Ординатура / Офтальмология / Английские материалы / Ophthalmic Ultrasound A Diagnostic Atlas 2nd edition_ DiBernardo, Greenberg_2006
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Figure 8–1 Optic nerve normal. The probe is placed temporally |
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with the patient fixating in primary gaze. |
Figure 8–2 Normal. The nerve appears as a round, echolucent |
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lesion (arrows) adjacent to the globe. |
Figure 8–3 Normal. The A-scan probe is also placed on the temporal globe with the patient fixating in primary gaze.
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Figure 8–4 Normal. (A) Transverse B-scan of a normal optic nerve. (B) A-scan measurement showing the inner aspects of the arachnoid sheaths (arrows) of the anterior portion of the retrobulbar optic nerve. (C) A-scan measurement of the posterior portion of the nerve (arrows).
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Figure 8–5 Optic nerve normal using high resolution (20-MHz) probe. (A) Cross section of the normal retrobulbar optic nerve (arrow) using 10-MHz probe. (B) Cross section of the same nerve using 20-MHz probe.
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Figure 8–6 Disc elevation. (A) and (B) Axial echograms of both eyes of a patient with clinical evidence of disc elevation, confirmed by ultrasound (arrows).
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Figure 8–7 Drusen. (A) and (B) Transverse B-scan showing bilateral optic disc drusen (arrows).
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Figure 8–8 Drusen/phlebolith. Transverse B-scan showing a small calcification deep in the optic nerve (arrow) of a patient with a history of vascular occlusive disease.
Figure 8–10 Total cupping. Transverse scan showing a total (“bean-pot” configuration) optic disc in a patient with end-stage glaucoma (arrows).
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Figure 8–9 Small cupping. (A) Transverse scan showing mild excavation at the optic disc (arrow) and the retrobulbar optic nerve (ON). (B) Longitudinal scan showing excavation (arrow) and retrobulbar optic nerve (ON).
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Figure 8–11 Cupping using high-resolution (20-MHz) |
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probe. (A) and (B) Transverse scans of both optic nerves |
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showing total excavation (arrow). (C) and (D) Longitudinal |
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scans confirming total excavation.
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Figure 8–12 Fluid-positive 30 degrees. (A) The retrobulbar optic nerves are measured with the patient fixating in primary gaze. The probe is placed on the globe temporally, and the sound is directed posteriorly. (B) After measurements are obtained in the primary gaze, the patient is instructed to look 30 degrees toward the probe and the measurements are repeated.
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Figure 8–13. Fluid-positive 30 degrees. (A) Transverse B-scan showing the echolucent crescent (arrow) surrounding the optic nerve proper, indicative of increased subarachnoid fluid. (B), (D) A-scan measurements in primary gaze, anterior (B) and posteriorly
(D). Arrows show the inner aspects of the arachnoid sheaths. (C), (E) Measurements obtained with patient looking 30 degrees toward the probe. Arrows show significant decrease in the width of the nerve.
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Figure 8–14. Optic nerve atrophy. (A) Cross section of the normal right retrobulbar optic nerve (arrow). (B) Cross section of the atrophic left retrobulbar optic nerve (arrow). (C) Standardized A-scan measurement of the normal right optic nerve anteriorly (arrows). (D) Standardized A-scan measurement of the atrophic left optic nerve anteriorly (arrows). (E) Standardized A-scan measurement of the normal right optic nerve posteriorly (arrows). (F) Standardized A-scan of the atrophic left optic nerve posteriorly (arrows).
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Figure 8–15. Avulsion. (A) Transverse scan showing dense hemorrhage in the vitreous cavity and irregular shape of the retrobulbar nerve following traumatic avulsion (arrow). (B) Longitudinal image showing the characteristic dispersion of the hemorrhage emanating from the optic disc (arrow).
9
The Extraocular Muscles
Clinicians have relied on their clinical assessment of patients and radiologic studies to diagnose and treat patients with disorders involving the extraocular muscles. Computed tomography (CT) and magnetic resonance imaging (MRI) easily show enlargement of the extraocular muscles if the enlargement is marked. Slight changes in the size of the muscles may go undetected with these tests, however, especially if the size of the section imaged is too large or an oblique cut is made, making the muscles look erroneously asymmetric or enlarged. Of course, CT involves exposure to radiation, and both CT and MRI are more expensive than ultrasound.
Contact B-scan and standardized A-scan can be used to display the extraocular muscles from the inserting tendon at the globe to the muscle belly posteriorly. By B-scan the muscles display lower reflectivity than the surrounding orbital tissue because of the homogeneous nature of the muscle fibers. On standardized A-scan the extraocular muscles appear as a slight defect (area of lower reflectivity) within the highly reflective orbital fat. Although B-scan provides the topographic information (much like CT and MRI), the standardized
A-scan provides precise measurements of the muscle thickness and information about the reflectivity that allows for differentiation of disorders that cause muscle enlargement.
The normal values for the size of the extraocular muscles, as well as total volumes and acceptable differences between the muscle pairs have been established. Following the same prescribed B-scan examination techniques used for basic screening of the globe makes it relatively easy to look at the extraocular muscles in both cross-section (transverse) and radial (longitudinal) views. Once a single muscle has been imaged, it is recommended that the contralateral muscle then be displayed to determine any gross difference in thickness. The standardized A-scan can then be used to evaluate the muscle thickness and reflectivity.
Echography can be useful in distinguishing between normal muscle patterns and disorders such as thyroid eye disease, myositis, and mass lesions involving the extraocular muscles. Examples of normal images and each of the various disorders are included on the following pages.
Suggested Readings
Byrne SF, Gendron EK, Glaser JS, Feuer W, Atta H. Diameter of normal extraocular recti muscles with echography. Am J Ophthalmol 1991;112:706–713
Byrne SF, Green RL. Second Edition: Ultrasound of the Eye and Orbit. St. Louis: Mosby Yearbook; 2002
Siatkowski RM, Capo H, Byrne SF, et al. Clinical and echographic findings in idiopathic orbital myositis. Am J Ophthalmol 1994;118:343–350
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Figure 9–1 Normal. (A) Transverse scan showing the normal muscle in cross section (arrows). (B) Longitudinal scan showing the normal muscle from the insertion (arrow) to the muscle belly (M).
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Figure 9–2 Normal. (A) A-scan image of the normal inserting tendon of the medial rectus muscle (arrow). (B) A-scan image of the normal muscle belly with typical moderate reflectivity (arrow).