FESS imaging - the role of MDCT

Transcription

1 FESS imaging - the role of MDCT Poster No.: C-0179 Congress: ECR 2013 Type: Educational Exhibit Authors: J. Plascak, K. Makaruha, B. Klasic, L. Kavur, V. Vidjak; Zagreb/HR Keywords: Image verification, Diagnostic procedure, CT, Head and neck, Ear / Nose / Throat DOI: /ecr2013/C-0179 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 31

2 Learning objectives The purpose of this poster is to show how a systematic approach to evaluation of paranasal sinuses in all 3 planes with MDCT gives the surgeon precise preoperative anatomical road maps for planning the surgical procedure. It also highlights clinically relevant anatomic variants which can affect the operative technique, as well as the pathology encountered inside the sinuses such as mucosal thickening, opacifications, masses, associated bony changes, etc. Background Multidetector computed tomography is currently the modality of choice for evaluation of paranasal sinuses and is routinely performed prior to functional endoscopic sinus surgery as an integral part of surgical planning used to create preoperative anatomical road maps. Combined with nasal endoscopy it enables the best treatment plan and operative technique for the patient. Patient preparation prior to examination is of outmost importance. There should not be any signs of acute sinusitis, otherwise extensive mucosal abnormalities and inflammatory fluids will distort the anatomy that the surgeon will encounter after the restitution of normal mucosal thickness (Figures 1 and 2). The purpose of imaging is to highlight the normal anatomy of drainage pathways and clinically relevant anatomic variants which can affect the operative technique and increase the risk of developing endoscopic surgical complications, as well as to point out the pathology encountered inside the sinuses (mucosal thickening, opacifications, masses, associated bony changes, etc.). Recent studies showed that the quality of life improved in 85% of patients following FESS, with a mean follow-up time of 31,7 months (6). However, the procedure itself is not without (1) complications. The incidence of major complications of FESS is 0,4-1,3 % with CSF leak being the most severe, and the most common being the synechiae formation, while other include bleeding (injury to anterior ethmoidal artery, sphenopalatine artery and internal carotid artery), orbital injury, orbital hematoma, optic nerve injury, maxillary nerve injury, meningitis, brain injury, brain abscess formation, nasolacrimal duct injury and epiphora. (2). Page 2 of 31

3 The most common indication for FESS is inflammatory disease of the paranasal sinuses, and it has become the primary surgical approach for chronic rhinosinusitis refractory to medical treatment. Other common indications include: recurrent acute sinusitis, nasal polyposis, antrochoanal polyps, mucoceles, epistaxis, choanal atresia, cerebrospinal fluid leak, dacryocystorhinostomy, orbital decompression and optic nerve decompression, as well as certain tumor pathology (2). Images for this section: Fig. 1: Acute inflammatory phase Page 3 of 31

4 Fig. 2: After resolution of the acute inflammatory phase Page 4 of 31

5 Imaging findings OR Procedure details 93 patients were analyzed with 64-slice MDCT and from the raw data axial, coronal and sagittal 2-mm thick contiguous images were created with bone and soft tissue algorithms. No contrast was used except in case of neoplastic lesions and vascular pathology. We divided the sinusal cavities according to their drainage pathways into two main groups : Anteriorly draining group of sinuses (frontal, anterior ethmoidal and maxillary sinuses (through the anterior ostiomeatal complex - OMC) drain into the middle meatus of the nasal cavity). Posteriorly draining group of sinuses (posterior ethmoidal cells and sphenoid sinus (through sphenoethmoidal recess -posterior OMC) drain into the superior meatus of the nasal cavity). In each group we selected some anatomical variants and diseases that can affect drainage pathways of particular sinuses and may predispose the patient for developing intra / post operative complications. From the surgical point of view three anatomic areas, corresponding to the narrowest tracts of drainage pathways, are crucial for endoscopic surgery planning: the ostiomeatal (8) unit (OMU), the frontal recess, and the sphenoethmoid recess, and they should be mentioned in the report. Special attention should be given to uncinate process, ethmoidal bulla and anterior ethmoidal artery because they serve as surgical landmarks. Ostiomeatal unit (OMU) represents a functional unit that includes ethmoidal infundibulum, maxillary sinus ostium, ethmoidal bulla, and uncinate process that represents the key structure of OMU. Anatomic variants of the OMU structures are relatively frequent; they can be classified as anomalies of size, shape, orientation and entity of pneumatization (8). Large ethmoidal bulla, concha bullosa or lamellar concha with nasal septal deviation and spur are quite common and may interfere with the endoscopic access to the middle meatus and obstruct the drainage pathway of the antrum by narrowing the infundibulum as well as the middle meatus. Page 5 of 31

6 Hypoplastic maxillary sinus along with dehiscence and medial deviation of the lamina papyracea and their relationship with uncinate process must be noted prior to surgery because they can represent a high risk for intra-orbital penetration. Accessory ostium of the maxillary sinus at the level of planned surgical antrostomy must be mentioned because both ostia (main and accessory) must be included in the antrostomy to guarantee an effective drainage and to avoid the phenomenon of mucus recirculation, and therefore to prevent a persistent mucus discharge from the maxillary sinus. (8) Frontal sinus drains through frontal recess whose anterior border is formed by the Agger nasi cell and the posterior limit is marked by bulla lamela (if pneumatized - ethmoidal bulla), while the medial and lateral borders depend on the variable type of the superior (7) attachment of the uncinate process (six possible variations) and on the lateral surface of the most anterior portion of the middle turbinate. Superior attachment of the uncinate process is one of the most important surgical anatomical landmarks and it should always be mentioned in the report. It effects the opening of the frontal recess into the middle meatus that can be medial (first 3 types of attachment) (7) or lateral (4-6 types of (7) attachment) to the uncinate process. The most common type of attachment is to lamina papyracea (52%), while other possible attachments are posteromedial wall of Agger nasi cell, junction of the middle turbinate with the cribriform plate, middle turbinate and skull (7) base. Correct assessment of the frontal recess opening is essential in planning the proper endonasal approach and the adequate exposure of the frontal sinus. Anatomical variations of Agger nasi cell can affect the size of frontal sinus ostium and the shape of the recess. The weakest area of the whole anterior skull base is located where the anterior ethmoidal artery enters the lateral lamella after having crossed the lamina papyracea and the ethmoidal labyrinth. Normally it courses through the bone canal and serves as a surgical landmark. When it courses below the skull base through the ethmoidal air cells, the artery can be inadvertently injured during FESS. Retraction of a severed artery into the orbit can cause an orbital hematoma, which requires urgent decompression. Special attention should be given to anatomical variants of the ethmoid sinus roof because slope, thickness and asymmetries in the height of the ethmoid roof affect the prevalence of intracranial penetration during FESS (deeply located olfactory fossa places the thin vertical lamella at risk of penetration during endonasal surgery and puts the Page 6 of 31

7 anterior ethmoidal artery, which courses along the most lateral aspect of the cribriform plate, at risk). (8) Onodi cells (hyperpneumatized posterior ethmoidal air cells that extend in a posterior direction above the sphenoid sinus and may be in close contact with the optic nerves which are then at risk during the surgery) - are important to identify because their presence may alter the surgeon's endoscopic approach to that area. Pneumatization of the anterior clinoid process and pterygoid processes along with the focal areas of dehiscence of the bony walls of the sphenoid sinus especially over the optic nerve, Vidian nerve and internal carotid artery should be described, as well as their possible protrusion into the sphenoid sinus (8). Imaging : 1. Anteriorly draining group of sinuses Frontal, anterior ethmoidal and maxillary sinuses (through the anterior ostiomeatal complex - OMC) drain into the middle meatus; some anatomical variants and diseases in this area will affect drainage pathways of these sinuses. Anatomy - important anatomical landmarks (Figure 3), and anatomical variants that should be mentioned in the report (Figures 4-10). Frontal sinus drains through frontal recess whose anterior border is formed by the Agger nasi cell (Figure 11) The superior attachment of the uncinate process determines the drainage pattern of the frontal sinus (Figure 13). Location of the anterior ethmoidal artery (Figure 12). Sinonasal disease - pathology encountered inside the sinuses (Figures 14-17). 2. Posteriorly draining group of sinuses It includes the sphenoid sinus which drains through spheno-ethmoidal recess (posterior OMC) into the superior meatus and posterior ethmoidal cells which drain directly into the superior meatus. Anatomical variants that may predispose the patient for developing intra / post operative complications (Figures 18-22). Special attention should be given to anatomical variants of the ethmoid sinus roof (Figure 23). Sinus disease - pathology encountered inside the sinuses (Figures 24-25). Page 7 of 31

8 Images for this section: Fig. 3: Important anatomical landmarks (HS-hiatus semilunaris, PU-uncinate process, MT-middle turbinate, EI-ethmoidal infundibulum) Page 8 of 31

9 Fig. 4: Septal deviation with spur Page 9 of 31

10 Fig. 5: Large concha bullosa of the right middle turbinate and lamellar concha of the left middle turbinate. This combination along with the septal deviation and spur is quite common and may interfere with the endoscopic access to the middle meatus and obstruct the drainage pathway of the antrum by narrowing the infundibulum as well as the middle meatus.(3) Page 10 of 31

11 Fig. 6: Concha bullosa of the left middle turbinate complicated with polyp - impossible to see through the endoscope and may serve as a focal area of sinus disease. Page 11 of 31

12 Fig. 7: Pneumatization of the uncinate process. The uncinate process is the key landmark for the surgeon and may considerably vary in size and attachment patterns which affect the frontal sinus drainage pathway. Page 12 of 31

13 Fig. 8: Infraorbital (Haller) air cell may narrow the maxillary sinus ostium, especially if infected. Page 13 of 31

14 Fig. 9: Left maxillary sinus septum with polyp inside a separated compartment - if not recognized may lead to inadequate drainage of that part of the antrum. Page 14 of 31

15 Fig. 10: Extensive pneumatization of maxillary alveolus resulting in presence of dental roots inside the sinus predisposing the patient for recurrent maxillary sinusitis due to dental disease. There is also a paradoxical turn of the right middle turbinate which, if large, may impair access to the OMC. Page 15 of 31

16 Fig. 11: Large Agger nasi cell - the most anterior ethmoidal cell that forms the anterior boundary of the frontal recess - an important surgical landmark. It also affects the size of frontal sinus ostium and the shape of the recess. Page 16 of 31

17 Fig. 12: Anterior ethmoidal artery canal that serves as a surgical landmark. Page 17 of 31

18 Fig. 13: The uncinate process attached to lamina papyracea is the most common type of attachment (in 52 % of cases).(7) As a result, the frontal recess empties medial to the uncinate process and is separated from the ethmoidal infundibulum. Page 18 of 31

19 Fig. 14: Sinusitis in bone window : look for air - fluid levels, mucosal thickening, bony remodeling and thickening. Page 19 of 31

20 Fig. 15: Sinusitis in soft tissue window : look for type of opacification (hyperdensity on non- contrast scans stands for inspissated secretions, blood or fungus). Page 20 of 31

21 Fig. 16: Retention cyst in left maxillary sinus : bone window - no bony remodeling or thickening. Page 21 of 31

22 Fig. 17: Retention cyst in left maxillary sinus : soft tissue window - hypodense lesion whose density is consistent with fluid. Page 22 of 31

23 Fig. 18: Sellar type of sphenoid sinus pneumatization (the most common, in 86 % of cases). Type of pneumatization is determined in relation to pituitary fossa - sellar type increases the possibility of damaging the pituitary gland. Other types of pneumatization include pre-sellar (in 11% of cases) and conchal (in 3%).(4) Page 23 of 31

24 Fig. 19: Onodi cells are important to identify because they may be in close contact with the optic nerves which are then at risk during the surgery so their presence may alter the surgeon's endoscopic approach to the sphenoid sinus. Page 24 of 31

25 Fig. 20: Pneumatization of the anterior clinoid process on the left - look for any signs of dehiscence in the wall of optic canal. Page 25 of 31

26 Fig. 21: Both vidian canals are protruding into the sphenoid sinus which puts them at risk during sphenoid sinus surgery. Page 26 of 31

27 Fig. 22: Location of the foramen rotundum (FR) and optic canal (OC) in relation to sphenoid sinus. Close proximity of foramen rotundum associated with its dehiscent bony coverings may result in trigeminal neuralgia in case of sphenoid sinus pathology. Page 27 of 31

28 Fig. 23: Low lying and medially sloping fovea ethmoidalis on right side (arrow). Slope, thickness and asymmetries in the height of the ethmoid roof affect the prevalence of intracranial penetration during FESS (deeply located olfactory fossa - higher risk of penetration). Page 28 of 31

29 Fig. 24: Posterior ethmoidal cells filled with inflammatory content - bone window Page 29 of 31

30 Fig. 25: Extensive polyposis of the sphenoid, ethmoid labyrinth, frontal sinus and nasal cavity : soft tissue window - mucosal polypoid thickening, opacified air cells. Page 30 of 31

31 Conclusion Computed tomography plays an essential role in preoperative assessment of the paranasal sinuses. It affects the surgical approach and warns the surgeon about important anatomic variations he will encounter during the procedure which consequentially lowers the intra/post operative complications that may develop. It should be analyzed in all 3 planes. References Hoang JK, Eastwood JD, Tebbit CL, Glastonbury CM. Multiplanar Sinus CT: A Systematic Approach to Imaging Before Functional Endoscopic Sinus Surgery. AJR 2010; 194:W527-W536 Stammberger H. FESS - Endoscopic Diagnosis and Surgery of the Paranasal Sinuses and Anterior Skull Base. Endo-Press, Tuttlingen Beale TJ, Madani G, Morley SJ. Imaging of the paranasal sinuses and nasal cavity: normal anatomy and clinically relevant anatomical variants. Semin Ultrasound CT MR Feb;30(1):2-16. BJ. Bailey and JT. Johnson. Head and Neck Surgery - Otolaryngology. Lippincott Williams & Wilkins; 4th edition:2006. Vaid S, Vaid N, Rawat S, Ahuja AT. An imaging checklist for pre-fess CT: framing a surgically relevant report. Clin.Radiol May;66(5): Epub 2011 Feb 1. Damm M, Quante G, Jungehuelsing M, Stennert E. Impact of functional endoscopic sinus surgery on symptoms and quality of life in chronic rhinosinusitis. Laryngoscope, Feb 2002; 112(2):310-5 Landsberg R, Friedman M. A computer-assisted anatomical study of the nasofrontal region. Laryngoscope, 2001; 111: Maroldi R, Nicolai P. Imaging in Treatment Planning for Sinonasal Diseases. Berlin: Springer-Verlag: Personal Information Page 31 of 31