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

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6.1.2.3.5

Choroidal Detachment

Choroidal hemorrhage and choroidal detachment may be easily mistaken for a choroidal tumor, especially when a rupture of Bruch’s lamina has occurred (Mafee 1996). The imaging characteristics of choroidal detachment are discussed in detail in Sect. 6.1.4.

6.1.3

Inflammatory Disorders

6.1.3.1

Primary Inflammation: Scleritis

Even though the sclera is not highly vascularized, it may be affected by diverse inflammatory processes such as metabolic (gout), bacterial, fungal, or viral conditions. It is also one of the predominantly affected structures in one form of local idiopathic orbital inflammation (Mafee 1998). Presentation may be acute or chronic (Watson 1982) and is classified into an anterior and posterior form. The clinical presentation of a slowly progressing, painful thickening and flush of the sclera may be indicative of anterior scleritis, while the posterior form exhibits proptosis and eventually decreased vision, due to thickening of the sclera and choroid with choroidal folds. Posterior scleritis is less common, predominantly affecting women, and sometimes requires imaging. Histologically, it may present as

W. Müller-Forell and S. Pitz

diffuse or localized, nodular, necrotic, or granulomatous inflammation. Due to the inflammatory reaction with leakage of proteinaceous edema fluid into the interstice of the uvea and Tenon’s capsule, scleral sequesters and exudative retinal detachment may be seen in the vicinity of the inflammatory process (Flanders et al. 1989; Mafee 1998) (Fig. 6.20).

Depending on the grade of the inflammatory process, CT and MRI of scleritis is characterized by scleral thickening with contrast enhancement (Figs. 6.20–6.22). Subretinal effusion, clearly seen on ultrasound, may also be demonstrated and appear hyperintenseonT1-weightedandhyperintenseonT2- weighted MR images. Unlike melanoma, no enhancement is found in the nodular form of posterior scleritis (Harnsberger 1990; Mafee 1998).

6.1.3.2

Secondary Inflammation

6.1.3.2.1

Behçet Syndrome

Typical clinical manifestations of Behçet syndrome, first described in 1937 by the Turkish dermatologist H. Behçet, are the triad of recurrent oral ulcers (98%), genital ulcers (88%), and intraorbital inflammation (76%), the latter involving the anterior and/or posterior ocular chambers. The disease is characterized by periods of remission and exacerbation (Banna and El-Ramahi 1991); ocular involvement has been described as an indicator of systemic dis-

ease (Foster et al. 1991).Although rare, with a prevalence of less than 1 to 10,000, it is over 5 times more common in men than in women (Atmaca et al.1996); the third decade is the preferred age of onset, and people of the Middle East and Japan have a greater risk of being affected (Foster and Nguyen 2000). By definition, the identification of at least two of the main symptoms enables the diagnosis to be established, while other common symptoms include thrombophlebitis, arthralgia, or arthritis. In rare cases, neurological symptoms may be identified, indicating a secondary involvement of the central nervous system and an aggravation of the disease, (Kupersmith 1993) (see 7.3.2.1.2.1). The main feature of cerebral CNS involvement of this multisystem, immune-related vasculitis is chronic, relapsing, inflammatory cellular infiltration around venules and capillaries, resulting in dural sinus thrombosis, infarctions, or aseptic meningitis (Chajek and

Fainaru 1975; Kupersmith 1993; Zierhut et al. 1997; Wechsler et al. 1999).

Ocular and oral lesions most frequently represent the first clinical signs. The classic ophthalmologic finding in approximately one-third of cases is a sterile granulomatous anterior uveitis, presenting with pathognomonic hypopyon iritis, occasionally accompanied by aqueous effusion, and frequently followed by panuveitis. Recurrent iridocyclitis may result in

visually significant cataract, as well as in anterior and posterior synechia formation with subsequent glaucoma (Foster and Nguyen 2000). Retinal phlebitis and/or retinal vein thrombosis with exudates and hemorrhages are the classical posterior segment findings (Foster and Nguyen 2000; Kupersmith 1993) (Fig.6.23).Theleadingneuro-ophthalmologicalsymp- tom is unior even bilateral optic neuropathy.

Most of the secondary inflammatory ocular processes are not differentiated by modern imaging techniques, although these may help in clarifying the suspected underlying disease. The clinical differential diagnosis includes all causes of retinal microangiopathy, i.e.,AIDS-related retinal microvas culopathy with iridocyclitis, systemic lupus erythematosus (SLE), herpes retinitis and encephalovasculitis, infectious vasculitis, and Crohn disease as well as other rather rare diseases (Kupersmith 1993).

Only in rare cases does the first clinical presentation of Behçet disease not include the classical triple symptom complex of recurrent ulcerations of the oral and genital region and ocular inflammation, but involvement of the brain is observed in immunerelated vasculitis (Chajek and Fainaru 1975; Banna and El-Ramahi 1991; Wechsler et al. 1999). These patients may present with dural sinus thrombosis or neurologic deficits resulting from brainstem and motor system involvement rather than affection of

the sensory system. The presence of central nervous system dysfunction indicates a severe, unfavorable, long-term course of the disease, even when a remittance and relapse without neurologic symptoms may occur (Kupersmith 1993; Akman-Demir et al. 1999; Wechsler et al. 1999).

Histopathology is characterized by perivascular lymphocytic infiltration and areas of minimal demyelination in the vicinity of the affected vessels, especially the veins, capillaries, and possibly the arterioles (Fukuyama et al. 1987; Numano 2000). They present as infarctions, best demonstrated on T2weighted MR images, and are often seen in the brainstem (Fig. 7.78). Some authors consider the presence of cerebral venous thrombosis to be the first symptom of neuro-Behçet disease (Huss et al. 1992;

Humberclaude et al. 1993; Proebstle et al. 1996;

Tohme et al. 1997).

6.1.3.2.2 Sarcoidosis

Sarcoidosis is a chronic, multisystemic, granulomatous disorder of unknown etiology, involving any organic system, with clinical symptoms of central nervous system affection in approximately 10% of patients (Clark et al. 1985; Hayes et al. 1987; Rothova 2000) (see Sect. 7.3.2.2.3). Direct central nervous and ocular involvement may mimic a large number of more common diseases. Most of the central nervous system sarcoidotic granulomas have an affinity for the meningeal layers (Lexa and Grossman 1994); uveitis as a frequent and early feature of sarcoidosis is a common ophthalmoscopic finding (Rothova 2000), but rarely seen on imaging (Fig. 6.24). In the differential diagnosis of optic nerve or optic nerve sheath involvement, the idiopathic orbital inflammation may look very similar (Carmody et al. 1994).

6.1.4

Miscellaneous Lesions

6.1.4.1

Detachment of the Different Layers of the Globe

In rare cases, detachment of different layers of the globe may present as the only or accompanying feature of choroidal and/or retinal pathology. In healthy people, these layers are not separated by spaces, but these may be created in the course of pathologic disorders due to an accumulation of either serous or hemorrhagic fluid (Mafee 1996).

As described in the chapter on anatomy, the ocular globe consists of three primary layers:

1.the sclera,

2.the uvea,

3.the retina.

The sclera represents the outer coat and is composed of collagen-elastic tissue.

The uvea also consists of three components: the choroid, the ciliary body, and the iris. The choroid is located between the sclera and the retina, and both structures are separated by Bruch’s membrane, a 5-layer membrane formed by the basal lamina of retinal pigment epithelium (RPE) and the choriocapillaris, respectively.

The retina is histologically composed of seven layers. However, two principal parts may be distinguished from a functional point of view: (1) a thin inner layer, harboring sensory cells (photoreceptors), first and second order neurons, as well as neuroglial elements; (2) the hyaloid membrane of the vitreous body (membrana limitans interna) is located adjacent to the inner layer. The retinal pigment epithelium,the outer layer of the retina,nourishes the retina together with the vessels of the choroid (Mafee 1996; Bron et al. 1997).

Only under pathologic conditions, when an accumulation of fluid or hemorrhage may occur, do possible spaces between these layers become visible and distinguishable by imaging techniques. A thorough knowledge of the anatomic features of the detachment enables the differentiation of three potential spaces, each exhibiting a characteristic configuration on CT and/or MR (see Table 6.1):

1.the posterior hyaloid space. Posterior hyaloid detachment in adults over 50 years of age is caused by physiologic liquefaction of the vitreous body. In myopic individuals, it may generally occur at a younger age. Posterior hyaloid detachment may also occur in infants with (PHPV or in traumatic disease (Fig. 6.25, 6.28). On imaging, it presents as gravitational layering fluid (Goldberg and Mafee 1983; Mafee 1996).

2.the subretinal space. Retinal detachment is characterized by a V-shaped configuration of the detached retinal layers. The apex is characteristically directed towards the optic disc, resulting from the attachment of the retina to the optic nerve centrally and to the pars plana of the ciliary body. This configuration does not extend to the ciliary body, as the retina terminates peripherally at the ora serrata. This is an important differential diagnostic criterion to choroidal detachment (Mafee 1996).

Although very thin and beyond the limits of resolution on CT and/or MRI, the significant contrast difference between subretinal effusion (mostly hyperintense on MRI) and the vitreous cavity outlines the retina. Retinal folds (Fig. 6.27d), mainly seen on coronal/sagittal MRI, represent detached and folded retinal leaves (Mafee 1996). Any choroidal lesion may eventually produce retinal detachment (Figs. 6.26, 6.3), most frequently seen in adults as neoplasms like malignant melanoma and choroidal hemangiomas.

3.the subchoroidal space. Choroidal detachment may occur in two different forms with different imaging characteristics, i.e., serous and hemorrhagic choroidal detachment. Although the etiology of both forms may be similar, as they may occur after intraocular surgery, penetrating ocular injury, or inflammatory disorders (Mafee and Peyman 1984; Mafee et al. 1988; Mafee 1996), hemorrhagic detachment presents as a lens-like configuration, sometimes difficult to differentiate from retinal detachment. Even if large and irregular, it is defined

by the more parallel configuration of subchoroid hemorrhage (Fig.6.27),caused by the fixation of the choroid by the posterior ciliary arteries and veins at the optic disc and macula (Weiter and Ernest 1974; Mafee and Peyman 1987; Mafee 1996).

Serous choroidal detachment is characterized by a crescent or ring-shaped formation, isodense or sometimes hyperdense on CT and hyperintense on T2weighted MRI (Weiter and Ernest 1974; Mafee and Peyman 1987; Mafee 1996). The underlying cause of serous choroidal detachment is essentially ocular hypotony as a result of inflammatory diseases, or ocular surgery (mainly filtrating glaucoma surgery) (Wing et al. 1982; Mafee and Peyman 1984; Mafee et al. 1988). Increased permeability of the choroidal capillaries caused by ocular hypotony leads to diffuse swelling of the entire choroid followed by choroidal effusion (Fig. 6.23, Fig. 6.29, Fig. 6.6), choroidal edema, and finally fluid accumulation in the potential subchoroidal space, seen as choroidal detachment (Mafee 1996).

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6.1.4.2

Traumatic Lesions (Including Foreign Bodies, Penetrating Injuries, and Vitreous Hemorrhage)

Physiologically, the globe (eyeball), its neurovascular structures and muscles are protected by the bony orbit and shock-absorbing retrobulbar fat. Nevertheless,the globe,as the most anterior and therefore most exposed structure of the visual system, is extremely vulnerable. On the other hand, the external integrity of the globe and orbit should never lead to the assumption of intact, unaffected retroglobal orbital structures, since innocuous orbital trauma may produce devastating functional deficits (Fig. 6.30). Injury of the globe may occur as a component of major facial trauma or as an isolated event (Fig. 6.31). Different causes as, e.g., motor vehicle (car/motorcycle) accidents (Fig. 6.32) or sports-related injuries might contribute to the relatively common occurrence of orbital trauma (Johnston 1975). Orbital injuries may be divided into blunt trauma and penetrating injuries. While the former are due to an impact with low velocity forces, the latter are the result of impact at proportionally high energy with penetration of the

W. Müller-Forell and S. Pitz

object (Anderson et al. 1982). While most metallic foreign bodies are well-tolerated, copper and iron may cause purulent inflammation, and by far more disastrous, almost immediate severe toxic damage of the retinal photoreceptors. Iron may induce retinal siderosis, while organic foreign bodies (e.g., wood) are likely to cause microbial endophthalmitis (Grant 1974; Gerkowicz et al. 1985; Ho et al. 1996;

Carmody 2000).

The care of these patients requires an interdisciplinary approach by different specialized physicians (general surgeons, neurosurgeons, radiologists, ophthalmologists). CT is the diagnostic method of choice in traumatic lesions involving the orbit. It is readily available and enables both accurate visualization of bony and soft-tissue injuries and exact localization of (mostly ferromagnetic) foreign bodies without the risk of dislocation. In cases of extreme swelling of the lid, where ophthalmoscopy is impossible, CT can visualize the full extent of the injury rapidly and accurately (Fig. 6.33).

There is a great variety of injuries to the globe,ranging from rupture (Fig. 6.34) to dislocation of the lens (Figs. 6.35–6.37), and vitreous (Fig. 6.32), retrohyaloid

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Fig. 6.32. Axial CT of a 20-year-old woman with bilateral vision loss (maximum dilation of the left pupil, no light reaction) 20 h after a frontal car accident (wearing seat belt at time of accident). Diagnosis: right globe rupture with air inclusions, rupture and hematoma of the right optic nerve, fracture of the left optic canal with injury to the left optic nerve. Note the fracture of all middle face bones and bilateral orbital walls, swelling of the medial and lateral rectus muscle, suspicion of intramuscular hematoma (plaster splint of the nasal bones)

Fig. 6.33. A 69-year-old man with blunt orbital trauma. Ophthalmoscopy was impossible due to the severely swollen lid. Indication for imaging was the exclusion of a retrobulbar hematoma; CT showed a regular orbit in addition to the preseptal conjunctival and lid edema

Fig. 6.34. A 43-year-old male car accident victim. Diagnosis: rupture of the left bulb. Axial CT