Учебники / Pediatric Sinusitis and Sinus Surgery Younis 2006

Figure 3 Establishment of a nasal airway to identify all posterior choanal structures and the posterior fontanella area. Abbreviations: PF, posterior fontanelle; S, septum; IT, inferior turbinate; asterisk, eustachian tube orifice.

paranasal sinuses. Monopolar or bipolar suction cautery is helpful if discrete bleeding points are encountered during the surgery. However, excessive cauterization should be avoided to minimize crusting and prolonged healing in these areas.

Identification of the Medial Floor of the Orbit and/or Bony Crest of the Antrostomy

For more limited disease of the ostiomeatal complex, an uncinectomy and exposure of the maxillary sinus natural ostium may be all that is necessary. However, if further ethmoidal work is required or if there is significant anatomical distortion or polyp disease, then the medial orbital floor (MOF) should be identified prior to proceeding with an ethmoidectomy. As the surgeon gains more experience, this step may merely require visualizing the superior margin of the maxillary sinus natural ostium (representing the anterior MOF), obviating the need for a wider antrostomy. In patients with more advanced disease and/or anatomical distortion due to prior surgery, a wider antrostomy is performed. This immediately identifies the bony ridge of the antrostomy, the MOF, and the posterior wall of the maxillary sinus.

In the absence of any normal osteomeatal complex references, or when difficulty is experienced identifying the natural ostium of the maxillary sinus, the maxillary sinus should be entered through the posterior fontanelle, superior to the posterior one-third of the inferior turbinate (Fig. 4). This

Figure 4 In situations where an uncinate is not readily identified, safe entry through the posterior fontanelle (arrow), over the posterior one-third of the IT, is preferred. A frontal curette assures proper penetration through both layers of muscosa (nasal and maxillary sinus) to avoid inadvertent creation of a maxillary sinus mucocele. Abbreviation: IT, inferior turbinate.

approach will ensure the surgeon remains a safe distance from the orbit floor, which rises superiorly at this level. Once the posterior wall of the maxillary sinus and MOF are identified by palpation with a probe and endoscopic visualization, a wide antrostomy is created by removing most of the posterior fontanelle (Fig. 5).

The site of the natural ostium is incorporated into the maxillary antrostomy to reduce the chances of circular mucous flow. This is achieved by following the MOF and the horizontal portion of the antrostomy ridge to a point just behind the convexity of nasolacrimal duct where the MOF appears to be approximating the lamella of the inferior turbinate.

When performing an antrostomy through the posterior fontanelle area, care must be taken that the nasal, as well as the medial maxillary sinus mucosa of the fontanelle area, is penetrated. Failure to do so may result in the formation of a maxillary cyst, or mucocele, due to lateral elevation of the medial maxillary sinus mucosa and concomitant disruption of the natural ostium.

The MOF and bony ridge of the antrostomy provide the surgeon with the correct anteroposterior trajectory, as the surgeon dissects posteriorly, starting with the anterior ethmoid and subsequently into the posterior ethmoid and sphenoid sinuses. The MOF must always be kept in view on the

Figure 5 Completion of a wide middle meatal antrostomy with incorporation of the natural osteal area just behind the NL, at the level of the medial O. The PM identifies the approximate level (in the coronal plane) of the anterior wall of the sphenoid, more medially adjacent to the septum, and 7 cm from the columnella. The small arrows identify the bony ridge of the antrostomy (horizontal portion superiorly, and the vertical portion posteriorly). Abbreviations: NL, nasolacrimal duct; O, orbital floor; PM, posterior wall of the maxillary sinus.

video monitor and be constantly referred to throughout the surgery. Failure to visualize the superior margin of the antrostomy alerts the surgeon that he/she is proceeding in a more superior direction towards the skull-base.

The camera alignment on the monitor screen must also be periodically checked to ensure that it has not been inadvertently rotated. The opening of the antrostomy should face medially in the sagital plane, parallel to the nasal septum, with the horizontal portion of the antrostomy ridge projecting in an anteroposterior direction towards the orbital apex. The posterior wall of the maxillary sinus, as seen through the antrostomy, demarcates the approximate level, in the coronal plane, of the anterior wall of the sphenoid sinus, or posterior wall of the posterior ethmoid.

Anterior Ethmoidectomy

The anterior ethmoid cells border the horizontal bony ridge of the antrostomy (Fig. 6). The surgeon first performs an inferior ethmoidectomy (anterior and/or posterior, depending on disease extent) to identify the medial orbital wall inferiorly. At this point, the surgeon must begin regularly palpating the eye prior to exenterating any additional ethmoidal cells. By looking for movement in the orbital wall, any bony dehiscence will be identified. The orbital

Figure 6 The anterior ethmoid cavity (ethmoid bulla, adjacent wall of the infundibulum, and suprabullar air cells) is found medial to the horizontal portion of the antrostomy ridge (small arrows). The PM, IT, and MT are also noted. Abbreviations: PM, posterior wall of the maxillary sinus; IT, inferior turbinate; MT, middle turbinate.

wall, once identified, represents the lateral limits of the dissection and is followed posteriorly or superiorly as needed (see posterior ethmoid and sphenoid dissection below).

In advanced disease, the surgeon initially maintains a safe distance of approximately 10 mm as he/she proceeds around the antrostomy ridge posteriorly (Figs. 7 and 8), in an inferomedial direction. The posterior ethmoid and sphenoid are identified as described below. A retrograde dissection of the superior ethmoid cells is later performed, only after the roof and lateral wall of the posterior ethmoid or sphenoid are identified to determine the superior and lateral extent of dissection, respectively.

Posterior Ethmoidectomy

The posterior ethmoid cells may be entered safely through the most horizontal portion of the middle turbinate lamella. Endoscopically, this location is identified by drawing a line from the posterior MOF (adjacent to the bony ridge) to the nasal septum. Another line is drawn along the vertical portion of the antrostomy ridge. A third or optional line is drawn along the free edge of the middle turbinate, or free edge of the basal lamella, if the middle

Figure 10 Probe introduced into the inferior aspects of the posterior ethmoid sinus, at the level (solid black line), and just medial to the transitional area of the antrostomy ridge (where the horizontal and vertical portions meet). The AE, MT, and basal lamella of the middle turbinate (asterisk) are identified. Columnellar measurement to this area is approximately 5 cm. Abbreviations: AE, anterior ethmoids; MT, middle turbinate.

sphenoid sinus is entered and identified medially, adjacent to the nasal septum, approximately 7 cm from the base of the columnella, at the level of the posterior MOF. The sphenoid sinus will be entered consistently in its inferior to middle third, which also corresponds to the location of the sphenoid ostium in most cases (Fig. 12). If the maxillary natural ostium or anterior antrostomy ridge is used as a reference point, then the sphenoid will be entered slightly more inferiorly, where thicker bone may be encountered, and needs to be removed with curettes or thinned with cutting burrs.

Frontal Sinusotomy

The frontal sinus is identified as shown in Figure 13 by drawing a line parallel to the bony nasolacrimal duct and directed superiorly from the anterior border of the antrostomy (i.e., natural ostium area) to a point several millimeters behind the anterior attachment of the middle turbinate. The correct point of entry will be directed superomedially away from the wall of the orbit and anteriorly away from the anterior ethmoid artery.

Palpation is key to identifying the posterior wall of the frontal sinus and opening the frontal sinus ostium, if indicated. The septations that comprise the roof of the suprabullar cells and the agger nasi, or frontal, cells are gently displaced inferoanteriorly to avoid inadvertent penetration

Figure 11 Probe introduced into the sphenoid sinus further along the same line drawn from the posterior MOF to the nasal septum. Entry into the sphenoid is through its natural ostium area, adjacent to the S. A good portion of the middle turbinate basal lamella has been removed to improve visualization of the nasal septum. The AE and the majority of the PE cavities are identified superior to this line. The PM demarcates the coronal plane of the anterior wall of the sphenoid sinus. Abbreviations: MOF, medial orbital floor; AE, anterior ethmoid; PE, posterior ethmoid sinus; PM, posterior maxillary sinus; S, septum.

through the anterior skull-base at the level of the anterior ethmoid artery, which represents the transitional area into the frontal recess and ostium. As with the ethmoid, maxillary, and sphenoid sinuses, an attempt is made to preserve as much of the frontal recess and frontal ostium mucosa to diminish the chances of prolonged healing or fibrosis with possible stenosis (Fig. 14).

CONCLUSIONS

The MOF and adjacent bony ridge of the antrostomy, when combined with columnellar measurements, are easily identifiable and consistent anatomical landmarks providing even the most inexperienced surgeon with reliable information to find all of the paranasal sinuses and other critical skull-base and orbital structures. None of the landmarks is affected by the presence of significant inflammatory disease or prior surgery. These reference points may better assist the rhinologic surgeon in determining the correct anteroposterior trajectory during ESS. A step-wise approach to the ethmoid labyrinth and

Figure 14 Completed F, looking superiorly with a 30 telescope. The Sp, PM, S, and NL are also seen. Abbreviations: F, frontal sinusotomy; Sp, sphenoid; PM, posterior maxillary sinus; S, septum; NL, nasolacrimal duct.

dependent sinuses, utilizing these consistent reference points, may minimize the chance of inadvertent intracranial or intraorbital complications in the face of significant anatomical distortion due to disease or prior surgery.

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