![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/00-retrosigm.jpg)
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
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/a1.jpg)
Types of skin incision and working angle
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Fig. 1. Right sided oblique skin incision starting from pinna to C2.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/021.jpg)
Fig. 2. Straight incision down to bone is made followed with subperiosteal muscle elevation.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/031.jpg)
Fig. 3. Muscle dissection exposing the Asterion and mastoid.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/041.jpg)
Fig. 4. Drilling a shaft over the sigmoid sinus outer edge, from the asterion to the mastoid tip.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/051.jpg)
Fig. 5. Mastoid air cells are exposed. The asterion (the lower edge of the sigmoid transverse junction is used as landmark for drilling.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/061.jpg)
Fig. 6. Craniotomy using the high speed drill.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/071.jpg)
Fig. 7. The bone flap should be carefully elevated in order to avoid sinus and dural laceration.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/081.jpg)
Fig. 8. The exposed mastoid air cells should be thoroughly waxed in order to avoid CSF leakage.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/091.jpg)
Fig. 9. End result of the craniotomy.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/101.jpg)
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.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/111.jpg)
Fig. 11. Sufficient CSF release from cisterna magna provides sufficient brain relaxation and obviates the need for the use of fixed brain retractors.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/121.jpg)
Fig. 12. The cerebrovascular structures of the CP angle are exposed. Dynamic retraction is used.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/131.jpg)
Fig. 13. The dura over the IAC is cut for creation of flap pointing downwards.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/141.jpg)
Fig. 14. Exposure of the superior lip of the IAC.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/151.jpg)
Fig. 15. Opening of the IAC using 3mm high speed drill.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/161.jpg)
Fig. 16. Exposure of the dura in the IAC after drilling.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/171.jpg)
Fig. 17. Waxing the exposed mastoid air cells is an important step in the prevention of the postoperative CSF leak.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/181.jpg)
Fig. 18. The VII nerve is identified using a intraoperative monitoring.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/191.jpg)
Fig. 19. Dissection the tumor off the nervous structures.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/201.jpg)
Fig. 20. Internal debulking.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/211.jpg)
Fig. 21. Dissection of the tumor from the facial nerve.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/222.jpg)
Fig. 22. Final view after gross total tumor removal. The VII nerve is responding to stimulation and is anatomically and functionally preserved.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/231.jpg)
Fig. 23. Dura is closed in a watertight fashion.
![Image](https://3datlasofneurologicalsurgery.org//images/2022/08/19/241.jpg)
Fig. 24. The bone flap is replaced using Craniofix.