Surgery by Kaare Fugleholm and Jacob Springborg
The retrosignoid approach is the most used exposure for posterior fossa skull base surgery.
It provides a wide exposure to the CP angle and its neurovascular structures.
The retrosignoid approach is the most used exposure for posterior fossa skull base surgery.
It provides a wide exposure to the CP angle and its neurovascular structures.
Case presentation
Types of skin incision and working angle
Fig. 1. Right sided oblique skin incision starting from pinna to C2.
Fig. 2. Straight incision down to bone is made followed with subperiosteal muscle elevation.
Fig. 3. Muscle dissection exposing the Asterion and mastoid.
Fig. 4. Drilling a shaft over the sigmoid sinus outer edge, from the asterion to the mastoid tip.
Fig. 5. Mastoid air cells are exposed. The asterion (the lower edge of the sigmoid transverse junction is used as landmark for drilling.
Fig. 6. Craniotomy using the high speed drill.
Fig. 7. The bone flap should be carefully elevated in order to avoid sinus and dural laceration.
Fig. 8. The exposed mastoid air cells should be thoroughly waxed in order to avoid CSF leakage.
Fig. 9. End result of the craniotomy.
Fig. 10. Dura is opened in a semicircular fashion close to the edge of the sigmoid sinys. H- or X-shaped incision should be avoided because of difficulties with later closure.
Fig. 11. Sufficient CSF release from cisterna magna provides sufficient brain relaxation and obviates the need for the use of fixed brain retractors.
Fig. 12. The cerebrovascular structures of the CP angle are exposed. Dynamic retraction is used.
Fig. 13. The dura over the IAC is cut for creation of flap pointing downwards.
Fig. 14. Exposure of the superior lip of the IAC.
Fig. 15. Opening of the IAC using 3mm high speed drill.
Fig. 16. Exposure of the dura in the IAC after drilling.
Fig. 17. Waxing the exposed mastoid air cells is an important step in the prevention of the postoperative CSF leak.
Fig. 18. The VII nerve is identified using a intraoperative monitoring.
Fig. 19. Dissection the tumor off the nervous structures.
Fig. 20. Internal debulking.
Fig. 21. Dissection of the tumor from the facial nerve.
Fig. 22. Final view after gross total tumor removal. The VII nerve is responding to stimulation and is anatomically and functionally preserved.
Fig. 23. Dura is closed in a watertight fashion.
Fig. 24. The bone flap is replaced using Craniofix.