Morphometric Analysis of Bone Resection in Anterior Petrosectomies

Scratching in the minefield: using intertriangles line to safely perform anterior petrosectomy

PURPOSE

The transpetrosal-transtentorial approach provides a practical and safe surgical corridor for the treatment of petroclival region lesions. Any inaccuracies while performing this surgical technique can result in catastrophic results; nevertheless, this can be prevented under the guidance of a detailed anatomical orientation. An "intertriangles line" was defined to preserve the internal auditory canal (IAC) and cochlea during extradural bone drilling.

METHODS

The anatomical study consisted of two groups: the cadaveric head and the skull group. A literature-based landmark and criteria list was created to examine the borders of the Kawase triangle/space and evaluate the anatomical structures that may be at risk during drilling for anterior petrosectomy.

RESULTS

A total of 20 cadaveric head sides and 30 dried skull sides were examined. The rhomboid area was divided into two triangles with a common the intertriangles line. In all dissections, the IAC was found to be localized posterior to the "intertriangle line". A minimum distance of 1 mm for the Internal Carotid artery and 2 mm for the IAC can serve as threshold values to be considered by the surgeon during drilling for petrosectomy.

CONCLUSIONS

Kawase's area resembles a minefield, in which every step and manipulation should be considered. A minimal but effective resection of the cranial base is needed to increase safety and decrease morbidity during skull base surgery. Furthermore, this study investigated accessible and prominent landmarks to establish a feasible area of triangles and define the intertriangles line to guide the neurosurgeon under microscope and avoid IAC injury.

Use of the Anatomage Virtual Table in Medical Education and as a Diagnostic Tool: An Integrative Review

Studies on human anatomy mainly depend on cadaver dissection. New technology devices have progressed to improve anatomy teaching, such as the 3D Anatomage virtual dissection table. There is a shortage and deficiency in information about the uses and benefits of the Anatomage table. The aim of this article was to review and assess the current evidence about the advantages of the Anatomage virtual table in medical education and curricula of medical courses, and its utility in diagnosis. The current study is a comprehensive systematic review. A search was conducted on online medical and scientific databases. Twenty-nine articles relevant to the content of the current research topic were selected. Based on this review, the use of the Anatomage table is valuable for anatomy learning outcomes, and most of the research supported it as an important anatomy tool in addition to cadaveric dissection. The Anatomage table in association with human dissection can improve knowledge retention of anatomy. It is an important tool for understanding organ variation. Anatomage is now considered an important tool for the educational training programs of medical students and residents and for disease diagnosis and prognosis. Anatomage can make the curriculum more interesting and valuable. Utilizing the Anatomage table can help medical and paramedical students and residents by assisting them to understand anatomy in a better way. It will also improve radiological knowledge and facilitate pre-planning for surgeries. Finally, it has a crucial role during exceptional circumstances such as pandemics.

Anatomage - the virtual dissection tool and its uses: A narrative review

Advancement in technology has given students and institutes an educational, interactive, and diagnostic aid with virtual reality functionality known as the Anatomage table. This review analyses the various spheres of the medical field where the 3D virtual tool is being used and assesses its acceptability, convenience, and practical application. A search for relevant studies in various databases namely Pubmed, Embase, Wiley Library, and Google Scholar was performed, and the data was compiled to understand the use of the Anatomage table. The search yielded a total of 24 studies that focused on the use of the Anatomage table. Eleven articles focused on using Anatomage as a learning tool and 13 described the perception of the Table. Anatomage table offers an excellent tool for learning anatomy by virtual dissection. The tool is not only used as a teaching aid, but also as a diagnostic and planning tool in residency programs. Adding the tool as an educational aid boosts the existing curriculum and helps to counter the challenges with cadaveric dissection. The equipment cost and its maintenance charges may be a deciding factor for the underutilization of the tool in developing countries.

Accuracy of the Anatomage Table in detecting extranodal extension in head and neck cancer: a pilot study

Purpose: To assess whether the three-dimensional reconstructions of preoperative computed tomography (CT) scans are helpful for establishing extranodal extension (ENE) in head and neck carcinoma. Approach: Patients with a histological diagnosis of ENE ( pENE + ) were considered "cases" and patients with negative histological examination for ENE ( pENE - ) were considered "controls." Cases and controls were divided into two groups: a major nodes (MaN) group (lymph nodes on CT > 15    mm ) and a minor nodes (MiN) group (lymph nodes on CT ≤ 15    mm ). The preoperative CT scans were uploaded to the Anatomage Table and were randomly and blindly provided to the radiologist for assessment. The findings at the Anatomage Table were compared with those of CT and magnetic resonance imaging (MRI) scans. Results: Analysis of data from the MaN group showed that the Anatomage Table had a higher percentage of concordance with histopathological examination (90%) than the CT and MRI scans. The Anatomage Table had 100% sensitivity in identifying all pENE + patients, associated with a lower specificity. The negative predictive value of 100% allowed identification of pENE - patients. In the MiN group, on the other hand, sensitivity was lower, related to a high number of false-negative results. Conclusions: The Anatomage Table could represent a useful tool for preoperatively establishing the extranodal extension of cervical lymph node metastasis.

Middle Cranial Fossa Approach: Anatomical Study on Skull Base Triangles as a Landmark for a Safe Anterior Petrosectomy

Objective  The Kawase approach provides access to the petroclival and posterior cavernous sinus regions, cerebellopontine angle, and upper basilar artery territory. Nevertheless, it remains one of the most challenging approach for neurosurgeons, due to the considerable related morbidity and mortality. The goal of this study was to evaluate the relationship between anatomical landmarks and their possible variations, and to measure the extension of the Kawase space, to define the reliability of these landmarks while performing an anterior petrosectomy. Design  Using eight cadaveric specimens (15 sides), an anatomical dissections and extradural exposure of the Kawase area were performed. Settings  A two-step analysis of the distances between the mandibular branch of the trigeminal nerve (V3) and the structures at risk of iatrogenic damage was performed. Main outcome measures  We measured the distance between V3 and the basal turn of the cochlea, and between V3 and the internal acoustic canal (IAC), analyzing the limits of bone resection without causing hearing damage. Results  We analyzed eight cadaveric (15 sides) formalin-fixed heads injected with colored silicone: four males and four females of Caucasian race (mean age: 73.83 years). We found a mean distance of 10.46 ± 1.13 mm between the great superficial petrous nerve (GSPN) intersection with V3 and the basal turn of the cochlea, and of 11.92 ± 1.71 mm between the origin point of V3 from the Gasserian ganglion and the fundus of the IAC. Conclusion  The knowledge of the safe distance between the most applicable anatomic landmarks and the hearing structures is a practical and useful method to perform this approach reducing related comorbidity.

Endoscopic transorbital route to the petrous apex: a feasibility anatomic study

BACKGROUND

While the subtemporal approach represents the surgical module milestone designed to reach the petrous apex, a novel ventral route, which is the superior eyelid endoscopic transorbital approach, has been proposed to access the skull base. Accordingly, we aimed to evaluate the feasibility of this route to the petrous apex, providing a qualitative and quantitative analysis of this relatively novel pathway.

METHODS

Five human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy of the University of Barcelona. After proper dissection planning, anterior petrosectomy via the endoscopic transorbital route was performed. Specific quantitative analysis, as well as dedicated three-dimensional reconstruction, was done.

RESULTS

Using the endoscopic transorbital approach, it was possible to reach the petrous apex with an average volume bone removal of 1.33 ± 0.21 cm³. Three main intradural spaces were exposed: cerebellopontine angle, middle tentorial incisura, and ventral brainstem. The first one was bounded by the origin of the trigeminal nerve medially and the facial and vestibulocochlear nerves laterally, the second extended from the origin of the oculomotor nerve to the entrance of the trochlear nerve into the tentorium free edge while the ventral brainstem area was hardly accessible through the straight, ventral endoscopic transorbital trajectory.

CONCLUSION

This is the first qualitative and quantitative anatomic study concerning details of the lateral aspect of the incisura and ventrolateral posterior fossa reached via the transorbital window. This manuscript is intended as a feasibility anatomic study, and further clinical contributions are mandatory to confirm the effectiveness of this approach, defining its possible role in the neurosurgical armamentarium.