Ординатура / Офтальмология / Английские материалы / Neuro-Ophthalmology_Kidd, Newman, Biousse_2008

Figure 3–20 Gross conjunctival chemosis and restriction of eye movements because of an atheromatous carotico-cavernous fistula.

Young women are typically affected by idiopathic orbital myositis, which presents with a severe prodromal retrobulbar ache before the onset of diplopia and limitation of eye movement. The pain is worse with stretching of the affected muscle(s), and slight ocular redness and episcleral edema are not uncommon. CT shows affected muscles to be enlarged along their entire length (Fig. 3–21), unlike the more localized, posterior muscular engorgement with thyroid eye disease. Treatment is with high-dose prednisolone (1 mg/kg/day). This provides almost immediate relief of pain and rapid improvement of eye movements, and the dosage is tapered down to 20 mg/day over a few days; steroid reduction below this dosage should be slower and the patient considered for steroid-sparing therapy or low-dose orbital radiotherapy if symptoms recur with reduction in treatment.

Acute dacryoadenitis presents as headache, followed shortly by variable swelling and erythema of the upper lid and later with red eye or diplopia. The affected lacrimal gland may be palpable in the superotemporal quadrant and is generally exquisitely tender. In contrast, chronic dacryoadenitis is usually painless and may be associated with a nontender mass with dry eye (and dry mouth in Sjo¨gren’s syndrome) (Fig. 3–22). Imaging shows an enlarged gland, often bilateral and asymmetrical in sarcoidosis or other systemic conditions, that tends to mold to the globe and does not destroy bone; acute severe inflammation also will demonstrate spillage of changes into the preseptal upper lid tissues and overlying the temporalis fossa (Fig. 3–23). Acute dacryoadenitis should be treated with nonsteroidal anti-inflammatory drugs, with a rapid improvement of symptoms; failure to settle should raise a suspicion of underlying infection or some other source of inflammatory stimulus, such as a neighboring leaking dermoid or tumor. Any lacrimal mass persisting for more than 3 months should be regarded as possible malignancy and investigated with CT, with a view to incisional or excisional biopsy of the mass.

With the exception of characteristic orbital apex syndrome, all patients with diffuse idiopathic inflammation of the orbit should undergo biopsy because the imaging changes are nonspecific and very similar to those seen with infective inflammation, lymphoma, or carcinoma. Inflammation is a tissue response and

Figure 3–21 Localized vascular dilatation and swelling overlying the lateral rectus muscle in a patient with idiopathic orbital myositis. Computed tomography (CT), for another patient, shows a uniform expansion of the left medial rectus; the expansion extending into the parabulbar muscle tendon unlike the muscular enlargement of thyroid eye disease.

not a diagnosis and may arise with many orbital diseases—for example, quite commonly with lacrimal gland malignancy. The term pseudotumor should be abandoned in favor of “idiopathic inflammatory disease,” the term idiopathic, which constantly reminds the clinician to search for an underlying cause for the inflammation. Likewise, the use of a trial of systemic steroids (with the exception of myositis, orbital apex inflammation, or thyroid eye disease) should be discontinued because almost all orbital processes—but especially hematologic malignancies, low-grade infections, and tumor-induced inflammation—show a gratifying response to this treatment modality.

Thyroid Eye Disease

Thyroid eye disease is the most common adult cause of unilateral or bilateral proptosis. With an approximately sixfold female predominance, it commonly presents in the third and fourth decades with irritable and watering eyes, ocular redness, upper lid retraction, and puffiness of the lids (especially in the mornings); restriction of eye movements, with diplopia, and proptosis or optic

Figure 3–22 Bilateral chronic dacryoadenitis because of Sjo¨gren’s syndrome, with enlargement of the left lacrimal gland from secondary lymphoma.

Figure 3–23 Smooth enlargement of the left lacrimal gland, with molding around the globe because of mild dacryoadenitis.

neuropathy are later manifestations of more severe disease. Both the eye and the vision may be jeopardized by corneal exposure (because of the incomplete blink cycle and incomplete lid closure), by gross proptosis, by uncontrolled ocular hypertension, or by optic nerve compression.

Eye symptoms and signs (Table 3–3) occur in up to 40% of patients with hyperthyroidism (Graves’ disease) but in only a small minority of patients with Hashimoto’s thyroiditis or primary myxedema; the high incidence in Graves’ disease suggests a shared antigen between the thyroid and orbit; the prime candidate is the TSH receptor. Circulating activated T lymphocytes infiltrate orbital tissues and release proinflammatory mediators, causing fibroblast activation and glycosaminoglycan (GAG) deposition, and this cellular infiltration and tissue edema results in proptosis because of expansion of orbital tissues during the active, inflammatory (“wet”) phase. With resolution of the inflammation,

84Neuro-Ophthalmology: Blue Books of Neurology

TABLE 3–3 Common Characteristics of Thyroid Eye Disease and

Main Contributory Mechanisms

subsequent fibrosis of perimysial connective tissue during the inactive (“dry”) phase leads to muscular scarring and restriction of eye movements; unfortunately the accumulation of GAGs—and proptosis because of this tissue deposition—is largely irreversible.

CT generally reveals bilateral enlargement of one or more extraocular muscles, with the inferior and medial recti are affected most often (Table 3–4); enlargement of the oblique muscles is distinctly rare. Other features include increased orbital fat, which often shows a “streaky” opacity, and outward bowing of the thin orbital walls with long-standing disease (Fig. 3–24). Optic neuropathy is associated with orbital apex crowding and less proptosis (rather than elongation of the optic nerve), and the posterior part of the medial rectus is often disproportionately enlarged (Fig. 3–25). Imaging is particularly important with unilateral disease (lymphoma or reactive lymphoid hyperplasia may masquerade as unilateral thyroid eye disease) and to exclude underlying sinus disease or craniofacial anomalies in patients being

Figure 3–25 Orbital apex crowding in a patient with bilateral compressive optic neuropathy in thyroid eye disease.

considered for orbital decompression. MRI scanning, particularly STIR sequences, identifies inflammatory edema in the extraocular muscles, but the investigation is expensive and contributes little to clinical findings.

Although most patients with thyroid eye disease have abnormal thyroid function, some appear to remain biochemically euthyroid and the only detectable abnormality may be raised serum levels of thyroid autoantibodies. Treatment of Graves’ thyrotoxicosis tends to improve eye signs, although medically induced under activity may also exacerbate ophthalmopathy and should be avoided by regular blood tests. Radioiodine treatment will cause a flare-up of ophthalmopathy in a minority, and this is best avoided by early thyroxine replacement. Smoking should be discouraged, as this carries a markedly (about sevenfold) greater risk of significant ophthalmopathy.

There are several scales for assessing the activity of thyroid eye disease, but most patients have only mild symptoms and signs requiring, for example, ocular lubricants and sunglasses during control of their thyroid function; should upper lid retraction or incomplete lid closure persist, this can be dealt with surgically when eye signs are stable. When a patient has diplopia, increasing eyelid swelling, or proptosis, systemic immunosuppression should be instituted early in the active phase—before irreversible GAG deposition and fibrosis—and an objective deterioration in visual function, or a threat of corneal ulceration, is an indication for urgent ophthalmic intervention. Systemic immunosuppression, to reduce the degree of inflammation and secondary orbital congestion, is most likely to benefit patients with clear signs of clinical activity, or with muscular inflammatory edema shown on STIR-sequence MRI. High-dose systemic steroids (either intravenous methyl prednisolone [typically 1 g/day] or oral prednisolone [about 80 mg/day]) are given and the patient monitored for improvement over the first week: When there is a subjective and objective improvement, the steroid dosage is tapered gradually to 20 mg daily while the patient is referred for lowdose (2000 to 2400 cGy) lens-sparing radiotherapy to the posterior tissues of the orbit; such radiotherapy may, however, be contraindicated in diabetics because of the risk of exacerbating retinopathy. Steroids can normally be tailed off over about 6 to 8 weeks after completion of orbital radiotherapy. Gastric protection and control of hyperglycemia or hypertension should be instituted as

Figure 3–27 Patient after surgical correction of marked right upper retraction—the preoperative level is the same as that of the unoperated left side.

maximal decompression may be indicated. Acute orbital decompression is indicated if, despite high-dose systemic steroids, visual function deteriorates.

Orbital Osseous Disease

There are many benign lesions of periorbital bone; most of these are very rare and cured by surgical excision.

One tumor, meningioma of the greater wing of the sphenoid, is relatively common and may lead to proptosis, eyelid swelling, and progressive visual impairment; this visual loss is manifest as impaired color perception, a decreasing acuity, and loss of visual field sensitivity. Sphenoid wing meningioma, commonest in women in the fifth and sixth decades, is associated with hyperostosis of the sphenoid wing and soft tissue tumor extending into the lateral part of the orbit, the temporalis muscle fossa, or the anterior pole of the middle cranial fossa (Fig. 3–3). The tumor is probably driven by progestogens and affected patients should avoid progesterone-base hormone replacements. Surgical resection of these tumors is a major neurosurgical procedure, is incomplete in many cases (because of en-plaque involvement of the dura), and carries a significant risk of visual loss; there is also a belief that surgical manipulation of meningiomas may accelerate their growth pattern. Relief of progressive optic neuropathy may, however, be provided by medial orbital decompression; this may relieve compression of the optic nerve but not disturb the tumor itself. Radiotherapy is probably of benefit in slowing growth of meningiomas, but the high dosage required is likely to lead to later blindness from radiation optic neuropathy.

MALIGNANT ORBITAL DISEASES

Primary and secondary orbital malignancy is rare, occurs at any age, and must be considered whenever there is a rapidly or relentlessly progressive disease, an inflammatory picture, or when an apparently benign disease displays atypical behavior.