Ординатура / Офтальмология / Английские материалы / Imaging of Orbital and Visual Pathway Pathology_Muller-Forell_2005

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6.3.3.2

Abscess Secondary to Ethmoid/Sphenoid Sinusitis, Mucocele/Pyocele

An involvement of the extraconal space or the face in inflammatory disease of the paranasal sinuses is most

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Fig. 6.117a–c. A 49-year-old man with acute, complete vision loss of the right eye. Diagnosis: pyocele of the right ethmoid with spontaneous ipsilateral subperiostal hematoma. CT: a Axial contrast-enhanced image with complete mucous filling of the middle, characteristically widened right ethmoidal cells, and marginal contrast enhancement. Note the significant protrusion of the right eye. b Axial contrast-enhanced view at the level of the superior ophthalmic vein with an isodense, homogeneous mass. c Coronal view showing the subperiostal mass in the superior orbit with the characteristic, sharp margin of the space-occupying formation. The absence of contrast enhancement both in the mass and at its margin leads to the suspicion of hematoma, and to the exclusion of the presence of a subperiosteal abscess

commonly caused by mucoceles (Figs. 6.118, 6.119). Mucoceles contain a mucous sac lined by mucous membrane and most commonly result from inflammatory obstruction of the ostium of the affected sinus (primary mucocele). Secondary mucoceles are posttraumatic, postoperative, or are seen in neoplastic

Fig. 6.120. A 61-year-old woman with febrile state and history of a head injury with frontal sinus involvement. Diagnosis: pyocele. Coronal contrast-enhanced CT: dislocation of orbital structures including the right globe by a very large cele of the supraorbital recess of the right frontal sinus, showing contrast enhancement at the margin, and occupying the entire nasal volume

Fig. 6.121a,b. A 55-year-old man with subfebrile state and a prominent left orbital protrusion. Diagnosis: orbital complication due to pyocele of the ethmoid cells. Contrast-enhanced CT: a Axial view with intraorbital extension of the ethmoidal cell enlargement. Note marginal contrast enhancement and an intraorbital, postseptal formation, indicating intraorbital involvement of the inflammatory process. b Coronal bone window with a defect in the lateral wall of the enlarged, infected ethmoidal mucocele

ent ways, depending on the extent of hydration of the sinus secretions. In the presence of high serous fluid (free water) content, the sinus appears hypointense on T1-weighted and hyperintense on T2-weighted images (Fig. 6.119). At increasing dehydration, hyperintense signals may be seen on both T1-weighted and T2-weighted images. When the secretions become inspissated, the signal intensities may decrease in both weightings, simulating a normal air content of the sinus. In order to avoid false-negative findings, CT should therefore be the method of choice in clinically suspected mucocele (Harnsberger 1990; Hasso and

Lambert 1994).

The definition of postoperative complication after sinonasal surgery may sometimes be challenging for both surgeons and neuroradiologists. A subperiosteal abscess represents a rare complication of sinonasal pathology (Fig. 6.123), as well as a secondary infection with development of an orbital apex syndrome with cranial nerve palsies (Fig. 6.124).

precise delineation of soft and bony tissue, especially in combination with bone SPECT, a sensitive technique for the detection of osteomyelitis of the skull in patients without prior surgery (Seabold et al. 1995).

The differential diagnosis should take into consideration other rare lesions as, e.g., cholesterol granuloma (Kuroiwa et al. 2000). Although able to cause bone destruction, these nevertheless benign lesions with a strong male preponderance occur at a characteristic site immediately adjacent to the lacrimal fossa (Fig. 6.127) (Hill and Mosely 1992). Especially in nonpneumatized bone, the underlying pathology is thought to be posttraumatic, postsurgical, or postinflammatory,even in the absence of a history of trauma (Dobben et al. 1998).

6.3.3.3

Miscellaneous (Subperiosteal Hematoma, Osteomyelitis, Cholesterol Granuloma)

Postoperative subperiosteal hematoma is a rare, but severe complication after sinonasal operation (Fig. 6.125), demanding surgical decompression in emergencies. In contrast to a diffuse retrobulbar hematoma, the sudden onset of subperiosteal hematoma and its substantial mass can lead to complete vision loss.

Cranial osteomyelitis, primarily arising from complications of paranasal sinus infections and often resistant to medical therapy, represents a somewhat rare disorder, especially when a hematogenous etiology is suspected (Fig. 6.126). CT and MRI provide a

Fig. 6.125. A 35-year-old woman with acute exophthalmos developing a few hours after a nasal sinus operation. Diagnosis: subperiosteal hematoma. Coronal CT: sharply defined, biconvex, homogeneous, hyperdense, space-occupying lesion at the orbital roof with caudal dislocation and flattening of the superior rectus (arrow) and superior oblique (arrowhead) muscle, completely shaded ethmoidal cells. (With permission of Müller-Forell and Lieb 1995b)

6.3.4

Lacrimal Gland

The spectrum of lacrimal gland pathology represents a challenge, because it poses special problems for the differential diagnosis and management, due to the superolateral, extraconal, intraorbital location of the gland and the respective surrounding structures. Lacrimal gland lesions, mainly presenting as an unspecific enlargement of the gland, can be classified both as epithelial and nonepithelial lesions, the former including largely neoplastic disorders, while the latter consist mostly of congenital, inflammatory, but also neoplastic conditions (Mafee et al. 1999b).

6.3.4.1

Congenital Lesions (Dermoid Cysts)

Dermoid cysts arise from epithelial remnants in embryonal epithelial tissue. They exhibit a tendency to develop along the bony structures of the orbit, especially along the suture. Their incidence varies depending on the definition, but they account for about one-quarter of all orbital biopsies. Superficial dermoid cysts occur primarily in the lateral aspects of the brow (Fig. 6.128) or the medial upper eyelid and are manifest already within the 1st year of life (Fig. 6.129). However, removal can be delayed unless the lesion is growing rapidly or causing recurrent bouts of inflammation. Dermoid cysts must be distinguished from deep orbital dermoids,which constitute 4%–6% of orbital tumors (Mortada 1971; Pear

1970; Pollard and Calhoun 1975; Reim et al. 1975;

Hurwitz et al. 1982; Shields et al. 1986; Smirniotopoulos and Chiechi 1995).

Macroscopically, orbital dermoids are round to oval-shaped, encapsulated tumors, filled with various skin appendices and fatty material. Histologically, the typical dermoid is outlined by a keratinizing squamous epithelium with dermal appendices such as hair follicles and sebaceous glands (Dithmar et al. 1993).

In addition to the clinical examination, which is sufficient for most superficial orbital dermoids, ultrasound A- and B-scans are helpful, because these demonstrate a sharply outlined lesion with a capsule and low reflective contents, thus making CT or MRI rarely necessary (Ossoinig 1975; Rochels et al. 1986).

CT reveals a sharply delineated, cystic tumor of low, sometimes negative density, due to the presence of fatty components (Figs. 6.128, 6.129). Contrast enhancement may be seen in the capsule, and calcifications are occasionally detected and may be helpful in the differentiation from mucoceles. Shallow impression of the bone is a common feature (Fig. 6.128). In some (rare) cases, a bony defect along the frontozygomatic suture may cause a so-called dumbbell-shaped orbital dermoid with a small portion extending into the fossa temporalis (Wackenheim et al. 1977; Wende et al. 1977; Tadmor and

New 1978; Grove 1979; Zilkha 1982; Samuelson et al. 1988; Sathananthan et al. 1993).

MRI demonstrates dermoids and epidermoids as sharply outlined lesions with a hypointense signal similar to the signal in the presence of water on T1-