Level I to III craniofacial approaches based on Barrow classification for treatment of skull base meningiomas: surgical technique, microsurgical anatomy, and case illustrations
ABSTRACT Although craniofacial approaches to the midline skull base have been defined and surgical results have been published, clear descriptions of these complex approaches in a step-wise manner are lacking. The objective of this study is to demonstrate the surgical technique of craniofacial approaches based on Barrow classification (Levels I-III) and to study the microsurgical anatomy pertinent to these complex craniofacial approaches.
Ten adult cadaveric heads perfused with colored silicone and 24 dry human skulls were used to study the microsurgical anatomy and to demonstrate craniofacial approaches in a step-wise manner. In addition to cadaveric studies, case illustrations of anterior skull base meningiomas were presented to demonstrate the clinical application of the first 3 (Levels I-III) approaches.
Cadaveric head dissection was performed in 10 heads using craniofacial approaches. Ethmoid and sphenoid sinuses, cribriform plate, orbit, planum sphenoidale, clivus, sellar, and parasellar regions were shown at Levels I, II, and III. In 24 human dry skulls (48 sides), a supraorbital notch (85.4%) was observed more frequently than the supraorbital foramen (14.6%). The mean distance between the supraorbital foramen notch to the midline was 21.9 mm on the right side and 21.8 mm on the left. By accepting the middle point of the nasofrontal suture as a landmark, the mean distances to the anterior ethmoidal foramen from the middle point of this suture were 32 mm on the right side and 34 mm on the left. The mean distance between the anterior and posterior ethmoidal foramina was 12.3 mm on both sides; the mean distance between the posterior ethmoidal foramen and distal opening of the optic canal was 7.1 mm on the right side and 7.3 mm on the left.
Barrow classification is a simple and stepwise system to better understand the surgical anatomy and refine the techniques in performing these complex craniofacial approaches. On the other hand, thorough anatomical knowledge of the midline skull base and variations of the neurovascular structures is crucial to perform successful craniofacial approaches.
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ABSTRACT: The study determines the distribution patterns of ethmoidal foramina (EF) evaluate how they are affected by gender or bilateral asymmetry, and highlights the surgical implications on the anatomical landmarks of the orbit. Two hundred and forty-nine dry orbits were assessed. The number and pattern of EF were determined and distances between the anterior lacrimal crest (ALC), anterior (AEF) middle (MEF), posterior (PEF) ethmoidal foramina and between PEF and the optic canal (OC) were measured. The patterns of EF were classified as type I (single foramen) in 4 orbits (1.6%), type II (double foramina) in 152 (61%), type III (triple foramina) in 71 (28.5%), and type IV (multiple foramina) in 22 orbits (16.4%). Two orbits were found with five EF and a single orbit with six EF. A significant gender difference was observed for ALC-AEF distance (P ≤ 0.03), in males 23.53 ± 2.86 (20.67-26.39) versus females 22.51 ± 3.72 (18.79-26.23) mm. Bilateral asymmetry was observed for ALC-AEF distance (P ≤ 0.01). The distances ALC-AEF and ALC-PEF varied significantly according to EF classification (P ≤ 0.03 and P ≤ 0.02). The navigation ratio from ALC-AEF, AEF-PEF, and PEF-OC, in Greek population was "23-10-4 mm". A variation in the number of EF was found, ranging from 1 to 6, with the first report of sextuple EF. Although measures were generally consistent across genders and side, there are significant differences across ethnicities. These findings suggest that surgeons must consider population differences in determining the anatomical landmarks and navigation points of the orbit. Clin. Anat., 2013. © 2013 Wiley Periodicals, Inc.Clinical Anatomy 05/2014; 27(4). DOI:10.1002/ca.22303 · 1.16 Impact Factor