ENDOSCOPIC ANATOMY OF THE PTERYGOPALATINE FOSSA: RESULTS OF A CADAVERIC DISSECTION IN A TRAINING PROGRAM Pedro Cavilhas, MD 1a ; Sílvia Pereira, MD 1a ; Filipa Oliveira, MD 1a ; João Pimentel, MD 1a ; Pedro Escada, MD 1b , PhD 2 ; José Madeira_da_Silva, MD 1c , PhD 2 1 Hospital Egas Moniz, Lisboa, Portugal – Otolaryngology, Head and Neck Surgery Department (a: resident, b: senior surgeon, c: director); 2 Faculty of Medical Sciences, Universidade Nova de Lisboa, Portugal ABSTRACT INTRODUCTION: Extended transnasal endoscopic approaches are considered difficult and rarely performed except in selected cases. Teaching the surgical anatomy and access to specific areas adjacent to the nose and paranasal sinuses is limited to some advanced courses and has not been easily available in regular residency training programs. Surgical access to the pterygopalatine fossa is considered difficult because of its protected position and its complex neurovascular anatomy. However, endonasal approach of the region using rod lens endoscopes is easily performed if surgical skills are acquired in a well oriented program of cadaveric dissection and training. The purpose of this poster is to demonstrate the results of one of these programs in which residents, assisted by senior surgeons, develop their own expertise and autonomy. METHODS: The study was performed in the Faculty of Medical Sciences and the Department of Thanatology of the Lisbon Delegation of the Portuguese Medico-Legal Institute, after institutional authorizations were obtained and in accordance to the laws in force. Residents were allowed to dissect several fresh cadavers and obtain access the pterygopalatine fossa using endoscopes and proper instrumentation. During the endoscopic dissection of the pterygopalatine fossa, photographs were taken using the Karl Storz Telepak™ portable endoscopic documentation unit. RESULTS: Endoscopic exposure of the pterygopalatine fossa was obtained in a step-by-step manner using the middle meatal transantral approach and preserving turbinates. A U shaped subperiosteal flap was elevated in the lateral wall of the posterior middle meatus, in order to identify the ascending process of bone palatine and sphenopalatine pedicle. The orbital process of the palatine bone was then removed, followed by the posterior wall of the maxillary sinus, using Kerrison rongeurs. After opening the periosteum of the posterior aspect of the maxilla, the anterior and posterior compartment of the pterygopalatine fossa were meticulously and systematically explored and photographed. CONCLUSIONS: Programs of cadaveric dissection and training directed to otolaryngology residents, developed and assisted by senior surgeons, can be effective in the acquisition of surgical skills in seldom performed advanced endoscopic techniques, particularly in the endoscopic access to the pterygopalatine fossa. CONTACTS Pedro Cavilhas, MD, Otolaryngology H&N Surgery Resident Hospital Egas Moniz, Lisbon, Portugal Email: pcavilhas@chlo.min-saude.pt Phone: 00351 21 043 20 50 Website: http://www.hegasmoniz.min-saude.pt / INTRODUCTION It is consensual, not only among medical community but also within society, that dissection of human cadavers is an essential tool in pre- graduate and postgraduate medical training. Reflecting this concept, the actual Portuguese law 1 authorizes the use of cadavers of people who have expressed, in life, their desire to donate the body for scientific purposes (usually few people) but also of those who have not manifested in life the desire to not donate their body (and whose corpses have not been claimed within the legal deadlines). Before the use of the cadaver for scientific purposes, the non-donor condition of the individual is always confirmed in the Non-Donors National Register (RENNDA) 2 . Except for temporal bone dissection, the national Otolaryngology residency program in Portugal 3 do not specifically refer to the practice of cadaver dissection, as a way of learning anatomy and training surgical techniques. Therefore, the initiative to promote teaching activities of experimental surgery in cadavers relies on the trainees themselves, or on those responsible for the training programs at each academic hospital. Otolaryngology residents at the Egas Moniz Universitary Hospital in Lisbon, Portugal, have had the possibility to attend postgraduate Endoscopic Sinus Surgery courses with cadaveric dissection, organized in partnership with the Department of Anatomy of the Faculty of Medical Sciences, but also participate, with the supervision of senior faculty surgeons, in regular surgical training sessions on cadavers in the National Institute of Legal Medicine, in Lisbon. In theses cadaveric training sessions some of the most performed surgical techniques are those using endoscopes for accessing the nasal cavity and sinuses. However, more extended applications of the endoscopic approach were also performed. One of these extended applications is the surgical access to the pterygopalatine fossa (PPF). This approach is considered difficult because of the protected position and the complex neurovascular anatomy of the region and is seldom recommended, except in selected cases, making it an improbable surgery for residents. Nevertheless, endonasal approach of the region using rod lens endoscopes can be achieved by residents if surgical skills are acquired in a well developed program of cadaveric dissection and training. The purpose of this poster is to demonstrate the results of one of these programs in which residents, assisted by senior surgeons, develop their own expertise and autonomy in dissecting PPF. METHODS This study was performed in the Department of Thanatology and Forensic Pathology of the National Institute of Legal Medicine, in Lisbon. Cadaveric dissections were performed in accordance to the legal rules applied. Appropriate bibliography related to surgical technique and anatomy was reviewed 4,5,6,7,8,9 . After demonstrative and staged supervised cadaveric dissections for training, residents were allowed to obtain access to the PPF using 0º endoscopes and proper instrumentation. For image documentation, a dissection was performed on the fresh cadaver of a 73 year-old male with no signs of sinus pathology. Photographs were taken using the Karl Storz Telepak™ portable endoscopic documentation unit. RESULTS Endoscopic exposure of the pterygopalatine fossa (PPF) was obtained in a step-by-step manner. We used the middle meatal transantral approach, preserving turbinates and avoiding the modified Caldwell-Luc approach, minimizing potential morbidity when used in vivo. The anterior and posterior limits of the left middle meatus and its main surgical landmarks, including the uncinate process, were identified. We proceeded with the unciformectomy, followed by the antrostomy at the expense of the posterior fontanelle. The ascending process of the palatine bone (APP) was identified, as well as the posterior wall of the antrum (PWA) (Fig. 1). The next step was the elevation of a U-shaped posterior based mucosal flap of the medial surface of the APP, centered in the sphenopalatine foramen (SPF) using a Freer elevator (Fig. 2). Once exposed, part of the bone of the APP was removed with a Kerrison rongeur in order to open the SPF (Fig. 3). The thin bone of the PWA was then removed, with a Kerrison rongeur and curettes, exposing the periosteum of the anterior wall of PPF (Fig. 4). Cutting this periosteum exposed the anterior structures of the FPP: fat and blood vessels (Fig. 5). The maxillary artery (MA) had a tortuous route inside the PPF and its terminal branch, the sphenopalatine artery, was divided into two branches as it passes through the SPF. Removal of the anterior fat, sectioning of the sphenopalatine pedicle and lateral displacement of the MA exposed the pterygopalatine ganglion (PPG) and its 3 major branches: the vidian nerve (Vid) (Fig. 7), coming posteromedially from the vidian canal; the maxillary nerve branch (V2b) (Fig. 7) coming superolaterally from the maxillary nerve (V2); and the greater palatine nerve (GPN) (Fig. 8) descending into the greater palatine canal. CONCLUSIONS Programs of cadaveric dissection and training directed to otolaryngology residents, developed and assisted by senior surgeons, can be effective in the acquisition of surgical skills in seldom performed advanced endoscopic techniques, particularly in the endoscopic access to the pterygopalatine fossa. ACKNOWLEDGMENTS We thank to Dr. Francisco Costa Santos, Director of the Department of Thanatology and Forensic Pathology of the National Institute of Legal Medicine in Lisbon, as well as his staff, for the facilities conceded for the elaboration of this study. We thank to Prof. Dr. Carlos B. Ruah for the critical review of the manuscript. We thank to Marta Villar for the graphic design consulting. REFERENCES 1. Ministerio da Justiça. Decreto-Lei nº 274/99 de 22 de Junho - Utilização de cadáveres para fins de ensino e investigação científica. Diário da República - I série-A. 1999;169:1-6. 2. Ministério da Saúde. Decreto-Lei nº 244/94 de 26 de Setembro - Regulamento do RENNDA. Diário da República - I série-A. 1994;I série A: 5780-5782. 3. Saúde Md. Portaria nº 1024/99 de 18 de Novembro - Programa de formação do Internato Complementar de Otorrinolaringologia. Diário da República - I série-B. 1999;269:8210-8213. 4. Alfieri A, Jho HD, Schettino R, Tschabitscher M. Endoscopic endonasal approach to the pterygopalatine fossa: anatomic study. Neurosurgery. 2003;52:374-78; discussion 378-80. 5. DelGaudio JM. Endoscopic transnasal approach to the pterygopalatine fossa. Arch Otolaryngol Head Neck Surg. 2003;129:441-446. 6. Douglas R, Wormald PJ. Pterygopalatine fossa infiltration through the greater palatine foramen: where to bend the needle. Laryngoscope. 2006;116:1255-1257. 7. Fortes F, Sennes L, Carrau R et al. Endoscopic Anatomy of the Pterygopalatine Fossa and the Transpterygoid Approach: Development of a Surgical Instruction Model. Laryngoscope. 2008;118:44-49. 8. Osawa S, Rhoton AL, Seker A, Shimizu S, Fujii K, Kassam AB. Microsurgical and endoscopic anatomy of the vidian canal. Neurosurgery. 2009;64:385-411; discussion 411-2. 9. Theodosopoulos PV, Guthikonda B, Brescia A, Keller JT, Zimmer LA. Endoscopic approach to the infratemporal fossa: anatomic study. Neurosurgery. 2010;66:196-202. Fig.1) Seeker instrument entering the left maxilary sinus after unciformectomy and antrostomy (A). MT=middle turbinate. PWA=posterior wall of antrum (maxilary sinus). Yellow arrow pointing to the MT tail and presumptive localization of sphenopalatine foramen. MT PWA A Fig.2) Elevation of the mucosa flap with a Freer elevator exposed the ascending process of palatine (APP) bone and the emergency of sphenopalatine pedicle (yellow arrow). Flap MT APP * * MT PPF Fig.4) After additional removal of bone from the APP (the anterior bone border of sphenopalatine foramen) its contents were appreciated (yellow arrow). It can be seen that the sphenopalatine artery is divided in two branches (yellow asterisks). The black arrow points to the thin bone border of PWA exposing the periosteum underneath. Fig.7) After sectioning the sphenopalatine pedicle, with lateral displacement of maxillary artery, the pterigopalatine ganglion (PPG) was exposed, as well as the vidian nerve (Vid) and the maxillary nerve branch (V2b) going to the PPG. PE=posterior ethmoid. SS= anterior wall of the sphenoidal sinus. SS PE Vid PPG V2b Fig.5) After cutting the periosteum, the anterior contents of PPF were exposed. F=fat. MA=maxillary artery. APP=ascending process of palatine. Yellow asterisks point to sphenopalatine artery branches. MA MA F APP * * F Fig.3) After removing part of the ascendent process of palatine (APP) and part of the thin bone of the posterior wall of the antrum (PWA) the periosteum of the anterior wall of PPF was exposed (yellow asterisks). SWA=superior wall of antrum. The yellow arrow points to the sphenopalatine pedicle. The black arrow points to the crista ethmoidalis. A cell of the posterior ethmoid (PE) can be identified. MT PWA SWA PE APP * * Fig.6) After removing the anterior fat of PPF the maxillary nerve (V2) and the infraorbitary nerve (ION) were exposed. Although not clearly seen, the V2 branch (V2b) going to the pterigopalatine ganglion can be inferred (yellow arrow). MA=maxillary artery. Asterisks mark the 2 sphenopalatine arteries. ION V2 MA MA V2b * * Fig.8) In this image the greater palatine nerve (GPN) can be seen descending from the PPG into the greater palatine canal. The GPN and PPG hide behind the pterigoid process (PP). SS=anterior wall of the sphenoidal sinus. PPG=pterygopalatine ganglion. PPG GPN APP SS PP