The foramen spinosum: a landmark in middle fossa surgery

The foramen spinosum is an easily identifiable landmark in microsurgery of the middle cranial fossa, and knowledge of the variations in its relationship to the surrounding neurovascular structures is important when operating in this area. We studied the anatomical relationship of the foramen spinosum to the foramen ovale, the mandibular branch of the trigeminal nerve, the greater superficial petrosal nerve, and the petrous part of the internal carotid artery in 12 cadaver heads. We also tried to define an external landmark for early identification of the location of the foramen spinosum in ten dry skulls. We found considerable variations in the anatomy around the foramen spinosum. This knowledge may improve the identification and preservation of the neurovascular structures when using approaches to the middle cranial foss

Petroclival meningiomas

7 page(s

Utilization of fluorescein for identification and preservation of the facial nerve and semicircular canals for safe mastoidectomy : a proof of concept laboratory cadaveric study

OBJECTIVE: Mastoidectomy can be a very challenging procedure for many reasons. The normal anatomy can be distorted because of inflammatory processes and tumors and recurrences. Avoiding injuries to the semicircular canals (SCCs) and facial canal is mandatory, and there is need to find a way to recognize the facial nerve and SCCs for safe performance of mastoidectomy. We describe, as a proof of concept, a novel technique to drill the mastoid while allowing the surgeon to recognize and avoid injuries to vital structures, in the cadaver. METHODS: Four fresh cadaveric heads (8 sides) were prepared by cannulating the major vessels at the level of the neck. After removal of the mastoid cortex, indocyanine green was injected in the vessels. The sigmoid sinus alongside the facial nerve and SCCs was skeletonized using the drilling guidance provided by the fluorescence. The mucosa covering the air cells of the mastoid is very well vascularized compared with the thick bone representing the outer layer of the SCCs and facial canal. Consequently, after the indocyanine green injection, the mucosa shines whereas the bone does not. The fluorescence guides the drilling displaying air cells that are safe to remove. RESULTS: Eight mastoidectomies were performed, resulting in optimal drilling with no injuries to the facial canal and SCCs. CONCLUSION:With this novel technique, it is possible to perfectly skeletonize the facial nerve and the SCCs in the cadaver. We think that this technique can be an adjunct in the armamentarium of trainees that are not familiar with the anatomy of the temporal bone and eventually of neurosurgeons facing lesions that require the removal of various degrees of the mastoid.4 page(s

A Technical note on endonasal combined microscopic endoscopic with free head navigation technique of removal of pituitary adenomas

Pituitary surgery exemplifies the continuous refinement of surgical techniques. The transsphenoidal approach is the approach of choice to treat most pituitary adenomas. We report here, as a technical note, an operative nuance that represents an encompassment of various technical steps that we utilize in our current surgery, including the corroboration of navigation system on a free head with combined use of endoscope and microscope techniques.7 page(s

Parasagittal Meningiomas, Part 1: Presentation and Diagnosis

4 page(s

Microanatomy and Surgical Approaches to the Infratemporal Fossa: An Anaglyphic Three-Dimensional Stereoscopic Printing Study

Objective: The infratemporal fossa (ITF) is a continuation of the temporal fossa between the internal surface of the zygoma and the external surface of the temporal bone and greater wing of the sphenoid bone that is sitting deep to the ramus of the mandible. The principal structure to understanding its relationships is the lateral pterygoid muscle. Other important structures are the medial pterygoid muscle, the maxillary artery, the pterygoid venous plexus, the otic ganglion, the chorda tympani nerve and the mandibular nerve. In this study, we describe the microsurgical anatomy of the ITF, as viewed by step-by-step anatomical dissection and also through the perspective of three lateral approaches and one anterior surgical approach. Methods: Eight cadaver specimens were dissected. In one side of all specimens, an anatomical dissection was done in which a wide preauricular incision from the neck on the anterior border of the sternoclidomastoid muscle at the level of the cricoid cartilage to the superior temporal line was made. The flap was displaced anteriorly and the structures of the neck were dissected followed by a zygomatic osteotomy and dissection of the ITF structures. On the other side were the surgical approaches to the ITF. The combined infratemporal and posterior fossa approach was done in two specimens, the subtemporal preauricular infratemporal fossa approach in two, the zygomatic approach in two, and the lateral transantral maxillotomy in two. The anatomical dissections were documented on the three-dimensional (3D) anaglyphic method to produce stereoscopic prints. Results: The lateral pterygoid muscle is one of the principal structures to enable understanding of the relationships into the ITF. The tendon of the temporal muscle inserts in the coronoid process at the ITF. The maxillary artery is the terminal branch of the external carotid artery that originates at the neck of the mandible and runs into the parotid gland. In our dissections the maxillary artery was lateral to the buccal, lingual, and inferior alveolar nerves. We found the second part of the maxillary artery superficial to the lateral pterygoid muscle in all specimens The anterior and posterior branches of the deep temporal artery supply the temporal muscle. In two cases we found a middle deep temporal artery. The different approaches that we used provided different views of the same anatomical landmarks and this provides not only safer surgery but also the best choice to approach the ITF according with the pathology extension. Conclusions: The ITF is a complex region on the skull base that is affected by benign and malignant tumors. The study through different routes is helpful to disclose the relationship among the anatomical structures. Although the authors have shown four approaches, there are a variety of approaches and even a combination of these can be used. This type of anatomical knowledge is essential to choosing the best approach to treat lesions in this area

Comparison of the Exposure Obtained by Endoscope and Microscope in the Extended Trans-Sphenoidal Approach

Objective: Trans-sphenoidal surgery is often combined with other approaches for the treatment of middle cranial base tumors. By combining a maxillotomy with trans-sphenoidal approach, significantly wider exposure to these regions is gained. However, endoscope-assisted techniques have also been used for sellar and parasellar and upper clival regions. Methods: An extended trans-sphenoidal approach was performed on 10 cadaver heads using the operating microscope and was repeated with a 0-degree endoscope. The mean horizontal and vertical distances were measured and pictured for each technique, and both distances were compared using a parametric paired Student's t-test. Results: The mean horizontal distances in the 10 specimens were 19.5 ± 1.8 mm by microscope and 27.5 ± 2.2 mm by endoscope, and the mean vertical distances were 25.8 ± 1.9 mm by the microscope and 34.5 ± 3.5 mm by the endoscope. Conclusion: The aim of this study was to quantify the amount of exposure obtained with an extended trans-sphenoidal approach and to compare both endoscopic and microscopic techniques. Using the endoscope in conjunction with the operating microscope may provide additional exposure and better access in skull base surgery