Planum Sphenoidale

Imaging to Assess the Pattern of Growth of Naso-Ethmoidal Neoplasms

Neoplasms arising from ethmoid sinus or nasal cavity do not usually have a well defined bony box to completely fill before extending through its walls to become symptomatic, as in maxillary sinus neoplasms. Unilateral or bilateral nasal obstruction, possibly leading earlier to endoscopic or CT examination, is more frequently observed than in maxillary tumors (Fig. 9.9). Therefore, imaging findings may range from the detection of a nasal polypoid lesion to the demonstration of a large naso-ethmoidal mass abutting the bony framework of a complex bony box including in its boundaries the lamina papyracea, the lacrimal pathways, the medial maxillary wall, the nasal septum, and the anterior cranial fossa floor. In addition, naso-ethmoidal tumors may extend into the frontal sinus and involve nasal bones - anteriorly - or into the sphenoid sinus - posteriorly. Less frequently, the nasopharynx or the soft palate are invaded via the choana.

More often than in maxillary sinus tumors, a naso-ethmoidal neoplasm has already invaded the

Squamous Carcinoma Sphenoid Sinus

Fig. 9.8a-f. Mandibular nerve demonstrated on 0.5 mm enhanced VIBE images. A-d Four different axial levels show the course and some of the major branches of the mandibular nerve (V3). The left mandibular nerve (a) is imaged at the level of the foramen ovale, the right immediately below, where three branches are detectable, probably accounting for medial pterygoid (1), temporomasseteric (2), and middle deep temporal (3) nerves. Middle meningeal artery (MMA) b Two branches of the mandibular nerve are imaged on left side, while on right side the morphology of the nerve changes to give off (c) a large anterior trunk (black arrowheads), more clearly demonstrated on left side (black arrowheads on d), which is probably the lingual nerve. d Inferior alveolar nerve (IAN) is the largest trunk of the nerve; it gives off other small branches (black arrows on d). Right pterygopalatine artery (white arrowheads on a-d). e Coronal MPR shows the mandibular nerve (V3) surrounded by enhancing venous plexus. Meckel cave (arrowheads) and third cranial nerve (III) within the cavernous sinus are shown. f The sagittal MPR shows part of the extracranial course of the mandibular nerve (V3): lingual nerve (black arrow); inferior alveolar nerve (arrowheads); internal carotid artery (ICA); internal jugular vein (IJV)

Fig. 9.8a-f. Mandibular nerve demonstrated on 0.5 mm enhanced VIBE images. A-d Four different axial levels show the course and some of the major branches of the mandibular nerve (V3). The left mandibular nerve (a) is imaged at the level of the foramen ovale, the right immediately below, where three branches are detectable, probably accounting for medial pterygoid (1), temporomasseteric (2), and middle deep temporal (3) nerves. Middle meningeal artery (MMA) b Two branches of the mandibular nerve are imaged on left side, while on right side the morphology of the nerve changes to give off (c) a large anterior trunk (black arrowheads), more clearly demonstrated on left side (black arrowheads on d), which is probably the lingual nerve. d Inferior alveolar nerve (IAN) is the largest trunk of the nerve; it gives off other small branches (black arrows on d). Right pterygopalatine artery (white arrowheads on a-d). e Coronal MPR shows the mandibular nerve (V3) surrounded by enhancing venous plexus. Meckel cave (arrowheads) and third cranial nerve (III) within the cavernous sinus are shown. f The sagittal MPR shows part of the extracranial course of the mandibular nerve (V3): lingual nerve (black arrow); inferior alveolar nerve (arrowheads); internal carotid artery (ICA); internal jugular vein (IJV)

Fig. 9.9. Adenocarcinoma of left nasal fossa. Coronal plane CT demonstrates a soft tissue mass occupying the left nasal cavity. Erosion of the perpendicular plate and lateral displacement of the medial wall of the left maxillary sinus suggest the presence of a tumor contralateral nasal fossa and ethmoid at diagnosis (Fig. 9.10).

Small lesions may be very difficult to demonstrate with imaging techniques. Moreover, their precise site of origin may become apparent only at surgery, particularly when the nasal fossa is completely filled by tumor.

Regarding orbital invasion, recent evidence in the medical literature supports a more conservative approach on condition that the periorbita is not invaded, as in this occurrence the eye can be spared without increasing local recurrences or survival and adequate postoperative function can be maintained (Roux et al. 1997; Imola and Schramm 2002). Therefore, the first priority of imaging consists in assessing the integrity of the periorbita (Curtin and Rabinov 1998). In case of ambiguous findings of orbital invasion on imaging studies, it will be necessary to clearly inform the patient about the potential need of orbital clearance, although only intra-operative mapping of

Mucocele SphenoidalePlanum Sphenoidale

Fig. 9.10a-d. Adenocarcinoma of right ethmoid sinus. TSE T2 (a), plain and enhanced T1 (b-c) images obtained in the axial plane show a non homogeneous soft tissue mass which has both focal and large areas of hyperintensity on TSE T2 (asterisk). The tumor projects into the right sphenoid sinus (white arrow) causing sinus blockage. Dehydrated mucus has intermediate signal on all sequences; it is separated from the bony walls by thickened smooth mucosa. The adenocarcinoma causes focal displacement of the medial wall of the right maxillary sinus (arrowheads). Nasal septum invasion with contralateral extent is better shown on enhanced T1 (black arrows). On coronal plane (d) the tumor causes focal bulging of the medial wall of right maxillary sinus (arrows). Cribriform plate is normal, suggesting possible endonasal approach the orbital wall(s) - with gross examination and frozen sections - provides clear-cut information. In this setting, it should be noticed that the negative predictive value of MR (Maroldi et al. 1996) is higher than its positive predictive value, recently reported to be about 80% by Eisen et al. (2000) (Fig. 9.11).

The second priority of imaging consists in assessing the relationship between the lesion and the anterior cranial fossa floor. Findings provided by CT and MR are relevant in predicting the need for craniofacial resection. Coronal TSE T2 sequences are indicated to assess the integrity of the hypoin-tense interface between sinonasal and intracranial structures, which corresponds to bone/periosteum independently from the grade of bone mineralization (Fig. 9.12-9.16). Enhanced SE T1 on sagittal and coronal planes are particularly useful to grade intracranial extent (Fig. 9.17) , and to differentiate between extra-dural and trans-dural invasion (El-Beltagi et al. 2002; Ishida et al. 2002) (see chapter 4).

In evaluating the relationship between a naso-eth-moidal tumor mass and orbit/anterior cranial fossa floor, one should consider that these structures are mostly made by thin osseous layers, easily displaced and remodeled, particularly the lamina papyracea and the cribriform plate. However, displacement and

Planum Sphenoidale

Fig. 9.11. Large adenocarcinoma arising from left ethmoid, invading both nasal fossae and left maxillary sinus. On fat sat coronal T2 marked displacement and remodeling of left lamina papyracea is shown. A residual hypointense, continuous, interface separates tumor from orbital content indicating that the lesion is confined by the periorbita (arrowheads)

Fig. 9.11. Large adenocarcinoma arising from left ethmoid, invading both nasal fossae and left maxillary sinus. On fat sat coronal T2 marked displacement and remodeling of left lamina papyracea is shown. A residual hypointense, continuous, interface separates tumor from orbital content indicating that the lesion is confined by the periorbita (arrowheads)

Spread Ethmoid Tumors Diagram

Fig. 9.12. a Schematic drawing of a naso-ethmoidal mass non-contacting the ethmoid roof. In this setting, if the histological type does not contraindicate surgery, micro-endoscopic endonasal approach is feasible. b Adenocarcinoma (intestinal type) of right ethmoid (T) separated from the ethmoid roof by a small mucocele (M), which causes focal remodeling of the planum sphenoidale (arrowheads). Olfactory tracts (long white arrows); fluid retention within both posterior ethmoid sinuses (asterisks)

Fig. 9.12. a Schematic drawing of a naso-ethmoidal mass non-contacting the ethmoid roof. In this setting, if the histological type does not contraindicate surgery, micro-endoscopic endonasal approach is feasible. b Adenocarcinoma (intestinal type) of right ethmoid (T) separated from the ethmoid roof by a small mucocele (M), which causes focal remodeling of the planum sphenoidale (arrowheads). Olfactory tracts (long white arrows); fluid retention within both posterior ethmoid sinuses (asterisks)

Adenocarcinoma Ethmoid

Fig. 9.13. a Schematic drawing of a naso-ethmoidal mass contacting the ethmoid roof. In this setting, if the histological type does not contraindicate surgery, micro-endoscopic endonasal approach is feasible. b Recurrent adenocarcinoma of right ethmoid abutting the lamina cribrosa and the fovea ethmoidalis (black arrowheads), whose signal is normal. The tumor also abuts the lamina papyracea (white arrowheads), not transgressed. A focal area of neoplastic involvement is seen in the inferior aspect of the lamina papyracea (thin white arrows). A residual hypointense signal still separates tumor from intraorbital fat, possibly consisting with non-invaded periorbita. Definitive intraoperative assessment is necessary

Fig. 9.13. a Schematic drawing of a naso-ethmoidal mass contacting the ethmoid roof. In this setting, if the histological type does not contraindicate surgery, micro-endoscopic endonasal approach is feasible. b Recurrent adenocarcinoma of right ethmoid abutting the lamina cribrosa and the fovea ethmoidalis (black arrowheads), whose signal is normal. The tumor also abuts the lamina papyracea (white arrowheads), not transgressed. A focal area of neoplastic involvement is seen in the inferior aspect of the lamina papyracea (thin white arrows). A residual hypointense signal still separates tumor from intraorbital fat, possibly consisting with non-invaded periorbita. Definitive intraoperative assessment is necessary b a a

Right Lamina Papyracea

Fig. 9.14a-c. a Schematic drawing of a naso-ethmoidal mass partially eroding the ethmoid roof. In this setting, if the histological type does not contraindicate surgery, micro-endoscopic endonasal approach is feasible. Definitive intraoperative assessment is necessary. b Recurrent adenocarci-noma (intestinal type) of left ethmoid extended into the sphenoid sinus (T). Focal thinning of the hypointense interface corresponding to the planum sphenoidale (arrowheads) indicates partial erosion of bone by the tumor, still confined by the bone/periosteal barrier. Olfactory tracts (white arrows). The area included in the white box is magnified on an enhanced T1 image (c). The different signals of the bone/periosteal layer (short black arrows), thickened dura (white short arrows), and CSF (arrowheads) are shown in detail. When compared with TSE T2, the residual bone/periosteal layer appears thinner because it enhances. The dura overlying the focal bulging is homogeneously thickened (white arrows) and has signal intensity slightly lower than the underlying tumor and enhancing periosteum

Fig. 9.14a-c. a Schematic drawing of a naso-ethmoidal mass partially eroding the ethmoid roof. In this setting, if the histological type does not contraindicate surgery, micro-endoscopic endonasal approach is feasible. Definitive intraoperative assessment is necessary. b Recurrent adenocarci-noma (intestinal type) of left ethmoid extended into the sphenoid sinus (T). Focal thinning of the hypointense interface corresponding to the planum sphenoidale (arrowheads) indicates partial erosion of bone by the tumor, still confined by the bone/periosteal barrier. Olfactory tracts (white arrows). The area included in the white box is magnified on an enhanced T1 image (c). The different signals of the bone/periosteal layer (short black arrows), thickened dura (white short arrows), and CSF (arrowheads) are shown in detail. When compared with TSE T2, the residual bone/periosteal layer appears thinner because it enhances. The dura overlying the focal bulging is homogeneously thickened (white arrows) and has signal intensity slightly lower than the underlying tumor and enhancing periosteum b a c

Sphenoidale

Fig. 9.15. a Schematic drawing of a naso-ethmoidal mass with intracranial extradural extent. In this setting, if the histological type does not contraindicate surgery, anterior cranial resection is required. b Naso-ethmoidal squamous cell carcinoma (T) causes focal invasion of the planum sphenoidale where the CSF signal is effaced. Tumor extends intracranially (arrowheads)

Fig. 9.15. a Schematic drawing of a naso-ethmoidal mass with intracranial extradural extent. In this setting, if the histological type does not contraindicate surgery, anterior cranial resection is required. b Naso-ethmoidal squamous cell carcinoma (T) causes focal invasion of the planum sphenoidale where the CSF signal is effaced. Tumor extends intracranially (arrowheads)

Planum Sphenoidale

Fig. 9.16. a Schematic drawing of a naso-ethmoidal mass with intracranial intra-dural extent. In this setting, if the histological type does not contraindicate surgery, anterior craniofacial resection is indicated. b Large naso-ethmoidal neuroendocrine carcinoma with bilateral orbital involvement, with marked displacement of orbital muscles on right side (short arrows). Intracranial intradural invasion is also present (long arrows). Breaking of the dura, replaced by tumor signal (white arrows), is better shown on the sagittal enhanced T1 image (c). Adjacent thickened dura (black arrows)

Fig. 9.16. a Schematic drawing of a naso-ethmoidal mass with intracranial intra-dural extent. In this setting, if the histological type does not contraindicate surgery, anterior craniofacial resection is indicated. b Large naso-ethmoidal neuroendocrine carcinoma with bilateral orbital involvement, with marked displacement of orbital muscles on right side (short arrows). Intracranial intradural invasion is also present (long arrows). Breaking of the dura, replaced by tumor signal (white arrows), is better shown on the sagittal enhanced T1 image (c). Adjacent thickened dura (black arrows)

Sphenoidale Planum Sphenoidale Skull Base

Fig. 9.17a-c. Adenocarcinoma of right ethmoid sinus with intracranial intradural invasion. a On axial T2, bilateral edema of the olfactory lobe (white arrows) raises the suspect of cerebral invasion. On left side, an oval area with signal lower that the edematous surrounding brain tissue effaces the bright signal of CSF - close to the left aspect of the crista galli (black arrows). Post-contrast sagittal images (b) demonstrate invasion of the anterior skull base floor (white arrowheads) with intracranial spread and upwards displacement of an irregularly thickened dura (white arrows). Posterior to the area of intracranial invasion the dura is regularly thickened suggesting reactive change. c Linear enhancement into the sulci (arrows) on both olfactory lobes is consistent with leptomeningeal invasion. The ill-defined hypointensity surrounding the tumor invading the right olfactory groove indicates brain invasion and edema b a c remodeling is not exclusively related to tumor growth, as it may occur also in case of a mucocele secondary to mucus drainage blockage by a neoplasm.

Furthermore, intestinal-type adenocarcinoma, which is one of the most frequently encountered naso-ethmoidal malignancies, has a proper fluid component mimicking a mucocele (Fig. 9.10, 9.11b). Therefore, in presence of a naso-ethmoidal mass, any solid tissue within a mucocele-like lesion should raise the suspect of intestinal-type adenocarcinoma.

Conversely, true mucoceles should be differentiated from fluid-content areas of this specific histotype.

Meticulous attention should be paid to the evaluation of lacrimal system, particularly if epiphora is present, as imaging is highly accurate in predicting neoplastic invasion (89%) (Eisen et al. 2000). CT and MR findings indicating lacrimal pathways involvement are: dilation of the lacrimal sac, lacrimal bone and/or nasolacrimal duct walls erosion, and abnormal signal within the duct replacing its normal mucosa.

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