Intraconal Anatomy of the Anterior Ethmoidal Neurovascular Bundle: Implications for Surgery in the Superomedial Orbit

Background The anterior ethmoidal artery (AEA) branches from the ophthalmic artery in the superomedial intraconal space. The feasibility of management of lesions arising from the superomedial intraconal space via an endoscopic endonasal approach has not been sufficiently explored. Objective To yield a detailed anatomic description of the anterior ethmoidal neurovascular bundle and its variants to serve as the foundation for possible management of lesions in the superomedial intraconal space. Methods Eight cadaveric specimens (16 sides) were dissected using an endonasal approach, tracing the AEA proximally through the superomedial intraconal space. Furthermore, the anatomy of adjacent structures was noted, and distances from the anterior ethmoidal foramen to the origin of the AEA at the ophthalmic artery were measured. Results Supraorbital cells were found in 13/16 sides (81.25%), and a bony dehiscence of the anterior ethmoidal canal was observed in 5/16 sides (31.25%). The nasociliary nerve, ophthalmic artery, superior division of the oculomotor nerve, superior rectus muscle, and levator palpebrae superioris were routinely identified in the superomedial intraconal space. The AEA passed through a corridor between the medial rectus and superior oblique muscles after arising from the ophthalmic artery (lateral to the foramen) in all specimens. The average distance from its origin to the anterior ethmoidal foramen was 5.19 ± 0.98 mm. Conclusion Anatomically, it is feasible to access the superomedial intraconal space via an endoscopic endonasal approach. This study provides the anatomical basis for procedures in the superomedial intraconal space.

ORBITAL MORPHOLOGY WITH REFERENCE TO BONY LANDMARKS. 20 La morfología de la órbita en relación a los parámetros óseos

Las órbitas óseas son cavidades del esqueleto situadas a cada lado de la nariz. Se conocen las diferencias raciales en las medidas orbitales. El objetivo del presente estudio era determinar las distancias de varias fisuras y foramen en la órbita en relación a ciertos puntos de referencia óseos / quirúrgicos sobre los márgenes orbitales en la población india, lo que puede ser útil durante la cirugía orbital. La distancia de canal óptico (OC), fisura orbitaria superior (SOF), fisura orbital inferior (IOF) y forámenes lagrimales (LF) se mide a partir de puntos de referencia como cresta lacrimal anterior (ALC) para la pared medial, muesca/foramen supra orbital (SN) para la pared superior, sutura cigomática frontal (FZ) de la pared lateral y un punto en el margen inferior (OIM) justo encima del agujero infraorbitario. Se midió la distancia del foramen etmoidal anterior y posterior (AEF y PEF) de ALC. Se observó la presencia de foramen etmoidal media (MEF) y forámenes lagrimales (LF).La distancia media de OC fue 39,71 ±2,67 mm(deALC), 45,11 ±3,4 mm(de SN) , 48,32 ±2,8 mm(de FZ ) y 45,97 ±3,9 mm(de OIM). La distancia segura para el nervio óptico para cada pared orbital se calcula restando5 mmde la distancia más corta medida. The bony orbits are skeletal cavities located on either side of the nose. Racial differences in orbital measurements are known. The aim of the present study was to determine the distances of various fissures and foramen in the orbit with reference to certain bony / surgical landmarks on the orbital margins in Indian population which can be useful during various surgical procedures. The distance of optic canal (OC), superior orbital fissure (SOF), inferior orbital fissure (IOF), lacrimal foramen (LF) were measured from landmarks like anterior lacrimal crest (ALC) for medial wall, supraorbital foramen/ notch (SON) for superior wall, fronto-zygomatic suture (FZ) for lateral wall and a point on inferior margin (IOM) just above the infraorbital foramen. Distance of anterior and posterior ethmoidal foramen (AEF and PEF) from ALC was measured. The incidence of middle ethmoidal foramen (MEF) and lacrimal foramen (LF) was noted. The mean distance of OC was 39.71 ±2.67 mm(from ALC), 45.11 ±3.4 mm(from SN), 45.97 ±3.9 mm(from FZ) and 48.32 ±2.8 mm(from IOM). The safe distance for optic nerve for each orbital wall was derived by subtracting5 mmfrom the shortest measured distance.

Level I to III craniofacial approaches based on Barrow classification for treatment of skull base meningiomas: surgical technique, microsurgical anatomy, and case illustrations

Object 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. Methods 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. Results 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. Conclusions 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.

Radiological anatomy of the anterior ethmoidal artery for functional endoscopic sinus surgery

Aim:This study investigated the extent to which the anterior ethmoidal artery and anterior ethmoidal foramen could be reliably identified on routine coronal sinus computed tomography scans. Where they could be identified, the relationship of these structures with the vertical height of the skull base, and their distance from an anterior landmark, were measured.Methods:Fifty consecutive coronal sinus computed tomography scans were viewed independently by two observers. Scans were reviewed when the observers' opinions differed.Results:Inter-observer concordance was high. The anterior ethmoidal foramen was visualised in 95 per cent of cases bilaterally and in the remaining 5 per cent unilaterally. The anterior ethmoidal artery was visualised in 33 per cent of scans. The anterior ethmoidal foramen was at skull base level in 72 per cent of sides studied, and below it in the remainder. The distance from the lacrimal crest to the anterior ethmoidal foramen was 22.4 mm (mean; standard deviation 3.7).Conclusion:The anterior ethmoidal foramen is a reliable landmark on coronal computed tomography scans of the paranasal sinuses. From this, the position of the anterior ethmoidal artery can be inferred.