant difference in mean depth of dural plate between normal ears or CSOM ears or CSOM with choesteatoma regarding sidedness, age and gender.
We conclude that in patients with CSOM, the tegmen is significantly lower and this is a predictive risk during surgery. This level is not affected by gender, age and side of affected ears. The level of the middle cranial fossa dural plate should be assessed from temporal CT scans before surgery, and surgeon should be aware of this important point to avoid possible complications.