Maxillary Sinus

Frontal Sinus and Frontal Recess

Anterior pneumatization of the frontal recess into the frontal bone gives rise to the frontal sinus (Fig. 2.6). In the sagittal plane its ostium can be identified as the narrowest part of an hourglass space, the upper part widening into the frontal sinus, and the lower emptying into the middle meatus through the frontal recess. The latter is not a true tubular structure, as the term "nasofrontal duct" might indicate. In effect, the size and shape of the frontal recess are largely dictated by the adjacent structures: the agger nasi cells anteriorly, the ethmoidal bulla posteriorly, the vertical portion of the uncinate process and the middle turbinate on medial and lateral aspects (Fig. 2.7).

Particularly, the medial and lateral borders of the frontal recess depend on the variable type of the superior attachment of the uncinate process. Six variations have been identified by Landsberg and Friedman (2001) (Fig. 2.8). In type 1, insertion on lamina papy-

Maxillary Sinus

Fig. 2.5a-i. Axial plane. a Level of the alveolar process, teeth roots are seen. The inferior portion of medial pterygoid plates - hamulus - is detected (h). Alveolar recess of maxillary sinus (arMS) b Hard palate level. Greater (GPC) and lesser (LPC) palatine canals result from the articulation of the vertical portion of the perpendicular plate of the palatine bone with the maxillary bone. Opening of the canal - the greater palatine foramen (GPF) - appears as an ovoid groove on the right side. c The inferior concha and the surrounding inferior turbinate (IT) are demonstrated. An accessory ostium is located within the posterior third of the medial maxillary sinus wall (ao). d Level of the inferior aspect of the nasolacrimal ducts (NLD). The postero-superior limit of the middle turbinates reaches the choanae (MT). e Level of the middle meatus. The uncinate processes (UP) attach onto the medial aspect of the NLD. The narrow space between the UP and the medial maxillary sinus wall belongs to the ethmoid infun-dibulum (EI). Arrowheads indicate the ground lamella of the MT, signing the border between anterior and posterior ethmoid labyrinth (see also f), into which the inferior tip of the superior turbinates (ST) projects. f The ethmoid bullae (B) border the posterior limit of the EI. Rostrum of the sphenoid bone (rs). g The vertical portion of the UP (vUP) attaches onto the vertical lamellae of the MT on both sides. A clear separation between anterior and posterior ethmoid cells (PEC) cannot be identified on axial planes. The narrow channel-like olfactory fissure (asterisks) reach the sphenoethmoidal recess where the ostium of the right sphenoid sinus appears as a small opening close to the midline (oSS). Common lamina onto which the middle, superior (and supreme) turbinates attach (L). Arrowheads indicate the thin lamina papyracea. h Olfactory groove (OG) level. Because the groove extends down into the labyrinth, it results bordered by ethmoid cells. The thin vertical lamella of the cribriform plate (vlCP) separates the groove from the ethmoid cells. i At the level of the mid crista galli (CG) the olfactory groove is bordered laterally by the thicker frontal bone - fovea ethmoidalis (FE). suOC, supraorbital ethmoid cell

Fig. 2.6a-d. Same patient as in Fig. 2.5. a,b Right side. c,d Left side. a Sagittal plane closer to midline. From the hourglass ostium of the frontal sinus (oFS) the mucus follows a curved path (broken curved arrow) into the frontal recess between the agger nasi cell (A) and the anterior surface of the bulla (B). Asterisks on (a) and (b) indicate the course of the hiatus semilunaris bordered by the un-cinate process - horizontal (hUP) and part of the vertical portion - and the bulla. suR, suprabullar recess. c Sagittal plane closer to midline. The left frontal sinus ostium is wider than on the opposite side. Because the agger nasi cell (A) is smaller, the frontal recess is more vertically oriented (broken curved arrow). d On a more lateral plane the horizontal portion of the uncinate process is demonstrated (hUP). Asterisks indicate the hiatus semilunaris. Small arrows on (a)/(b) and (d) point to the opening of small anterior ethmoid cells into the bulla ethmoidalis

Agger Nasi Cell

Fig. 2.7a-f. The left vertical portion of the uncinate process inserts on both the lateral surface of a large agger nasi cell (A) and the lamina papyracea. As a result, the frontal recess runs medial to the uncinate process (broken curved white arrows). Moreover, a terminal recess (TR) is created between the superior surface of the bulla and the insertion of the UP onto the lamina papyra-cea. On coronal scans the agger nasi cell may be differentiated from the bulla ethmoidalis because it is located anterior to the infundibulum ethmoidalis. On the right side, a large bulla is associated with a paradoxically curved middle turbinate (opposite arrows). Pneumatization of the vertical lamella of left middle turbinate (lamellar concha, LC)

Fig. 2.7a-f. The left vertical portion of the uncinate process inserts on both the lateral surface of a large agger nasi cell (A) and the lamina papyracea. As a result, the frontal recess runs medial to the uncinate process (broken curved white arrows). Moreover, a terminal recess (TR) is created between the superior surface of the bulla and the insertion of the UP onto the lamina papyra-cea. On coronal scans the agger nasi cell may be differentiated from the bulla ethmoidalis because it is located anterior to the infundibulum ethmoidalis. On the right side, a large bulla is associated with a paradoxically curved middle turbinate (opposite arrows). Pneumatization of the vertical lamella of left middle turbinate (lamellar concha, LC)

Infundibulum Ethmoidale Left Ethmoidalis

Fig. 2.8a-c. a The vertical portion of the unci-nate process inserts onto the lamina papyracea [type 1, according to LaNdSbERg and FRiEdmaN (2001)] - right side - and onto the upper aspect of middle turbinate (type 6) - left side. b Bilateral insertion of the uncinate process onto the lateral aspect of the middle turbinate. c Same patient as in (b). The vertical portion of both uncinate processes (vUP) reaches the vertical lamella (vlMT) of the middle turbinates

Fig. 2.8a-c. a The vertical portion of the unci-nate process inserts onto the lamina papyracea [type 1, according to LaNdSbERg and FRiEdmaN (2001)] - right side - and onto the upper aspect of middle turbinate (type 6) - left side. b Bilateral insertion of the uncinate process onto the lateral aspect of the middle turbinate. c Same patient as in (b). The vertical portion of both uncinate processes (vUP) reaches the vertical lamella (vlMT) of the middle turbinates b c

Ground Lamella Middle Turbinate

racea, and type 2, insertion on the posteromedial wall of agger nasi cells, the middle turbinate serves as the medial border of the recess and the uppermost unci-nate process provides its lateral limit. In type 3, a double insertion - to lamina papyracea (anteriorly) and to the junction of middle turbinate on cribriform plate (posteriorly) - is present. In type 4-6 - insertion to the junction of middle turbinate with the cribriform plate, to the fovea, to the middle turbinate, respectively - the uppermost uncinate process becomes the medial border of the recess, the bulla and lamina papyracea being the lateral limit.

As a result, the frontal recess may empty medial to the uncinate process being separated from the eth-moidal infundibulum (type 1-3), or it may run laterally to the uncinate and join the ethmoidal infundibulum (type 4-6).

Because the frontal recess is bordered, anteriorly, by the agger nasi cells, its width on the sagittal plane depends on the extent of their pneumatization (Fig. 2.6). Furthermore, the posterior border may also vary: it is formed by a single and continuous bony wall when the ground lamella of the bulla eth-moidalis reaches the ethmoid roof. Otherwise, when the ground lamella of the bulla does not insert on the skull base, the frontal recess communicates with a narrow space (sinus lateralis or retrobullar recess) extending above (suprabullar recess cell) and behind the bulla, posteriorly bordered by the ground lamella of the middle turbinate.

Anterior ethmoidal cells developed from the frontal recess may extend into the frontal sinus itself (bulla frontalis), making it rather difficult to distinguish the true frontal sinus from a bulla frontalis cell. Frontal b a c cells have been defined by Bent et al. (1994) to derive from the anterior ethmoid sinus behind the agger nasi and to pneumatize the frontal recess above the agger nasi. Four types have been recognized: a single or several - a tier - frontal cell(s) located over the agger nasi identify type 1, and type 2, respectively. A single large cell extending cephalad into the frontal sinus belongs to type 3. Type 4 identifies a single isolated cell within the frontal sinus (Figs. 2.9-2.11). If not properly identified on a pre-surgical CT examination, the frontal cells type 3 and 4 may be mixed up for the real frontal sinus, potentially resulting in an incorrect procedure.

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Responses

  • Joshua
    What is the opening to the maxillary sinus called?
    7 years ago

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