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Updated: Jul 3, 2026
Microvascular Decompression: Salient Surgical Principles and Technical Nuances
Published on: July 5, 2011
Middle fossa approach: microsurgical anatomy and surgical technique from the neurosurgical perspective
Necmettin Tanriover1, Galip Zihni Sanus, Mustafa Onur Ulu
1Department of Neurosurgery, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey. nctan27@yahoo.com
Background:
The purpose of this study was to call attention to the subtemporal approach directed through the petrous apex to the IAM. We studied the microsurgical anatomy of the middle floor to delineate a reliable angle between the GSPN and the IAM to precisely localize and expose the IAM from above. A new technique for the elevation of middle fossa floor in an anterior-to-posterior direction has also been examined in cadaveric dissections and performed in surgery.
Methods:
The microsurgical anatomy of the middle fossa floor was studied in 10 adult cadaveric heads (20 sides) after meatal drilling on the middle fossa. Five latex-injected specimens were dissected in a stepwise manner to further define the microsurgical anatomy of the middle fossa approach. The middle fossa approach is illustrated in a patient for the decompression of the facial nerve to demonstrate the surgical technique and limitations of bone removal.
Results:
Elevation of middle fossa dura in an anterior-to-posterior direction leads to early identification of the GSPN, where the nerve passes under V3. The most reliable and easily appreciated angle to be used in localizing the IAM is between the IAM and the long axis of the GSPN, which is approximately 61 degrees . Beginning drilling the meatus medially at the petrous ridge is safer than beginning laterally, where the facial and vestibulocochlear nerves become more superficial. The cochlea anteromedially, vestibule posterolaterally, and superior semicircular canal posteriorly significantly limit the bone removal at the lateral part of the IAM.
Conclusions:
The surgical technique for the middle fossa approach which includes an anterior-to-posterior elevation of middle fossa dura starting from the foramen ovale and uses the angle between the IAM and the long axis of the GSPN to localize the meatus from above may be an alternative to previously proposed surgical methods.
Insights
This study introduces a new middle fossa approach for accessing the internal auditory canal (IAM). The technique uses the greater superficial petrosal nerve (GSPN) angle for precise localization, offering a safe surgical alternative.
Area of Science:
- Neurosurgery
- Microsurgical Anatomy
- Skull Base Surgery
Background:
- The subtemporal approach to the internal auditory canal (IAM) via the petrous apex is explored.
- Microsurgical anatomy of the middle cranial fossa floor is crucial for safe IAM access.
- A novel technique for elevating the middle fossa floor was investigated.
Purpose of the Study:
- To highlight a subtemporal approach to the IAM through the petrous apex.
- To define a reliable angle between the greater superficial petrosal nerve (GSPN) and the IAM for precise localization.
- To examine a new technique for anterior-to-posterior elevation of the middle fossa floor.
Main Methods:
- Microsurgical anatomy of the middle fossa floor studied in 20 cadaveric sides.
- Latex-injected specimens dissected stepwise to detail the middle fossa approach.
- Surgical technique demonstrated in a patient for facial nerve decompression.
Main Results:
- Anterior-to-posterior dura elevation facilitates early GSPN identification.
- A 61-degree angle between the IAM and GSPN provides reliable IAM localization.
- Medial meatal drilling is safer; anatomical structures limit lateral bone removal.
Conclusions:
- The described middle fossa approach offers an alternative surgical method.
- Utilizing the GSPN-IAM angle aids in precise IAM localization from above.
- Anterior-to-posterior dura elevation from the foramen ovale is key to the technique.
