Ординатура / Офтальмология / Английские материалы / Clinical Ophthalmic Echography_Harrie_2008

Echography is a valuable diagnostic technique for the evaluation of orbital pathology. The incredible advances in computerized imaging capability with computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scanning have seemingly supplanted the role of ultrasound in orbital diagnosis, but this modality has much to offer. B-scan still occupies an important niche especially in the anterior half of the orbit, but A-scan brings a unique capability to the orbit by providing quantitative data for the evaluation of orbital lesions. The ability to accurately measure structures, such as the optic nerves, extraocular muscles, and lacrimal glands, in conjunction with tissue pattern analysis of tumors and other lesions

complements the morphological analysis provided by the other imaging modalities.

Orbital diagnosis requires a systematic and methodical approach including a careful history, physical examination, and the judicious and cost-effective use of imaging technology. A common presentation of many kinds of orbital pathology is proptosis. This term is usually applied to space-occupying lesions, whereas exophthalmos generally applies to the protrusion of the eyes seen in Graves’ orbitopathy.

Patients with prominent eyes are encountered commonly in general ophthalmic practice. The patient herself or a family member may have noticed the change in eye position or the practitioner may be the first to bring it to the attention of the patient.

TR was a 6-year-old child who had been treated with glasses and patching for anisometropic amblyopia and accommodative esotropia over several years. His vision in the right eye was 20/25 on the most recent examination and the left had improved with therapy to 20/50. His family had changed their health insurance and because their ophthalmologist was not on the plan they elected to seek consultation with a different doctor. He noted that the patient’s left eye appeared prominent under amplification by the high plus spectacle lenses the child was wearing. Hertel exophthalmometry was performed and showed a measurement of the right eye of 15 mm and the left of 18. He also documented the presence of a subtle afferent pupil defect on the left side.

Echography was performed and revealed thickening of the left optic nerve of 6.98 mm compared to 3.4 mm on the right. The nerve substance was thickened and the optic nerve sheaths appeared normal (Fig. 211). The 30° test was negative,

FIG. 211. A-scan of optic nerve glioma (arrows)

FIG. 212. Magnetic resonance imaging of optic nerve glioma (arrow)

which supported a solid process of the left optic nerve as opposed to excess optic nerve sheath fluid. The echographic findings were consistent with an optic nerve glioma.

This diagnosis was supported by MRI scanning that demonstrated fusiform optic nerve enlargement on the left back towards the optic chiasm (Fig. 212). The chiasm appeared uninvolved by the tumor. It was elected to follow the child without treatment with serial MRI scans to ensure that the neoplasm was not growing posteriorly. The treatment

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of the amblyopia with glasses and patching was continued.

Exophthalmos can be simulated by retraction of the upper lids. Their normal position is just above the superior limbus and elevation above this level can give the appearance of prominence of the globe. The most common cause of retraction is thyroid-related eye disease. The causes of this finding are multifactorial and according to Doxanas and Anderson35 include sympathetically innervated muscle contraction, infiltration of the levator muscle by glycopro-

Case Study 113. Optic Nerve Glioma

teins and mucopolysaccharides, and overaction of the levator palpabrae/superior rectus muscle complex in response to a fibrotic inferior rectus muscle that tethers the globe with resultant hypotropia.

The spectrum of Graves’ disease ranges from simple hyperkinetic lid retraction to congestive ophthalmology with conjunctival chemosis and edema of orbital tissues. It is possible to image the levator/superior rectus complex by echography and thickening of these structures may be an early echographic sign of Graves’ orbitopathy.

SB is a 43-year-old woman with a history of radioactive iodine treatment of hyperthyroidism 10 years before she presented to her ophthalmologist with the complaint that “my eyes seem bigger.” She stated that her thyroid hormone levels had recently been checked and were normal. Examination revealed vision in both eyes of 20/20 and normal slit-lamp examination. There was 1 mm of scleral show bilaterally and mild lid lag. Hertel exophthalmometry was performed and measured 18 mm OD and 19 mm OS.

A-scan demonstrated normal to upper limits of extraocular muscle quantitative measurements bilaterally. However B-scan qualitatively showed thickening of the levator/superior rectus complex (Fig. 213). She was diagnosed with early congestive Graves’ ophthalmopathy and was advised to be followed up in 6 months or to return sooner if she noted symptoms, such as reduced vision or diplopia.

FIG. 213. B-scan of superior rectus (small arrow)/levator (large arrow) complex in Graves’ disease

CJ is a 53-year-old woman with a history of hyperthyroidism who noted prominence of her eyes over several months. She was referred to an endocrinologist who diagnosed Graves’ orbitopathy and referred her for echographic confirmation. This showed several thickened extraocular muscles bilaterally, which was consistent with her diagnosis. She was lost to follow-up for several years and then presented to her endocrinologist with the concern that her left eye was “bulging out more.” Exophthalmometry measurements were basically unchanged from the previous ones (OD 20 mm and OS 22mm). An MRI scan showed borderline enlargement of several muscles, but no mass lesion was detected. An orbital surgeon was consulted and recommended orbital decompression.

She sought a second opinion and was referred for echography, which showed that the muscle measurements had actually decreased from the ones taken 3 years ago (Fig. 214). Her increasing

eye prominence was felt due to increased lid retraction and not from extraocular muscle thickening. She was given the option for a relatively simple levator recession operation to lower the left upper lid and advised not to undergo orbital decompression with its greater risk of complications.

If the examiner suspects proptosis, it is recommended that he stand behind the seated patient without leaning forward and look down at the top of her head. Then her head is gently tilted back and normally her supraorbital ridges should first be seen followed by the malar prominences. The corneas are not normally seen unless proptosis is present. This is especially apparent if the eyes are asymmetric in their protrusion forward. Another technique is to place a card so it simultaneously touches the supraorbital ridge and malar prominence. The eyeball should not be in contact with the card unless it is proptotic. The impression of proptosis should be confirmed by exophthalmometry measurements.

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In some cases of orbital pathology the globe is not proptosed, but is displaced in the horizontal plane. Inferior displacement suggests a lesion in the lacrimal gland or superior orbit such as lymphoma, lateral displacement is suspicious for a lesion in the ethmoid or sphenoid sinus, medial displacement suggests lacrimal gland enlargement, and superior displacement suggests a lesion in the maxillary sinus.

The 30 cc space comprising the orbit is subject to a wide variety of pathological states. An accurate differential diagnosis is dependent upon a combination of clinical history and examination in conjunction with appropriate imaging studies. In spite of such careful analysis the clinician is not uncommonly surprised at the final pathological diagnosis.

A systematic approach is essential to clinical diagnosis in the orbit. Ben Simon et al.36 propose a system of orbital tumor diagnosis primarily based on CT and MRI findings. Utilizing the combination of location, content (e.g., density and contrast enhancement on CT and intensity on MRI), soft tissue characteristics, bone characteristics, and associated features a systematic approach to orbital lesions is outlined.

An example of such an integrated diagnostic scheme with the incorporation of echographic findings is shown as applied to a cavernous hemangioma, the most common orbital tumor in adults (Table 1).

Such a scheme can be generated for almost all of the orbital pathology encountered in clinical practice with high diagnostic accuracy for many lesions. An expanded table is illustrated in Part VIII. The ultimate objective of the practitioner is to make a correct diagnosis without the need to surgically invade

TABLE 1. Example from Table 3 in Part VIII.

Cash Study 115. Noncongestive Graves’ Disease

the orbit for diagnostic biopsy. This goal is realistic for a number of conditions but uncommon entities, such as orbital myxoma or orbital fibroma, require biopsy to make the final diagnosis.

The general categories of disease processes that can affect the orbit include neoplastic, inflammatory/ infectious, vascular, and traumatic. There are many different entities that can involve the orbit and relatively few ways in which they can interact with the tissues in the crowded bony orbital space. The history is the first step in placing orbital pathological processes into one of these categories. The patient’s perception of a change in appearance is often the basis for presentation to the clinician. Her concern about an eye that appears larger on one side or an eyelid abnormality noted when applying her makeup may be the reason she has sought medical consultation.

Orbital tumors often present with some type of displacement of the globe in either the anterior/ posterior direction or in the coronal plane with horizontal or vertical misalignment. Benign lesions tend to grow slowly and a considerable amount of time may pass before the patient becomes aware of the abnormal eye position.

This is especially true with axial proptosis, which often is not evident unless someone besides the patient views the eyes off angle. The globe can be pushed forward to a considerable degree before it is recognized. Exophthalmometry is an important tool to quantitate the amount of proptosis. Migliori37 studied normal subjects and found that Caucasian males had average exophthalmometry measurements of 16.5 mm to 21.5 mm and females averaged 15.5 mm to 20 mm. Black adults averaged about 2 mm more than whites for both men and women.

TP is a 43-year-old woman who presented with the complaint that her eyelashes were brushing against her glasses for the past several weeks. Examination found vision in the right eye of 20/25 and the left of 20/20. She had full range of extraocular movements and no horizontal or vertical displacement of the eye. Hertel exophthalmometry was performed and OD measured 24 mm with OS at 17 mm. Her driver’s license photo had been taken 5 years previously and there was no apparent proptosis of the right eye when the picture was inspected with a magnifying lens. Fundus examination was remarkable for the presence of choroidal folds in the right eye.

Echography was performed and an intraconal well-outlined mass was noted on B-scan. A-scan revealed medium internal reflectivity and angle

kappa with a “saw-tooth” pattern consistent with a cavernous hemangioma (Fig. 215). The lesion decreased from 15 mm to 13 mm upon compression by the probe through the closed lid for over a minute. No spontaneous vascularity was noted.

The patient underwent an excision of the tumor, which was easily removed in toto with the aid of a cyroprobe. The pathological diagnosis was a cavernous hemangioma (Fig. 216) with characteristic large blood-filled cystic spaces.

Another tumor that may be found in the retrobulbar space with resultant axial proptosis is the hemangiopericytoma. This potentially malignant lesion has been confused with cavernous hemangioma on imaging studies, but A-scan characteristics are usually quite helpful in distinguishing between these two entities.

HO is a 42-year-old woman who presented with the complaint that her left eye appeared larger than her right. She was not exactly certain when the problem started but felt it was probably over several months. Examination found vision in both eyes of 20/20 and 5 mm of left proptosis on Hertel exophthalmometry. Fundus examination was normal and no choroidal folds were noted. CT scanning revealed a rounded isodense lesion behind the globe that mildly enhanced after the injection of a contrast agent. The differential diagnosis included a cavernous hemangioma.

Echography showed an encapsulated moderately echolucent tumor on B-scan with irregular low- to-medium reflectivity and moderate vascularity on A-scan (Fig. 217). The regular “sawtooth” pattern typical of cavernous hemangioma was not appreciated so the ultrasound findings were inconsistent with this diagnosis and more typical for other well-circumscribed lesions, such as hemangiopericytoma, neurilemoma (Antoli A type Schwannoma), neurofibroma, or histiocytoma.

Because of the malignant potential of this tumor, a total excision of the lesion was performed and pathology confirmed a hemangiopericytoma. The patient was followed up every 3 months with clinical examination and echography for the first year with plans to increase the time interval to every 6 months the second year and then annually.

Lesions in the medial orbit such as frontal ethmoidal mucoceles tend to displace the globe laterally as they grow. A mass effect is created as it pushes into the orbit behind a very thin layer of bone on the surface. Internally a mucous membrane-lined cavity filled with mucinous material is found.

FIG. 217. Top: A-scan of hemangiopericytoma (vertical arrows). Bottom: B-scan of the lesion (arrow)

GB is a 52-year-old woman with a history of chronic sinus disease who visited her daughter whom she had not seen for almost a year and was noted to have a left eye that “was pushed way off to the left.” The patient had not been aware of this but did notice it after her daughter’s comments. She presented to an ophthalmologist who measured lateral displacement of the left eye of 5 mm compared to the right. This measurement was performed by placing one end of a millimeter ruler on the middle of the nose on the same horizontal level as the center of the pupil. This measurement was then repeated for the opposite eye. The patient had a full range of motility and had experienced no diplopia.

Echography was performed and revealed an encapsulated lesion in the left superior nasal orbit. B-scan demonstrated a high reflective surface suggestive of calcification. A-scan showed low internal reflectivity. The probe was placed on the inferotemporal globe and directed to the 11:00 orbit. As it was angled over the lesion, a high spike “jumped up” and then disappeared as the probe was angled a little further. This phenomenon was consistent with a bone defect in the lateral wall of the frontal ethmoid sinus. The first spike was reflected from the normal medial orbital wall but this disappeared when the defect was encountered. The second spike then arose as a reflection of the sound beam from the medial wall of the sinus because the beam passed into the sinus without hindrance. As the probe was angled further the sound beam once again was reflected by the orbital bone that bounded the sinus cavity (Fig. 218). These findings were very consistent with a mucocele causing a bone defect. Echo spikes

were also detected from the right ethmoid sinus cavity and both maxillary sinuses, consistent with chronic sinusitis.

FIG. 218. Top: A-scan of orbital portion of mucocele (vertical arrows). Bottom: A-scan of extension of mucocele into sinus (vertical arrows)