Quantification of the advantages of the extended frontal approach to skull base

Quantitative Anatomical Studies in Neurosurgery: A Systematic and Critical Review of Research Methods

BACKGROUND

The anatomy laboratory can provide the ideal setting for the preclinical phase of neurosurgical research. Our purpose is to comprehensively and critically review the preclinical anatomical quantification methods used in cranial neurosurgery.

METHODS

A systematic review was conducted following the PRISMA guidelines. The PubMed, Ovid MEDLINE, and Ovid EMBASE databases were searched, yielding 1667 papers. A statistical analysis was performed using R.

RESULTS

The included studies were published from 1996 to 2023. The risk of bias assessment indicated high-quality studies. Target exposure was the most studied feature (81.7%), mainly with area quantification (64.9%). The surgical corridor was quantified in 60.9% of studies, more commonly with the quantification of the angle of view (60%). Neuronavigation-based methods benefit from quantifying the surgical pyramid features that define a cranial neurosurgical approach and allowing post-dissection data analyses. Direct measurements might diminish the error that is inherent to navigation methods and are useful to collect a small amount of data.

CONCLUSION

Quantifying neurosurgical approaches in the anatomy laboratory provides an objective assessment of the surgical corridor and target exposure. There is currently limited comparability among quantitative neurosurgical anatomy studies; sharing common research methods will provide comparable data that might also be investigated with artificial intelligence methods.

The Extended-Sphenoid Ridge Approach: A New Technique for the Surgical Treatment of Skull Base Tumors in Pediatric Patients

The sphenoid ridge approach (SRA) was initially described as a surgical technique for treating vascular pathologies near the Sylvian fissure. However, limited studies have systematically explored the use of skull base techniques in pediatric patients. This study investigated an extended variation in the sphenoid ridge approach (E-SRA), which systematically removed the pterion, orbital walls (roof and lateral wall), greater sphenoid wing, and anterior clinoid process to access the base of the skull.

OBJECTIVE

This report aimed to evaluate the advantages of the extradural removal of the orbital roof, pterion, sphenoid wing, and anterior clinoid process as a complement to the sphenoid ridge approach in pediatric patients.

PATIENTS AND METHODS

We enrolled 36 patients with suspected neoplastic diseases in different regions. The E-SRA was performed to treat the patients. Patients were included based on the a priori objective of a biopsy or a total gross resection. The surgical time required to complete the approach, associated bleeding, and any complications were documented.

RESULTS

Our results demonstrated that the proposed a priori surgical goal, biopsy, or resection were successfully achieved in all cases. In addition, using the E-SRA technique was associated with a shorter operative time, minimal bleeding, and a lower incidence of complications. The most frequently encountered complications were related to dural closure.

CONCLUSIONS

The extended sphenoid ridge approach represents a safe and effective option for managing intracranial tumors in pediatrics.

The evolving role of the oculoplastic surgeon in skull base surgery

PURPOSE OF REVIEW

Classical orbital approaches in skull base surgery have involved large incisions with extensive bone removal resulting in prolonged recovery with associated morbidity and mortality. The purpose of this review is to explore recent advances in skull base surgery that are applicable to the orbital surgeon.

RECENT FINDINGS

Transnasal endoscopic surgery provides access to the medial 180 degrees of the orbit. Access to the lateral 180 degrees may be obtained using transmaxillary and transcranial techniques. Transorbital approaches and multiport techniques further expand the reach of the skull base surgeon. These minimally invasive techniques are supplanting the classical pterional, frontotemporal, frontotemporal orbitozygomatic, frontal, and subfrontal approaches.

SUMMARY

The role of the orbital surgeon in skull base surgery is changing. Transnasal and transcranial approaches to orbital disorders using minimally invasive techniques are becoming more common. In addition, transorbital access to the skull base, paranasal sinuses, and anterior and middle cranial fossa is offering new opportunities for the orbital surgeon.

Quantification and comparison of neurosurgical approaches in the preclinical setting: literature review

There is a growing awareness of the need for evidence-based surgery and of the issues that are specific to research in surgery. Well-conducted anatomical studies can represent the first, preclinical step for evidence-based surgical innovation and evaluation. In the last two decades, various reports have quantified and compared neurosurgical approaches in the anatomy laboratory using different methods and technology. The aim of this study was to critically review these papers. A PubMed and Scopus search was performed to select articles that quantified and compared different neurosurgical approaches in the preclinical setting. The basic characteristics that anatomically define a surgical approach were defined. Each study was analyzed for measured features and quantification method and technique. Ninety-nine papers, published from 1990 to 2013, were included in this review. A heterogeneous use of terms to define the features of a surgical approach was evident. Different methods to study these features have been reported; they are generally based on quantification of distances, angles, and areas. Measuring tools have evolved from the simple ruler to frameless stereotactic devices. The reported methods have each specific advantages and limits; a common limitation is the lack of 3D visualization and surgical volume quantification. There is a need for a uniform nomenclature in anatomical studies. Frameless stereotactic devices provide a powerful tool for anatomical studies. Volume quantification and 3D visualization of the surgical approach is not provided with most available methods.

The 1-piece transbasal approach: operative technique and anatomical study

OBJECT

The transbasal approach (TBA) is an anterior skull base approach, which provides access to the anterior skull base, sellar-suprasellar region, and clivus. The TBA typically involves a bifrontal craniotomy with orbital bar and/or nasal bone osteotomies performed in 2 separate steps. The authors explored the feasibility of routinely performing this approach in 1 piece with a quantitative cadaveric anatomical study, and present an operative case example of their approach.

METHODS

Seven latex-injected cadaveric heads underwent a 1-piece TBA, followed by additional bone removal typical for a traditional 2-piece approach. Six surgical angles relative to the pituitary stalk, as well as the surface area of the orbital roof osteotomy, were measured before and after additional bone removal. The vertical angle from the frontonasal suture to the foramen cecum was measured in all specimens. In addition to an anatomical study, the authors have used this technique in the operating room, and present an illustrative case of resection of an anterior skull base meningioma.

RESULTS

Morphometric results were as follows: the vertical angle from the frontonasal suture to the foramen cecum ranged from 17.4° to 29.7° (mean 23.8° ± 4.8°) superiorly. Of the 6 surgical angle measures, only the middle horizontal angle was increased in the 2-piece versus the 1-piece approach (mean 43.4° ± 4.6° vs 43.0° ± 4.3°, respectively; p = 0.049), with a mean increase of 0.4°. The surface area of the orbital osteotomy was increased in the 2-piece versus the 1-piece approach (mean 2467 mm(2) ± 360 mm(2) vs 2045 mm(2) ± 352 mm(2), respectively; p < 0.001). The patient in the illustrative clinical case had a good outcome, both clinically and cosmetically.

CONCLUSIONS

The 1-piece TBA provides an alternative to the traditional 2-piece approach. It allows easier reconstruction, potentially decreased operative time, and improved cosmesis. While more of the orbital roof can be removed with the 2-piece approach, this additional bone removal offers only a small increase in 1 of 6 surgical angles that were measured.

Refining the Indications for the Addition of Orbital Osteotomy during Anterior Cranial Base Approaches: Morphometric and Radiologic Study of the Anterior Cranial Base Osteology

Objectives In anatomic and radiologic morphometric studies, we examine a predictive method, based on preoperative imaging of the anterior cranial base, to define when addition of orbital osteotomy is warranted.

Design Anatomic and radiographic study.

Setting In 100 dry skulls, measurements in the anterior cranial fossa included three lines and two angles based on computerized tomography (CT) scans taken in situ and validated using frameless stereotactic navigation. The medial angle (coronal plane) was the intersection between the highest point of both orbits and the midpoint between the two frontoethmoidal sutures to each orbital roof high point. The oblique angle (sagittal plane) was the intersection at the midpoint of the limbus sphenoidale.

Results No identifiable morphometric patterns were found for our classification of anterior fossae; the two-tailed distribution pattern was similar for all skulls, disproving the hypothetical correlation between visual appearance and morphometry. Orbital heights (range: 6.6–18.7 mm) showed a linear relationship with medial and oblique angles, and they had a linear distribution relative to angular increments. Orbital heights > 11 mm were associated with angles ≥ 20 degrees and more likely to benefit from orbitotomy.

Conclusion Preoperative CT measurement of orbital height appears feasible for predicting when orbitotomy is needed, and it warrants further testing.

Image-guided anatomical and morphometric study of supraorbital and transorbital minicraniotomies to the sellar and perisellar regions: comparison with standard techniques

OBJECT

Minimally invasive approaches have been proposed for the treatment of anterior cranial base pathology. Whereas earlier studies have quantified surgical exposure by referring to the opening on the surface, this cadaveric morphometric study redefines the concept of working area by examining the deep exposures afforded by several different approaches. Specifically, the authors systematically quantify and compare the operative exposure afforded by the pterional, supraorbital, and transorbital keyhole approaches to the sellar, suprasellar, and perisellar regions, including the anterior communicating artery complex.

METHODS

Pterional, supraorbital, and transorbital approaches were sequentially performed in 5 embalmed cadaveric heads on both sides. Preoperative and postoperative CT scans were obtained for frameless stereotactic navigation and measurements. Using reproducible anatomical landmarks, 6 triangles were defined to systematically measure the working area, depth of the surgical window, and angle of observation for each approach. Areas of the triangles were calculated using the Heron mathematical formula based on stereotactic navigation measurements. Ten sets of data were analyzed.

RESULTS

The pterional, supraorbital, and transorbital keyhole approaches provided progressively increasing working areas. The transorbital approach was associated with significantly increased exposure when compared with the pterional approach (p < 0.01). The transorbital approach was associated with a shallower depth of the surgical window when compared with either the supraorbital (p < 0.05) or pterional (p < 0.01) approach. The angle of basal view increased 56.6% with the transorbital approach (p < 0.001) when compared with the supraorbital approach. The transorbital route provided greater exposure on deeply located midline and contralateral structures.

CONCLUSIONS

In refining the concept of working area as deep rather than superficial in the surgical field, the authors quantified the 6 triangles whose boundaries were relative to the target structures to be exposed in the approach. The authors' morphometric findings support the use of the supraorbital and transorbital approaches as a valid alternative to the pterional approach for the treatment of sellar and perisellar pathology. The transorbital approach combines the advantages of minimal invasiveness with those of cranial base techniques.

Anterior skull base fractures: guidelines for treatment

Cranial base fractures still represent a challenging issue. A multidisciplinary approach and the contribution of different specialists is mandatory. There is still a controversy regarding the correct approach to these trauma due to the diversity of opinions as well as surgical approaches and timing.

A review of 59 consecutive patients with lesions of the anterior cranial base operated on using the subcranial approach

INTRODUCTION

Lesions of the anterior cranial fossa are still a challenge for the surgeon. Since Joram Raveh introduced the concept of a subcranial approach in 1978 it has been used in the treatment of lesions extending into the anterior cranial fossa. Our experience with the subcranial approach during the past 8 years at Turku University Central Hospital is described.

PATIENTS

Fifty-nine consecutive patients underwent surgery using the subcranial approach for treating various benign and malignant neoplasms, for repair of frontobasal-midfacial fractures, and for repair of cerebrospinal fluid leaks.

METHODS

Patient records were retrospectively reviewed, with special focus on surgical technique, early outcome, and complications.

RESULTS

Nineteen of the patients were operated on because of combined fronto-naso-orbital and skull base fractures, 37 were tumour cases, and 3 patients required surgical repair for cerebrospinal fluid leakage. Significant complications consisted of two cases of meningitis. However, they were successfully treated with antibiotics. The most common late complaint was olfactory nerve dysfunction (44), other late complications such as diplopia (4), enophthalmos (2), scar tissue in the nasal cavity (2), and trigeminal nerve dysfunction (2) were also encountered.

CONCLUSION

The subcranial approach affords exposure to the orbital, sphenoethmoidal, and clivus regions, as well as to the nasal and paranasal cavities. On the basis of this review, it is concluded that it is a safe and effective approach for treating lesions involving the anterior skull base.