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

6.4.2

Inflammatory Lesion

6.4.2.1

Optic Neuritis (with or without Multiple Sclerosis)

Optic neuritis may be defined as an acute, unilateral or bilateral loss of central visual acuity, associated with central scotoma, loss of contrast sensitivity, color vision, stereopsis, and an afferent pupillary defect with or without associated retroocular pain

on eye movement, as well as a reduced amplitude of the P100 component of the visual evoked potential (VEP) (Kakisu et al. 1991; Youl et al. 1991). The most common underlying pathologies are multiple sclerosis and acute disseminated encephalomyelitis (ADEM) (Fig. 6.189) (see also Sect 7.3.2.2.4.2). In 12%–30% of patients, acute optic neuritis is the first symptom of clinically not yet fully developed multiple sclerosis (Figs. 6.190, 6.191) (Christiansen et al. 1992; Frederiksen et al. 1992; Corona-Vasquez et al. 1997). Infections may also be responsible for

optic neuritis of different etiologies, which not only affect patients with human immunodeficiency virus (HIV) infection, where sporadic cases of various etiologies have been reported, but also immunocompetent patients. The various agents responsible for clinical symptoms include cytomegalovirus (causing retinitis and/or papillitis), varicella zoster, syphilis (leading to papillitis and perineuritis), mycosis, tuberculosis, and toxoplasmosis infections (Winward et al. 1989;

McLeish et al. 1990; Gunduz and Ozdemir 1994;

Nenning et al. 1994). Optic neuropathy is also known in patients suffering from autoimmune vasculitis and/ or systemic lupus erythematosus (Dutton et al. 1982;

Smith and Pinals 1982; Kira and Goto 1994), or paranasal infection (Sanborn et al. 1984). In rare cases,puerperal immune-mediated changes have been reported as responsible for activation of optic neuritis with relapsing multiple sclerosis (Leiba et al. 2000), and we saw optic neuritis in a patient with idiopathic inflammatory disease of the optic nerve and sheath

(Fig. 6.183). However, in some cases, the triggering etiology remains unknown, despite extensive neurological and neurophysiological examination (Fig. 6.191).

Although secondary lesions of the optic nerve may be seen on CT, MRI is the imaging method of choice in the detection of intrinsic optic nerve lesions. The areas most frequently affected in optic neuritis are the intraorbital and intracanalicular portions of the optic nerve, while lesions of the chiasm (Fig. 7.10) or the papilla are rare (Kerty et al. 1991; SartorettiSchefer et al. 1997). In addition to an increased signal on T2-weighted and FLAIR images the majority of patients (81%) show contrast enhancement of the affected nerve as a sign of blood-optic-nerve barrier (BOB) disruption not only in acute but in even in persistent (more than 4 months) neuritis. Although it is no specific marker, as it is seen in a variety of inflammatory, ischemic, and tumorous disorders, multiple sclerosis is the most common underlying pathology in these cases (Sartoretti-Schefer

et al. 1997). Focal thickening of the optic nerve or enhancement of the optic nerve sheath is less frequent, the latter occurring in perineuritis, a local variant of idiopathic orbital inflammation (Char et al. 1990), or in multiple sclerosis, preceding clinical symptomatology of optic neuritis (Beck et al. 1993; Sartoretti-Schefer et al. 1997). Focal contrast enhancement in acute demyelinating lesions is best demonstrated with fat-suppressed sequences (Guy et al. 1992; Sartoretti-Schefer et al. 1997). For differential diagnostic reasons, it is important to know that direct tumor infiltration of the optic nerve and sheath is known, especially in breast carcinoma and lymphoma (as leptomeningeal carcinomatosis), but with a nonspecific appearance, thus requiring consideration of the clinical history for a definite differential diagnosis (Char et al. 1990).

As mentioned elsewhere, optic neuritis may be the first symptom of multiple sclerosis, which is why a thorough evaluation of the brain should be performed (see Sect. 7.3.2.2.1). The finding of white matter lesions (3 mm or larger in diameter, at least one lesion periventricular or ovoid) allows us to determine whether or not these patients are at high risk for the development of clinically definite MS (Poser et al. 1984; Horowitz et al. 1989; Balcer 2001; Poser and Brinar 2001). Consequently, an effective treatment for optic nerve neuritis with intravenous methylprednisolone followed by oral prednisone and interferonbeta 1-a has been shown to reduce the development

of clinically definite MS (Balcer 2001; Soderstrom 2001). In monosymptomatic optic neuritis, the visual deficit after 6 months is generally mild (Cleary et al. 1997). The prognosis of recovery is related to the MRI findings, as the location of acute optic neuritis in the intracanalicular portion of the optic nerve and a lesion greater than 17.5 mm are thought to lead to only incomplete or partial visual recovery (Dunker and Wiegand 1996).

6.4.2.2

Neuromyelitis Optica (Devic’s Syndrome)

Neuromyelitis optica (Devic’s syndrome), with the clinical syndrome of an acute and mostly simultaneously onset of (often bilateral) optic neuritis with total blindness and transverse myelitis of the cervical or upper thoracic spinal cord, is thought to be a disorder different from MS (van der Knaap and Valk 1995; Filippi et al. 1999; Wingerchuk et al. 1999). About 50% of patients die within several months of onset, mainly caused by respiratory failure as a consequence of cervical myelitis, another 15% of patients are reported to have a poor neurological outcome, while only about 35% of the patients are found to achieve a (nearly) complete recovery (van der Knaap and Valk 1995; Edwards-Brown and Bonin 1996; Margeaux et al. 1999; Wingerchuk et al. 1999). Along with optic nerve lesions and brain involvement, MRI shows single lesions of the cervi-

cal cord on T2-weighted images (Fig. 6.193), usually longer than two vertebral segments, and contrastenhancing optic nerve lesions (Barkhof et al. 1991; Filippi et al. 1999; Wingerchuk et al. 1999).

6.4.2.3

Miscellaneous (Ectopic Pituitary Adenoma, Sphenoid Meningioma, Aneurysm)

Pituitary adenomas arising at a distance from the pituitary gland are rare. They develop as a result of defects in embryological migration and are found mostly in the sphenoid sinus or in the suprasellar region (Lloyd et al. 1986; Dyer et al. 1994; Hat-

tori et al. 1994; Kikuchi et al. 1994b; Luk et al. 1996). In most cases, they manifest with pituitary dysfunction similar to findings in prolactinoma, Cushing disease, or acromegaly. To our knowledge, no case with hormone inactive ectopic pituitary adenoma in the clinoid process, presenting only with visual loss caused by optic nerve compression at the optic canal, has previously been reported

(Fig. 6.194).

Despite a small diameter, the location of even small lesions in the vicinity of the optic canal may lead to optic nerve compression with residual visual deficit to loss of vision, whether the pathology arises from meningioma of the anterior clinoid process

(Fig. 6.195) or an aneurysm of the internal carotid/ ophthalmic artery (Fig. 6.196).

The diagnosis of optic nerve atrophy is usually made on clinical grounds. The typical clinical findings are relative afferent pupillary deficit, visual field loss, and optic disc swelling or atrophy. The vast majority are caused by ischemic or inflammatory processes, and the diagnosis may be adequately based on clinical findings and anamnestic data. However, the work-up may require imaging when compressive neuropathy is suspected (Burde et al. 1992). The hallmark of compressive disease, requiring a decision as to whether or not surgical therapy is needed, is painless, progressive loss of visual function (Fig. 6.197) (Lee and Brazis 1998).

6.4.3

Traumatic Lesions

In traumatic disorders of the face and orbit, the optic nerve may be one of the structures involved (Fig. 6.198), but single lesions of the optic nerve are rare. In cases where the extent of the injury is at variance with the clinical presentation, high-resolu- tion CT may detect even small fractures as shown in Fig. 6.199.