Criteria For Orbital Exenteration

CT and MR Findings of Orbital Invasion

Most nasosinusal neoplasms invade the orbit through the floor (maxillary sinus squamous cell carcinomas) or the medial wall (ethmoid adenocarcinomas). The other walls are less frequently involved by primitive tumors. In fact, it is more likely to observe this path of orbital invasion by recurrent neoplasms or metastases. Apart from the infrequent event of perineural spread along the infraorbital nerve, rarely tumors extend into the orbit through the fissures or canals.

As both the medial wall and the orbital floor are very thin, they are often displaced by tumors arising

Orbital Exenteration
Fig. 4.8. Adenocarcinoma of left ethmoid abutting the lamina papyracea. Mild sclerotic changes combined with focal areas of erosion are shown

in the adjacent sinuses (Fig. 4.8). Chronic pressure exerted by the mass is usually associated with thinning and demineralization of the wall or erosion.

Surgical strategy is controversial in the presence of erosion of the lamina papyracea. According to some authors this condition indicates orbital exenteration (KETchAM et al. 1973). Nevertheless, criteria defining the indications for orbital preservation or exentera-tion have changed throughout the last three decades. Recent evidence in the surgical literature supports a conservative approach even in the presence of bone erosion on condition that the periorbita is not invaded (Lund et al. 1998; Cantu et al. 2000). More re cently, data provided by other investigators (Tiwari et al. 2000 Imoia and SchRAMM 2002; ) advocate more advanced criteria for orbital preservation. An additional distinct fascial layer surrounding the periocular fat and separating it from the periorbita has been reported by Tiwari et al. (1998). Invasion of the fascia prevents orbital preservation. In the series by Imoia and SchRAMM (2002), full thickness periorbital invasion was treated by microscopically assisted dissection, enabling even limited removal of the orbital fat.

Thus, imaging the periorbita is crucial for CT and MR. Prediction of orbital invasion has been based on the detection of positive findings graded through progressive steps: tumor contacting the periorbita (sensitivity of CT and MR 90%); fat obliteration (positive predictive value: CT 86%, MR 80%); extraocular muscle involvement (positive predictive value of MR 100%) (Eisen et al. 2000). Overall, CT proved to be more accurate than MR. By comparison, in our series of 49 si-nonasal malignancies the absence of orbital invasion has been correctly predicted in 40 orbits with tumor contacting the wall more than 10 mm of length (negative predictive value of CT 75%, MR 100%) (Maroidi et al. 1996, 1997). Detection of a hypointense/absent linear signal indicating the periorbita was the more specific predictor with overall accuracy of MR significantly better than CT (95.4% vs 81%) (Fig. 4.9-4.13).

Sinonasal Tumors And Periorbita

Fig. 4.9a-c. Squamous cell carcinoma of left maxillary sinus. On coronal TSE T2 (a) and VIBE (b), upward displacement of the orbital floor by the tumor is observed. A hypointense interface between the mass and the orbital fat can be recognized (long arrows). Tumor invades the middle meatus (short arrows) blocking the anterior ethmoid. Hypointense fluid (high protein concentration) within the ethmoid bulla (asterisk). On sagittal GD-enhanced T1 (c) a hypointense interface cannot be demonstrated, only the sharp limits suggest that the lesion is limited by the periorbita

Fig. 4.9a-c. Squamous cell carcinoma of left maxillary sinus. On coronal TSE T2 (a) and VIBE (b), upward displacement of the orbital floor by the tumor is observed. A hypointense interface between the mass and the orbital fat can be recognized (long arrows). Tumor invades the middle meatus (short arrows) blocking the anterior ethmoid. Hypointense fluid (high protein concentration) within the ethmoid bulla (asterisk). On sagittal GD-enhanced T1 (c) a hypointense interface cannot be demonstrated, only the sharp limits suggest that the lesion is limited by the periorbita

Orbital Exenteration

Fig. 4.10a-d. Spindle cell naso-ethmoid carcinoma. The hypointensity of the lamina papyracea/periorbita can be appreciated only in its anterior third (black arrowheads). In the posterior two thirds of the medial orbital wall, neoplastic spread through the lamina papyracea/periorbita (black arrows) appears as several short solid finger-like projections into the orbital fat. An ethmoid cell wall - same thickness of the papyracea - can be adequately detected by MR (white arrowheads). Invasion of the right nasal bone (white long arrow). In the same patient as (a), TSE T2 (b), Gd-enhanced T1 (c) and VIBE (c) coronal planes show invasion of the medial orbital wall with solid - and enhancing - tissue (arrowheads) replacing the orbital fat medially to the rectus inferior muscle (1). Invasion of the lateral orbital floor (small white arrows on b and opposite arrows on c) is also present. The signal void of the infraaorbital artery is surrounded by tumor (2). Ophthalmic artery (3), minimal dural thickening at the fovea ethmoidalis (4)

Fig. 4.10a-d. Spindle cell naso-ethmoid carcinoma. The hypointensity of the lamina papyracea/periorbita can be appreciated only in its anterior third (black arrowheads). In the posterior two thirds of the medial orbital wall, neoplastic spread through the lamina papyracea/periorbita (black arrows) appears as several short solid finger-like projections into the orbital fat. An ethmoid cell wall - same thickness of the papyracea - can be adequately detected by MR (white arrowheads). Invasion of the right nasal bone (white long arrow). In the same patient as (a), TSE T2 (b), Gd-enhanced T1 (c) and VIBE (c) coronal planes show invasion of the medial orbital wall with solid - and enhancing - tissue (arrowheads) replacing the orbital fat medially to the rectus inferior muscle (1). Invasion of the lateral orbital floor (small white arrows on b and opposite arrows on c) is also present. The signal void of the infraaorbital artery is surrounded by tumor (2). Ophthalmic artery (3), minimal dural thickening at the fovea ethmoidalis (4)

Sinonasal Non Hodgkin Limfoma

Fig. 4.12a-c. Sinonasal non-Hodgkin lymphoma. Permeative pattern of invasion through the lamina papyracea (black arrows) and extent into the maxillary sinus along the bony walls (white arrows). The horizontal and lateral (vertical) lamella of the cribriform plate are well demonstrated on TSE T2 [short black arrow on (a)]. Focal dural enhancement is appreciated on (b) at the level of the orbital plate of the frontal bone (white arrow). Lacrimal sac dilatation (asterisk)

Fig. 4.12a-c. Sinonasal non-Hodgkin lymphoma. Permeative pattern of invasion through the lamina papyracea (black arrows) and extent into the maxillary sinus along the bony walls (white arrows). The horizontal and lateral (vertical) lamella of the cribriform plate are well demonstrated on TSE T2 [short black arrow on (a)]. Focal dural enhancement is appreciated on (b) at the level of the orbital plate of the frontal bone (white arrow). Lacrimal sac dilatation (asterisk)

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