Combined petrosal approach

Fig. 1 and 2. The skin incision for the combined petrosal approach is started 1 cm in front of the tragus, curves superiorly and posterior behind the ear and ends below the mastoid tip. A skin flap is developed.

Fig. 3 and 4. After the skin flap is retracted, two separate muscular flaps are developed: one from temporalis muslcle retracted superior and anterior; second muscular flap from the suboccipital musculature, dissected and retracted inferiorly.

Fig. 5. The subperiosteal muscle dissection is completed. The structures revealed are the digastric groove, asterion, the spine of Henle, root of zygoma, temporal squama.

Fig. 6. Image presenting the localization of the transverse and sigmoid sinuses as well as the labyrinth and the facial nerve. Cortical mastoidectomy is performed with boundaries: tip of the mastoid, posterior wall of the outer ear canal, asterion.

Fig.7. After completing the mastoidectomy the sigmoid sinus, as well as the persigmoid dura and mastoid antrum are exposed. The petrous ridge and the tegmen tympany are removed revealing the middle fossa dura, sino-dural angle, as well as superior petrosal sinus.

Fig. 8 The three semicircular canals are exposed. The facial nerve passes just below and lateral to the lateral semicircular canal. The posterior semicircular canal is parallel to the posterior fossa dura. Endolymphatic sac is also shown.

Fig. 9.  Final view after the retrolabyrinthine exposure. The dura is exposed both anteriorly and posteriorly to the sigmoid sinus.

Fig. 10.  View after the craniotomy has been performed which exposes the supratentorial dura as well as the posterior fossa dura. (cadaver dissection and the operative image) Note the course of the transverse and sigmoid sinuses.

Fig. 11.  The dissection of the middle cranial fossa is commenced from back to front manner, which avoids damage to the greater superficial petrosal nerve. The labyrinthine block is also visible.

Fig. 12.  High magnification view of foramen spinosum and the middle meningeal artery. The tip of the scissors are pointing a branch to the facial nerve which should be preserved.

Fig. 13.  The petrous apex is drilled in the boundaries described in the anterior petrosectomy chapter in the booklet.

Fig. 14.  The IAC is unroofed.

Fig. 15.  Exposure of the segments of the facial nerve. Drilling of the middle fossa floor in order to expose the geniculate ganglion.

Fig. 16.  The geniculate ganglion is revealed. The cochlea is exposed at the cochlear angle.

Fig. 17.  Nerves at the IAC exposed.

Fig. 18 and 19. The supratentorial dura is opened. Care is taken not to injure the vein of Labe. Two hemostats are used to clamp the superior petrosal sinus.

Fig. 20 and 21 The superior petrosal sinus as well as the presigmoid dura are cut. The tentorium is split and care is taken not to injure the IV nerve which runs at the tentorial edge.

Fig. 22 and 23 After the tentorium is split the IV nerve and SCA are identified in the ambient cistern. The III nerve is visualized in the interpeduncular cistern.

Fig. 24. Dura in the posterior cranial fossa is opened. The dissector is pointing at the lower cranial nerve complex.

Fig. 25. The Meckel’s cave is opened. Trigeminal nerve could be followed from the exit zone from the brainstem to the entrance in the Meckel’s cave.
Trochlear nerve is also pointed medial and superior to the V nerve.

Fig. 26. After the tentorium is split (technique discussed in detail in the anterior petrosectomy chapter). The IV cranial nerve is exposed.

Fig. 27. The dura is closed and covered with dural sealant.

Fig. 28. The bone flap is replaced and secured with Craniofix and low profile titanium screw and plating system.

Fig. 29. The muscle flap is closed in a watertight fashion.