EXERCISE 20

ENDOSCOPIC ENDOMEATAL DISSECTION OF PETROUS APEX

Dear surgeons,
These are endoscopic endomeatal dissection pictures of petrous apex and clivus approaches.

STEP A- ENDOSCOPIC ENDOMEATAL FRONT GATE TO SKULL BASE

This is endoscopic FRONT GATE to the skull base. It is bounded
1 – Anteriorly by ICA
2 – Superiorly by labyrinthine and HFN and IAC
3 – Posteriorly by vertical FN
4 – Antero inferiorly by carotid foramen
5 – Postero inferiorly by jugular bulb. Endoscopic dissection of this area is area is very important
Labelling :
1) Vertical ICA
2) Horizontal ICA
3) Medial petrous apex area
4) Lareral petrous apex and trans clival approach route
5) Exposed TM joint

STEP B – AREA OF DISSECTION
The lined area available for dissection of skull base througth endoscopic endomeatal approach is shown here
Labelling:
4) IAC

STEP C – 360 DEGREES EXPOSURE OF ICA.
The ICA including horizontal, posterior genu and vertical parts are skeletonized 360 degrees.
Lateral and medial petrous apex and the IAC is exposed.
Labyrinthine, horizontal and vertical portions of facial nerve is exposed
Labelling:
1) Tm joint
2)Vertical ICA
3) Labyrinthine FN
4) IAC
5) HFN

STEP D – DISPLACEMENT OF ICA
The 360 degrees exposed ICA is displaced posteriorly. After displacement of ICA, visualises petrous apex completely
Labelling:
1) H. ICA
2) Vertical ICA
3) Petrous apex
4) Posterior genu of ICA

STEP E – POSTERIOR GENU OF ICA
There is 1 cm space is available infront of ICA to approach clivus.
Through this route the clivus can be approached with endoscopes
Labelling:
A) space available anterior to ICA for skull base approaches
B) petrous apex area

STEP F – INTACT FELLOPIAN CANAL AND CAROTID BRIDGE APPROACH.
Once Vertical FN is skelotinized with 360 degrees exposure of ICA , the medial petrous bone and skull base can be entered through medial side these ICA and FN
Labelling:
1) ICA
2) Vertical ICA
3) Space between ICA and TM joint

So dear surgeons these are the complete EXERCISES OF ENDOSCOPIC ENDOMEATAL DISSECTION OF TEMPORAL BONE.
In addition to normal microscopic temporal bone dissection exercises, these endiscopic temporal bone exercises give additional clear anatomical details of the temporal bone, based upon these basic exercises surgeon can proceed to EXTENDED ENDOSCOPIC SKULL BASE DISSECTION EXERCISES further.
In future, we will start the EXTENDED ENDOSCOPIC ENDOMEATAL DISSECTION OF LATERAL SKULL BASE.