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Middle meatus Hiatus semilunaris superior Maxillary sinus Maxillary sinus, natural ostium Infraorbital cell (Haller cell) Uncinate process and Uncinectomy Frontal recess Middle turbinate, basal lamella Posterior ethmoid Onodi cell Sphenoid sinus Internal carotid artery Cavernous sinus Inspected to assess (a) the shape and size of the middle Turbinate (b) the ethmoid bulla (c) the free margin of the uncinate process and the line of attachment to the frontal maxillary process The frontal recess always continues with the mucosa on the lateral surface of the middle turbinate and is located anteriorly to the frontal wall of the ethmoid bulla and communicates with the ethmoid infundibulum The location may vary depending on the number and volume of the pneumatized cavities in the frontal bone, the nasal bone, the lacrimal bone and the agger nasi, and may not always be visible through the middle nasal meatus The drainage opening of the hiatus semilunaris superior, visible from the conchal sinus (the space between the middle turbinate and the medial wall of the ethmoid bulla) communicates with the lateral sinus posterior to the ethmoid bulla. The lateral sinus is formed by: 1. Suprabullar recess (anterior and superior parts) Inferior by ethmoid bulla Superior by fovea ethmoidalis 2. Retrobullar recess (posterior and inferior parts) Anterior by ethmoid bulla Posterior by oblique portion of basal lamella When the ethmoid bulla is attached to the ethmoid roof superiorly there is no suprabullar recess; when the bulla attaches to the basal lamella of the middle turbinate inferoposteriorly there is no retrobullar recess. Posterior nasal fontanelle between the inferior margin of the ethmoid bulla and the horizontally oriented inferior margin of the uncinate process. If an opening becomes visible in this area before the inferior half of the uncinate process is resected, this always belongs to the accessory maxillary ostium. The natural maxillary ostium lies lateral to the uncinate process and comes only into sight after resection of the uncinate process. Is a three-dimensional cavity, is located lateral to the hiatus semilunaris inferior, a two-dimensional opening between the free margin of the uncinate process and ethmoid bulla. Neighbouring structures: ◦ Frontal wall of ethmoid bulla posteriorly. ◦ Uncinate process and the frontal maxillary process anteriorly. ◦ Lamina papyracea and the posterior nasal fontanelle laterally. ◦ Hiatus semilunaris inferior and the uncinate process medially. Prominence that runs from posterior to anterior along the superior maxillary sinus wall belongs to the infraorbital nerve The natural maxillary sinus ostium which normally has an elliptic shape. View of the natural ostium medially, the middle meatus, the side of the uncinate process facing the hiatus semilunaris and the inferior margin of the ethmoid bulla can be partially seen. Is located lateral to the uncinate process, at the level where superior vertical segment of uncinate process merges with inferior horizontal segment. The anterosuperior margin of the maxillary sinus ostium is of elliptic shape and located more laterally; its posteroinferior margin lies more medially, so when viewed through the 0° telescope a projection of the maxillary sinus ostium becomes visible. formed by pneumatization of the lacrimal bone developing towards the orbital floor, may narrow the maxillary ostium, and account for persistent or recurrent sinusitis if overlooked and not opened Once the 30° telescope is located in the maxillary sinus cavity the prominent Haller cell can be identified and incised below the inferior margin of the ethmoid bulla at the posterosuperior margin of the natural ostium. Using the sickle knife: Initially the uncinate process is incised with the sickle knife and then outfractured by use of Blakesley forceps, which is the usual approach for total uncinectomy. The procedure has certain disadvantages When the uncinate process is very close to the lamina papyracea, the sickle knife might superiorly fracture the lamina papyracea and the periorbital. In the event of a pneumatized uncinate process the incision might not reach as far as the ethmoid. CT image of the uncinate process located close to the lamina papyracea. The procedure has certain disadvantages If the incision, made at the inferior end of the horizontal portion of the uncinate process, is not carried backwards posteriorly to a sufficient extent, the remaining portion may impair vision of the maxillary sinus ostium If the incision is made too far anteriorly, the anterior portion of the maxilla - a thick bone - is encountered which in turn may impede the attempt of incising the uncinate process If the incision is made too close to the free margin of the uncinate process, uncinate remnants may obstruct vision of the foremost anterior ethmoid cells and agger nasi cells which need to be resected. Using the miniature backbiting nasal forceps: Once the first uncinate process incision has been made at the insertion point of the vertical and horizontal segments the maxillary sinus ostium should come into view; the lower half of the uncinate process is resected with a sharp curette, Stammberger antrum punch, or back-biting nasal forceps. The upper half of the uncinate process may be initially preserved to identify the frontal recess and its neighbouring ethmoid cells and finally resected in a controlled manner with a curette or through-cutting forceps. If the uncinate process bends laterally and inserts onto the lamina papyracea a blind end called terminal recess (recessus terminalis) appears lateral to the superior attachment of the uncinate process following uncinectomy Surrounded by: ◦ Agger nasi cells anteriorly ◦ Frontal cells posteriorly, and superiorly ◦ Lacrimal cells posteriorly and interiorly Preservation of the superior attachment of the uncinate process: ◦ Lacrimal cells, frontal cells, agger nasi cells and the terminal recess located lateral to it. ◦ Frontal recess located medial and posterior to it. The medial line of the frontal recess lies on the continuation of the lateral wall of the middle turbinate. In the event of a well pneumatized frontal bone, frontal cells can be found between the superior end of the uncinate process and the frontal recess There are no cells between the frontal recess and the lateral margin of the middle turbinate, and the recess is consistently anterior to the superior insertion of the anterior wall of the ethmoid bulla Excision of the ethmoid bulla is usually not necessary for identification of the frontal recess; the frontal recess can be traced by following the lateral portion of the middle turbinate, the anterior wall of the ethmoid bulla and the superior end of the uncinate process. The opening, superior to the anterior wall of the ethmoid bulla, lateral to the superior insertion of the bulla, posterior to the superior insertion of the uncinate process, and lateral to the frontal recess communicates with the frontal bulla The frontal bulla has a blind end at the floor of the frontal bone and should not be confused with the frontal recess. Three different points of insertion of the superior end of the uncinate process: ◦ Middle turbinate ◦ Lamina papyracea ◦ Skull base Might be attached to more than one point The ethmoid bulla is the largest and the most interiorly located among the anterior ethmoid cells. Safest entrance point is inferomedial. The bulla cavity can be exposed with a Blakesley forceps or a sharp curette. Once inside the bulla cavity the basal lamella of the middle turbinate can be identified by viewing backwards Is divided into two parts as oblique and horizontal. Horizontal portion must not be damaged because: ◦ Static stability of the middle turbinate is impaired, or necrosis of the middle turbinate postoperatively. ◦ Bleeding from branches of the sphenopalatine artery may be triggered. Shape of oblique portion may be variable depending on degree of pneumatization of anterior and posterior ethmoid cells. ◦ Pneumatization of the suprabullar recess: insertion of basal lamella to skull base superiorly is located posterior to nferior part of oblique segment ◦ Pneumatization of retrobullar recess: inferior part of basal lamella assumes a more posterior position and superior attachment to skull base assumes a more anterior position When the anterior wall of the ethmoid bulla and the superior attachment of the basal lamella of the middle turbinate are elevated. anterior to posterior, the frontal recess and hiatus semilunaris superior medially, and in lateral position the frontal bulla, the superior boundary of the suprabullar recess and the superior boundary of an anterior ethmoid cell The frontal bulla, lateral to the frontal recess constitutes the roof of the frontal cells and may be pneumatized towards the orbital roof; in such cases a Supraorbital cell can be seen Anterior ethmoid artery, usually passing through a thin bony canal, enters the ethmoid roof laterally from the lamina papyracea and extends anteromedially towards the middle turbinate Divides the ethmoid fovea into: ◦ anterior ethmoid fovea ◦ posterior ethmoid fovea The anterior ethmoid artery limits the anterior fovea fovea posteriorly, not the frontal recess The cavity lateral to the anterior ethmoid roof delineated by the anterior ethmoid artery posteriorly is a supraorbital cell, located superomedially to the orbit and posterior to the frontal bulla Once the bony lamellae adjacent to the frontal recess are completely removed the frontal sinus lumen can be viewed through its ostium or canal. The vertical lamella of the middle turbinate is attached to the cribriform plate of the ethmoid sinus medial to the fovea. (weakest skull base) Nasal cells may form as a result of pneumatization anterior to the frontal recess and posterior to the superior insertion of the uncinate process Access to the posterior ethmoid cells is achieved once the oblique portion of the basal lamella of the middle turbinate has been reached. The safest point for the initial dissection of the basal lamella is the inferomedial portion Once the superior portion of the basal lamella is removed and the skull base comes into view, the posterior ethmoid artery travelling from lateral to medial almost parallel to the coronal plane of the skull base can be identified on average 12 mm behind the anterior ethmoid artery The posterior ethmoid artery travels in a thin bony canal at the skull base. The artery is usually accompanied by the ethmoid nerve in the same bony canal but, as seen in the example above, the posterior ethmoid artery and posterior ethmoid nerve may also run separately The anterior wall of the sphenoid sinus can be identified by: ◦ lies inferomedial to the ethmoidectomy cavity and at a distance of 6.5 cm on average from the anterior maxillary crest in adult. ◦ lies 1 cm anterior and superior to the superior boundary of the choana. The sphenoethmoid recess lies superolateral to the vertical crus formed by the basal lamella of the middle turbinate (2) - of an imaginary "Y" formed by the posterior nasal fontanelle, the horizontal portion of the basal lamella of the middle turbinate and the orbital floor. The sphenoid sinus lies medial to the sphenoethmoid recess pneumatized posterior ethmoid cell superolateral to the sphenoid sinus. Optic nerve or even the internal carotid artery may run through it In the presence of an Onodi cell the anterior wall of the sphenoid sinus lies to the anterior, medial and inferior of it. Taking into account that the orbital apex lies 1-8 mm (5 mm on average) behind the posterior ethmoid artery can be helpful in locating the optic nerve. After the anterior wall of the sphenoid sinus is dissected and the opening enlarged, the lamella separating the sphenoid sinus and the Onodi cell attaching to the optic nerve come into view. The lamella segment adjacent to the optic nerve should not be resected. The prominences of the sella, optic nerve and internal carotid artery can almost always be identified when the sphenoid sinus cavity is inspected. the prominences of the maxillary nerve at the lateral wall and the vidian nerve at the inferior wall of the sphenoid sinus can occasionally be observed The internal carotid artery has been demonstrated by opening the posterolateral wall of the sphenoid sinus to expose structures which are associated with the risk of complications When the internal carotid artery is retracted medially, the veins of the cavernous sinus, the suspensory ligaments of the internal carotid artery and the abducent nerve superolateral come into view. When total sphenoidectomy is complete, the lamina papyracea is removed and the orbital apex can be identified without the risk of damaging the orbital periosteum, as in endoscopic optic nerve decompression The bony canal of the medial wall of the optic nerve is resected with a diamond burr or thin dissector and the Zinn's ring ligaments extending perpendicular to the longitudinal axis of the nerve at the level of the orbital apex are identified.