48 Artigo Original Anatomical Considerations of the Endonasal Transsphenoidal Approach Considerações anatômicas na abordagem transesfenoidal endonasal Alvaro Campero1,2 Abraham Campero2 Carolina Martins1 Alexandre Yasuda1 Albert Rhoton1 ABSTRACT RESÚMEN The sellar contents are separated from the sphenoidal sinus by Los contenidos de la silla turca se encuentran separados del a tiny sheath of bone that compris es the sellar floor, making seno esfenoidal por una delgada lámina de hueso que es el the transsphenoidal approach the most used surgical route to piso selar, haciendo que la vía transesfenoidal sea la ruta qui- intrasellar lesions. The transsphenoidal approach can be ini- rúrgica más utilizada para lesiones intraselares. El abordaje tiated in three different ways: 1) cutting the mucosa over the transesfenoidal puede ser iniciado de tres diferentes maneras: alveolar part of maxilla (sublabial transsphenoidal), 2) cut- 1) cortando la mucosa sobre la parte alveolar del maxilar su- ting along the anterior nasal mucosa adjacent to the columella perior (sublabial transesfenoidal), 2) cortando la mucosa na- (transeptal transsphenoidal), and 3) cutting the mucosa over sal anterior, adyacente a la columena (transseptal transesfe- the sphenoidal rostrum (endonasal transsphenoidal). Each noidal), y 3) cortando la mucosa sobre el rostro del esfenoides cavernous sinus has four dural walls. The lateral, superior (endonasal transesfenoidal). Cada seno cavernoso tiene 4 pa- and posterior walls are composed of endosteal and periosteal redes durales. Las paredes lateral, superior y posterior están dura leaflets. Unlike the other dural walls, the medial wall is compuestas por dos hojas (endosteal y perióstica), mientras formed of a single, thin dural sheath, an anatomical fact that que la pared medial posee una sola hoja dural, muy delgada, help explains the lateral expansion of a pituitary adenoma. In un hecho anatómico que podría explicar la expansión lateral the center, the diaphragm sellae has an opening through whi- de los adenomas hipofisarios. En el centro, el diafragma selar ch the infundibulum courses, linking the pituitary gland to the tiene una abertura a través de la cual el infundíbulo transcur- floor of the third ventricle. The morphology of this opening is re, uniendo la glándula pituitaria con el tercer ventrículo. La quite variable among individuals. On average, the anteropos- morfología de dicha abertura es muy variable. En promedio, terior distance of the diaphragm opening was 7.26 mm + 1.99 la distancia anteroposterior de la abertura es de 7.26 mm + mm, varying from 3.4 mm up to 10.7 mm. The lateral distance 1.99 mm, variando desde 3.4 mm hasta 10.7 mm. La distancia of the diaphragm opening was 7.33 mm + 2.79 mm, varying lateral de la abertura del diafragma es de 7.33 mm + 2.79 mm, from 2.8 mm up to 14.1 mm. variando desde 2.8 mm hasta 14.1 mm. Key-words : anatomy, diaphragma sellae, pituitary gland, Palabras-clave : abordaje transesfenoidal, anatomía, sphenoid sinus, transsphenoidal approach. diafragma selar, glándula hipófisis, seno esfenoidal. 1 Department of Neurological Surgery, University of Florida, Gainesville, Florida 2 Magister of Surgical Anatomy, School of Medicine, University of Tucumán, Argentina Recebido em fevereiro de 2008. Aceito em março de 2008. CAMPERO A, CAMPERO A, MARTINS C, YASUDA A, RHOTON A - Anatomical Considerations of the Endonasal Transsphenoidal Approach J Bras Neurocirurg 19 (2): 48-53, 2008 49 Artigo Original INTRODUCTION The pituitary gland and sella are located below the center of the brain in the center of the cranial base1. The sellar contents are separated from the sphenoidal sinus by a tiny sheath of bone that comprises the sellar floor, making the transsphenoi- dal approach the most used surgical route to intrasellar lesions. Herman Schloffer, in Austria, was the first in operate a patient with a pituitary tumor by a transsphenoidal approach2. After a period in disuse, the transsphenoidal approach resurged in the second half of the last century3, 4. Thus, over the last 30 years, the transsphenoidal approach became the first choice ap- proach to sellar lesions, being a relatively safe route with low 5 risk of complications, which reach up to 4% in major series . Figure 1 - The Nasal Cavity. A, sagittal cut through the skull. The right lateral wall The transsphenoidal approach can be initiated in three different of the nasal cavity presents the superior, middle and inferior nasal concha. The ways: 1) cutting the mucosa over the alveolar part of maxilla sphenoid ostia, located on the superior portion of the anterior wall of the sphenoid (sublabial transsphenoidal), 2) cutting along the anterior nasal sinus, are at the level of the superior concha. B, sagittal cut through the head. The inferior edge of the superior nasal concha corresponds to the floor of sella, while mucosa adjacent to the columella (transeptal transsphenoidal), the inferior edge of the middle nasal concha are at the level of the floor of the and 3) cutting the mucosa over the sphenoidal rostrum (endo- sphenoid sinus. C, the left half of the facial skeleton has been removed to expose nasal transsphenoidal). The aim of this paper is to study the the left half of the nasal septum. The anterior part of the osseous nasal septum anatomical landmarks for the endonasal transsphenoidal ap- is formed above by the perpendicular ethmoid plate and below by the vomer. D, a sagittal cut has been performed through the head, preserving the nasal septum. proaches. Anterior to the perpendicular ethmoid plate and vomer, there is the cartilaginous septum. The nasal septum is covered by vascular mucosa. Cart., cartilage; Eth., ethmoid; Inf., inferior; Max., maxilla, maxillary; Mid., middle; Sup., superior; Sphen., sphenoid, sphenoidal; Palat., palatine; Perp., perpendi- cular. ANATOMICAL CONSIDERATION SPHENOID BONE AND SPHENOID SINUS (FIGS. 2A-D) NASAL CAVITY (FIGS. 1A-D) The sphenoid bone is located in the center of the skull base, in The nasal cavity is limited above by the anterior cranial fossa, front of the temporal and occipital bones and posterior to the laterally by the orbits and maxillary sinuses and inferiorly by frontal and ethmoid bones. Its anterior aspect resembles a bat the hard palate. Its walls are covered by respiratory mucosa. It with wings outstretched. It has a body, and paired greater and is wider inferiorly and communicates with frontal, ethmoidal, lesser wings and pterygoid processes. The pituitary gland lies maxillary and sphenoidal sinuses by way of the nasal meati over the sella on the cerebral surface of the body of the sphe- which open under cover of the superior, middle and inferior noid. The sella protrudes inferiorly into the body, which in turn nasal concha. The cavity is divided along midline by the na- faces anteriorly and superiorly the nasal cavity. The intimate sal septum, whose anterior part is septal cartilage. The bony contact of the body of the sphenoid with the nasal cavity below septum is comprised by the perpendicular plate of ethmoid an- and pituitary gland above has led to the transsphenoidal route tero-superiorly and by vomer postero-inferiorly. The posterior being the operative approach of choice for most sellar tumors. border of the perpendicular plate attaches to the sphenoid ros- trum and it is at this level that fracture of the bony septum is The sphenoid sinus is a space created by pneumatization of the produced during endonasal transsphenoidal approach to reach sphenoid body anterior and inferior to the sella. The sphenoid midline. The aspects of the anterior nasal apertures vary among sinus is subject to considerable variation in size, shape and de- individuals. Their edges are formed by a U-shaped cartilage gree of pneumatization and, in the adult, can be divided by and fibrous tissue, making them flexible enough to accept the multiple bony septae, which are often located off midline. The introduction of the endonasal speculum, even in small, delica- ostia for the sinus are located in a superior position related to te-featured individuals. The lateral wall of the nasal cavity has the floor of the sinus, at each side of midline, at the level of the the superior, middle, and inferior nasal conchae, bellow each posterior portion of the superior concha and both are used as of which is a corresponding superior, middle, or inferior nasal landmarks during the performance of the endonasal transsphe- meatus. CAMPERO A, CAMPERO A, MARTINS C, YASUDA A, RHOTON A - Anatomical Considerations of the Endonasal Transsphenoidal Approach J Bras Neurocirurg 19 (2): 48-53, 2008 50 Artigo Original noidal approach. However, in some cases the finding of the os- cavernous sinus has four dural walls that comprise a set of ve- tia is difficult. Kim et al. suggest that the ostium should ideally nous plexus, the cavernous segment of the carotid artery and be searched from a superior and medial aspect in relation to the its intracavernous branches, the abducens nerve, the sympathe- posteroinferior end of the superior turbinate6. tic branches and a variable amount of fat. Each superior wall combines along midline to form the sellar diaphragm, which, by its turn, forms the roof of the sella and partially covers the pituitary gland, except by an opening through which the pitui- tary stalks courses. Laterally to the diaphragm is located the oculomotor triangle, the space where the oculomotor nerve en- ters the cavernous sinus. The oculomotor cistern, an arachnoi- dal and dural cuff, accompanies the oculomotor nerve through the cavernous sinus roof to the area just below or anterior to the lower edge of the tip of the anterior clinoid process7. The lateral, superior and posterior walls are composed of endosteal and periosteal dura leaflets. Unlike the other dural walls, the medial wall is formed of a single, thin dural sheath, an anato- mical fact that help explains the lateral expansion of a pituitary adenoma.