objectives:
1- Describe a classification for the si-
nus tympani (ST) different types
based on their otoendoscopic
and surgical anatomy in relation
to their development theories.
2- Evaluate possible approaches to
each of its types.
3- Eliminate the discrepancy between
the various methods used
to
describe it in literature.
Methods:
Fifty-five temporal bones were
dissected, and the anatomical details
were studied utilizing an operating
microscope and otoendoscopes of
different angles. In addition, the ST
anatomy and relations were studied
in two hundred temporal bones CT
scans. Results:
Four distinct types of ST could be
observed. Type 1, the most common
type, it was pneumatized and consisted
of an orifice and cavity. Type
2,
the well pneumatized type, the
cavity
was deep enough posteriorly
to
exceed the level of the mastoid
segment
of the facial nerve in any direction.
Type 3, the common posterior
tympanic sinus, in which ST communicated
with the upper posterior
tympanic
sinus proper or with a retro-ponticulus
up-ward extension.
Type
4, the non- pneumatized type,
was
shallow with no true orifice and
cavity.
Type 1 and 4 were mainly approached
via the trans-canal route.
Type 2 and 3 required a combined
trans-canal and trans-mastoid
approaches.
Endoscopic trans-canal approach alone was satisfactory for
types 1and 4 but to less extent type
3.
Conclusions:
ST shape and extension both de-
pend mainly on the extent of its
pneumatization, which in turn influences
its relations to the surrounding
structures
in the retro-tympanic area.
Extensively
or unusually pneumatized
types need special or combined
approaches.