OCR Text |
Show <I;, 1986 Raven Pres" New York Fifth International Symposium on Orbital Disorders Avinoam B. Safran, M.D. The Fifth International Symposium on Orbital Disorders was held in Amsterdam, Holland, September 8-11, 1985. Participants from 34 countries attended the meeting, which takes place every 4 years. Lectures presenting current concepts in diagnosis and management of orbital disorders were given by prominent clinical researchers in the field. In parallel sessions, 137 free papers were delivered, many of which were of definite interest to neuro-ophthalmologists. Space does not permit the review of all the valuable papers presented, but some will be briefly mentioned. Nuclear magnetic resonance imaging is a developing process. It now allows nine slices of the orbit to be obtained in only 2.3 minutes. Because of eye motion, Bilaniuk (Philadelphia, PA) found that the shorter scanning time often provided better images than did the higher-resolution scans that require more time. The importance of the use of surface coils in orbital evaluation was also emphasized. A characteristic signal pattern of choroidal melanoma was demonstrated: The signal intensity was noted to be greater than that of muscle tissue on Tl-weighted images and less on T2-weighted images. Because of a difference in signal intensity it was possible to distinguish a retinal detachment from the tumor. In the case of pseudotumor of the orbit, the infiltrative process was shown to be well delineated on Tlweighted images, better than with computed tomographic scanning. Optic nerve gliomas showed a variable pattern. There are some indications that it might be possible to differentiate them from perioptic meningiomas by various magnetic resonance imaging clues, including greater heterogen- From the Neuro-ophthalmology Unit, Dl'partml'nt of Ophthalmology, Geneva University Hospital, Gl'nl'va, Swilzl'r1and. Address correspondence and reprint rl'qul'sts to Dr. A. B. Safran at Neuro-ophlhalmology Unit, Department of Ophthalmology, Geneva University Hospital, CH-1211 Geneva 4, Switzerland. 120 eity and increase in signal on T2-weighted images. Interestingly, in cases of Recklinghausen's disease, magnetic resonance imaging also allows the detection of numerous neurofibromas located in the tissues of the head and neck. Bilaniuk felt that there was no better technique than magnetic resonance imaging for determining the degree of involvement in neurofibromatosis. Bilaniuk also emphasized that magnetic resonance imaging examinations should be avoided in patients with intraocular metallic foreign bodies because, if the latter are ferromagnetic, they could be dislodged by the procedure. Artefacts can be caused by several factors, including intravascular flow (software will shortly be available that will remove this type of artefact) and eye makeup (many brands of mascara contain iron oxide). The dark crescent that occasionally appears around the optic nerve in coronal cuts most often is an artefact resulting from chemical shift; it should not be mistaken for a perioptic meningioma. Several of these observations were also supported by those of Moseley (London, U.K.) and Cabanis (Paris, France). In addition, Moseley stressed the use of magnetic resonance imaging for diagnosing arteriovenous shunts in the orbit, whereas Cabanis emphasized the advantages of using the so-called neuro-ocular plane for neuroradiologic evaluation of visual pathways and demonstrated how dental metal induced magnetic resonance imaging artefacts, which can mimic orbital fractures. Kingsley (London, U.K.) examined a series of patients with orbital lesions by means of intravenous digital subtraction angiography. He concluded that, using this technique, intracranial vessels limit the diagnosis of orbital disorders, carotid- cavernous fistulae cannot be excluded, resolution of individual vessels is poor, and, When investi~ atio~ by means o~ ~arotid angiography is requited, mtravenous dlgltal subtraction angiog- FIFTH INTERNATIONAL SYMPOSIUM 121 raphy may not be sufficient. This view was also supported by the observations of Vignaud (Paris, France). In contrast to computed tomographic scanning and orbital phlebography, ultrasonography allows the evaluation of pulsatility and compressibility of the dilated superior ophthalmic vein. This was emphasized by h~rgensen (Hamburg, F.R.G.), who evaluated 40 patients with this condition by means of B-scan ultrasonography. In cases of carotid- cavernous fistulae, the superior ophthalmic vein demonstrated pulsation upon digital compression of the orbital soft tissue, whereas incompressible dilated veins were found in patients with cavernous sinus thrombosis. Orbital masses and infiltration were associated with a compressible, but not pulsating vein. With standardized A- and B-scan echography, Ossoinig (Iowa City, IA) was able to detect and evaluate dilatation of the "vertical vein," which is a direct anastomosis between the anterior portion of the superior ophthalmic vein and the inferior ophthalmic vein. This vessel takes a vertical course in the retrobulbar area, between the medial rectus and the optic nerve. Evaluation of the "vertical vein" is important, particularly in cases of superior ophthalmic vein thrombosis. It also is a sensitive indicator of clinical evolution in arteriovenous fistulae. In patients with Graves' disease, the optic nerve has been shown to be enlarged. Ossoinig further demonstrated the importance of dynamic evaluation of echographic optic nerve measurement by successively evaluating optic nerve widths (a) in the primary position, (b) in 30° abduction, and (c) after eye movement exercise, once again in the primary position. In normal subjects, upon lateral gaze, because of both the stretching of the optic nerve and subarachnoid fluid posterior expulsion, width values obtained are lower upon 30° abduction than in the primary position (the optic nerve is "dry") and return to previous level when the eyes are brought back into the primary position. In patients with Graves' optic neuropathy, Ossoinig showed that width values did not return to normal in the third stage of the examination. This was interpreted to be the result of increased pressure of extraocular muscles at the apex, which did not allow the subarachnoidal liquid to return around the optic nerve after posterior expulsion upon lateral gaze. This disturbance in liquid circulation was considered to be one of the pathogenic mechanisms of optic neuropathy in the condition. Echographic changes may precede functional changes of optic neuropathy in Graves' disease, and, like tonometry, indicate patients who are at risk. According to Ossoinig, however, these morphological changes of the optic nerve should not be taken into account in the treatment of optic neuropathy. Frazier Byrne, Novinski, Glaser, and Schatz (Miami, FL) demonstrated A- and B-mode echographic differences between papilledema and optic nerve drusen, and showed that various causes of an enlarged optic nerve can be distinguished using this technique. In contrast to solid thickening of the perineural sheets, an increase in subarachnoid fluid is associated with reduction in optic nerve diameter upon lateral gaze. In addition, glioma and meningioma demonstrate distinctive reflective patterns on both A- and B-mode echograms. Poujol (Paris, France) demonstrated A- and B-mode echographic patterns of optic disc vessels, cupping, coloboma, and colobomatous cysts, and discussed the peculiar image of the optic nerve head meningioma. Fine-needle aspiration biopsy is considered by a number of clinicians to be a valuable diagnostic procedure. This view was supported by Van Herde (Amsterdam, Holland) and Naeser (Uppsala, Sweden), drawing on their clinical experience. However, when not performed according to a well-established protocol, such as the one recently popularized by Kennerdell, it may prove extremely dangerous. A survey was conducted by Liu (Detroit, IL) among oculoplastic and orbital surgeons who use this diagnostic technique. Information was obtained concerning 152 patients. Observations were divided into two groups: the first with 138 patients in whom the diagnostic procedure was performed by orbital or oculoplastic surgeons, the second with 14 patients who underwent biopsy by general ophthalmologists and who were later referred to orbital or oculoplastic surgeons. No serious complications were reported in the first group, whereas complications in the second group of patients included three deaths, three cases of blindness, and two perforated globes. The causes included the use of too-long needles and non-sterile techniques. Although orbital decompression is generally beneficial to patients with optic neuropathy resulting from Graves' disease, the procedure is not always uneventful. Kennerdell (Pittsburgh, PA) indicated that several patients had been referred to him for medicolegal consultation after they experienced loss of vision in one eye following orbital decompression. This can occur as a result of optic nerve compression during surgery or postoperative hemorrhage. Although rare, these com- 1Clin Neuro-ophthalmol. Vol. 6, No.2, 1986 /22 A. B. SAFRAN plications should be borne in mind when considering orbital decompression for esthetic reasons. That intensive plasmapheresis followed by immunosuppressive treatment for 3-6 months could be beneficial in severe Graves' disease was suggested by Schrooyen, Vinnand, and Glinoer (Brussels and Liege, Belgium). Eight of nine treated patients showed improvement just days following plasmapheresis. No rebound effect was noted following discontinuation of therapy, but three patients showed recurrence after 3 months, although this was reported to be easily controlled with immunosuppressive drugs. Combined short-term prednisone therapy and radiotherapy in Graves' disease was felt by Ouwerkek, Wijngaarde, Hennemann, et al. (Rotterdam, Holland) to be superior to prednisone alone because of a lower recurrence rate and fewer side effects. Incidentally, the authors noted an increase in visual evoked response latency following radiotherapy. , Clill Neuro-ophtltallllol. Vol. 6. No.2. 1986 A tentative explanation for the usual relative sparing of pupillary sphincter function with lesions of the oculomotor nerve in the cavernous sinus and the orbit was given by Ishikawa, Inagi, Kashima, et al. (Tokyo, Japan). They performed a microscopic study of the course of oculomotor nerve and its branches, following extraction of the sphenoid bones (including cavernous sinus and orbit) from eight cadavers. The study indicated that, in the cavernous sinus, the oculomotor nerve divided into superior and inferior branches some 4.3 mm from the orbital apex; the superior branch then subdivided into some fine branches whereas the inferior branch did not separate up to the orbit. The ratio of the superior to the inferior branch was about 0.3. The authors suggested that these findings might indicate that the superior branch is more vulnerable than the inferior one, which may explain the relative preservation of pupillary function in the above-mentioned conditions. |